# What about a turbocharged P36?



## pinsog (Dec 23, 2015)

We all know the P39 and P40 never received a turbocharger making both of them a dog above 15,000 feet or so. The P35 was never a good performer, poor handling/turning ability and poor workmanship (leaking wing tanks). But the P35 got a turbocharger and became the P43 Lancer with good performance at the time of 350 mph plus and 1200 hp at 25,000 feet while still retaining poor handling and poor workmanship. 

The P36 on the other hand, had an excellent climb rate and exceptional maneuverability. What about installing either a Wright 1820 or P&W 1830 with a turbocharger in the P36? It would gain some weight but still shouldn't weigh as much as a P40 or F4F Wildcat and still have 1200 hp at 25,000 feet. Should still retain much of its handling, certainly no worse than the P40 which still turned well, should still out climb a P40 or Wildcat rather easily and do at least 350 mph plus (I would think it would be faster than a P43 Lancer) putting it on a level footing with the Spitfire and ME109 and Zero.

Thoughts?


----------



## GregP (Dec 23, 2015)

You are the first person I have ever heard mention poor workmanship in a Seversky aircraft. We happen to fly one, a 2-PA / AT-12, and the workmanship is very good. It was basically a 2-seat P-35.

The P-35 didn't have self-sealing tanks, but I haven't heard much about leaks other than when they were strafed by Japanese aircraft. Without self-sealing tanks, that is to be expected.

Perhaps you could tell me the source of the "poor workmanship" claim?


----------



## FLYBOYJ (Dec 23, 2015)

pinsog said:


> The P35 was never a good performer, poor handling/turning ability and poor workmanship (leaking wing tanks)



The P-35 represented a first generation all-metal monoplane fighter. The overall workmanship of the over all aircraft was excellent (I've seen one up close), it did have a wet wing, and if you ever worked around one, they all leak! I read varying articles about this aircraft but very few from someone who actually flew one. No doubt the P-35 was obsolete by the time the war started. Where did you get this assessment for this aircraft?!?!


----------



## FLYBOYJ (Dec 23, 2015)

Wow Greg, we're psychic friends!!!

Reactions: Like Like:
1 | Like List reactions


----------



## pinsog (Dec 23, 2015)

Perhaps I should retract or rephrase the 'poor workmanship' comment. I have seen multiple sources on the P35 and especially the P43 Lancer having leaking fuel tanks. The AVG turned down the P43 due to leaking fuel tanks. As I understand it, wasn't it a wet wing without actual tanks?


----------



## pinsog (Dec 23, 2015)

I guess our post crossed in space. So all wet wings leak…learned something new today. Wonder why they would do such an arrangement on a fighter plane that gets shot at??? Where did I get assessment on P35? Multiple places. Everything I have read (admittedly much of it was in cyber space) including just the specs showed it to be slow, poor climbing and poor turning.


----------



## FLYBOYJ (Dec 23, 2015)

pinsog said:


> I guess our post crossed in space. So all wet wings leak…learned something new today. Wonder why they would do such an arrangement on a fighter plane that gets shot at??? Where did I get assessment on P35? Multiple places. Everything I have read (admittedly much of it was in cyber space) including just the specs showed it to be *slow, poor climbing and poor turning*.



By what standards? During the 1930s it was state of the art, by 1940 it was "slow, poor climbing and poor turning." I could compare a P-51 to an F-15 and make the same assessment!

There's a book about Alexander de Seversky and it tells all about the P-35.


----------



## pinsog (Dec 23, 2015)

By what standards: I would compare it directly to the P36 since they were designed at the same time and the P35 comes off very poorly except in range. 


Specifications (P-35A)[edit]
Data from The American Fighter[34]
General characteristics

Crew: One
Length: 26 ft 10 in (8.17 m)
Wingspan: 36 ft 0 in (10.97 m)
Height: 9 ft 9 in (2.97 m)
Wing area: 220 ft² (20.43 m²)
Empty weight: 4,575 lb (2,075 kg)
Loaded weight: 6,118 lb (2,775 kg)
Max. takeoff weight: 6,723 lb (3,050 kg)
Powerplant: 1 × Pratt Whitney R-1830-45 Twin Wasp radial engine, 1,050 hp (783 kW)
Performance

Maximum speed: 290 mph (252 knots, 467 km/h) at 12,000 ft (3,660 m)
Cruise speed: 260 mph (226 knots, 418 km/h)
Range: 950 mi (826 nmi, 1,530 km)
Service ceiling: 31,400 ft (9,570 m)
Rate of climb: 1,920 ft/min (9.8 m/s)
Wing loading: 27.8 lb/ft² (135.8 kg/m²)
Power/mass: 0.172 hp/lb (0.282 kW/kg)

Specifications (P-36A)[edit]
Data from Curtiss Fighter Aircraft: A Photographic History 1917-1948[24]
General characteristics

Crew: 1
Length: 28 ft 6 in (8.7 m)
Wingspan: 37 ft 4 in (11.4 m)
Height: 8 ft 5 in (2.6 m)
Wing area: 235.94 ft² (21.92 m²)
Empty weight: 4,567 lb[25] (2,076 kg)
Loaded weight: 5,650 lb (2,560 kg)
Max. takeoff weight: 6,010 lb[25] (2,732 kg)
Powerplant: 1 × Pratt Whitney R-1830-17 Twin Wasp air-cooled radial piston engine, 1,050 hp (783 kW)
Performance

Maximum speed: 313 mph (272 knots, 500 km/h) at 8,500 ft, 2,960 m
Cruise speed: 270 mph (235 knots, 432 km/h)
Range: 625 mi (543 nmi, 1,006 km) at 270 mph (419 km/h), 860 mi (748 nmi, 1,385 km) at 200 mph
Service ceiling: 32,700 ft (9,967 m)
Rate of climb: 3,400 ft/min (17 m/s)
Wing loading: 23.9 lb/ft² (116.8 kg/m²)
Power/mass: 0.186 hp/lb (306w/kg)

These are from Wiki, I know I know, but anyway, the P36 beats the P35 rather badly on everything but range. But, when a turbocharger was added to the P35, its performance up high was better than anything the US had at the time except for the P38. So, what if they had installed the same turbocharged engine in the P36 with its exceptional handling and climb rate? Would a turbocharger and the plumbing fit in a P36?


----------



## GregP (Dec 23, 2015)

The only person I know who flies a Seversky semi-regularly is John Maloney and I've asked him about the AT-12 / 2-PA we have. He loves it and says it climbs and flies very well / handles beautifully, but is a bit slow compare with the WWII fighters. That is to be expected with a 975 HP engine in an airframe that was upsized a bit and give a pot belly to house the air and exhaust ducting for the supercharger to become the P-47 with 2,000 HP.

As for the P-36, it is one of my favorites of the time. It is definitely supposed to handle far better than a P-40.


----------



## pinsog (Dec 23, 2015)

Greg, could the turbocharger and plumbing from a P43 Lancer be put into the P36 airframe? Or is it too small?


----------



## GrauGeist (Dec 24, 2015)

Keep in mind that while the P-36 was a great performer, it also was lacking self-sealing tanks and suitable cockpit armor.

It was also lightly armed, with 1 .30 MG and 1 .50 MG, although later models were a little better equipped, with twin .50 MG in the cowl and 2 (or 4) .30 MGs in the wings.

So adding a supercharger wouldn't do much good unless you added the armor and self-sealing tanks...and now you're in the league of the P-40, weight-wise.


----------



## pinsog (Dec 24, 2015)

GrauGeist said:


> Keep in mind that while the P-36 was a great performer, it also was lacking self-sealing tanks and suitable cockpit armor.
> 
> It was also lightly armed, with 1 .30 MG and 1 .50 MG, although later models were a little better equipped, with twin .50 MG in the cowl and 2 (or 4) .30 MGs in the wings.
> 
> So adding a supercharger wouldn't do much good unless you added the armor and self-sealing tanks...and now you're in the league of the P-40, weight-wise.



Agree that the weight would go up and quite possibly match the P40. BUT you would also have 1200 hp up to 25,000 feet. Pilot would definitely need a sheet of armor behind his seat and head, self sealing tanks, weapons: Against Japan I would give it 2 synchronized 50's. If it fought against Germany either 2 synchronized 50's and 1 50 in each wing, or 4 50's in the wing and no fuselage guns. What I wouldn't do is weight it down with 6 50's like they did the F4F4 Wildcat and later P40's. 

Back to my other question: Would the same turbo charger setup the P43 used fit in the P36? Or is the P36 too small?

(glad you responded GrauGeist, didn't you say your uncle flew P36's?)


----------



## GrauGeist (Dec 24, 2015)

pinsog said:


> Agree that the weight would go up and quite possibly match the P40. BUT you would also have 1200 hp up to 25,000 feet. Pilot would definitely need a sheet of armor behind his seat and head, self sealing tanks, weapons: Against Japan I would give it 2 synchronized 50's. If it fought against Germany either 2 synchronized 50's and 1 50 in each wing, or 4 50's in the wing and no fuselage guns. What I wouldn't do is weight it down with 6 50's like they did the F4F4 Wildcat and later P40's.
> 
> Back to my other question: Would the same turbo charger setup the P43 used fit in the P36? Or is the P36 too small?
> 
> (glad you responded GrauGeist, didn't you say your uncle flew P36's?)


The R-1830-17 of the P-36 was going to be slightly different than the R-1830-49 of the P-43. The supercharger would require quite a bit of additional space, too.

And yes, my Uncle was assigned the P-36, but was never able to use it in combat.


----------



## GregP (Dec 24, 2015)

I think it could be put in but, rather than add bumps and bad aerodynamic things, I'd probably opt to add a short fuselage plug with enough space for it. Sort of a short plug behind the engine while trying to keep the pilot as far forward as possible. If you were to add it behind the pilot, you'd probably need a pot belly like the P-47 for all the ducting.

It could probably easily be worked out today but with 1938 technology, I'm not sure the result would be as good as it might be otherwise. It would likely be better than the P-43, though. I would love to have seen a turbocharged P-36 with an R-2000 in it.

Conversely, it would have been nice to actually build and fly a turbocharged P-40, too. I have often wondered if an increase power at altitude would have made the P-40 a contender of some merit, particularly an XP-40Q that might have morphed into a production P-40Q.

Of the two, I think offhand that the P-36 would probably have been easier to debug and get into service in a timely fashion, but could be wrong.


----------



## FLYBOYJ (Dec 24, 2015)

pinsog said:


> By what standards: I would compare it directly to the P36 since they were designed at the same time and the P35 comes off very poorly except in range.
> 
> 
> Specifications (P-35A)[edit]
> ...



I think you need to make the comparison to the original Hawk 75 and the AP-1 during the 1936 competition between the two aircraft. This is mentioned in the book about de Seversky. I also found this;

_"When the design was first offered to the Army on May 24, 1935, three different power plants were proposed, and the prototype actually experienced four engine changes within a year’s testing. For the generous 236-square-foot area wing, a new NACA 2300-series airfoil was chosen, with less drag than the Clark CHY profile used by Seversky. Using a unique retractable landing gear whose wheels rotated as they folded back flat within the wings, the Model 75 had a 700-hp Wright XR-1510-C5 when test pilot H. Lloyd Child made the first flight on May 13, 1935. 

Top speed was estimated as a modest 253-mph at 10,000 feet, but this experimental radial engine was replaced in July by a 775-hp Wright XR-1670-5, which promised 263 mph. Neither of these power plants was accepted for Air Corps production, so another air-cooled radial, the 750-hp Pratt Whitney R-1535 adopted by the Army for attack and observation planes, powered the Curtiss Model 75 when it appeared on August 7 for the Army competition. 

The larger Wright R-1820 on Seversky’s entry gave it an advantage in speed. When Curtiss complained, the Secretary of War set back the contract competition to April 15, 1936. Don Berlin’s Hawk was flown again as Model 75B on April 4, 1936, powered by an 850-hp single-row Wright XR-1820-G5 Cyclone, and with indentations behind the cockpit to help visibility. Curtiss estimated the top speed of their Hawk as 294 mph with the Cyclone, or 297 mph if provided with a Twin Wasp, but only 285 mph was actually obtained during the tests. 

Although Seversky won the Fiscal 1936 contract, Curtiss did get an order on August 7, 1936, for three Y1P-36s. The first Y1P-36, was delivered to Wright Field with a twin-row Pratt Whitney R-1830-13 and Hamilton propeller on March 4, 1937, and was soon followed by its two service test companions. The gear-driven supercharger built into the back of the R-1830-13 yielded 1,050-hp for takeoff and 900-hp at 12,000 feet with 92-octane fuel, giving the Y1P-36 a top speed of 295 mph. 

Fiscal 1938 funds would allow purchase of about 220 new pursuits, so both companies tried again with bids opened April 2, 1937. Specification 98-605 called for 300-mph and deleted the old bomb rack requirement; the Air Corps then didn’t want its fighters diverted to ground- attack work. 

Seversky offered its AP-1 at $15,900 each, while Curtiss wanted $18,720 for its P-36. This time the lowest bidder lost. Curtiss won the largest fighter contract since 1918: for 210 P-36s on July 30, 1937." _

P-35 to P-42 by Ray Wagner - Page 1


----------



## tomo pauk (Dec 24, 2015)

The proposed turboed P-36 would be the interesting thing. The P-36 have had 'normal' fuel tanks, so one of the shortcomings of the P-35 (and F2A, for that matter) would've not surfaced. It is a question of whether the turbo intercooler will be reasonably blended in the airframe, to keep the drag manageable. The fuselage tank (then was named 'overload fuel tank') would lost much of it's capacity if the turbo is located behind the pilot, but that should not be that a great problem.


----------



## pinsog (Dec 24, 2015)

FLYBOY, do you have any information on how well the P35 turned compared to the P36? Or how the P35 turned and climbed in general? 

GregP, I agree that packaging the turbo immediately behind the engine, all in front of the pilot might be preferable, just lengthen the nose. GregP, was it you that said somewhere else on this forum that Curtis proposed a 1200 hp 2 speed, 2 stage P&W for the P36 with a 355 MPH top speed? 

GregP and FLYBOY, you both work on these things, I don't. With 70 years of hindsight, would you go for a turbocharged P36? Or a 2 speed, 2 stage P36? I just personally think the P40 was a step backward for the US at the time. It did gain some speed, but it lost turning ability, climb, its altitude performance was bad and it was always slower than a P39. I think continued development of the P36 would have been the way to go, especially against the Japanese.


----------



## tomo pauk (Dec 24, 2015)

The turbo immeditely behind the engine won't work on the state of the art in the USA during the ww2; one needs air cooled turbne blades to help out. The 2-stage P-36 would be interesting, if a bit too late vs. P-40. Leading us to the P-40s main quality - being in volume production when needed. BTW, the 'some speed' gain vs. P-36 was 50 mph, a major improvement in anybody's book.

The P-40 was no push over vs. Japanese aircraft, especially the Army types like the Ki 27 or Ki 43. Adding the self sealing fuel tanks, pilot protection and heavy armament and the required airframe strength will limit the performance of any P-36, with with any type of supercharging.


----------



## FLYBOYJ (Dec 24, 2015)

I've read somewhere that the P-35 was too harmonized for a fighter. The link I provided has a quote from Charles Lindberg that quoted him saying that the P-36 "was a better flying aircraft." Aside from that that's about all I heard about the P-35, but you could look at it's power to weight ratio and wing loading and draw your own conclusions.

With hindsight being 20-20, I think a two-stage blower would have been a better option in lieu of a turbocharger, considering engineering resources available at the time. As fighter airframe development was moving along pretty quickly during that period, some technologies like aviation turbos and superchargers were just catching up, and also remember, all this development had to be undertaken with depression-era dollars. Lastly you had some builders and military planners who were not visionaries and there were many obsolete concepts attempted during the same period that squandered away time and money - I think the Bell XFM Airacuda was the poster child of this situation.


----------



## GrauGeist (Dec 24, 2015)

The P-35 may have had some potential, but the airframe wasn't "clean" by virtue of it's design.

The "greenhouse" cockpit, the maingear stowage and other factors all created a good deal of drag.


----------



## pinsog (Dec 24, 2015)

GrauGeist said:


> The P-35 may have had some potential, but the airframe wasn't "clean" by virtue of it's design.
> 
> The "greenhouse" cockpit, the maingear stowage and other factors all created a good deal of drag.
> 
> View attachment 308133



I agree. I think the P36 with a turbocharger behind the pilot would have been the plane to go with instead of the P35/P43 Lancer that got the turbo instead. If they could get a P43 Lancer up to 356 mph with a 1200 hp turbocharged engine, wonder what a P36 could have gotten up to? Plus, the P36 would have had much better handling and a much better rate of climb.


----------



## pinsog (Dec 24, 2015)

FLYBOYJ said:


> I've read somewhere that the P-35 was too harmonized for a fighter. The link I provided has a quote from Charles Lindberg that quoted him saying that the P-36 "was a better flying aircraft." Aside from that that's about all I heard about the P-35, but you could look at it's power to weight ratio and wing loading and draw your own conclusions.
> 
> With hindsight being 20-20, I think a two-stage blower would have been a better option in lieu of a turbocharger, considering engineering resources available at the time. As fighter airframe development was moving along pretty quickly during that period, some technologies like aviation turbos and superchargers were just catching up, and also remember, all this development had to be undertaken with depression-era dollars. Lastly you had some builders and military planners who were not visionaries and there were many obsolete concepts attempted during the same period that squandered away time and money - I think the Bell XFM Airacuda was the poster child of this situation.



I have "Republics P47 Thunderbolt" by Bodie, I plan on re reading the P35/P43 section for the next 2 days at Christmas to refresh my memory. (I think I just skimmed over that part the first time)


----------



## GregP (Dec 24, 2015)

On the other hand, if you have to land the P-35 gear-up, there is very little airframe damage. Considering when the P-35 was designed, the arifields at the time and their relative small number, this was perhaps a very good design for a fledgling modern air force whose pilots had never flown a retractable gear airplane much.

For peak performance, I agree the P-36 was a better aircraft, but the P-35 served well while it served. You well might write off a P-36 in a gear-up landing, but it would certainly out-perform the P-35 in almost every category. Probably the turning point was when all aircraft had a radio so the tower could scold the pilot if he was landing gear-up. Without a radio, all you could do was watch it happen.


----------



## GrauGeist (Dec 24, 2015)

That might be a good consideration for a trainer, Greg, but the performance penalty the maingear cowlings imposed put the aircraft at risk in a confrontation.

A bellied airframe has the potential to be recovered, but if it's shot down in combat, it's most certainly a loss.


----------



## pinsog (Dec 24, 2015)

GrauGeist said:


> That might be a good consideration for a trainer, Greg, but the performance penalty the maingear cowlings imposed put the aircraft at risk in a confrontation.
> 
> A bellied airframe has the potential to be recovered, but if it's shot down in combat, it's most certainly a loss.



Are you referring to the P35 or the P36? I agree that the P35 was not the aircraft we needed. On the other hand, I think they had spent the time and money putting a turbocharged radial into the P36 instead of the Allison V12, they could have had a competitive high altitude fighter in production when the war started. But I have to rely on people such as GregP and FLYBOY, since they work on these things, to tell me if the turbo and plumbing would fit in the P36 behind the cockpit, or if I am completely wrong.


----------



## GregP (Dec 24, 2015)

What I was saying is the P-35 with the half-exposed wheels was a good choice for an air force just learning retractable fighters. The P-36 was very probably a much better combat aircraft, but the P-35 gave great service to our cadre of pilots who initially fought in WWII. By the time they transitioned into more modern types, they probably had already done their "gear up landing training."


----------



## GrauGeist (Dec 24, 2015)

pinsong, I was referring to the P-35.

Greg, I can see where your going, with the semi-retracted maingear, but I would suppose that an advanced trainer would be far better with this feature. Also, consider this: with fully retractable maingear, the airframe bellies flat, with or without a powered prop-strike...the damage is not as bad as it may seem (depending on the energy contained in the initial contact), however, with the semi-retracted gear, the inertia of the gear-up landing is carried over by the friction of the gear cowling and the airframe pitches forward, shoving the nose into the ground (much like a P-47 or Fw190 under excessive braking). This seems far more stressful to the airframe and more potential damage to the engine (powered prop-strike or not).

The A-10 does have the semi-retractable gear and it has successfully served it's purpose and many occasions, so it is a sound idea.


----------



## tomo pauk (Dec 24, 2015)

Now that we're at the P-40 pros cons, would some kind soul delete or rectify the claim in Wikipedia entry about the type:



> The P-40's *lack of a two-speed supercharger* made it inferior to Luftwaffe fighters such as the Messerschmitt Bf 109 or the Focke-Wulf Fw 190 in high-altitude combat and it was rarely used in operations in Northwest Europe.



The lack of two-speed supercharger on (most of) P-40s had nothing to do with the type's lack of performance at high altitude.


----------



## gjs238 (Dec 24, 2015)

tomo pauk said:


> Now that we're at the P-40 pros cons, would some kind soul delete or rectify the claim in Wikipedia entry about the type:
> 
> 
> 
> The lack of two-speed supercharger on (most of) P-40s had nothing to do with the type's lack of performance at high altitude.



Done

Reactions: Like Like:
1 | Like List reactions


----------



## GregP (Dec 24, 2015)

To the earlier question, I go with Joe here. I think a 2-stage supercharger would have been the way to go, and I would have opted for a 2-stage P-36 if I had the choice. The P-35 was good for its day but outmoded by the time we were actually in WWII. I would have transferred all of them to training fields and that could well be where they would up ... I never really tracked down what the ultimate fates of the P-35 inventory were.

I could be that had Curtiss developed the P-36 for the R-2800 by enlarging it a bit, it might have been a better P-47. I would not propose that as an alternate history thread, but certainly would as an alternate possibility had the P-47 failed miserably after some effort at sorting it out. In fact, they DID need some effort to sort it out, but it turned out pretty darned well. Meanwhile, Curtiss faded. To bad for an old-school aircraft company to let things go the way they did.

Bad outcomes can be overcome. Bad management is state difficult to escape from since the bad managers seldom put their own names on the layoff list.


----------



## FLYBOYJ (Dec 24, 2015)

I would still have issues with a P-35 belly landing - although the bulging landing gear fairings may keep most of the belly off the ground, I would wonder what type of stress would be placed on the wheel well and wing.

The later model P-36 IMO was one of the most under rated fighters of WW2, giving it better high altitude performance might have made it a game changer. Although it wasn't a speed demon, it performed well in combat.

For what it's worth, from Wiki;

_On September 20, Sergeant André-Armand Legrand, pilot of the H75A-1 n°1 in the Groupe de Chasse II/5 La Fayette was credited of the first Allied air victory of World War II on the Western front with shooting down one Messerschmitt Bf 109E of the Luftwaffe 3/JG53, over Oberhern. During 1939–1940, French H75 pilots claimed 230 air-to-air kills (of a total of 1,009 air-to-air kills by the French Air Force during the 1939-40 time period) and 81 probable victories in H75s against only 29 aircraft lost in aerial combat. *While making up only 12.6% of the French Air Force single-seater fighter force, the H75 accounted for almost a third of the air-to-air kills during the 1940 Battle of France*. Of the 11 French aces of the early part of the war, seven flew H75s. The leading ace of the time was Lieutenant Edmond Marin la Meslée with 15 confirmed and five probable victories in the type. H75-equipped squadrons were evacuated to French North Africa before the Armistice to avoid capture by the Germans. While under the Vichy government, these units clashed with British aircraft over Mers el-Kébir and Dakar. During Operation Torch in North Africa, French H75s fought against U.S. Navy F4F Wildcats, losing 15 aircraft while shooting down seven American aircraft. From late 1942 on, the Allies started re-equipping the formerly Vichy-controlled French H75 units with P-40s and P-39s._


----------



## wuzak (Dec 24, 2015)

I seem to recall that there was a P-36 variant fitted with a two stage R-1830 - an experimental installation. Perhaps for the XP-42?


----------



## pinsog (Dec 24, 2015)

I have a book on the P36 that gives several individual pilot accounts of the aircraft. One pilot flying for, I think The Netherlands, against the Japanese, reported in a dogfight that a Hamp pulled up and was climbing away from him, he pulled up behind the Hamp in his P36 AND CAUGHT THE HAMP IN A STEADY CLIMB and shot him down. Not something you read about before late 1943 or early 1944. He also reported that his P36 could outturn a Hamp in a slow speed dogfight. Like I said, I think with a 2 speed 2 stage P&W 1830, 2 synchronized 50's, 1 sheet of armor behind the pilot, and self sealing tanks and this could have equalized the field from the beginning of the war until the Hellcat, Corsair, P38 and P47 came along.

Also, same book said all of the P36's that got airborne during Pearl Harbor were being used for gunnery training and were only armed with a single synchronized 30. One pilot reported being 10 or 20 feet behind a Japanese torpedo bomber and unloading all the ammo he had from that one gun into the plane, which dropped off smoking. He had to evade another plane and doesn't know if it crashed or not. I would like to suggest that no early war Japanese single engine plane would have lasted more than a few seconds in front of a 50 in that situation before bursting into flame. That is why I suggest that 2 slow firing, synchronized 50's with say 250 rounds each are better than 30's with any ammo count even if the 30's fired twice as fast.


----------



## tomo pauk (Dec 25, 2015)

The XP-42 was with the 1-stage, 2-speed supercharger. In one of it's many iterations, I especially like the one with individual exhaust stacks and fan for cooling under the 'short cowling', all akin to what Fw 190 had. The P-40 with the 2-stage R-1830 mated, no guns ammo, was supposed to do 385 mph.

With that said - both the P-36 and Zero climbed good and turned good when sported next to no protection, plus light armament ammo load. Add some protection, heavier draggier battery of armament, heavier draggier engine (due to the intercoolers) and heavier structure so the G limits are met - that would meant that a great deal of performance gain is cancelled out. The radial in question won't allow for any overboosting until water injection arrives in late 1943, unlike the V-1710 that can be overboosted, officialy or otherwise.
On the other hand, if the non-protected and weakly armed fighter is okay, press on with P-40 (no suffix), while deleting the wing LMGs. This means 360 mph fighter out from the box, that would be much a better climber than the overweight P-40E usually used by USAF in 1942.

Tailoring the future fighter on what we know the Japanese had in 1942, while neglecting what was known the Germany and UK have in production is not that a great idea, no offense on the Christmas


----------



## pinsog (Dec 25, 2015)

tomo pauk said:


> The XP-42 was with the 1-stage, 2-speed supercharger. In one of it's many iterations, I especially like the one with individual exhaust stacks and fan for cooling under the 'short cowling', all akin to what Fw 190 had. The P-40 with the 2-stage R-1830 mated, no guns ammo, was supposed to do 385 mph.
> 
> With that said - both the P-36 and Zero climbed good and turned good when sported next to no protection, plus light armament ammo load. Add some protection, heavier draggier battery of armament, heavier draggier engine (due to the intercoolers) and heavier structure so the G limits are met - that would meant that a great deal of performance gain is cancelled out. The radial in question won't allow for any overboosting until water injection arrives in late 1943, unlike the V-1710 that can be overboosted, officialy or otherwise.
> On the other hand, if the non-protected and weakly armed fighter is okay, press on with P-40 (no suffix), while deleting the wing LMGs. This means 360 mph fighter out from the box, that would be much a better climber than the overweight P-40E usually used by USAF in 1942.
> ...



All good points. BUT, the book I have on the P36 talked about French pilots, naming them by name, who were saved by the backseat armor in 1940 over France. I have a couple of books on the Battle of Britain, and supposedly the Spitfire and Hurricane had self sealing fuel tanks during the BOB but it seems like many, if not most of the British pilots shot down during the BOB were horribly burned. Not sure why. Were early British self sealing tanks not very effective? They also speak of the P36 EASILY out turning everything in the air including the Spitfire and the Hurricane. The P36/P40 did not have the high speed control issues the Japanese Zero had. The book I have on the P36 also speaks of the durability of the P36 during the Battle of France, with many of them returning just riddled with bullets but still bringing their pilots home safely. If the Spitfire, Hurricane and ME109 can add some armor, decent weapons and self sealing tanks and still have good performance, then I see no reason why a 2 speed 2 stage 1830 in a P36 couldn't do the same thing. 

The P47 Thunderbolt, by Bodie says that the P43 Lancer was faster than a Spitfire II above 20,000 feet (I think it was 20,000) and the P43 weighed between 7400 and 8400 pounds. If a P36 could fit the same turbocharged 1830 with the turbo behind the seat, I still think you have an early war game changer.


----------



## Vincenzo (Dec 25, 2015)

JoeB reported this result for the Hawk 75: 38 losses for 23 Bf 109 in the BoF, the best french fighter, 
in the Phoney war: 15 losses for 13 Bf 109 (not all Emil, Nikademus reported for 23 Bf 109 idk what is the missprint)
In Operation Torch around 10 losses for 5 victory on F4F
Pearl Harbour 1 P-36 loss for 2 Zero
NEI: 5 Hawk and 12 CW-21 losses for 3 (at max) Zero in the alone Hawk engagement of campaign
Burma: 7 Mohawk for 7 Oscar
East Africa no fighter vs fighter combat for the Mohawk

I've no data for the finnish Curtiss, i'm sure we can get losses and claims for our finnish agent/s, for soviet losses... we have a russian agent? 

thanks to waybackmachine we had the finish Curtiss claimed 190 1/3 enemy planes for 15 losses


----------



## tomo pauk (Dec 25, 2015)

There were several reasons why the P-36 could outmaneuver the Spit or 109, most if not all related to the favorable wing loading. Light engine, light armament battery ammo, generous wing size - yes. the aircraft will be very maneuverable, plus it will climb well. Lets add weight and drag and see what happen.
The comparison vs. the Spit, 109 or Hurri give us some clues. Eg. the Spitfire V sported greater protection, with no apreciable gain in performance despite 200 HP more at 19-20 kft vs. SPit I. The version with cannons, two let alone 4 was there with Spit I or II, was as fast as the Spit I. Engine weight did not changed, while the swap for the 2-stage R-1830 will add weight on the P-36, as will the added protection and 'lethality pack'.
The Hurricane II was barely faster than th Hurri I, esp. the 4 cannon variant - added firepower and protection eat up the gain in power.
Bf 109E gained some 80% power vs. the Jumo powered predecessors, vs. 10-20 % more the 2-stage engine will give to the P-36. I don't buy we'd see the desird effect here with that kind of increase in power. The 109F featured one cannon less for less drag, wholesale modification of performance-stealing items (nose, tail struts, tail wheel, radiators) plus anothe 15% or increase in power - unlike the new P-36 that will receive more engine- and weapon-related drag weight.

For the reality check, we can look at the P-40F - with no less power vs. the 2-stage R-1830, far less powerplant drag, better use of exhaust thrust - it was barely topping 360 mph. Swap the Packard Merlin with 2-stage R-1830 and we are at 350 mph?

What kind of performance, armament and protection is required for the early war game chager?


----------



## fastmongrel (Dec 26, 2015)

Interesting pdf all about self sealing fuel tanks

http://explodingfueltanks.com/pdf/ExplodingFuelTanks-chapter1.pdf

Reactions: Like Like:
2 | Like List reactions


----------



## pinsog (Dec 26, 2015)

fastmongrel said:


> Interesting pdf all about self sealing fuel tanks
> 
> http://explodingfueltanks.com/pdf/ExplodingFuelTanks-chapter1.pdf



Great article! After reading that, it doesn't look like the P36 was as outmoded as they like to lead us to believe. Doesn't appear that Spitfires and Hurricanes were armored and the "self sealing" fuel tanks were less than adequate at best. With a 1200 hp P&W 1830, delete the 30 caliber wing guns, keep 2 synchronized 50's with 250 rpg, add a 73 pound armor plate behind the seat and I think it would have been more effective than the Hurricane. German fuel tanks could withstand 30 caliber rifle hits, but not hits from a 50 bmg. No wonder German bombers could make it back to base riddled like a sieve from dozens, if not hundreds of .303 rounds where just a few 50's would have ruptured the fuel tank and started a fire.


----------



## fastmongrel (Dec 26, 2015)

pinsog said:


> Great article! After reading that, it doesn't look like the P36 was as outmoded as they like to lead us to believe. Doesn't appear that Spitfires and Hurricanes were armored and the "self sealing" fuel tanks were less than adequate at best. With a 1200 hp P&W 1830, delete the 30 caliber wing guns, keep 2 synchronized 50's with 250 rpg, add a 73 pound armor plate behind the seat and I think it would have been more effective than the Hurricane. German fuel tanks could withstand 30 caliber rifle hits, but not hits from a 50 bmg. No wonder German bombers could make it back to base riddled like a sieve from dozens, if not hundreds of .303 rounds where just a few 50's would have ruptured the fuel tank and started a fire.



The Spitfire and Hurricane did have rear armour for the pilot by the time of the Battle of Britain. The Spitfire fuel tank was between the pilot and the engine and had a double layer Aluminium fire resistant bulkhead protecting the pilot from flames sometimes for long enough to bail out if he was capable and a big lump of V12 protecting it from the front. The Hurricane had Linatex coated self sealing tanks in the wing roots but if the tank was hit and burnt the flames went into the cockpit which had no fire bulkhead, most burnt RAF pilots around 80% flew Hurricanes. The 109E in use in the BoB I am not sure of some say the fuel tank under the cockpit was armoured but not self sealing some sources say it was self sealing. Possibly a modification in light of experience.

Armouring the fuel tank wasnt a great idea its not the penetration that makes it burn its the exit hole which because of deforming and tumbling caused by penetrating the armour is much bigger. Sounds strange but an unarmoured self sealing tank is safer than an armoured self sealing tank. The safety of the self sealing varies with how much fuel is in it a nearly empty tank can explode a nearly full tank is a lot less likely to explode but will burn. A choice between a hanging or a firing squad admittedly.


----------



## tomo pauk (Dec 26, 2015)

To give the credit to the P-36 - it never received the up-rated R-1830s, not even the up-rated R-1820s (Twin Wasps and cyclones, respectively). The Twin Wasps used in the P-36 were not even with military rating, though there is a rumor that French and Finns were pushing their US-produced radials above specs.

Then we have a slight confusion about the engine types - there were several '1200 HP' R-1830s, that differed considerably. That is before we start tossing in the 2-stage variants. The R-1830-17 have had 1200 HP for take off, and 1050 HP at 6500 ft, not much of performance will be there. The R-1830-23 is not the '1200 HP' R-1830, having 1100 HP for take off, but also 950 HP at 14300 ft, due to the change in supercharger gearing vs. the -17. Will be a bit better at altirude, but still the power is too low to really compete. One engine built.
The things got more interesting with the -33, that was used on P-66 and some early non-turbo B-24s, but not on the P-36. It received the 2-speed supercharger drive, new carb, the high gear is with still greater multiplication than the (only) gear of the -23, it gives 1000 HP at 14500 ft at 2700 rpm, that being max continuous rating.

So yes, the P-36 with a better engine and just 2 HMGs should probably be good for 340-350 mph in 1941/42. Question remains - is that what the Allies need?


----------



## pinsog (Dec 26, 2015)

tomo pauk said:


> To give the credit to the P-36 - it never received the up-rated R-1830s, not even the up-rated R-1820s (Twin Wasps and cyclones, respectively). The Twin Wasps used in the P-36 were not even with military rating, though there is a rumor that French and Finns were pushing their US-produced radials above specs.
> 
> Then we have a slight confusion about the engine types - there were several '1200 HP' R-1830s, that differed considerably. That is before we start tossing in the 2-stage variants. The R-1830-17 have had 1200 HP for take off, and 1050 HP at 6500 ft, not much of performance will be there. The R-1830-23 is not the '1200 HP' R-1830, having 1100 HP for take off, but also 950 HP at 14300 ft, due to the change in supercharger gearing vs. the -17. Will be a bit better at altirude, but still the power is too low to really compete. One engine built.
> The things got more interesting with the -33, that was used on P-66 and some early non-turbo B-24s, but not on the P-36. It received the 2-speed supercharger drive, new carb, the high gear is with still greater multiplication than the (only) gear of the -23, it gives 1000 HP at 14500 ft at 2700 rpm, that being max continuous rating.
> ...



I believe the US needed it more than the British needed it. Early in the war the US needed something to compete with the Japanese on equal footing. We had 1 airplane that could climb, the P38 and it wasn't quite ready and there weren't enough of them. The P39C had a very good clim rate up to 12000 or 15000 (3700 fpm up to 10,000 feet) feet and then the Allison engine fell on its face. Then the US added 1,000 pounds of stuff to it, called it the P39D and dropped the climb rate down to 2700 fpm. The US needed a plane that had performance at 20,000 feet that was reasonable for the time period. It would have been reasonable to take a P36, 1200 hp, add a 75 pound chunk of armor behind the pilot seat, 2 50's through the prop, remove the 30's and it could have, I believe, held its own against anything in the world in 1940, 1941 and even 1942 without anything special or out of the timeline happening. Yes the Spitfire and ME109 were both faster, but the P36 could easily outturn either plane. It had a fast roll rate, its climb rate was in the ballpark with either plane(in fact, if it climbed at 3400 fpm with 1050 hp, it might have out climbed the Spit and 109 if a 1200 hp engine was installed). It could dive fast without the controls getting stiff. It was already tough, the French can tell us about its ability to sustain damage and we know radials are tough engines. 

The US needed fast climbing planes at Guadalcanal. Faster, better turning planes on Midway Island. The British could have used a plane with 50 BMG during the BoB(even if it only had 2 and they were slower firing synchronized guns) Wake Island, the Philipines, Port Moresby. Anywhere we had the P39 and P40 in the early part of the war, I think a slightly updated P36 would have done better.

Whats not to like?

Reactions: Like Like:
1 | Like List reactions


----------



## tomo pauk (Dec 27, 2015)

A good deal of the answer to the last question can be drawn exactly with the unloved (on the West) P-39. 
The P-39D introduced self-sealing tanks, 262 lbs of armor, another pair of LMGs, now with 4000 rounds for the 4 of the LMGs. There were also up to 3 (three) radio sets. So let's revert to the non-self sealing tanks, delete all armament ammo but the two synchronised HMGs, and cut their ammo load to 2 x 250 instead of 2 x 500 rds, reduce the pilot protection. That saves us indeed a great amout of weight and also cuts a bit of drag, so the resulting lightweight Airacobra climbs better and it is faster than the P-39C. That was able to do 379 mph at 16100 ft (here), ie. it is in league of Spitfire V and Bf 109F1/F2. Cutting on drag weight buys us how much, 10 mph, so the 'P-39 light' makes now almost 390 mph? The improvement of the RoC is much better.

The statement of 'the Allison engine fell on its face' does not hold the water here. The P-39D and subsequent carried the armament battery as heavy as the P-38 (paying the same drag penalty), that have had 2 such engines, turboed to boot. Let's try doubling up the armament on the Bf 109E, or install 4 cannons on the Spitfire I and see how good they perform.

For the P-40, the similar analysis can be performed. Delete 4 LMGs from the wings, and the 'P-40B light' makes 360 mph. In 1941/42, that is 30 mph better than Ki-43, and not worse than Zero.

So what should the USAF buy, the 380-390 mph P-39 or 340-350 mph P-36, or 360 mph P-40?



> The US needed fast climbing planes at Guadalcanal. Faster, better turning planes on Midway Island.



Indeed there was the need for the faster fighters. I'd propose a greater emphasis on the production of the P-38 in 1941, with the Hudsons and the like farmed out to another manufacturers, plus starting out with another production source. Then, the USAF can start the purchase process on the P-51, the 1st example arrived ot Wright Field for testing in late August 1941. We can bet dollars for donuts that a P-51 with only 2 HMGs would've been another 10 mph faster than the one with it's full battery (4 LMGs, 4 HMGs) and climb better.
Then we have the lightweight P-39 and P-40, each a better proposal than the improved P-36.

The USN and Marines also need to work on the escort job and navigation, plus the correct flight path to the seaborne target, failings in those categories cost them much more men and machines than IJN fighters and AAA. 



> Yes the Spitfire and ME109 were both faster, but the P36 could easily outturn either plane.



Let's not expect from the adversary to make mistakes. The 380-400 mph Bf-109F won't turn with anybody, they knew better. RAF/RAAF pilots, as well as their US coleagues also learned soon not to enter into a turning fight if it can be avoided. 
A good turner will have no advantage when chasing bombers, and here the bigger punch is essential. Two sysnchronised BMGs are not a good example of a big punch. That leads us to:



> The British could have used a plane with 50 BMG during the BoB(even if it only had 2 and they were slower firing synchronized guns)



That is not a winning proposal. The 340 mph P-36, even if we can have such one in 1940 does not offer anything over the Spitfire, or the Hurricane I with Merlin XX engine. The BMG in service in 1940 does 600 rpm, not 800, synchornised it is less than 500 rpm. The 8 .303s in Hurricane or Spitfire do 9600 rpm combined, vs. how much, 950 rpm with P-36 considered. 

The ammo for the BMG in 1940 is not the ammo of 1944 either, the Soviet API is yet to be copied.


----------



## pinsog (Dec 27, 2015)

tomo pauk said:


> A good deal of the answer to the last question can be drawn exactly with the unloved (on the West) P-39.
> The P-39D introduced self-sealing tanks, 262 lbs of armor, another pair of LMGs, now with 4000 rounds for the 4 of the LMGs. There were also up to 3 (three) radio sets. So let's revert to the non-self sealing tanks, delete all armament ammo but the two synchronised HMGs, and cut their ammo load to 2 x 250 instead of 2 x 500 rds, reduce the pilot protection. That saves us indeed a great amout of weight and also cuts a bit of drag, so the resulting lightweight Airacobra climbs better and it is faster than the P-39C. That was able to do 379 mph at 16100 ft (here), ie. it is in league of Spitfire V and Bf 109F1/F2. Cutting on drag weight buys us how much, 10 mph, so the 'P-39 light' makes now almost 390 mph? The improvement of the RoC is much better.
> 
> The statement of 'the Allison engine fell on its face' does not hold the water here. The P-39D and subsequent carried the armament battery as heavy as the P-38 (paying the same drag penalty), that have had 2 such engines, turboed to boot. Let's try doubling up the armament on the Bf 109E, or install 4 cannons on the Spitfire I and see how good they perform.
> ...



I agree with you on the P39. I would delete all the wing guns, maybe install fuel tanks in the wings, keep the 2 50's in the nose and replace the 37 with either a 20mm that worked(we all know of the US 20mm problem) or a 3rd 50, and put a 100 pound sheet of armor behind pilot seat and head. BUT that still doesn't solve the Allisons lack of power at altitude.

P36B 

WAR DEPARTMENT 
AIR CORPS, MATERIEL DIVISION 
Wright Field, Dayton, Ohio 
September 25, 1939
ENGINEERING SECTION MEMORANDUM REPORT ON 
Curtiss P-36B Airplane, A.C. No. 38-20

Serial No: 19-430-1001-A
SUMMARY
1.	Object -- High speed of Curtiss P-36B with and without camouflage. Airplane equipped with Pratt and Whitney R-1830-23 engine rated 950 hp at 2700 rpm and 1100 hp at 2700 rpm for take-off, three-bladed constant speed propeller, Dwg. No. 512CC1.5 range 20° to 45° at 42" radius. Landing gear retracted, carburetor cold, cockpit cabin and ventilator closed, wing flaps neutral, cowl flaps closed. Airplane flown with full gas and oil load. Weight of camouflage paint was 7.0 lbs.

2.	Test results at 950 bhp at 2700 rpm at 17,000 ft.:
a.	Speed without camouflage was 317.5 mph.

b.	Speed when camouflaged with water color paint was 316.0 mph.

￼￼￼￼￼Hurricane

Aeroplane and Armament Experimental Establishment 
Boscombe Down 
12th June 1940
Hurricane L.2026 
(Merlin III) 
(Rotol Constant Speed Airscrew) 
Comparitive Performance Trials 
under
Normal and Overload conditions


SUMMARY
At Full Throttle
Height Feet	Speed M.P.H	Time to Climb Mins	Rate of Climb ft/min
S.L 0 0
2000 0.75 2610
5000 276 1.9 2625
10000 291 3.8 2640
15000 307 5.85 2250
20000 316 8.35 1675
25000 307 12.0 1100
30000 292 18.3 530

When the P36 has the proper engine, this one available in 1939 vs the BoB Hurricane with the constant speed prop, the Hurricane has less performance below 20,000 feet in both speed and climb and turn. The P&W in the P36 had no WEP at the time. Wonder what the best high altitude P&W 1830 would have done for it in 1941 and 1942?

As far as 2 50's vs 8 30's

http://explodingfueltanks.com/pdf/ExplodingFuelTanks-chapter1.pdf

The German self sealing tanks were made to stand up to 30 caliber bullets, none of them worked for 50's at the time. British pilots had to start aiming at the engines because they couldn't set the tanks on fire. Adding to that, the British supposedly didn't aim all of their 8 guns on the same spot, they sort of used an "open choke shotgun" pattern, losing the effect a concentrated pattern would have had. French pilots during the Battle of France had 6 7.5 mm machine guns and they reported having to close to 50 meters or less to bring down German bombers. They reported that closing to 50 meters brought them in range of the Germans defensive guns causing unnecessary losses. They reported that with heavy machine guns they could have brought them down from 200 yards and stayed out of effective range of the Germans defensive guns. 

Personally, I would go for 2 50 BMG knowing that a single round would punch a large hole in a fuel tank(or an engine, or a person) and a few more should ignite it.

During the BoB the ME109 was a 348 mph plane, the P36 was a 315 mph plane that could easily outturn anything in the battle, climb with the 109 and Spitfire and with a tough radial engine.


----------



## Lefa (Dec 27, 2015)

Finnish Forces - Finnish Curtiss P-36 Hawk

There some information to P 36 in Finnish use.

Reactions: Like Like:
1 | Like List reactions


----------



## GrauGeist (Dec 27, 2015)

pinsog said:


> I agree with you on the P39. I would delete all the wing guns, maybe install fuel tanks in the wings, keep the 2 50's in the nose and replace the 37 with either a 20mm that worked(we all know of the US 20mm problem) or a 3rd 50, and put a 100 pound sheet of armor behind pilot seat and head. BUT that still doesn't solve the Allisons lack of power at altitude.


Having only two .50 MGs is not making this much of a fighter.

The ability of the U.S. fighters to deliver such a heavy knockout punch to the Axis types was because of the multiple .50s, especially the P-38, that had centerline mounted MGs which didn't rely on convergence to maximize their effect.

It seems to me, that the P-39's cannon could have been deleted and have, instead, 6 .50 MGs (two cowl and 4 in the wings).

And why so much armor for the pilot? There is an engine back there that makes a very handy piece of armor.


----------



## tomo pauk (Dec 27, 2015)

pinsog said:


> I agree with you on the P39. I would delete all the wing guns, maybe install fuel tanks in the wings, keep the 2 50's in the nose and replace the 37 with either a 20mm that worked(we all know of the US 20mm problem) or a 3rd 50, and put a 100 pound sheet of armor behind pilot seat and head. BUT that still doesn't solve the Allisons lack of power at altitude.



I like the '3-gun' P-39 proposal.
The V-1710 E4, as installed in the P-39C/D, was making a bit more power than the DB 601A of the BoB vintage, so the problem was not so great. It beacames a big problem when requiring it to propel through the air the hefty gun battery and protection package, that includes both sheet metal and 2 times the BP glass. SO deleting of heavy items from the P-39 solves a good deal of the V-1710's altitude 'problem'.



> When the P36 has the proper engine, this one available in 1939 vs the BoB Hurricane with the constant speed prop, the Hurricane has less performance below 20,000 feet in both speed and climb and turn. The P&W in the P36 had no WEP at the time. Wonder what the best high altitude P&W 1830 would have done for it in 1941 and 1942?



Comparing the P-36 with the Hurricane model that is out of production before BoB ended is a damning with a faint praise. Hurricane IIa (8 .303s) was good for 342 mph at 22000 ft, and we can hope that a P-36 will equal that in 1941, once the 2-stage R-1830 is available in quantity..
The R-1830 never got water injection in ww2 to the best of my knowledge, so no WER for it.



> The German self sealing tanks were made to stand up to 30 caliber bullets, none of them worked for 50's at the time. British pilots had to start aiming at the engines because they couldn't set the tanks on fire. Adding to that, the British supposedly didn't aim all of their 8 guns on the same spot, they sort of used an "open choke shotgun" pattern, losing the effect a concentrated pattern would have had. French pilots during the Battle of France had 6 7.5 mm machine guns and they reported having to close to 50 meters or less to bring down German bombers. They reported that closing to 50 meters brought them in range of the Germans defensive guns causing unnecessary losses. They reported that with heavy machine guns they could have brought them down from 200 yards and stayed out of effective range of the Germans defensive guns.



There was a reason for the British to have the 'open choke' spread in times - that will give more chances for the rookie pilots to score any hits. Cutting the combined rate of fire by 90% and cancelling the 'open choke' will mean far less hits for those pilots - not everybody was Sailor Malan.



> During the BoB the ME109 was a 348 mph plane, the P36 was a 315 mph plane that could easily outturn anything in the battle, climb with the 109 and Spitfire and with a tough radial engine.



The Bf 109 pilot will not turn with anybody if he can help it, though it was no slouch in turning. 
I'd kindly ask for hard data that will confirm that any P-36 will climb with 109(E?) and/or Spitfire.


----------



## tomo pauk (Dec 27, 2015)

GrauGeist said:


> ...
> It seems to me, that the P-39's cannon could have been deleted and have, instead, 6 .50 MGs (two cowl and 4 in the wings).



With 6 HMGs and their heavy ammo, were back to the too heavy P-39. 



> And why so much armor for the pilot? There is an engine back there that makes a very handy piece of armor.



There was a plate to protect the oil tank - perhaps with just 3 BMGs in the nose the oil tank can be relocated in the nose, thus that armor can be deleted? Also cures the tail heaviness the P-39 was sometimes accused of.

Armor layout of the P-39: picture.


----------



## FLYBOYJ (Dec 27, 2015)

Lefa said:


> Finnish Forces - Finnish Curtiss P-36 Hawk
> 
> There some information to P 36 in Finnish use.



_"In Finnish service, the Hawk was well-liked, affectionately called Sussu ("Sweetheart"). The Finnish Air Force enjoyed success with the type, credited with 190⅓ kills by 58 pilots, between 16 July 1941 and 27 July 1944, for the loss of 15 of their own."_

Thanks for that post - again I think shows how underrated this aircraft was.


----------



## fastmongrel (Dec 27, 2015)

FLYBOYJ said:


> _"In Finnish service, the Hawk was well-liked, affectionately called Sussu ("Sweetheart"). The Finnish Air Force enjoyed success with the type, credited with 190⅓ kills by 58 pilots, between 16 July 1941 and 27 July 1944, for the loss of 15 of their own."_
> 
> Thanks for that post - again I think shows how underrated this aircraft was.



I think it shows how good the Finnish Airforce were.


----------



## FLYBOYJ (Dec 27, 2015)

fastmongrel said:


> I think it shows how good the Finnish Airforce were.



It does and they were - but it would have been kind of hard achieving that record without the right equipment.


----------



## tomo pauk (Dec 27, 2015)

Now that we're talking about the BoB, in the Hurricane variants article (here) at Wikipedia there couple of hits that landed wide from the mark, that I'd again ask kind people to rectify (the bolded part):



> Lower down the situation was a little more even. The Rolls-Royce Merlin engine gave more power at low altitude than the Daimler-Benz DB 601 used in the Bf 109, *on account of a different supercharger design. The DB601A-1 did not start to outperform the Merlin III and XII until above 15,000 ft (4,572 m).*



Namely - the surplus power was due to higher boost used since the higher octane fuel was used; DB 601A didn't outperform the Merlin III, let alone the XII at altitude during the BoB.


----------



## fastmongrel (Dec 27, 2015)

FLYBOYJ said:


> It does and they were - but it would have been kind of hard achieving that record without the right equipment.



I sometimes like to wonder what they could have done with Chain Home and all the planes, equipment and backup the RAF had. Never mind executing his generals after the Winter War debacle Stalin would have probably suffered severe lead poisoning himself.

Instead of the EU we might now be part of the FU (Finnish Union) though I doubt the Finns would f**k it up quite as convincingly as the EU has managed.


----------



## pinsog (Dec 27, 2015)

GrauGeist said:


> Having only two .50 MGs is not making this much of a fighter.
> 
> The ability of the U.S. fighters to deliver such a heavy knockout punch to the Axis types was because of the multiple .50s, especially the P-38, that had centerline mounted MGs which didn't rely on convergence to maximize their effect.
> 
> ...



3 gun fighter, 2 synchronized and 1 through the prop hub. Be nice if the US had a good 20 mm cannon at that time, 2 50's and 1 20mm through the hub with a lot of ammo would have been a great combination at that time. I think 6 50's would have been too heavy for the HP in 1941-1942


----------



## pinsog (Dec 27, 2015)

tomo pauk said:


> I like the '3-gun' P-39 proposal.
> The V-1710 E4, as installed in the P-39C/D, was making a bit more power than the DB 601A of the BoB vintage, so the problem was not so great. It beacames a big problem when requiring it to propel through the air the hefty gun battery and protection package, that includes both sheet metal and 2 times the BP glass. SO deleting of heavy items from the P-39 solves a good deal of the V-1710's altitude 'problem'.
> 
> 
> ...



I couldn't copy and paste the specific part of this, so go down until you get to the P36C data for climb. 
http://www.wwiiaircraftperformance.org/P-36/P-36_Operation_and_Flight_Instruction.pdf

I understand why they used the "open choke" aiming, but I still think it was a dumb idea based on a flawed concept. If they are having to close within 50 yards because 1. their guns suck 2. they can't hit anything Then let them close to within 50 yards with 2 synchronized 50's, at least a 50 will punch through a self sealing fuel tank and leave a big hole in both sides. At least a 50 will do critical damage to an engine. At least a 50 might punch through the pilots thin backseat armor. 

Using that silly "open choke" spread with 30 caliber weapons against medium bombers with self sealing tanks and some armor would be like shooting buzzards with an open choke shotgun and #9 birdshot "Did you kill any?" "Not a single one, but I know a few pellets hit them"


----------



## pinsog (Dec 27, 2015)

tomo pauk said:


> With 6 HMGs and their heavy ammo, were back to the too heavy P-39.
> 
> 
> 
> ...



Agree with everything you say here.


----------



## GrauGeist (Dec 27, 2015)

I find it interesting how the discussion has gone to great lengths to say the P-36 needed more MGs in order to increase it's effictiveness and yet, at the same time, the P-39 needs to reduce it's MGs (to less than the suggested P-36 enhancements) - in order to be more effective


----------



## pinsog (Dec 27, 2015)

GrauGeist said:


> I find it interesting how the discussion has gone to great lengths to say the P-36 needed more MGs in order to increase it's effictiveness and yet, at the same time, the P-39 needs to reduce it's MGs (to less than the suggested P-36 enhancements) - in order to be more effective



On the P36, I said "delete all wing guns and only have 2 50's with 250 rounds each" So for a French P36 I am trading 6 7.5mm guns for 2 50 BMG's. On the American version, I am trading 5 30's and 1 50 for 2 50 BMG. I am definitely not adding more guns.


----------



## GrauGeist (Dec 27, 2015)

The early P-36 had a single .30 and a single .50

The later configurations deleted the .30 and replaced it with a .50 and in some cases, the armament was as high as six .50 MG, which would prove to be a very effective and deadly combination on many types.

The P-39 only had four .50 MGs to start with and keep in mind that the cowl MGs only had 200 rounds per weapon as well as a slow RoF because of the syncronization. The wing mounted MGs had only 300 rounds per unit. The M4 37mm cannon was really not nessecary and could be omitted, retaining the 4 MGs and saving over 200 pounds.

If the P-39 were to have the wing MGs removed and a .50 put in the M4's place, you would have a fighter that is VERY lightly armed and next to worthless in a fight. What good is increasing the performance it it can't do anything when it gets there?


----------



## pinsog (Dec 28, 2015)

GrauGeist said:


> The early P-36 had a single .30 and a single .50
> 
> The later configurations deleted the .30 and replaced it with a .50 and in some cases, the armament was as high as six .50 MG, which would prove to be a very effective and deadly combination on many types.
> 
> ...



Of all the info I have on the P36, nothing mentions 6 50's. It starts out as 1 30 and 1 50, then 1 30 1 50 synchronized with 1 30 in each wing, then 1 30 1 50 synchronized and 2 30's in each wing. French planes had 6 7.5 mm guns. Nothing, nowhere ever mentions 6 50's on a P36.

The P39, if it had 2 synchronized 50's and 1 50 through the prop would be fine for nearly anything through 1942. In fact, except for the big 4 engined flying boat, it would be fine for anything in Japan until the end of the war. Dauntless dive bombers shot down several airplanes with just 2 50's synchronized through the prop. How many P38, P39, P40, Spitfires, Hurricanes, ect were shot down by KI43 Oscars with just 2 12.7mm guns firing through the prop? Zeros and early war ME109's had very limited cannon ammo and used synchronized LMG when they ran out of cannon rounds. I would rather have a slow firing 50 than any LMG. 

Overloading of underpowered fighters is what troubled all the early war US fighter planes. As I stated at the beginning, I would rather be behind a 109 or a Zero with 2 synchronized 50's than be in front of him with 6 50's


----------



## GregP (Dec 28, 2015)

One of the better fighters of the early war was the A6M Zero. It had 2 MG and 2 cannons. You could select cannons, MGs or both. Very many airplanes were shot down using only 2 guns by the Axis side. I'm not too suree why we couldn't do the same if the occasion arose.

I think the P-39 could have been good with a decent cannon, 2 cowling MGs of 50-cal / 7.62 mm, and a 2-stage supercharger. The Bf 109 seemed to manage just fine with similar armament on a lot of occasions.

The P-36 could have done just fine with 4 MGs of 50-cal or 2 MGs and 2 cannons.


----------



## pinsog (Dec 28, 2015)

GregP said:


> One of the better fighters of the early war was the A6M Zero. It had 2 MG and 2 cannons. You could select cannons, MGs or both. Very many airplanes were shot down using only 2 guns by the Axis side. I'm not too suree why we couldn't do the same if the occasion arose.
> 
> I think the P-39 could have been good with a decent cannon, 2 cowling MGs of 50-cal / 7.62 mm, and a 2-stage supercharger. The Bf 109 seemed to manage just fine with similar armament on a lot of occasions.
> 
> The P-36 could have done just fine with 4 MGs of 50-cal or 2 MGs and 2 cannons.



I would love to have seen the P39 with 2 synchronized 50's and a good RELIABLE 20mm cannon. Ditch most of the armor except for a 100 pound plate behind the pilot and add fuel tanks to the wings. Could have been a great asset.

I think 2 synchro 50's and may 2 50's in the wings of a P36 would be about all it needed to carry


----------



## GrauGeist (Dec 28, 2015)

pinsog said:


> Of all the info I have on the P36, nothing mentions 6 50's. It starts out as 1 30 and 1 50, then 1 30 1 50 synchronized with 1 30 in each wing, then 1 30 1 50 synchronized and 2 30's in each wing. French planes had 6 7.5 mm guns. Nothing, nowhere ever mentions 6 50's on a P36.


I meant 6 MGs...my bad.
P-36A-3: 6 .30 MGs (two cowl, four wing)
There was a 50 pound difference between the .30 and the .50...so granted, 6 .30 MGs weighed 186 pounds, where 6 .50 MGs would weigh bout 500 pounds.

Personally, I always thought that 4 fifties (2 in each wing) would have been ideal.

There were several other multiple gun configurations either used or tested, both for the USAAC/USAAF and foreign customers.

This would include the 23mm Madsen trial on a P-36A



pinsog said:


> Overloading of underpowered fighters is what troubled all the early war US fighter planes. As I stated at the beginning, I would rather be behind a 109 or a Zero with 2 synchronized 50's than be in front of him with 6 50's


And how many times did an IJN fighter get on a Wildcat's tail and use all it's ammo trying to bring it down?

Let's be realistic here:
If the USAAF thought that two or three MGs would have been sufficient, then why was there 8 aboard the P-47?
Why did the USN feel that six .50 MGs were needed on their aircraft?

Having a couple fifties to peck away at an enemy because of "weight" and other excuses is not good logic.

The A6M's armament was a throwback to the 1930's ideology as was the early P-36 and the F2A and so on.

The Italians made some excellent aircraft, but they too, were lightly armed:
M.C200 with (2) 12.7mm in wings
M.C202 with (2) 12.7mm in the cowl and (2) 7.7mm in the wings

At least the G.55 was an improvement with it's (2) cowl 12.7mms and (3) 20mm cannon


----------



## tomo pauk (Dec 28, 2015)

pinsog said:


> I couldn't copy and paste the specific part of this, so go down until you get to the P36C data for climb.
> http://www.wwiiaircraftperformance.org/P-36/P-36_Operation_and_Flight_Instruction.pdf



Thank you for the link, guess I'd should've remeber that Mike's site host it 
The RoC for the P-36C shows 2150 fpm at 15 kft, and 1400 fpm at 20 kft; the Bf 109E has 2500 fpm at 15 kft and maybe 1980 fpm at 20 kft. The Spitfire I (eg. N.3171) was good for 2340 fpm at 15 kft, 1840 fpm at 20 kft, max boost (where available) +6.25 psi. Spitfire II is better by some 10% than the Mk.I.
At lower altitudes both P-36 versions are better than Bf 109, with P-36 using 100 oct fuel (moot point for the UK and US). The P-36 sports no protection here?
With both Spitfire and P-36 using 100 oct fuel I doubt that P-36 will come ahead.

On the other hand, we don't have data for the P-36 (B?) with -23 engine, that one should indeed come close to the RoC of the Bf 109E/Spit I at altitude, while loosing some RoC under 10000 ft. 



> I understand why they used the "open choke" aiming, but I still think it was a dumb idea based on a flawed concept. If they are having to close within 50 yards because 1. their guns suck 2. they can't hit anything Then let them close to within 50 yards with 2 synchronized 50's, at least a 50 will punch through a self sealing fuel tank and leave a big hole in both sides. At least a 50 will do critical damage to an engine. At least a 50 might punch through the pilots thin backseat armor.



The concept sounds now silly, but methinks it was based good deal on the reality - it was claimed that most of the pilots were lousy shots, especially novices, in any air force. Having four, unsynchronised BMGs would perhaps make more sense than relying on just two, further slowed via synchronisation? The BMG of 1939-40 was not the BMG of 1944.


----------



## tomo pauk (Dec 28, 2015)

GrauGeist said:


> ...
> The P-39 only had four .50 MGs to start with and keep in mind that the cowl MGs only had 200 rounds per weapon as well as a slow RoF because of the syncronization. The wing mounted MGs had only 300 rounds per unit. The M4 37mm cannon was really not nessecary and could be omitted, retaining the 4 MGs and saving over 200 pounds.
> If the P-39 were to have the wing MGs removed and a .50 put in the M4's place, you would have a fighter that is VERY lightly armed and next to worthless in a fight. What good is increasing the performance it it can't do anything when it gets there?



Dave, the P-39 started out with 2 HMGs and 2 LMGs, all four in the nose, firing synchronised, plus of course the cannon. 
The 3 BMGs might impart a lasting impression on the pilots of fighter aircraft, at least from 1941 on when the BMG was at 800 rpm unsynchronised and maybe 550 synchronised.


----------



## Lefa (Dec 28, 2015)

https://fi.wikipedia.org/wiki/Luettelo_Lentolaivue_32:n_ilmavoitoista_ja_sotatoimitappioista

There is a list squadron 32 gains and losses.

MT is Bf109 G6
FR is Fokker D XXI
HC is Hurricane
CU is Curtis
LG is Lagg 3

Squadron worked for 44 of the last month of summer assault against the enemy troops, that why the rest of the losses caused by the anti-aircraft defense.


----------



## pinsog (Dec 28, 2015)

GrauGeist said:


> I meant 6 MGs...my bad.
> P-36A-3: 6 .30 MGs (two cowl, four wing)
> There was a 50 pound difference between the .30 and the .50...so granted, 6 .30 MGs weighed 186 pounds, where 6 .50 MGs would weigh bout 500 pounds.
> 
> ...



I read that the 23mm Madsen cannon was tried by the Finns but it cut the top speed from 310 or so down to about 280 or so, so they removed them.

I definitely would WANT more firepower than 2 synchronized 50's, as long as it wasn't at the expense of too much performance. But since the Allison powered P40 gained 1000 pounds with just the engine change maybe 2 synchronized 50's and 2 in the wings would be just fine in a P36. 

Please remember that when the early Zeros and ME109's ran out of cannon ammo, 60 rpg, they both had 2 synchronized 30 caliber guns. Fuel tanks and pilots were VERY well protected against 30 caliber fire, that is why I would substitute as few as 2 fifties for as many as 6 30's. In the Battle of Midway, many of the Dauntless dive bombers returned to their carriers and the fuel tanks had MULTIPLE HITS from 30 caliber bullets, the fuel tanks still did not leak! In fact, in a report after the battle it was said if an airplane has hits in its self sealing fuel tank the tank needs to be filled up when the airplane lands because if the tank is left empty, the self sealing rubber will dry out and it will start leaking, putting the airplane out of service. I don't believe a Dauntless would have stood up to multiple 50 BMG through its fuel tanks and still got home. It would either have caught fire or the fuel would simple have drained out of the holes. I know the British scratched several German planes out of the air in the BoB with 30 caliber guns, but I think the kill rate would have been much higher with 4 50's.

Anyway, those are the reasons I think 2 synchronized 50's would be adequate at the beginning of the war, but if the P36 could carry them, then I would add 2 more wing 50's


----------



## pinsog (Dec 28, 2015)

tomo pauk said:


> Thank you for the link, guess I'd should've remeber that Mike's site host it
> The RoC for the P-36C shows 2150 fpm at 15 kft, and 1400 fpm at 20 kft; the Bf 109E has 2500 fpm at 15 kft and maybe 1980 fpm at 20 kft. The Spitfire I (eg. N.3171) was good for 2340 fpm at 15 kft, 1840 fpm at 20 kft, max boost (where available) +6.25 psi. Spitfire II is better by some 10% than the Mk.I.
> At lower altitudes both P-36 versions are better than Bf 109, with P-36 using 100 oct fuel (moot point for the UK and US). The P-36 sports no protection here?
> With both Spitfire and P-36 using 100 oct fuel I doubt that P-36 will come ahead.
> ...



I agree with what you said here. That -23 engine, available in 1939, looks like it would have made the P36 a real performer, wish we had climb data. Look at the climb rate from sea level to 15,000, very impressive. Did they improve the high altitude performance of the P&W 1830 over the -23 model between 1939 and 1941?


----------



## pinsog (Dec 28, 2015)

tomo pauk said:


> Dave, the P-39 started out with 2 HMGs and 2 LMGs, all four in the nose, firing synchronised, plus of course the cannon.
> The 3 BMGs might impart a lasting impression on the pilots of fighter aircraft, at least from 1941 on when the BMG was at 800 rpm unsynchronised and maybe 550 synchronised.



Agree with Tomo Pauk 100% on this


----------



## tomo pauk (Dec 28, 2015)

pinsog said:


> I agree with what you said here. That -23 engine, available in 1939, looks like it would have made the P36 a real performer, wish we had climb data. Look at the climb rate from sea level to 15,000, very impressive. Did they improve the high altitude performance of the P&W 1830 over the -23 model between 1939 and 1941?



Yes, the power got a bit up with the -33, stated already in post #41 here, gain was some 50+ HP above 14500 ft. The R-1830-33 was installed in the P-66, among other A/C, giving decent performance, but nothing sparky. Please note that it is also an engine with supercharger driven via 2-speed gearing, meaning that the power will be decent also at lower altitude.
Similar engine was sometimes installed in the F4F (they also got the Cyclones), P&W could not churn out the needed quantity of the 2-stage R-1830s to meet the demand of the F4F airframe production until the end of 1942?


----------



## buffnut453 (Dec 28, 2015)

FLYBOYJ said:


> There's a book about Alexander de Seversky and it tells all about the P-35.



Coming late to this thread so have some catching up to do. 

Joe, can you provide the title of the book? Sounds interesting. I continue to be amazed at the courage of the P-35 pilots in the Philippines flying against the Japanese...took a lot of guts!


----------



## GrauGeist (Dec 28, 2015)

buffnut453 said:


> Coming late to this thread so have some catching up to do.
> 
> Joe, can you provide the title of the book? Sounds interesting. I continue to be amazed at the courage of the P-35 pilots in the Philippines flying against the Japanese...took a lot of guts!


You think tangling with the Japanese in a P-35 is impressive, how about the P-26 that successfully locked horns with the Japanese and actually held up well against the A5M, A6M and downed several bomber types.


----------



## pinsog (Dec 28, 2015)

I would MUCH rather have been in a P36 than a P35 under those circumstances. In fact, I would have rather been somewhere else completely!


----------



## GrauGeist (Dec 28, 2015)

pinsog said:


> I would MUCH rather have been in a P36 than a P35 under those circumstances. In fact, I would have rather been somewhere else completely!


A quick bit of off-topic trivia:
The air battles between the P-26 and the A5M over China were the world's first combat between all metal, monoplane fighters.


----------



## fastmongrel (Dec 28, 2015)

Didn't know that fact. If I had been asked to guess I would said it was over Spain between I-16s and 109s


----------



## GrauGeist (Dec 28, 2015)

fastmongrel said:


> Didn't know that fact. If I had been asked to guess I would said it was over Spain between I-16s and 109s


You would have been very close, as the Rata encountered the Bf109 not long after the P-26 clashed with Japanese elements, both events happening in 1937


----------



## GregP (Dec 29, 2015)

I got a PM from one of the members asking whether I had worked on our P-40 and whether I had ever seen a P-36. As it happens one of our pilot / members runs a restoration business and his company recently finished a brand new baby P-36. It flew in our last airshow before being shipped off to the owner. I thiough a pic might be nice.







The engine was freshly overhauled and everything was new and shiny. It started and flew without issue the whole weekend and should be a reliable performer for the owner in the UK. They did a formation flyby with the P-36 leading our Seversky AT-12 / 2-PA. Here is a video of it.


_View: https://www.youtube.com/watch?v=fg_qy4hHHJE_

Just FYI, they were doing passes because the aerobatic box was only open for the specific routines we had scheduled and this aircraft was a last-minute addition. Add to that the owner might not have cleared it on his insurance for aerobatic demos, public or private, and you can see why it was flybys only. We DID have aerobatic routines with warbirds, but not this one.

Typically it is with a Tigercat, Bearcat, P-51, P-38, Sea Fury, F-86, etc., though almost all of them have done it at one time or another. I've posted videos of the three F-86 show before in here.

Reactions: Like Like:
3 | Like List reactions


----------



## fastmongrel (Dec 29, 2015)

Cant beat the P&W sound 8)


----------



## gjs238 (Dec 29, 2015)

Wonder how it would perform with a V-1710 installed?
Oh, wait...


----------



## GregP (Dec 29, 2015)

The P-40 flies just fine. What it needed was a 2-stage supercharger since the UASSC/F removed the turbo that was planned. A lot of people in here have questioned whether the turbo could have been installed in the airframe, but here we are in a thread about installing one in the exact same airframe with another engine up front. Go figure.

The same people have said what the P-40 need was a Merlin, but the P-40F/L HAD a Merlin and didn't do any better. Naturally, it was a single-stage Merlin. Again, go figure.

All of that history is why I'd opt for a 2-stage, supercharged radial, assuming I was there, had 20-20 hindsight, and anybody actually listened.


----------



## bobbysocks (Dec 29, 2015)

I saw a reference for a "long nose " version of the p36....what was that or did it even exist.


----------



## pinsog (Dec 29, 2015)

GregP said:


> The P-40 flies just fine. What it needed as a 2-stage supercharger since the UASSC/F removed the turbo that was planned. A lot of people in here gave questioned whether the turbo could have been installed in the airframe, but here we are in a thread about installing one in the exact same arframe with another engine up front. Go figure.
> 
> The same people have said what the P-40 need was a Merlin, but the P-40F/L HAD a Merlin and didn't do any better. Naturally, it was a single-stage Merlin. Again, go figure.
> 
> All of that history is why I'd opt for a 2-stage, supercharged radial, assuming I was there, had 20-20 hindsight, and anybody actually listened.



I think if you had installed the 2 speed 2 stage P&W 1830 in the P36 airframe, 4 50's max, 1 sheet of armor 100 pounds behind the pilots back and head and you would have had performance like the KI43 had. The last model of the KI43 maxed out at 358 mph with I think 1,180 hp. The P36 did not lose its handling at high speed like many other fighters. If it could do 358 mph at around 20,000 feet, it would have been a handful for any other fighter on the planet at the time


----------



## bobbysocks (Dec 29, 2015)

got to remember how all of that figures into weight and balance. you may need to add counter weight or shift something to bring it back to correct CoG or you may end up with some very unsavory flight characteristics.


----------



## fastmongrel (Dec 29, 2015)

Was there any utility in using the R2180-A as a fighter engine for a P36


----------



## pinsog (Dec 29, 2015)

bobbysocks said:


> got to remember how all of that figures into weight and balance. you may need to add counter weight or shift something to bring it back to correct CoG or you may end up with some very unsavory flight characteristics.



Shouldn't be difficult balancing a P&W 1830, after all they hung an Allison V12 on the front and balanced it out


----------



## GrauGeist (Dec 29, 2015)

bobbysocks said:


> I saw a reference for a "long nose " version of the p36....what was that or did it even exist.


XP-37 = P-36 with a V-1710 installed

XP-42 = P-36 with an aerodynamic spinner and cowl designed to improve performance while retaining the R-1830 radial. This gave it the appearance of having a V-12.


----------



## tomo pauk (Dec 29, 2015)

GregP said:


> The P-40 flies just fine. What it needed as a 2-stage supercharger since the UASSC/F removed the turbo that was planned. A lot of people in here gave questioned whether the turbo could have been installed in the airframe, but here we are in a thread about installing one in the exact same arframe with another engine up front. Go figure.
> The same people have said what the P-40 need was a Merlin, but the P-40F/L HAD a Merlin and didn't do any better. Naturally, it was a single-stage Merlin. Again, go figure.
> All of that history is why I'd opt for a 2-stage, supercharged radial, assuming I was there, had 20-20 hindsight, and anybody actually listened.



The USAAC/F never removed the turbo from the original P-40 - it is hard to remove what was not present in the 1st place. 
The P-40 came to life exactly because it sported plain vanilla V-1710 - no turbo V-1710, nor the 2-stage R-1830, as neither of the 2 was a viable powerplant in early 1939 when XP-40 won for the Army contract, against the XP-37, XP-38, XP-39, AP-4 and XP-41. 
The only P-40 project with turbo was the XP-40H, that was in the design stage when IJN attacked P. Harbor. Curtiss got the contract to produce the P-47 (that they botched up miserably) and P-53/60 development contract(s), that never come to fruititon for one or another reason, the XP-40H got canned.
P-40 grow up as an overweight machine, and indeed not much is going to change when the 1-stage Merlin came aboard, though the speed and climb improved a bit over the P-30E, above 15000 ft. Both P-40E and F were about a *ton (~2200 lbs)* heavier than the Spitfire V, max weight but without external stores, while either having far less power, or thereabout. And we know that Spitfire V struggled vs. German opposition from mid 1941 on.

So indeed - unless the P-40 gets a considerable increae in engine power, preferably via the 2-stage Merlin or V-1710, it won't fare well vs. Luftwaffe. The lighweight P-40s, the ones in hands of AVG, flown by well trained pilots and using a primitive but workable early warning system, were capable to trash Ki-27s (no surprise) and IJA bombers, while not suffering vs. Ki-43.



pinsog said:


> I think if you had installed the 2 speed 2 stage P&W 1830 in the P36 airframe, 4 50's max, 1 sheet of armor 100 pounds behind the pilots back and head and you would have had performance like the KI43 had. The last model of the KI43 maxed out at 358 mph with I think 1,180 hp. The P36 did not lose its handling at high speed like many other fighters. If it could do 358 mph at around 20,000 feet, it would have been a handful for any other fighter on the planet at the time



The last model of Ki-43 have had 950-980 HP at ~20000 ft, same power as the 2-stage R-1830 that will be also a bit more draggier. The Soviet I-180 did, as a prototype, ~350 mph with engine giving 1000 HP at ~20000 ft, and it was a tiny aircraft. 
~350 mph is great for 1939, very good in 1940, good in 1941, behind the curve in 1942. The 2-stage R-1830 is not available in 1939 in the shape size as it was in 1941.
If 4 HMGs, no bullet proof glass and no self-sealing tanks are the standard, there is no reason not to have the P-39/40/51 outfitted as such, outperforming the proposed P-36 by smaller or bigger margin.


----------



## tomo pauk (Dec 29, 2015)

fastmongrel said:


> Was there any utility in using the R2180-A as a fighter engine for a P36



Looks like the engine was a flop, at least the pre-war engine of that name. There were two P&W engines named as such, the post war R-2180 was basically half of the Wasp Major of 28 cylinders.


----------



## bobbysocks (Dec 29, 2015)

pinsog said:


> Shouldn't be difficult balancing a P&W 1830, after all they hung an Allison V12 on the front and balanced it out



just a quick look at the 2 planes (P36 and P40 ) it looks like when they put the Allison on they moved the firewall to the rear...closer to the cockpit. it also looks like they extended the fuse and made it longer by 2 sections. that could just be an optical illusion between the pictures I was looking at.


----------



## GregP (Dec 29, 2015)

We've been over that before, Tomo. The designer's son says otherwise, and was around him for most of his life. Don Berlin left Curtiss in part because of frustration with not being allowed to make a better fighter. Most of the rest was probably due to inept Curtiss management coupled with good offers elsewhere.


----------



## tomo pauk (Dec 29, 2015)

With all due respect to the Mr. Berlin's son, he is mistaken on this one. There we have the talk of an eventually disgrunted Curtiss' employee, and unfortunately it is still a talk. The son was not there when USAF wen't shopping, nor he was at the Curtiss board of directors discussing what to offer, and they were muddling with two designs, plus the XP-40 in 1938/39 time frame. 
The XP-37 was the 'turbo XP-40', and while it give some good insight to the people institutions involved, we all know how far that aircraft was away from the viable combat aircraft that was needed ASAP to the USAC/F.


----------



## GregP (Dec 29, 2015)

There are two possibilities. You are correct or you are incorrect.

The evidence presented in his talk convinces me the other way, but it never came to pass, and the situation is unlikely to change at this late date, so the end result is the same as if you are correct. In the end, the result is what shapes history, so your position is what people will no doubt believe, for the most part.

You would find one of his talks interesting. At least, I did.


----------



## wuzak (Dec 30, 2015)

The P-40 came about because of the issues with the turbocharged P-37.


----------



## GregP (Dec 30, 2015)

True, but the P-37 was NEVER going to be a fighter. It was an experimental powerplant airframe. The cockpit was way too far back to be practical. That's one of the main reasons why they relocated the turbos on other U.S. planes to behind the cockpit. I'm definitely a tubocharger fan, but not especially of early efforts like WWII fighters. At that time, I believe multi-stage superchargers were the way to go.

In the end, they did just that with the Merlin in the P-51. I would like to have seen it in a P-63D with the bubble canopy. It never happened.

Looking just at airframes, a 2-stage Merlin in a Yak-3 might have been very interesting. Likewise a 2-stage Merlin in a Ki-61. But these are just pipe dreams and not anything realistic. The potential still makes me wonder a bit. Something as small as the shape and location of the carburetor airscoop on a Yak-3 makes 15 - 20 mph difference today. At least on the ones at Reno (not racing, but flying).


----------



## wuzak (Dec 30, 2015)

GregP said:


> True, but the P-37 was NEVER going t be a fighter. It was an experimental powerplant airframe. The cockpit was way too far back to be practical. That's one of the main reasons why they relocated the turbos on other U.S. planes to behind the cockpit.



The P-37 showed them that it wasn't going to work too well - at least at that point in the turbo's evolution.

btw, it wasn't the turbocharger that caused the cockpit to be pushed back on the P-37 - it was the radiator and inter-cooler, both of which were mounted in the space between the engine and the cockpit. The turbocharger was mounted under the engine.


----------



## GregP (Dec 30, 2015)

Can't think of a better place for a turbocharger, right under an engine that leaks an occasional bit of oil. The Allison was assembled with Tightseal, and it sometimes weeps a small oil trail. Not much, but a few drips on the hot side of a turbo isn't a good way to keep and airplane in one piece.


----------



## pinsog (Dec 30, 2015)

If your going to turboocharge something, turbocharge the P36. The B17 and P43 already had the bugs worked out, so turbocharge the P&W 1830, stick the turbo behind the pilot and now you have a plane that can outturn a Spitfire, radial engine toughness and 1200 hp up to 25,000 feet. You could have had this in production in 1940. The P43 flew in 1939.

Reactions: Like Like:
1 | Like List reactions


----------



## tomo pauk (Dec 31, 2015)

For some thing, I like the turboed P-36 more than other suggested upgrades.


----------



## pinsog (Dec 31, 2015)

tomo pauk said:


> For some thing, I like the turboed P-36 more than other suggested upgrades.



A turbocharged P36 was the original subject of this thread, we seemed to have talked about everything BUT a turbocharged P36. I wonder how much extra weight a turbocharger would add to the P36?


----------



## tomo pauk (Dec 31, 2015)

Bare turbo, B series, weights between 132 and 145 lbs. Add some piping to and fro, regulator, intercooler, should amount up to maybe 200-250 lbs. The table is worth taking a look: link, from here.

The pdf posted here might also be handy.


----------



## fastmongrel (Dec 31, 2015)

Thats a lot of weight to put behind the pilot and where does the equipment displaced by the Turbo go. Radio, Oxygen, Battery and IFF none of it easy to put in a wing.


----------



## pinsog (Dec 31, 2015)

Does anyone have the dimensions of a GE B series turbocharger? I looked on the net and couldn't find anything


----------



## fastmongrel (Dec 31, 2015)

The actual Turbo isnt very big its the pipework, intercooler and controls that are the space grabbers.


----------



## pinsog (Dec 31, 2015)

fastmongrel said:


> The actual Turbo isnt very big its the pipework, intercooler and controls that are the space grabbers.



They fit one in a P35 to make the P43, BUT I'm not sure how much bigger, if any, the P35 is than the P36.


----------



## tomo pauk (Dec 31, 2015)

pinsog said:


> Does anyone have the dimensions of a GE B series turbocharger? I looked on the net and couldn't find anything



Check out the pdf I've posted the link.


----------



## wuzak (Dec 31, 2015)

pinsog said:


> They fit one in a P35 to make the P43, BUT I'm not sure how much bigger, if any, the P35 is than the P36.



The P-43 had a wing span 1" greater than the P-35 and 2.7sq.ft more wing area, was 1'8" longer and ~1,400lb heavier.

And it was still without armour or self-sealing fuel tanks.


----------



## tomo pauk (Jan 6, 2016)

The crisp scheme of P-36, FWIW: picture

Reactions: Like Like:
1 | Like List reactions


----------



## pinsog (Jan 6, 2016)

Very nice Tomo. Wonder if a turbo would fit behind the fuel tank? If there was a balance issue, they could just move the engine forward a bit.


----------



## tomo pauk (Jan 6, 2016)

Reduce the height of the rear tank by half, and install the radio in the upper, rather than lower part of the fuselage?


----------



## pinsog (Jan 6, 2016)

That would cut fuel capacity too much…


----------



## tyrodtom (Jan 6, 2016)

Wouldn't placing a hot turbo-charger, directly behind the fuel tank make you just a little unsure about it's ability to take battle damage?
And the hot exhaust would probably have to go right under that fuel tank too.

This is a fighter, it's going to get shot at.


----------



## GregP (Jan 6, 2016)

Looking at the guns, you aren't going to move the cockpit forward much. Looks to me as if you could put the turbo farther back and to compensate without adding length, you could move the wings back a bit. But that would be a significant design effort. I'd go back to the 2-stage supercharger myself.


----------



## tomo pauk (Jan 6, 2016)

The decision to convert basic P-36 airframe to V-12 engine looks as good today as it looked than 75+ years ago


----------



## GrauGeist (Jan 7, 2016)

pinsog said:


> Very nice Tomo. *Wonder if a turbo would fit behind the fuel tank*? If there was a balance issue, they could just move the engine forward a bit.


And then you'd end up with this:

Reactions: Bacon Bacon:
1 | Like Like:
1 | Like List reactions


----------



## tomo pauk (Jan 7, 2016)

Not sure what's wrong with that...


----------



## fastmongrel (Jan 7, 2016)

tomo pauk said:


> Not sure what's wrong with that...



Except your not going to get a combat ready version before 1942 and then its still not going to be as good as a proper Jug


----------



## GrauGeist (Jan 7, 2016)

tomo pauk said:


> Not sure what's wrong with that...


Well Tomo, once you start running all the ducting and adding all the supercharger gear to the rear, then enlargen the fuselage to fit it all, you'll need to put a larger engine in. Then you'll need larger wings, so why not add larger fuel tanks...and while you're at it, add more MGs.

So basically, we started with a P-36 and after rebuilding it, we've created another P-47.


----------



## tomo pauk (Jan 7, 2016)

Perhaps you're right. Even if we got a combat capable version in 1941, the 1200 HP at 25000 ft acomplished by turboed radial are probably as good as 1100 HP at same altitude acomplished by turboed V-12 engine (less drag), and 1000 HP by non-turboed V-12 (less weight, bulk and drag, use of exhaust thrust). On the other hand, the American's don't have a V-12 in 1939-41 that can do 1000 HP at 25000 ft, so it is a turboed either R-1830 (that was done, the result was less than spectacular) or V-1710 (went good on P-38, not that good on XP-39, problematic in XP-37, probably usable but too late in XP-60A, unfortunately never materialized in XP-40H).

USAF can also use the R-2800 in non-turbo installation, either as single- or 2-stage versions, that would give them a very useful performing 1-engined fighter. Sorta the early Bearcat with a thinner wing and no fancy blow-off wing panel, or Tempest II-looking fighter.


----------



## GrauGeist (Jan 7, 2016)

I suspect that the real reason why the P-47 was able to perform as well as it did, is because it was a seven ton beast that beat the air into submission!


----------



## pinsog (Jan 7, 2016)

I wonder what the cutaway diagram of a P43 Lancer looks like? It shouldn't take until 1942 to have a turbocharged P36, they had the P43 flying in 1939 and it was ready long before 1942. (I'm still not sure it would fit either) But since an 1830 is much smaller than a 2800 the turbo system to feed it should be smaller also. They got it to fit in a P43. I think they were on to something when they built the P43, I just think they used the wrong airframe, they should have used the P36 instead.


----------



## GrauGeist (Jan 7, 2016)

Compare the transition from the P-35 to the P-43 and see how much the fuselage was changed to accomodate the powerplant.

If you were to attempt the same changes in the P-36, you will end up with a much different and much larger airframe.


----------



## pinsog (Jan 7, 2016)

I know it was stretched about a foot or so, wing was basically the same. But they stretched the nose of the P36 to become the P40. They stretched the FW190 to become the 190D. They stretched the ME109. Doesn't seem too insurmountable, but it may have indeed needed an entirely new airplane. Still seems like the P36 would have been good place to start


----------



## Shortround6 (Jan 8, 2016)

pinsog said:


> We all know the P39 and P40 never received a turbocharger making both of them a dog above 15,000 feet or so. The P35 was never a good performer, poor handling/turning ability and poor workmanship (leaking wing tanks). But the P35 got a turbocharger and became the P43 Lancer with good performance at the time of 350 mph plus and 1200 hp at 25,000 feet while still retaining poor handling and poor workmanship.
> 
> The P36 on the other hand, had an excellent climb rate and exceptional maneuverability. What about installing either a Wright 1820 or P&W 1830 with a turbocharger in the P36? It would gain some weight but still shouldn't weigh as much as a P40 or F4F Wildcat and still have 1200 hp at 25,000 feet. Should still retain much of its handling, certainly no worse than the P40 which still turned well, should still out climb a P40 or Wildcat rather easily and do at least 350 mph plus (I would think it would be faster than a P43 Lancer) putting it on a level footing with the Spitfire and ME109 and Zero.
> 
> Thoughts?



I think we have been over this before. The P-36 that some people seem to be enamored with was under armed and unprotected. It also only made the the published performance figures (if then) at _normal_ gross weight which means the rear fuselage fuel tank was empty. Fuel capacity of the tanks in the wing center section being little different than a Spitfire's fuel capacity. There were a few structural problems too, buckled wing skins around the landing gear and/or wing roots. 
The prototype P-40 was the 10th production P-36 pulled off the production line so 90% or more of any changes were forward of the firewall. Up gunning and fitting protection to the P-36 would have seen a similar rise in weight to the P-40. Beefed up structure to handle the increased weight of guns and protection. 
A more complicated engine installation also would increase weight. Unless you can convince the US Army to relax the 12G stress standard adding hundreds of pounds to the engine installation was also going to require weight gains other places. 

Please note that the engines used in the P-36 (American models) was good for 2700rpm only for take off. other wise it was limited to 2550rpm. later engines were rated at 2700rpm for take-off and military power and 2550rpm max continuous. they also gained 40-90lbs even for single speed single stage versions.

A P-40C gained 400lbs over the prototype P-40 (re-engined P-36) in empty weight (protection), 515lbs in basic weight (extra guns but no ammo) and 700lbs with ammo and fuel (internal). Granted around 90-100lbs could have saved by not filling the fuselage ammo bins with 380 rounds of .50 cal ammo each. 240-250 rounds would have given 30 seconds of firing time. 

A few pictures of the P-43 Lancer can be found here: Republic P-43C/D Lancer Question (72nd Aircraft)

The P-35/43 was a pretty portly fuselage compared to the P-36/40 fuselage. Seversky had designed a sort of general purpose fuselage for their early fighters and there wasn't much difference between the single seat and two seat versions. The R-1830 is 60-100lbs heavier than the V-1710 even in single stage form and adding stages and inter-coolers makes up the difference in radiators and coolant pretty quick. 
Most things are a trade off and while a turbo P-36 would certainly have been faster at 25,000ft it may very well have been slower at 15,000ft or under (extra drag)and time to altitude is also a bit suspect. Better but not to extent you might think. US climb figures using military power for the first 5 minutes and then MAX continuous after that.

Reactions: Like Like:
1 | Like List reactions


----------



## T Bolt (Jan 8, 2016)

Why not put the turbo ductwork on the outside of the fuselage like they did when they tried to put a turbo on the FW 190. Looks ugly and adds drag I'm sure, but would be a faster solution then rebuilding the whole fuselage to fit the ductwork inside


----------



## GrauGeist (Jan 8, 2016)

The KI-87 had an external installation.

Reactions: Like Like:
1 | Like List reactions


----------



## Shortround6 (Jan 8, 2016)

If you go the site in my previous post there are several pictures of the bottom of the P-43, sorry but I can't seem to get the pictures to show up here.
Think upside P-38. Turbo is exposed on the bottom of the rear fuselage 1/2 way between wing trailing edge and horizontal stabiliser leading edge. Exhaust pipe runs in an open trough at the bottom of the fuselage from about 1/2 way along the wheel wells back to the turbo.
The P-47 was one of the very few planes to hide the turbo completely inside the plane. Keeping the turbine blades cool took priority over streamlining most of the time. A turbine failure could destroy the aircraft if it was bad enough. Many turbo installations had scatter sheilds to protect crewmen from thrown blades.

Reactions: Like Like:
1 | Like List reactions


----------



## GregP (Jan 8, 2016)

Nice find, Shortround. Those are some interesting pics and I see in one of the magazines that there is a group considering the possibility of restoring a P-43 from the parts scrounged from several airframes. It would be good to see one flying again, even if it is the only one.

I know of at least 3 working turbos that are flying, too. Perhaps another can be assembled from good parts.


----------



## FLYBOYJ (Jan 8, 2016)

Great pics SR!!! Did anyone notice the welds on the ducting behind the camera? Hand welded, by today's standards really crude but functional...


----------



## FLYBOYJ (Jan 8, 2016)

Great P-43 pics here...

Forums / USAAF / USN Library / Republic P-43 Lancer - Axis and Allies Paintworks

Reactions: Like Like:
2 | Like List reactions


----------



## kool kitty89 (Apr 19, 2016)

GrauGeist said:


> The KI-87 had an external installation.
> 
> View attachment 308874





Shortround6 said:


> If you go the site in my previous post there are several pictures of the bottom of the P-43, sorry but I can't seem to get the pictures to show up here.
> Think upside P-38. Turbo is exposed on the bottom of the rear fuselage 1/2 way between wing trailing edge and horizontal stabiliser leading edge. Exhaust pipe runs in an open trough at the bottom of the fuselage from about 1/2 way along the wheel wells back to the turbo.
> The P-47 was one of the very few planes to hide the turbo completely inside the plane. Keeping the turbine blades cool took priority over streamlining most of the time. A turbine failure could destroy the aircraft if it was bad enough. Many turbo installations had scatter sheilds to protect crewmen from thrown blades.


I believe all turbochargers used operationally during the war (except maybe the P-47's cowl-shrouded arrangement -which incedentally would have been nice on the P-38M for hiding turbine glow) used exposed bare turbocharger installations with the turbine and exhaust manifold exposed to the slipstream. (this goes for the B-17 and B-24 too, there's exposed turbos there in the engine necelles, on the trailing edges of the undersides; not obvious in most pictures but it became super obvious after playing IL-2 some years back) The XP-39 used this mounting arrangement as well. (and a horrendously poor oil cooler, intercooler, carb intake, and even problematic wing-embedded radiator intake/outlet arrangement -I've been meaning to start a more focused topic for the P-39 though, including some of the ammunition configuration issues that came up in this thread, so I won't draw it out here and now)

The P-47's shrouded exhaust may have been a superior arrangement though as far as drag went. (in theory it could have reduced turbulence while producing a small amount of RAM+jet thrust from the turbine exhaust and air ducted over the hot turbine exhaust manifold -still probably net drag, but potentially at least negating a lot more drag than leaving it totally bare)




T Bolt said:


> Why not put the turbo ductwork on the outside of the fuselage like they did when they tried to put a turbo on the FW 190. Looks ugly and adds drag I'm sure, but would be a faster solution then rebuilding the whole fuselage to fit the ductwork inside


The turbo installation on the Fw 190 is an extremely poor example and definitely good evidence to leverage against the 'turbocharged P-40 was a bad idea' argument. (including the relatively good performance with the bare DB 603A and nature of inline engine vs radial -a turbocharged BMW 801 might have fared far better and indeed BMW had an exceptionally well configured turbocharged 801 'power egg' module that could have been fitted to the 190 with some adjustment for CoG -which was also done for Jumo 213 and DB 603 mountings for similar reasons of nose length and weight increase, but that 801 wasn't available to FW for testing, it appears to have been ready for production and even optimized for minimal strategic materials, but likely had material and production resources diverted to getting the BMW 003 into production instead -and FW doesn't appear to have made any attempts to mate the Hirth-manufactured turbocharger used with the 603 to a standard 801 model)




That said, I think the P-40 had some possible potential for turbocharging, but the P-36 was much better suited for such overall (or more likely P-40 regressed to R-1830 -like the P-40 fitted with a 2-stage 1830 for P&W trials that managed 385 MPH at altitude -albeit this was one of the original P-40 runs without armor or self sealing material added and also omitting the armament, but that's still much more impressive performance than either the XP-40 or XP-42 -though the XP-42's ultimate cowl/fan/spinner arrangement might have improved that 2-stage R-1830 installation as well).

The V-1710 trades a lot more when it's turbocharged, both added bulk/drag and loss of exhaust thrust. (the lack of a well-optimized de-turboed P-38 with RAM intakes and ejector exhaust is likely the only reason it doesn't show off some of these interesting characteristics -the Lightning Mk.I was a hack that made for the worst of both worlds and is not a useful example of the airframe's potential without turbochargers)


The R-1830 gains far less from exhaust thrust OTOH, and the P-36/P-40 airframe is already well matched to the R-1830's dimensions in height, but slims out quite a lot in width making room for bulging the fusealage sides somewhat for added ducting without increasing frontal area (and, more importantly, only modest increase in wetted area). Intercooler drag would be the bigger concern, namely from providing large enough scoops and ducting to allow sufficient airflow for the full turbo capacity (or end up stuck with the P-38's situation of insufficient intercooling and inability for the turbocharger to operate at full rated RPM due to excessive charge heating). Now, remember superchargers need intercooling too and similarly designed impellers/diffusors should produce simialr charge heating as well (and require similar cooling), but heat leakage from the exhaust turbine tends to lead to some degree of added charge heating as well, I believe. (I may be mistaken here) The bigger issue was that these were POWERFUL turbochargers intended to drive the R-1830 or R-1820 at full rated power up to vastly higher altitudes than the 2-stage superchargers in question were rated for, and while just using a smaller turbo seems an attractive option, I think they simply didn't exist in mass production or operational use (parts commonality with the B-17 or B-24 would be ideal, and those had critical altitudes well above the ~20,000 ft of early-war 2-stage superchargers) so that just leaves under-utilizing said turbo and eating the larger weight/bulk of that while sticking with more modest intercooling that could nestle into the cowl, grouped with the oil coolers (as with the F4F, F4U, F6F, etc) though designing the fusealage side ducting to act as a surface intercooler (like the P-38's wing intercoolers) as a pre-cooler for the main intercoolers in the nose/cowl might have helped a fair bit too. (a large, rear-mounted intercooler like the P-47 used probably wasn't the most practical idea here)

Additionally, using as similar design configurations as possible between the V-1710 powered P-40 and turbo or 2-stage supercharged R-1830 variants would also be best on the manufacturing end if multiple types ended up being manufactured or just to allow easier shifts from the P-40 (which was already in production in 1939) to a souped-up R-1830 derivative.

Turbocharging also has the potential advantage of being adapted to the 1450 HP R-2000 later in the war, since it never adopted a 2-stage supercharger and a 2-speed single stage unit would be less appealing to displace the 2-stage R-1830. (unless of course, demand for Curtiss's fighter drove P&W to implement a 2-stage R-2000) WEP or even unsanctioned overboost of the R-1830 itself would probably be limited by cooling fin design given the R-1830 never saw the substantial redesigns that the R-2800 did to allow its increased power levels. (water injection would be of little to no relevance here either, and switching to a late-war R-1820 with WEP and possibly water injection would have been a worse trade-off for drag than the R-2000)


As far as turbo installation goes: the P-47's overall ducting arrangement seems best, but likely with the air intake severely cut back (no massive intercooler to cater to and associated drag) and relatively minimalistic added belly contours to enclose exhaust ducting on either side of the lower fuselage/wing (yes, beneath the fuel tanks, just like the P-47, with associated insulation and firewalls added/modified if needed)


----------



## kool kitty89 (Apr 19, 2016)

The fuel capacity, armament, armor, and overall weight would be the remaining factors here, and are the real-world factors that already DID plague the P-40, particularly with the more substantial changes to the airframe the P-40D and later models saw. (lots of weight gain there, changing of the cockpit position, canopy, fuel tanks, new wing with .50" gun mounts -and initially hispano mount provisions in the D model- tons of weight gain due to structural redesigns, larger radiator and oil coolers, and added armor, modest gain in fuel capacity over the P-40C and loss over the P-40B -with its metal tanks and linatex style self sealing coating- or Hawk 75A-2, plus later extended rear fuselage to accomodate the Merlin's added weight iirc)

The critical factors here could ALSO have benefited the P-40 itself, careful attention to detail in keeping weight down, selecting armament optimized for fighter vs fighter combat (and lightly built bombers) over bomber interception, etc. (though the point was already made for the superiority of the .50 BMG during the BoB -or when employed against any linatex -or laminated leather- style external self sealing material on metal tanks, not well suited to 13 mm projectiles, let alone 20 mm -explosive and incendiary properties aside)



On armament: It should also be noted that it was the British, not the Americans that insisted on mounting more guns on the Kittyhawk/Warhawk, Wildcat/Martlet, and Mustang. Many Navy pilots preferred the 4-gun arrangement of the F4F (though the issues with kinks and jams in the F4F-3's installation weren't ideal, the lower weight and particularly higher ammunition capacity were preferred) this may also have been less from British Pilot preference, and more Air Ministry doctrine/thinking. (the Mustang I's 2x .303 and 4x .50 BMG would probably have served fine stripped to just 4x 50s, 2 synchronized, 2 in the wings -A-36 crews often removed the synchronized guns but that was with 4 .50 cal guns already in the wings) The P-51A, B, and C all sported 4 gun armaments and it wasn't until the D that the array of 6 became standard. (by which time it was more genuinely needed if still not always superior to the 4-gun arrangement, though the D was also heavier and poorer performing than the B/C for more reasons than the armament)

Improvements in the browning to up rate of fire (similar to the FN Browning) would have helped with synchronization losses too, even if such boosted speeds were witheld from standard unsynchronized use for conservative wear/reliability reasons. (even with the slower RoF, the nose mounted arrangement had advantages, especially if you could do away with wing guns entirely -mixed wing and nose guns is a bit less nice and takes training for both sorts of convergence and gunnery to make good use of, unlike the P-38 -the only all-nose armmed USAAF fighter) On the plus side, 550-600 RPM would reduce the barrel-burning nature of the M2 if fired too long. (for pilots a bit more naturally heavy on the trigger)


Starting with the Tomahawk as the base, adapting the wings to carry 1 .50 cal gun each (for a F2A-2 style armament) would have been a good compromise, but with the radial engine it might be possible to add 2 more .50s to the fuselage sides and go all-nose without much increase to drag, or any at all if hidden in the expanded fuselage sides along with turbo-supercharger outlet ducting. (obviously positioning the guns to avoid barrel heating of that air flowing into the nose intercoolers) With the Allison's change in nose geometry with the F-series, the guns would probably have to be omitted from the over-cowl position and possibly introduced under fuselage embedded above the radiator as well as 2 in the fuselage sides. (or possibly all four in the fuselage sides as cheek mounts, or ... in the case of a turbocharged V-1710, embedded in the fuselage 'cheeks' themselves caused by the necessary ducting)

Avoiding wing mounted guns also frees up a lot of space for potential fuel tankage without having to engineer fuel cell compartments around weapons compartments (and possibly be forced to add more mass outboard of the wing and compromise roll rate). Fuel tanks added to the region the wing guns would otherwise be (particularly all the useful space towards the center and leading edge of the thicker, inboard portion of the wing just outboard of the wheel housing) and could make the fighter into a good long-range intruder or high altitude escort fighter. (in the case of turbocharging or decent 2-stage supercharing ... or some proper refinement of a single stage allison supercharger to match/beat the Merlin rather than sticking with the known faults in favor of volume production -not to mention securing more funds to properly test WEP earlier and possibly even clear overrev for WEP) Leaving space for wing-mounted radiators would also be a huge help in reducing the P-40's drag, especially with the larger radiators needed to use power settings much beyond the old C series (V-1710-33)

Also remember how limited the armament of the BF-109F was and still somewhat modest 2x MG 131 and 1x MG 151/20 configuration. (4x synchronized .50s in the nose would be a fair match for that, especially given the Curtiss built fighters would be more rugged due to typical aggressive USAAF structural requirements)



On top of all that, remember the intrinsic adantages the P-36 and P-40 held over the Spitfire and Bf 109 (and to lesser extent 190 .... and massive effect Hurricane, Zero, and Oscar): exceptional roll rate, light controls at all speeds (but especially so at high speeds) and ability to out-maneuver other aircraft in similar ways to the P-47. This is important as it also meant that even in overweight configurations, the added dive 'thrust' of that weight could be exploited to full extent rather than having controls freeze up during a power dive. This is also a good reason to avoid putting lots of added weight in the outboard wing sections. (aside from perhaps tip-tanks ... in hindsight given their tendency to have winglet-like properties that reduce drag and increase aileron effectiveness -and thus roll rate when not filled with fuel)

The P-36/P-40 airframe was generally very clean and well designed for its era, cleaner than the P-43, F4F, F2A, and cleaner than the 109 and spitfire (look at the speeds it managed in spite of being overweight and underpowered). The F2A was never fitted with an R-1830, so the potential drag improvements there are harder to guess (performance with roughly similar R-1820s seems in the ballpark, but the F2A has a bulkier fuselage -if still much slimmer than P-43 and F4F- so it's harder to make even a general guess to that sort of pairing, plus the F2A had a smaller wing, but high-lift high-drag airfoil and thicker 18% root -then again, so did the F4U) I will say the P-36 benefitted more from the R-1830's slim size than the F4F did (which gained very little indeed given its large overall diameter and bulk -and wing area, when comparing R-1820s and 1830s of similar power/altitude performance) and the P-36 airframe almost certainly wouldn't have been as well matched to the FM-2's powerplant than the Wildcat was. (and for that matter, the non-water-injected earlier models of similar power at alitude could have been used on the F4F with little loss over the 2-stage R-1830 while the P-36 would gain far more from the drag reduction, especially with the eventual refinements offered by the XP-42 program -albeit more likely in time to be adopted with the R-2000)




And all that said, a final comment on a potentially more useful alternate use of Curtiss manufacturing and design ability: instead of second-sourcing the P-47, they could have taken on the task of developing a turbo-less P-38 derivative for medium/low-altitude duties (extremely useful in the MTO and PTO both as a fighter and fighter-bomber -though prior to those theaters becoming obvious in general, such a performance realm WAS the preferred specification for USAAF fighters pre-war, with a greater emphasis on cooperation and ground-attack ability). The P-38 was more expensive than the P-47 (and much more so than the P-40) true, but a stripped down derivative would be somewhat cheaper and more so easier to maintain and operate while also totally sidestepping the turbocharger problems the early P-38s were having on top of the compressibility issues far far worse in the high altitude flight envelope over Europe (due to cold and thin air allowing faster acceleration in a dive and lower ambient speed of sound). If that program was organized early enough, it might have even been possible to have a Curtiss P-38 accepted for operational duty before the P-38F arrived ... really it's not all that hard given just now long it took the P-38 to even get that far. (with Curtiss ignoring all but the problems relevant to operation at/below 15,000 ft or somewhat higher in warm climates -lack of heating and mach-tuck issues both avoided, they could have started shifting manufacturing and tooling up for the P-38 based on earlier models with only a few final detail changes left open to fix, particularly the wing fillet additions that eliminated the buffeting problem, while applying their experience with the P-40's intake/exhaust design to make a pretty efficient turbo-less nacelle for the P-38)

Given the problems the P-47G suffered this might have been no more foolproof, but it seems at least possible that they'd have fared better (and had somewhat more in common with P-40 experience and prior work) with the P-38. Second-sourcing the P-39 might have been more trouble too given its heavier use of new/novel technology than the P-38. (all the electrical equipment with miles of wiring -literal miles I believe- and some specialized modular mass production techniques for the airframe itself that worked very well for Bell but might not have been so nice for Curtiss)

In a best-case scenario, Curtiss engineers working on solving some of the P-38's problems independently of Lockheed might have been able to speed up progress on both fronts, sharing findings with Lockheed while keeping up with progress on that end as well. (plus, I believe the P-38 and P-40 already had some parts commonality in the curtiss electric propellers used on some models ... in fact the retention of that rather small 3-blade Curtiss-electric propeller late in the P-38's run has been criticized for being too small to properly take advantage of the added engine power, while the same has been argued against Curtiss for retention of that aging unit on the P-40 -the P-39, P-51, and P-47 all went though multiple propeller changes to rather significant degree while the P-38K's larger area 3-blade prop was refused for production due to delays on the assembly line it would cause ... not sure if any 4-blade props might have avoided that by retaining similar spinner diameter -the P-51 and P-39 both avoided nose geometry redesigns by keeping any prop/hub/spinner changes to ones compatible with the existing geometry) The P-40D and YP-38 obviously had to change nose/nacelle/spinner geometry due to the engine dimension and thrust-line changes ... and I assume lowering the engine mount to maintain the P-40B/C thrust line would have been more problematic. (or ... maybe it wouldn't have been if they'd moved the radiator(s) to the wings, allowing the upper nose geometry to remain more constant along with the thrust line ... and had more room at the top of the engine for cowl-mounted .50s)

Hmm, actually, yes, maintaining a more Tomahawk-like fuselage/nose structure and fitting a row of 4 guns to the nose top and/or sides (or possibly even 6 later on when the added firepower was needed) and relocating the radiators to the wing or wing center section (and making up the center section fuel space with wing-mounted cells) would have been one of the better options for the Allison powered P-40 as well, with or without turbocharger.




And some useful cross-sections of the P-40, Hawk-75, and P-47 for reference.

http://www.histaviation.com/Hawk_75_A-2_Drawing_1424x926.jpg (fuel tank capacity listed too -appears identical to the P-40B's arrangement with a total of 135 imp gal or 162 US gal)

http://images.fineartamerica.com/images-medium-large/p-40-tomahawk-iib-science-source.jpg (equivalent to the P-40C, note the modified fuel tank arrangements -these should be proper self-sealing cells, not modified metal tanks like the P-40B and Tomahawk IIA, with fuel capacity of 134 US Gallons or approximately 112 imp gal)

https://s-media-cache-ak0.pinimg.com/736x/f9/37/d0/f937d068f17625f9fb18c3f0986b87e2.jpg
P-40E 122.8 imp gallon capacity or 147.4 US gal (I believe it's officially 148 US gal, and slightly off due to rounding errors partially on the part of those imperial figures)


http://www.wardrawings.be/WW2/Image...-USA/Files/1-Fighters/P-47/Boards/Board-2.jpg
http://www.airwar.ru/image/idop/fww2/p36/p36-2.gif (for P-47 P-36 profile cross-section cutaway comparison)


Also remember the P-39 carried 120 US gal of self-sealing fuel cells in the inboard portion of the wing in spite of also housing 4x .30 cal guns (and capacity for 1000 RPG), so with proper attention to detail (and redesign of the wing ribs to accomodate cells) it should have been fairly easy to expand the P-40's fuel capacity substnatially, possibly while also embedding the radiator (and possibly oil coolers too) in the belly/wing-center section in place of those fuel tanks. (akin to the P-39's radiator and oil cooler core placement) The P-40 also gives a hell of a lot more space for adding a turbocharger than the P-39 does. (especially if compromising to use existing turbochargers aimed at capacities and altitudes perhaps a fair bit beyond the real needs of a fighter for the time -or at least not worth the trade-offs for weight and bulk of the unit AND intercooler installation ... the P-39 might have accomodated a SMALL rear/saddle mounted turbo had they been available)



Finally, aircraft designers (or engine manufacturers) could have taken the lead away from GE by working on liquid cooled intercooler designs rather than those huge air to air ones. (that would definitely make a turbo on the P-40 workable, and probably the P-39 too ... perhaps P-51 as well with the rear tank omitted and some CoG adjustment -remember turbos also mean better fuel consumption and range, particularly at cruise where exhaust thrust is useless anyway)

The P-38 and (especially P-47) would have benefitted somewhat less, but it would have been a far more elegant solution than the chin intercoolers on the P-38, and would have freed up fuselage space for some added fuel capacity in the P-47. (within CoG constraints, of course) Perhaps more significantly, it would have allowed the P-47 to lose much of its 'gut' along with the removal of that large intercooler. (OTOH, using a LIQUID intercooler on a radial engine might be problematic ... unless designed around using oil to cool it rather than water/glycol ... that might have been workable but the viscosity of oil might not promote good flow at the temperatures desired for air intercooling, in any case -oil or water- the radiator would likely be grouped up front with the oil coolers, thus leaving only a small turbocharger impeller air intake scoop needed at the rear -liquid intercoolers also make small targets, unlike the big block in the P-47's rear that could get holes punched in it and lead to a loss of manifold pressure)

The P-51 would NOT have been the aircraft that it was without the liquid intercooler exchange. A conventional air to air cooler (a la F4U/F6F -likely of similar size too, given the mass flow involved) would have added substantially more drag to the P-51 ... or anything using the 2-stage merlin for that matter. (the other option, of course, was no intercooler at all, a la the minimalistic V-1710 Aux stage -and a small number of 2-stage R-1830s for that matter; in which case either VERY high octane fuel was needed for WEP -like 100/150, or water injection had to be employed -which risks corrosion of the engine if used too soon before landing and shut-down -you need to burn off all traces of water and methanol in the system or risk corrosion, particularly to aluminum components in contact with the methanol -steel alloys and cast iron tolerate methanol/water fine, about as well as plain water, but aluminum is not so nice)


----------



## Shortround6 (Apr 19, 2016)

Please, please, _please !!!_ Forget about fuselage mounted .50 cal guns. The Big .50 took to synchronization about like cats take to water. British found that it often cycled under 500rpm when synchronized, maybe you could get it to 600rpm when the wing guns were doing 800-850rpm. With the weight of the .50 cal you want all the punch you can get for the installed weight, not crippled by synchronizing gear. There is a reason that only few planes used fuselage mounted .50s later in the war and they were legacy installations from the early part or even pre war design. (except for the P-75 and the less said about that the better)


----------



## GrauGeist (Apr 19, 2016)

Aside from the syncro issues, cowl mounted MGs take up a great deal of space that could be otherwise dedicated to engine components...


----------



## Shortround6 (Apr 19, 2016)

GE made two basic superchargers during WW II. The B series (developed from the F, go figure??) which was sized to handle engines from below 1000hp to around 1500-1600hp. Later versions were better for the higher power levels. The C series was supposed to handle from the mid/hi teens to something over 2000hp worth of airflow. again late war models were improved a bit. Please note that the B-29 used two "B: series turbos in parallel.
GE compressor designs really weren't the best, a fact that the turbine drive tended to hide. Since the exhaust had more than enough power to drive an inefficient compressor it didn't matter as much _until _you get to the intercooler design. The inefficient supercharger heats up the intake charge more for the same amount of compression as a more efficient supercharger.
However we really have no figures for how efficient the P&W supercharger/s were or at least not in common sources.
Intercooler design was also a constantly evolving "art".
U.S. Army doctrine was for the turbo installation to provide sea level air-pressure to the carb inlet (or carb deck) _at 100 degrees F. _
The engine supercharger providing the actual manifold boost. Usually between 44-49in (around 7-9lbs) which may have pretty close to the limit using US 100 octane fuel pre-war.
Not only does a 1400hp engine require 16-17% more induction airflow than a 1200hp engine, if you are using the same engine and just boosting the pressure using the turbo then the air going in the carb is hotter. The intercooler needs 16-17% more air to cool the intake charge assuming the intake charge _didn't _get hotter. With the extra temp you need even more airflow. P-38s changed the engine supercharger gear several times instead of trying to use the turbo to boost pressure so a good part of their problems was just added airflow rather than higher temperatures of the intake charge.
Inter-coolers, or more accurately, the companies that made them weren't all that common as Bell tried to out source them for the P-63 (not uncommon, many parts/sub assemblies were out sourced) but the company (or companies?) selected failed to even come up with prototype units in a timely fashion forcing bell to rely on water injection. I would bet that B-24s and B-17s used intercoolers form outside suppliers rather than build them in house.
Turbos got better and were allowed higher rpm in later models which helped airflow and pressure.
Please note that B-17s are sometimes listed as having different critical altitudes for the outboard engines and inboard engines due to differences in the intercooler ducting. And B-17s had a lot of room to arrange things compared to a single engine fighter.
Inter cooler design did get better but it was hardly pick the desired one out of a catalog 
Another look at the P & W test Hack;






Note what seems to be exhaust stains on the side behind the cowling and the absence of normal exhaust stubs like on the P-36 or F4F. Maybe not the exhaust thrust of a V-12 but better than a number of radials? Also please note the even worse view over the nose compared to a P-36 or P-40.


----------



## Shortround6 (Apr 19, 2016)

Another photo, B-24 under construction showing inter cooler core in the inner nacelle.






Now perhaps a bomber that runs at max continuous for long periods of time while climbing/forming up at relatively slow speeds needs a bigger inter-cooler than fighter that is moving faster (mass airflow per minute?), I don't know but intercoolers for turbo charged air cooled engines are not small items to tucked into convenient corners or nooks/crannies in an existing airframe. You also need smooth appropriate sized ducts to minimize internal drag and maximize the effectiveness of the intercooler core/matrix.


----------



## wuzak (Apr 19, 2016)

Shortround6 said:


> GE made two basic superchargers during WW II. The B series (developed from the F, go figure??) which was sized to handle engines from below 1000hp to around 1500-1600hp.



I believe the F stood for Form. The XP-39 used, IIRC, a Form 10 turbo, while the YP-37 used the Form 13, which was later redesignated B-1.


----------



## wuzak (Apr 19, 2016)

Shortround6 said:


> Another photo, B-24 under construction showing inter cooler core in the inner nacelle.
> 
> 
> 
> ...



That shows one advantage of a liquid to air intercoolers. 

The radiator, the part exposed to the airflow, can be remotely positioned for best aerodynamic effect.


----------



## Shortround6 (Apr 19, 2016)

It can be but the only engines to use liquid to air coolers were the RR ones and they are more properly called after coolers. They cool the intake charge _after _all the compressing is done. The American engines did _all_ of their cooling between the 1st and 2nd stag. 
I will grant that there was some sort of coolant passage in the supercharger housing on the Merlins and Griffon but the vast majority of the cooling was done in the matrix in the box at the rear of the engine. 
The Americans need to duct the air from the first compressor (either mechanical or turbo) to the cooler and then duct it back to the carb inlet with the carb mounted on the 2nd compressor housing on the turbo engines. 
RR just ran the intake air from the inlet to the carb, from the carb to the inlet of the 1st compressor, then to the inlet of the 2nd compressor and then to the after cooler and then to the intake manifold. 
The turbo system is a lot more stretched out to begin with and a small inter-cooler matrix isn't going to change a large part of the ducting.


----------



## Peter Gunn (Apr 21, 2016)

All fascinating stuff guys, learned a ton. I also found it entertaining that I can see this same set of discussions going on in the aviation industry offices of the time. Someone says "Hey, how about we try a turbocharger on the P-36" and they actually end up with the historic P-47, almost like here. Great stuff guys, enjoyed every post.


----------



## gjs238 (Apr 21, 2016)

kool kitty89 said:


> And all that said, a final comment on a potentially more useful alternate use of Curtiss manufacturing and design ability: instead of second-sourcing the P-47, they could have taken on the task of developing a turbo-less P-38 derivative for medium/low-altitude duties (extremely useful in the MTO and PTO both as a fighter and fighter-bomber -though prior to those theaters becoming obvious in general, such a performance realm WAS the preferred specification for USAAF fighters pre-war, with a greater emphasis on cooperation and ground-attack ability). The P-38 was more expensive than the P-47 (and much more so than the P-40) true, but a stripped down derivative would be somewhat cheaper and more so easier to maintain and operate while also totally sidestepping the turbocharger problems the early P-38s were having on top of the compressibility issues far far worse in the high altitude flight envelope over Europe (due to cold and thin air allowing faster acceleration in a dive and lower ambient speed of sound). If that program was organized early enough, it might have even been possible to have a Curtiss P-38 accepted for operational duty before the P-38F arrived ... really it's not all that hard given just now long it took the P-38 to even get that far. (with Curtiss ignoring all but the problems relevant to operation at/below 15,000 ft or somewhat higher in warm climates -lack of heating and mach-tuck issues both avoided, they could have started shifting manufacturing and tooling up for the P-38 based on earlier models with only a few final detail changes left open to fix, particularly the wing fillet additions that eliminated the buffeting problem, while applying their experience with the P-40's intake/exhaust design to make a pretty efficient turbo-less nacelle for the P-38)
> 
> Given the problems the P-47G suffered this might have been no more foolproof, but it seems at least possible that they'd have fared better (and had somewhat more in common with P-40 experience and prior work) with the P-38. Second-sourcing the P-39 might have been more trouble too given its heavier use of new/novel technology than the P-38. (all the electrical equipment with miles of wiring -literal miles I believe- and some specialized modular mass production techniques for the airframe itself that worked very well for Bell but might not have been so nice for Curtiss)
> 
> In a best-case scenario, Curtiss engineers working on solving some of the P-38's problems independently of Lockheed might have been able to speed up progress on both fronts, sharing findings with Lockheed while keeping up with progress on that end as well. (plus, I believe the P-38 and P-40 already had some parts commonality in the curtiss electric propellers used on some models ... in fact the retention of that rather small 3-blade Curtiss-electric propeller late in the P-38's run has been criticized for being too small to properly take advantage of the added engine power, while the same has been argued against Curtiss for retention of that aging unit on the P-40 -the P-39, P-51, and P-47 all went though multiple propeller changes to rather significant degree while the P-38K's larger area 3-blade prop was refused for production due to delays on the assembly line it would cause ... not sure if any 4-blade props might have avoided that by retaining similar spinner diameter -the P-51 and P-39 both avoided nose geometry redesigns by keeping any prop/hub/spinner changes to ones compatible with the existing geometry) The P-40D and YP-38 obviously had to change nose/nacelle/spinner geometry due to the engine dimension and thrust-line changes ... and I assume lowering the engine mount to maintain the P-40B/C thrust line would have been more problematic. (or ... maybe it wouldn't have been if they'd moved the radiator(s) to the wings, allowing the upper nose geometry to remain more constant along with the thrust line ... and had more room at the top of the engine for cowl-mounted .50s)



Have Curtiss manufacture the P-51 or even A-36 under license.


----------



## Shortround6 (Apr 21, 2016)

Ok, guys, lets remember that Curtiss _did _build 14 turbocharged hawk 75 fighters, they just used Allisons instead of P & W or Wright radials 










Slot around the fuselage over the wing was the exit for the intercooler.
The XP-37 was actually the original Hawk 75 prototype rebuilt and not a brand new airframe.

These 14 planes helped convinced the army that the turbo set up was still several years away from service use.
Not only turbo regulator problems but the turbines shedding buckets/blades.

P-36/Hawk 75 production was running down in the Spring of 1940 with the P-40 replacing it on the production lines ( simple to do, early P-40s kept a very large amount of the basic P-36/Hawk 75 structure) but this means that to bring the P-36 back with a turbo (or even without) you either need more production space (and jigs/fixtures) or cut back on P-40 production. Chances of a turbo P-36 really doing better than a P-40 is going to depend on cowl technology and better turbo installations that don't really exist until some point or points in 1942 which means production planes won't show up in numbers until some time in 1943 at which point you have a 1200-1350hp machine trying to fight what kind of opponents?

There is an interesting set of drawings of the Hawk demonstrator with two stage supercharger here:

The bulge in the bottom just behind the engine and in line with the front of the wing is the aux supercharger. The tunnel further back is the intercooler. The drawing _seems _to exaggerate the size of both items compared to photographs.
Again without 1943 production technology getting small intercoolers doesn't seem likely.

BTW using the engine coolant for a liquid inter-cooler is a non-starter. Trying to cool 150-200 degree air with 160-200 degree engine coolant (even after radiator before it is even higher, Mustang had max temp of 135 degrees centigrade/275 degrees Fahrenheit) doesn't seem like a good idea. Spitfire and Mustang both used separate liquid cooling circuits for their inter-coolers.


----------



## GregP (May 4, 2016)

If you click Shortround's link, you can see the drawing of the 2-stage, supercharged P-36. Here is a pic:






Didn't find another one, but also didn't look too long.

http://data:image/jpeg;base64,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 http://data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wCEAAkGBxMSEhUSExIWFRUVFRUVFRUWGBUVFRUVFRUXFhUVFRUYHSggGBolHRUVITEhJSkrLi4uFx8zODMtNygtLisBCgoKBQUFDgUFDisZExkrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrKysrK//AABEIAL4BCQMBIgACEQEDEQH/xAAbAAACAwEBAQAAAAAAAAAAAAACAwEEBQAGB//EAEUQAAEDAQQHBAcECAQHAAAAAAEAAhEDBBIhMQVBUWFxgZETUqGxBiIyQsHR8BRicuEVI1OCksLS8QczorJDRHODk6Oz/8QAFAEBAAAAAAAAAAAAAAAAAAAAAP/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/APoVYqi5Xq5wVJAErgVLghQTeUyhhSEDApQhGEAMzRBS0IoQLK6Ed1cQggKQFwCINQAWqITShKACuCIhRCDgpXALiEEqJXKQg5pUyuDVxCAgpQqZQSuUAqZQcSoJXIXIJlQuC4oCanpFNWIQKtKpFyvWlUHIIJUhBKm8gNG1qUCjaUDLqlDeUgoGMCm6uplHKAIUQmwohAsBTKIhCQghy4BcuQEhIXXlBKDguKiVyCIUgLlyCQVMoJXSgMlQhJXSgYiCUCilAZSyplAXIJXEoZXSgZSKsyqlNPlBFcqg8q5XVJxQASuQuXBAYKMJbSmAoCCKVAWjoWxNqvIcJaBJGU6ggqUimKbTZ+ze5mw4cMx4JUoGKZSryIOQMBUFRKAlBJCkICVN5ASFyi8oJQdK4FRC5BMrlAUlAJUBEhKDiVwK6EKA10oVEoDvIbygoUDAVEpd5ReQOplOlV6ZT5QFaCs2oVoWgqg9AC6VJQlAQKY0pKMFA4Fb3ot7T+A8155q2vR6sGmoSYAaDJ3H80DtPs/WTtaPCR8llFW7bpFlYgsIN2QSMVTKCVy6EKCZXXlwKEuQEVCguXSg6VMoJXXkBEobyEuXXkBXkV5LlSCgYCuLkEoXFAy8hKUXLr6BqiUq+ovoGlyAlLc9LNRA28uLkgPUF6C1ScnSqNN6s3kD7Q/BZ73q3aDgqLygK+plKldeQNvKQ5KvKQ5A8OV3R4D79M5PpuHMC8P9qzmYmBmcAFZ0TaG9q032i68NdJAumYLXbNnNB539Ivova2mabKRce0fWcAwZQC4kGYnJbWk3V3UHVrK+lVZDYqUntddcHesdYdgR6sYYr5h/iJRLbcWB0tvFrRiYF7ExrOPgF6j/AAqrEWzsaTXGj69Oq4MDWvYQ406tQSSH3mACZgOIlB6Gw6ZnCoIO0fELS+0N7wx3rM0tYLlZwG0pD7LIgoN9LcvN2TSNWmbpIc3Yc8Nh1cMVpUtLUyYJunfl1yQaBK4uVO1Wxrd5zgbNpOoKk3TQgOc31SYvtMgb42INa8uvJFOqHCWkEHWMQpLkDC5dKVeUXkDg5TfSA5dfQPD1xelByguQGXpZcgvISUDDUQdollyAuQONRAXpZKWXIGdou7RVy5deQXKLlblZ9nVyUD7QVnucrlc4Ki5BJcovIW44DE7ARPRc9pGYKAw5GCkhE0oGyvPaX9Gop1a9B4phrR2jHOcRUl8gNJmDIBg93BbwM4LA/wARKtT7I7s33WUajL4GdV7pa94PdZg3fLjlmGQNL2F7WMtNOo6oxt0OpuDfWBzcYJOBA2ANG0r0vo/6RWKz1W1qVGpMXD+tBEREltzEr5Vom10Wtq9reLnMmm4T+rqNMiRIDg4SDskHHFfSfRzQ1Oy2CpVtNMGtao7Njx61Ok2br4OLXOJnhCD29W12eu+9fcxx2gOb4EJlXRD4ll2oPunHm049F86stuu8Ft6P9JrmILuAj5oK+kWOa4Ye+QQRBnFLtXszGOBSfSbTLrTUD8BlhrN0RPHFUa1ucGQccQCMZAJEnDNBZZXwwJB2Z9FNqi6XnAgGYwvG66CdRyA/eKpCoHYA8CrVOHNuPEhBAtNbtA5rrpd0cBtbr5r0Fjt94C/g7EfdJBjDZwXn3WBzSHMIP4sD1HyVim9zGeuLpn3ouZ98SBnrQejJUSqFmtBEAgx1jnrCvSgmVEoSUuvWutLtg8dQQWZQFy8e3T9YWprGzUa4CaeGOLpcyciAOBiF68MJyB6FBBchLlYZYKpypvP7pXO0bV1tu73FrR4lBULkJcirMY32q9Bv/dYT0bKo2u0WUi6+0MI+62q7mCGjHmgtudglErK/TdJhLZqVGgYPDGtcTsc0uHUdEip6SM92k48XNHgAUG2Soledd6QvJ9Wm0cST5QrmjtMdobjgGuiRBkEDPgg3rO5Wr6zKVcZSrfaBBZr1cMVUv8VsWm0Usu0xzutqN/pVKppCmMDeG8vZ8QNaDPrU2uEObI3if7KsbLd9ipVbuDnkdCtC029g9iqCdQLgCdRGHq69qA20AT6pIje3k+YORQUhUtTfZeKg2OY0HqB8VP6aqN/zLKOLbzfE3grdDSQflZwTueI1ZTA8Sr1gfeD3Pomk1mJJIJO4XSZ1cZCCp+k6dOm2q9r6V+QwYOfljUAwwE4a5IOpZ+kG2a0U7rbQwEEFrajXsBj3DIiCMFct2lKVR0mz1XNgAXqZwA1D1Ttnms23tscXhSrNjul7fBzI2IM7QllsTbQBSoWY175DC6qXUw8HC5Te66HSMMM8kjTmm6leq6+SSDBnHLBZ9p0LRFbtqd+Q++GuODXTeB9kEgHHPVsTrToqo1rahcxweDdDSZwzERgdaBba0/kidWMXQTOvVPRZ5fiQJkK3SfTLLrqbr0+2DJM7RBQBUrXjEkkCOW4qz2hEBxgnHIudzAyWI6s4OIaHC6TF7AwNo1IqOliDideO1BtULI95/Vgk7gR5Lbsfo9bXx+pdxII8YRN0k+hRpdmKjH1GXr4ydJPs3dwyWDb9L2p2Lqr3jiZ2ZIPbWX0ert9t1Ng13ntHmVZdY6Lf8y10W4QQHXvKV8sdbXnWTzJ8FUr21w1Tt/sg+uG22BmdrB3NaT5gJQ09YQMDVfyA+K+SOt5IwPUSOoQi1P24/ux4BB9Wd6T2f3bO4/iqDyASa3pcAMLNRH4i53xXzLt6nfcDuMt6EoQ2XEkm8dYP5IPoL/Tmp7hot/BTYY6ykN9M7VVBLbS8CYN0XBPKNq8aD3rp3wJ+S6iQPZJAOMaj9bkHoLdp2vkatV5Oq849cVQfaX3S55FPHC/eM8CPkqVQh2ePFNs1jcPWpsIkRIkCOaBtG0lwJ9UgZwXeQaShZpFjjABnerdl9GqlTG/TbrN+rjG3CVp2f0SbeAfaW453W5DbecRI5IMJ1oB1DmlOqCZwwywXtG+jFhbnaC4/9WmPBow6rQs/o5o+JFRp4+v1mYQfO21nOMNBO4AlbOitHvYDUcDOAJ1NB1HeY8F6t9gsjcBVjgMMPw4a0D6Vlbh2jtRmHgH63IMejWJMDHUtT7JV7viPmninZc2v6H5p36j9oev5IH2jTNSSRTsrcIBcxrvG9hr2rKq6ftM/8rrx7IdNaoV6xyOW3Zx+aqPY5Bpt01Xky2gQdl9nS7HiEA0vVaQWtaThrERsgUwf9Sy5cPoo2VDt8EG1T01anui/SYHEDI+qDnjdHmtHS+mJ9SjULWtHtXSS5w1zeHqrzIe5F2hn2oQX3W5x9og5YgOGW27UjwVVlYXvWM/uvbsyPafApRqfeKi/vPQoDeGmbogH8QMcb+KtU7DQFlNSo6r+rqsaCLgb62JwkkxBPRZVSuYkDAmGk64zO4ea9D6VinSstnszXS6q5tR8mTeeADGwQIAQeQ0hYnBxdSBLDiAcHAHIEFIp1Xg+tTd0K9AWEe6epXXDs8T8UHmLWx9RziykRJM4HWcpVR+iKwxLDyg9Qvain9Z+RUGlw8PigJtEfY6VR1qpNexhJpF0VABPu8ivn40m4TccQCSYPrDEziF6LStsp3Hz7z2YnI02NOQxJJc52qIXny1j8WvGqQW4TGMYTEoF1rc98RcadZbr5HJI7N+t/hKe+xEag7e0r1Oj9CNYwSS+cZM4A5CEHlmUjGPyRQvVM0SL5MNAhoGBkEXp1bwgd6NNcZvxwCDApWRzhhH8QlQ6z1Bh2Z25HLbK2bT6LPaCab751CLvmqOjKNrcSBTN1riw3i2ARnmctUiUFaoA15Y6oGGGkEglpcRJBIxA3wgfSqNF4C83vNAezqMOS2rPoq033FzKN18Bwc6cAIwABXo7HZm0m3WANGcDASczkg+clz3HIng38lZstG0AyxlUHaGvb4r6EXx9FKfVP0EGRoSy1S09uMMLoM3p1k3TwzWtSF2QGsIOYc1zj1lQKrt3RDff3mj64oDa0D/hUTxFX+tT6kR2FPeQ6uD/APRCCT7zTyQOafu9D8kBkU/2UfhqVB5yjZd21hwrH4sVQ8vFcHD+xd80D6dnaDIfaQdoqj+hX7p/a2n/AMg/pWfQfjmfFac7z9ckGDWcdnx+CFjnj2QI2YDodSi0P4KuKpGvzQXB6wkHcdx2FLcDt80DX65x4HHcU0VQ7AGCMxrCAA/j9cSiv/Uhc5m9LLDt80D752+KRbasMd62pd2gGvzSa1VhBBOBwyQIr6YFUsDSLrIaRkRtkcs0el9JfaLRTOQa5gAGXqn5BeXraPqtqEsIicDeaPArS0TTfTlz2te6ZBvQGiNV1pxOsoPY9q3bH1vSXUzqqnmGH4LHNqqn3W/+w/yhS2pV2D+An/c4INN3ajJ7TxEeSTaa7hTffu43WtgkzMl2B1XWkfvKoX1dYdybTH86TaqjnNxBwxxu4dEGS5vbVbpOAxPAfmprWCmx7Zm46QYxIMSIlVbHbBTquvZGRPOQVoU6vbVBcF5rJJJvASQQBIx2oLNnsdkmXVKvCBHgZXoWads4wvGOBy5heXr0nif1dEDab3xcqDqB1vpjnPlKD3f6ds+qp1SqmnKH7SOAleJpWdxMNcDwDviFZ/RtfueLUHphp6iHBxJqAEEsIcGvAOLSRiAVlUdM3QQG4FznQMhecTAkSs8aIrd2OfyQu0bWHuu5GfBBpHT7hlTH8Th5Jb9P1Dk0Dm8+ZVBtjdrkfiY/zEp7dEvIkBp6+TmhAxumK5OBPACfgnm22kjExxDQgYyqzAXBuuj+lWKdSvqDD/D80B0aziPWeJ5nyITRUO1p5OP8yAVa4zpg8/k5H9pqa6HiUBCtvH8JRiqTrPIH4hKFrOug7x+SF1uH7N45IHGsRrd1HzXNrnf1Cqu0gzY7oPmg+3s39PzQatGu6fZHM/ILV7Z3dZ1K85Qt7Jz8/ktX7ezveaClaXEquGHerNoqn6Cql796C3QZuKfUs5MQ04ZHYqDS/aVboF208yghrcQ1zSCcpc6HcMc9yJ9mHdHmrLKAIhx6nBV6lVrCAXS3afaG4xmN6CvUoN7o6BJLQPdHgtR9MZxIIkHCDOSQ4DuoKcncOiNrz3ugTH7gq7y9Awv3u6rr27/UkQ7vI20zrJKBscPEqcf7NJQNo7imCg7UEGXX0BSe4uLXciQm0NBU2iAHRsL3RPCVoik7aoFEa3FAinoekPcaDvk+aZ9ipt7g4Apwos39SpdZ26mlAprG98Dk5GCzv+BUtpnYja07QOSAIb3j0KiG949CnFju8EuD3gg643aeUhLNFu2eqNpIPtJvaHvIK3Yt3+Kl1FmseATy7egNEnWgUwN2kdU0MnJ09FLbKNyPsG/QQLNnfqjp+ZSXteMweUfMK52YCjtAMwev5oKBB2kcQY65Im0nHeNxV011BcDm0dECqNITi3wBWl2bO4P4QqlGk2cJHDAeC0Oy++7qEHn7Q5+0Kob2sq7Wce6PBJLjuQLYw7T4fJNbR49T81AdwTO0OzwQOpWbcfritGhRMYjqFnU6x39E8VDtcgOo1zPYxHcMx+6fd8kTbSwjDVmIMjiNSrvB2lIfYpN6S13eH8w1hBbNdmwJbrQ3chpOk3XiHcoMa2z5akZohAo2huzySX2nYFYdTG5KfTCBQtBOScwuO1Ic0bFHJBaDDrKNtIayqsfUprLMe9HNA/AJbrYAlvs/3umKF1lA949EDftY2xyQuqg5GeRU07ON/RWGsAzaPFBV7Q71BrHYrpY3YOaEsacBHKEFA1HnIeCkNf8AQVh7CMvmuFVw/sgSyk7Wi7QjCUfbHZ5pg4eaAabz+acypOGPRHTa3b1Tm0h3kCXObvVaoGnWrz6W8Kg8BqACwLm81wqhNp1wgOg7HWtG9xSLNaWrQ+1M+74IMOpWb9BV31GonUt6DsUECsETa/NE2kNiMNQcyvGpMp2obEbSuDRvQEbUzYhbaW5EdJhRdbvR9kIwlBXtF1wgz8Rw2KoLQWe16zdTtY/ENfFXXBKLRsQBTtDXCQJHBA6tuPRc4XBIy1j4t2cE+nSvAOGREoK/aTqKi7OQd0V0UELwRhggqEXfdKX2z9nkrT2HaluZvQCK7tnkibaTkQChNILroCCzSdrmPFWxU2gclmtKNtbcg0CWHXB5KvVoTkfBAKxnoic07cc9yBYpEaz5IpAzbPMqsbQ4YSUHalBdLmx7KAOA/JVxUMKb+4IL9Oo0/wBk4O2D4KlRC0abUFaoXbFRrPOxbLm8VTqsCDNInNqJlPkrjaI2JtOm3YgXQYd/VXbp2KaYA1K1hsQf/9k=


----------



## Shortround6 (May 4, 2016)

Thank you Greg. 

I have only seen one other photo of this plane, more of a side view. 

I would note that the inter-cooler in the "pod" was meant to handle an engine rated at 1050hp max continuous (no military rating) at 2550rpm at 17,500ft. The engines used in production F4Fs (and some PBYs and some C-47s) were rated at 1000hp at 2550rpm at 19,000ft max continuous. 
The turbo charged engines were rated at 1200hp military (2700rpm) and 1100hp max continuous (2550rpm) at 25,000ft. 
Due to the thinner air and more compression needed by the aux stage/turbo an even bigger inter-cooler would be needed than the one used on this prototype.
It might be fast high up but performance at 15,000ft or under is going to take a real hit due the extra drag.


----------



## kool kitty89 (May 5, 2016)

The YP-37 is interesting, but it's not really a good example of a practical installation of a turbocharger (or V-1710 alone) in the airframe. (though on that note, a radial engine would at least make that turbo arrangement somewhat more reasonable with the much shorter length and lack of coolant radiators, but it'd still be a hose-nose, just maybe a tolerable one more like the F4U)

Do remember the long nose of the YP-37 wasn't primarily to accommodate the turbocharger, but to cram the radiators, main fuel tank and a bunch of other equipment all behind the engine.
Photo by jon farrelly

The radiator, intercooler, and aux fuel tank take up most of the space. (that nose-mounted turbo installation would be OK if the radiators had been moved to the wings, but not so good for a belly radiator due to obvious turbo exhaust injection -a P-39 style radiator arrangement might work, but require adding fuel tanks to the wings, and P-38 style embedded rear-fuselage radiators adds long coolant/oil plumbing AND intercooler ducting if it's moved rearward as well)

That said, a nose-mounted turbo might have been the better configuration for a radial engined Hawk 81 derivative too. (particularly given the added space in the nose already noted in the P&W Hawk 81 testbed -see below)

The 2-stage R-1830 still seems like an all-around more useful option for 1940-42. (and possibly an R-2000 after that ... it was never 2-stage supercharged, but did get a turbocharged installation in the XF5U, apparently with 1600 HP WEP)



Shortround6 said:


> Please, please, _please !!!_ Forget about fuselage mounted .50 cal guns. The Big .50 took to synchronization about like cats take to water. British found that it often cycled under 500rpm when synchronized, maybe you could get it to 600rpm when the wing guns were doing 800-850rpm. With the weight of the .50 cal you want all the punch you can get for the installed weight, not crippled by synchronizing gear. There is a reason that only few planes used fuselage mounted .50s later in the war and they were legacy installations from the early part or even pre war design. (except for the P-75 and the less said about that the better)


The Japanese and Finns both preferred Browning-derived .50 cals in the nose over ones in the wings, or used both (but in the Finns case, crammed 4 .50 cal FN brownings in the nose of the Myrsky)

And while FN brownings were substantially faster than American brownings, the loss in performance from synchronization should be proportionally high (ie 1000~1200 RPM down to 650~800) so the concentration of fire and better accuracy were felt to be worthwhile.

The lack of demand for synchronized .50s (outside the P-39) may have contributed to little/no improvement in their rate of fire. There were attempts to speed the .50 up to 1200 RPM during the war (and likely had some common engineering solutions to the FN examples) but none met the Army's stringent requirements for mechanical integrity (ironic given the lacking quality of the American hispanos). However, the examples that failed requirements at 1100-1200 RPM may have passed at 700-800 RPM synchronized. (lower RoF also obviously improved barrel wear, particularly with the browning's tendency to overheat the barrel during long bursts and burn out the rifling)


Additionally, at some point in a previous thread, I was convinced that the better rate of fire of .30 cal M1919s would be more worthwhile synchronized than .50s (particularly if twice as many could be mounted), but after reading the article linked earlier in this thread on the studies in fuel tank and armor vulnerability to .50s vs .30s, I'm convinced even slow firing .50s are more useful, particularly early-war. (and that a P-40 or P-36/Hawk-75 with a pair of .50s at 500 RPM in the nose would often have been superior to the full 8 LMGs used by the Spitfire and Hurricane when employed against german bombers -perhaps not fighters- ... particularly tanking into account the limited usage of incendiary bullets in .303 loadings during the BoB and more so for aircraft with the guns intentionally calibrated for maximum spread rather than harmonized at maximum effective range -that said, the F4F-3 or F2A/B239/339 with four .50s -synchronized+wing or all wing- would obviously be suprior to either, as would have been 4x wing mounted .50s on the Spit or Hurricane ... particularly FN brownings)




GrauGeist said:


> Aside from the syncro issues, cowl mounted MGs take up a great deal of space that could be otherwise dedicated to engine components...


This depends on the installation, and it's usually the ammunition boxes and ejection chutes that pose more of a problem for engine compartment space than the guns themselves. (this would likely be the main limiting factor for adding 2 more .50s to the P-39's nose armament and why it only had a capacity of 200 rounds for each of the existing guns -compared to 350 on the P-40B/C)

The P-51 had no trouble including a pair of .50s in the lower nose.

However, for a radial engine installation, the added frontal area provides more leeway for potential increases in armament and ammunition loads. (in this respect, the 9-cylinder R-1820 might actually be more useful as the gun barrels fit between the cylinder gaps, but honestly, adding small cheek bulges for the barrels -and possibly breeches- of the guns in the cowling and fuselage sides with the R-1830 would still likely result in much lower drag, aside perhaps from a turbo+intercooler installation, in which case the larger frontal area might allow for more of that added drag to be hidden as well -aside from turbos, there was also the likes of the R-1820-40 and -56 which both had exceptional altitude performance only beaten by the 2-stage R-1830s, but those would be better matched to the F4F than Hawk-75/81 style airframe -and likely better matched to the F4F than the -40 was to the F2A-2/3's smaller, slimmer airframe)





Shortround6 said:


> Turbos got better and were allowed higher rpm in later models which helped airflow and pressure.
> Please note that B-17s are sometimes listed as having different critical altitudes for the outboard engines and inboard engines due to differences in the intercooler ducting. And B-17s had a lot of room to arrange things compared to a single engine fighter.


Turbo controls early-war were also less than satisfactory, both confusing and far from foolproof with lack of features like automatic turbo RPM limiting. (no overrev protection, and this resulted in the majority of catastrophic failures or exploding turbochargers)

The P-47 seemed somewhat less dramatically impacted by such (aside from the turbo exhaust igniting the magnesium tailwheel strut/assembly and causing the prototype's tail control linkages to melt -and subsequent bailout and crash), but in any case it would probably be a better bet to avoid turbos if possible early-war. (the P-39 might have seen as many problems as the P-38 -compressibiltiy aside- had they pursued turbos more aggressively)

Multiple, insistent petitions from aircraft designers/manufacturers for improvements in V-1710 supercharging may have been more worthwhile. (and possibly specifying auxiliary supercharger installations that were more compatible with the single-stage dimensions and mounting requirements -ie thus making them useful on the P-40, P-51, and P-39 without substantial modification)



> Another look at the P & W test Hack;
> 
> 
> Note what seems to be exhaust stains on the side behind the cowling and the absence of normal exhaust stubs like on the P-36 or F4F. Maybe not the exhaust thrust of a V-12 but better than a number of radials? Also please note the even worse view over the nose compared to a P-36 or P-40.


That 'even worse' implies visibility in the P-40 and P-36 (and Hawk 75/81) was already poor, which it wasn't. The P&W test mule Hawk 81 actually appears to have maintained the dimensions of the P-40B/C (Tomahawk) rather closely, perhaps mainly for maintaining center of gravity. (the engine is definitely significantly farther forward than in the Hawk 75, and while part of that added length is likely also being used for the 2nd supercharger stage and intercooler+oil coolers, I suspect it also makes for some added compartment space between the engine and cockpit bulkhead for potential added weapons or fuel capacity)

In fact (synchronization argument aside) that added space for a forward reserve fuel tank might be more worthwhile than attempting to add outboard wing fuel tanks. (and instead modify the wings to accept 4 .50s like the P-40D did, but preferably avoided the added weight gain from wealth of other modifications the Hawk 87 saw over the 81, including perhaps avoiding the 20 mm requirement/provisions in the wings if that added any weight) Blast tubes in the wings might actually generate less drag than bulges in the cowling (at least with the twin-wasp ... Cyclone is another story entirely).

More space for fuel is also a bigger advantage over the turbocharger. Even the best turbo installation is going to compromise fuel space, and while turbo performance (with proper RPM, manifold pressure, and mixture settings) should improve fuel efficiency there's going to be a notable trade-off there. (the turbocharged R-1830 also didn't see the WEP ratings of the R-2800, so the 2-stage vs turbo P-47 discussion we had some time back wouldn't have the same weight here)


The P&W Hawk 81 (along with apparently all Hawk 75s) omitted a spinner from the propeller. This should reduce drag further, especially at high speed, but for some reason most American aircraft omitted spinners on radial engines. 

This has already come up in this thread:
Drag of radial-engined fighters

but I haven't yet seen an explanation for so many aircraft omitting a rather obvious component of streamlining. (weight savings is the only explanation I've ever seen, and rarely even that is cited -mostly in a few F2A articles) A well designed spinner and cowling should be simpler to achieve pre-war than a tight cowling and cooling fan (or narrow ram-intake cowling and cooling cuffs on the propeller -a la P2V) and seems to be what both Brewster and most Japanese developers worked towards (as well as XF4U and XF4F-3) but for some reason the P-36 never got one and all American military aircraft from 1941 onward also lacked them.

Post-war air racers added them in many cases too, and did achieve performance boosts (sometimes with tight cowlings and added fans, sometimes without), so they weren't useless.





Shortround6 said:


> It can be but the only engines to use liquid to air coolers were the RR ones and they are more properly called after coolers. They cool the intake charge _after _all the compressing is done. The American engines did _all_ of their cooling between the 1st and 2nd stag.
> I will grant that there was some sort of coolant passage in the supercharger housing on the Merlins and Griffon but the vast majority of the cooling was done in the matrix in the box at the rear of the engine.
> The Americans need to duct the air from the first compressor (either mechanical or turbo) to the cooler and then duct it back to the carb inlet with the carb mounted on the 2nd compressor housing on the turbo engines.
> RR just ran the intake air from the inlet to the carb, from the carb to the inlet of the 1st compressor, then to the inlet of the 2nd compressor and then to the after cooler and then to the intake manifold.
> The turbo system is a lot more stretched out to begin with and a small inter-cooler matrix isn't going to change a large part of the ducting.


I'd thought the Merlin intercooler was fed with air from the first supercharger stage and then fed into the 2nd stage ... in spite of seeing cut-away drawings to the contrary. Somehow I'd failed to realize those all depicted aftercoolers.

The 2-stage Allison (no intercooler/aftercooler at all) also moved the carburetor to behind the aux stage, unlike P&W configurations which seem to treat the Aux stage more like a turbocharger with the carb still mounted to the inlet of the integral stage. (which honestly is how I'd assumed the Allison configuration worked too)

https://encrypted-tbn0.gstatic.com/...CHYVU4V2dCtHQIiCEt8qBx5hwuFiYFdIl5jrcbjHa_tMo

reference pic of a 2-stage V-1710 from this interesting article:
http://www.enginehistory.org/Convention/2009/Presentations/SuperchargingAllison.pdf
(which also shows a V-1710 with merlin style aftercooler, including the installation in the XP-51J, plus neat notes on the 2-stage arrangements, including placing the carb between the supercharger stages improving altitude performance significantly ... though the added details makes it look even more like making the aux stage side-mounted would have been trivial, especially since the existing aux stage already used an articulated joint in the accessory drive extension shaft)

The Merlin's aftercooler arrangement would also explain why some post-war examples suffered from overcooling issues. (an intercooler arrangement should at least partially avoid this given the 2nd stage will be heating and re-mixing any fuel that's condensed in the intercooler rather than staying as condensed droplets in the aftercooler -granted, the P-38J had some overcooling issues as well)

Oddly, I've seen some references to a 'pre-cooler' for some of the Mikulin AM-35 or AM-37 articles. (this seems to either be a mistranslation, or reference to the supercharger outlet feeding into the carb intake, thus placing the aftercooler between the supercharger and carb and 'pre-cooling' the charge before entering the carb)





gjs238 said:


> Have Curtiss manufacture the P-51 or even A-36 under license.


The P-51 didn't become an Army-qualified/priority fighter aircraft until after Pearl Harbor, so much more war time production interrupted for Curtiss by the time tooling could get started. (hell, with the P-39's Bell-specific technology in both the modular production optimized bulkhead design and -especially- massive amounts of electrical equipment, that also seems potentially problematic for Curtiss)

With the P-38 already being an Army favorite pre-war priority and earlier development timeframe combined with the simplicity of omitting the turbocharger (and relying on Curtiss's fairly good ram intake and ejector exhaust design -and the wing root fillets Lockheed had developed during the YP-38's testing), they should have been reasonably well suited to license-building a non-turbocharged P-38D derivative that outperformed the Lockheed equivalent below 15,000 ft and was somewhat cheaper. (and avoided the high-altitude engine, cockpit heating, and compressibility problems, thus being service-ready prior to the P-38F and more satisfactory in all-around operations) Comparing 9.6 supercharged (1480 hp WEP at ~10,000 ft) V-1710 powered P-38 vs the equivalent J model with no ejector exhaust and added intercooler drag (and weight of turbo installation) would have been interesting to see too. That aside from overreving and overboosting the 8.8 V-1710. (I'd imagine the P-38 could have come close to the P-51's speed on similar engines but with better climb and acceleration due to power/weight advantage)


----------



## kool kitty89 (May 5, 2016)

Shortround6 said:


> P-36/Hawk 75 production was running down in the Spring of 1940 with the P-40 replacing it on the production lines ( simple to do, early P-40s kept a very large amount of the basic P-36/Hawk 75 structure) but this means that to bring the P-36 back with a turbo (or even without) you either need more production space (and jigs/fixtures) or cut back on P-40 production. Chances of a turbo P-36 really doing better than a P-40 is going to depend on cowl technology and better turbo installations that don't really exist until some point or points in 1942 which means production planes won't show up in numbers until some time in 1943 at which point you have a 1200-1350hp machine trying to fight what kind of opponents?
> 
> There is an interesting set of drawings of the Hawk demonstrator with two stage supercharger here:
> Untitled Document
> ...


Missed this before.

The P&W Hawk 81 testbed for the (X)F4F-3's engine certainly had the cowl technology in play in 1940, and ahead of the game compared to Curtiss's own work on the XP-42.


I believe the P-36/Hawk 75 with the external intercooler was an earlier experiment using the less refined non-production version of the 2-stage supercharged twin-wasp and is quite obviously a converted Hawk 75 or early P-36 given the wheel fairing and lack of wing guns. (or taped-over blast tubes as with the Hawk 81 conversion)

Given the development timeline for the 2-stage R-1830 and V-1710-39, the P&W experimental 1940 installation should have been a serious consideration for displacing the P-40D/Hawk 87 of 1941 while not disrupting Tomahawk production. (and also better avoiding the initial shortage of 2-stage engines the Wildcat suffered)

Competing with F4F engines might have been an issue, but the various 2-speed single-stage R-1830s (and especially R-1820s) should have mostly compensated. (for some reason the R-1820-40 was only fitted experimentally to the F4F, perhaps due to higher volumes of 2-stage twin-wasps by the time a production installation would have been ready, but that engine should have had better altitude performance than the single-stage R-1830s or 1820s used on Wildcats and Martlets and close to that of the FM-2 -though without the low altitude water injection boost; I wish I had more detailed performance specifications for that engine, but all indications of its use in the F2A-2/3 point to exceptional altitude performance for the time)

A 2-speed R-2000 with (presumably) similar or better critical altitude to the 2-speed R-1830 examples of 1940/41 (around 14,000 ft in high gear for the Wildcat/Martlet) should be fairly useful as well, lacking 2-stage adaptations of that. (and probably better in most situations than the V1650-1 due to lower weight and similar or better power -and possibly increased fuel capacity in the space between the engine and cockpit)

The R-2600 on the Hawk airframe has been discussed to death, and even if shortening the Hawk 81's nose to correct CoG would have matched the R-2600 fairly well, the weight, diameter, and altitude performance combined with need of broader chord or 4-blade prop to avoid a larger diameter prop (and impractical landing gear extensions) all make it unattractive. (not to get into some of the development and reliability problems the R-2600 saw during the war -rusty cylinder liners and undersized carburetors among other things, at least in A-20 usage). The increase in drag and weight would also compromise range and all around usefulness for anything other than interception and short-range fighter-bomber duties. (might be a good competitor to the Typhoon, but that's about it ... maybe Fw 190A -but again, with similarly limited range) Besides, if Curtiss was going to make an R-2600 powered fighter, the XP-46 would have been the right time/place to do it. (and honestly, a new airframe optimized around the R-2600's strengths probably would've been better than the existing XP-46, though probably still shorter ranged than the P-40D/E, but certainly good for the interceptor capacity the XP-46 seemed to be targeting)


----------



## Shortround6 (May 5, 2016)

I was half joking with the P-37 pictures, but only half. A book on aircraft power plants published in 1943 estimated about 400lbs and about 10 cu.ft. of space were needed for a turbo installation on a 1000hp class engine. Book was written by a Packard test engineer. Granted it was not a restricted book and therefore wasn't giving any military secrets away during war time so it may have been a bit behind the state of the art. 

There was nothing mystical or magical about the Hawk 75/P-36. It was a fighter of it's time (1936-38, prototype first flew on 6 May 1935) and had wing loading of about 24lbs per sq ft for a gross weight of 5700lbs (average of the A and C) and well coordinated/harmonized controls, in fact better than a good many of it's contemporaries. 
The P-40 _should _have retained many of it's good characteristics except for the large increase in weight and perhaps minor CG shift. 

Any attempts to fit more powerful or more sophisticated engine setups, more operational equipment (protection) and more armament are going to follow the path of the P-40 in the degradation of flying characteristics. 
The Allison was NOT responsible for the increase of around 2000lb in gross weight. Any radial version equipped with the same fuel tanks, armor and bullet proof windscreen and the same armament is going to following very closely to the P-40 in weight and if you want "trick" engine installations (like 2 stage or turbos) then you are going to wind up within a few hundred pounds of the equivalent P-40 and suffer from having higher drag. P-36 had 22% higher drag than the XP-40 and the P & W test hack had 8% higher drag. A turbo plane would have had higher drag than the P & W Test Hack due to larger intercooler (let alone adding guns).

There seems to have been something a bit out of wack with the Supercharger on the R-1830 as power increased only slightly going from 2550rpm to 2700rpm and a number of altitudes during propeller tests. Please note that changing from a 7.15 gear to a 8.0 gear on the P-36 changed the engine from 1050hp at 6500ft to 950hp at 14,300ft but cost 100hp at take-off. Two speed superchargers were about take-off power as much as they were about trying for any real altitude rating. C-47s flying the hump got two stage superchargers like the F4F. 

You can forget about the R-2000 as a fighter engine. P & W _may _have used the same supercharger as the R-1830. while take-off power jumped quite a bit, power at altitude didn't follow suit. Early versions with 1350hp for take-off were rated at 1000hp at 16,000ft (at best) and in 1942 that is nowhere near good enough. Later versions rated at 1450hp for take off got rated at 1100hp at 16,000ft (at 2700rpm) but that usually required a few modifications, like different bearings (plain instead of roller) and with a 2 speed R-2000 weighing about 1600lbs it pretty well cancels out the weight of the radiators and coolant of the Allison.
A two speed R-1830 could be good for 1200hp at take-off, 1200hp at 4900ft MIlitary in low gear and 1050hp at 13100ft in high gear. (all 2700rpm) while weighing 1495lbs. The R-2000s were good for either 1350hp at 2000ft low gear or 1450hp at 1000ft in low gear depending on take-off rating. 

We have no data on the breakdown rate of the FN guns. There were well over a dozen attempts to develop high rate of fire US .50 guns and while the US requirements may well have been too stringent a few of the attempts failed miserably well before getting even 1/5 of the required rounds fired. Some failures were rather simple like broken extractor hook but I believe in at least one case the gun was wrecked. Placement of guns _may_ have to do with other issues than rate of fire and "concentration" of fire. Like gun heating or design of the wings, adding gun bays that will hold .50 cal Brownings and ammo to existing structures may be more than some design teams wanted to deal with. Japaneses Navy however added big Brownings in the wing of the Zero.

Reactions: Like Like:
1 | Like List reactions


----------



## Shortround6 (May 5, 2016)

kool kitty89 said:


> Missed this before.
> 
> The P&W Hawk 81 testbed for the (X)F4F-3's engine certainly had the cowl technology in play in 1940, and ahead of the game compared to Curtiss's own work on the XP-42.



The test hack set it's speed record in Sept of 1942 I believe. Along time away from 1940. How long it took P & W to get to that point I don't know by they may have had the plane/airframe for over two years.


----------



## Shortround6 (May 5, 2016)

kool kitty89 said:


> Missed this before.
> 
> The P&W Hawk 81 testbed for the (X)F4F-3's engine certainly had the cowl technology in play in 1940, and ahead of the game compared to Curtiss's own work on the XP-42.



Addressed above.




> believe the P-36/Hawk 75 with the external intercooler was an earlier experiment using the less refined non-production version of the 2-stage supercharged twin-wasp and is quite obviously a converted Hawk 75 or early P-36 given the wheel fairing and lack of wing guns. (or taped-over blast tubes as with the Hawk 81 conversion)



Quite right, the plane in question was at the 1939 fighter trials along with two experimental Seversky's one with the same mechanical two stage supercharger used in the Curtiss and and the other with a turbo R-1930 which lead to the P-43.



> Given the development timeline for the 2-stage R-1830 and V-1710-39, the P&W experimental 1940 installation should have been a serious consideration for displacing the P-40D/Hawk 87 of 1941 while not disrupting Tomahawk production. (and also better avoiding the initial shortage of 2-stage engines the Wildcat suffered)



The installation was actually late 1938/early 1939 for the Curtiss and Seversky. While P & W got the Hawk 81 airframe in 1940 the picture above shows the plane in mid to late 1942. the engine was listed as the SSC7-G which was equivalent to the R-1830-86 used in the F4F-4 which doesn't show up until Dec of 1941, The earlier R-1830-76 had some operating troubles as the impellers/airflow had some miss matches that caused rumbling in the intake ducts (rapid pulses/shock waves as one impeller stalled or choked)



> Competing with F4F engines might have been an issue, but the various 2-speed single-stage R-1830s (and especially R-1820s) should have mostly compensated. (for some reason the R-1820-40 was only fitted experimentally to the F4F, perhaps due to higher volumes of 2-stage twin-wasps by the time a production installation would have been ready, but that engine should have had better altitude performance than the single-stage R-1830s or 1820s used on Wildcats and Martlets and close to that of the FM-2 -though without the low altitude water injection boost; I wish I had more detailed performance specifications for that engine, but all indications of its use in the F2A-2/3 point to exceptional altitude performance for the time)



The "exceptional altitude performance" was actually pretty mediocre. Military power was 1200hp at a whopping 1800ft in low gear and 1000hp at 13,500ft in high gear. It was the standard engine in Martlet Is and IVs. Please compare to the two speed engine in the F4F-3A or Martlet II & III. That R-1830 was good for 1200hp at 4900ft and 1000hp at 14500ft.

Edit, Lets not confuse cause and effect. The F2A-2/3 was around 900/600lb lighter than an F4F-3, difference between a Cyclone powered Martlet and a F2A is less but ammunition and fuel loads need to be taken into account. 

The Engine used in the FM-2 had about the same relation to the engine used in the Martlet I & IV as the R-2800 "C" did to the R-2800"B". New crankcase, new crank, new cylinders with a new system of making the fins and new cylinder heads. Quite possibly a new supercharger? 1300hp at 4000ft in low blower and 1000hp at 17000ft in high blower. Needed a stronger crankshaft in order to be rated at 1350hp for take-off.



> A 2-speed R-2000 with (presumably) similar or better critical altitude to the 2-speed R-1830 examples of 1940/41 (around 14,000 ft in high gear for the Wildcat/Martlet) should be fairly useful as well, lacking 2-stage adaptations of that. (and probably better in most situations than the V1650-1 due to lower weight and similar or better power -and possibly increased fuel capacity in the space between the engine and cockpit)



Covered in earlier post the R-2000 is both late (production _starts Dec 1941)_ and lacking in high altitude performance. Some of the two speed early (1350hp take-off) R-2000s were rated at 1100hp at 16,000ft Military and others at 1000hp at 14,000ft "Normal" just like some R-1830s only had a military rating in low blower. No Military rating in high blower.


----------



## wuzak (May 5, 2016)

kool kitty89 said:


> I'd thought the Merlin intercooler was fed with air from the first supercharger stage and then fed into the 2nd stage ... in spite of seeing cut-away drawings to the contrary. Somehow I'd failed to realize those all depicted aftercoolers.



Yes, the big heat exchanger you can see on the two stage Merlins and Griffons is an aftercooler. For referemce, the supercharger housing contained cooling water passages around the air flow path from 1st to 2nd stage compressors, so it had a small degree of intercooling.




kool kitty89 said:


> The 2-stage Allison (no intercooler/aftercooler at all) also moved the carburetor to behind the aux stage, unlike P&W configurations which seem to treat the Aux stage more like a turbocharger with the carb still mounted to the inlet of the integral stage. (which honestly is how I'd assumed the Allison configuration worked too)



Most production 2 stage Allisons had the carburettor mounted on the engine stage supercharger.

The V-1710's auxiliary supercharger was driven via a fluid coupling which meant that it operated much more like a turbocharger than the P&W systems, which used distinct gear ratios - HI, LO and Neutral. P&W engines tended to have an intercooler between the stages.




kool kitty89 said:


> The Merlin's aftercooler arrangement would also explain why some post-war examples suffered from overcooling issues. (an intercooler arrangement should at least partially avoid this given the 2nd stage will be heating and re-mixing any fuel that's condensed in the intercooler rather than staying as condensed droplets in the aftercooler -granted, the P-38J had some overcooling issues as well)



Over-cooling would most likely be a problem of the radiator airflow control.


----------



## Shortround6 (May 6, 2016)

Over cooling was a problem in low power cruise conditions, some post war Merlins (especially commercial) were fitted with charge heaters in the intake tract (if not in the heat exchanger box) to keep the mixture warm enough to prevent puddling or fuel condensation. 
Not a P-38/Allison problem alone


----------



## Shortround6 (May 6, 2016)

kool kitty89 said:


> The P&W Hawk 81 (along with apparently all Hawk 75s) omitted a spinner from the propeller. This should reduce drag further, especially at high speed, but for some reason most American aircraft omitted spinners on radial engines.
> 
> This has already come up in this thread:
> Drag of radial-engined fighters
> ...



Spinners were actually used for several different purposes.
one was to 'streamline" (shroud) the prop hub and blade roots which aren't very streamline as they rotate.





two was to sometimes assist in ground cooling. sounds counter intuitive but is true. Look at where the blades start to get an airfoil shape. that area of the cowl opening is going to have high pressure while in the inner blade root area and hub is going to be lower pressure. it was possible (depending on internal baffles and exit doors/ducts) for the airflow around the prop hub to reversed and air flowing forward around the prop hub while the plane was stationary. A few planes actually used a flat disc behind the prop to prevent this.




and yes the spinner was often used in an attempt to streamline the engine installation. However on many radials only about 10% of the airflow headed towards the engine was actually needed to cool it (depends on engine and speed) the other 90% has to routed around the cowling. At speed you will get a high pressure area in front of the engine that can extend in front of the propeller hub. a lot of the air was routed around the cowling by the shape of the cowling itself and this high pressure area.
I can't find any at the moment but there are photos of engine installations in wind tunnels using smoke that show this (a poor set can be found at Access forbidden!

Link does seem to work, in any case it is NACA report no 662, "Design of N.A.C.A. cowlings for radial air cooled engines."

Spinner design without good wind tunnel work was mostly guess work (or worked only at certain speeds/conditions) and use of spinners was by no means a universal cure for either drag or cooling problems.


----------



## kool kitty89 (May 8, 2016)

Shortround6 said:


> Spinners were actually used for several different purposes.
> one was to 'streamline" (shroud) the prop hub and blade roots which aren't very streamline as they rotate.
> 
> two was to sometimes assist in ground cooling. sounds counter intuitive but is true. Look at where the blades start to get an airfoil shape. that area of the cowl opening is going to have high pressure while in the inner blade root area and hub is going to be lower pressure. it was possible (depending on internal baffles and exit doors/ducts) for the airflow around the prop hub to reversed and air flowing forward around the prop hub while the plane was stationary. A few planes actually used a flat disc behind the prop to prevent this.


The introduction of cooling cuffs on some propellers (particularly some curtiss-electric ones) would make propeller blade roots being exposed more useful (especially with a cowling designed for it), but otherwise yes, spinners directing airflow outward and towards the hottest portion of the cylinders would be the most useful. (the P&W cowling actually looks like it would fit rather well with cooling cuffs OR a spinner, either way avoiding the drag and turbulence around the blade roots and hub and -in the spinner's case- potentially creating more of a ram airflow effect between the spinner and cowling)



> Spinner design without good wind tunnel work was mostly guess work (or worked only at certain speeds/conditions) and use of spinners was by no means a universal cure for either drag or cooling problems.


Curtiss's work with the XP-42 trials certainly seemed to show this, among other things. (particularly when cuffs and tight cowlings come into play -in some cases more useful than spinners+fans+tight cowlings and usually mechanically simpler)

The same should actually be true for annular radiator design for inline engines ... the right cowling (especially with cooling cuffs) might merit a smaller (or no) spinner than German examples used during the war. (though I'd imagine the conical hub covers at least reduced turbulent flow slightly compared to the clunkier bare hubs used in some cases)





Shortround6 said:


> The test hack set it's speed record in Sept of 1942 I believe. Along time away from 1940. How long it took P & W to get to that point I don't know by they may have had the plane/airframe for over two years.


Ah thanks, that makes some sense. So it was more in line with the ongoing XP-42 program and potentially somewhat related to it.

The P&W example also features ram intakes for the carb and oil/intercooler that the P-36 never featured (though F2A did, and twin-wasp wildcats had ram carb inlets while Cyclone ones seem not to)





Shortround6 said:


> I was half joking with the P-37 pictures, but only half. A book on aircraft power plants published in 1943 estimated about 400lbs and about 10 cu.ft. of space were needed for a turbo installation on a 1000hp class engine. Book was written by a Packard test engineer. Granted it was not a restricted book and therefore wasn't giving any military secrets away during war time so it may have been a bit behind the state of the art.
> 
> There was nothing mystical or magical about the Hawk 75/P-36. It was a fighter of it's time (1936-38, prototype first flew on 6 May 1935) and had wing loading of about 24lbs per sq ft for a gross weight of 5700lbs (average of the A and C) and well coordinated/harmonized controls, in fact better than a good many of it's contemporaries.
> The P-40 _should _have retained many of it's good characteristics except for the large increase in weight and perhaps minor CG shift.


There's also the one benefit from higher weight: dive acceleration (which was one of the P-36's weak points, particularly noted in British testing of the Hawk 75) which actually in some ways better fit the superior high-speed control surface response and roll rates compared to most others (particularly most non-American fighters).

Compromises other than just engine design would need to be made to keep weight down though, yes, particularly in the list of changes the Hawk 87 saw (the P-40E gained nearly 1000 lbs empty over a P-40B, though the P-40C had already gained some and the D/E radiator likely added weight and drag on its own, there were other structure changes, the heavier armament, increased self-sealing fuel tank capacity over the P-40C, among other things). If they could have taken the Hawk 81 airframe and introduced a new wing with 4 .50 cal guns without substantial changes in weight, it would have been much more competitive for the time. (either with the Allison or with the 2-stage R-1830).


On the general note of the P-37/40 though, I stumbled on these pages:
Curtiss P-40 Warhawk: One of WW II's Most Famous Fighters | HistoryNet
Military Aviation Archives - P-40 Warhawk Historical Development Photo Set
http://www.aerofiles.com/curtiss-yp37.jpg

I'd forgotten the original XP-40 conversion used an aft ventral radiator like that and ducted (non-ejector) exhaust ... and lacked a ram intake for the carburetor. It almost looks like portions of the conversion were for an alternate turbocharger installation compared to the YP-37. (or rather, alternate intercooler+radiator installation given the nose-mounted turbo didn't take up much space -though in the actual XP-40 the oil cooler appears to have taken the place of the turbo in a location rather similar to the eventual production Hawk 81 variants; regardless of there was any relation to an alternate turbo installation, the forward turbo and aft radiator arrangement would rather mirror the P-38's configuration, more so if wing leading edge intercooling had been attempted)

The lack of ejector exhausts, ram intake, and reduced power of the initial test engines obviously explain the modest performance of the initial XP-40 compared to the eventual V-1710-33 configuration.

Additionally, the XP-40K's belly radiator appears to be embedded between the landing gear pod protrusions and thus probably doesn't compromise the wing center section fuel capacity. (though at a glance, I'd think extending the radiator intakes further down the nose for better ram performance and possibly lower drag at high speeds would be better -which may have been what the XP-40Q eventually did with its small chin intake, though it moved the oil coolers to the wings whereas the XP-40K appears to leave the oil cooler between the two coolant radiators and retain its separate small ventral outlet used on all production P-40s) It also doesn't look like clearance in the belly is negatively impacted as far as the bomb/drop tank rack position is concerned.




> You can forget about the R-2000 as a fighter engine. P & W _may _have used the same supercharger as the R-1830. while take-off power jumped quite a bit, power at altitude didn't follow suit. Early versions with 1350hp for take-off were rated at 1000hp at 16,000ft (at best) and in 1942 that is nowhere near good enough. Later versions rated at 1450hp for take off got rated at 1100hp at 16,000ft (at 2700rpm) but that usually required a few modifications, like different bearings (plain instead of roller) and with a 2 speed R-2000 weighing about 1600lbs it pretty well cancels out the weight of the radiators and coolant of the Allison.
> A two speed R-1830 could be good for 1200hp at take-off, 1200hp at 4900ft MIlitary in low gear and 1050hp at 13100ft in high gear. (all 2700rpm) while weighing 1495lbs. The R-2000s were good for either 1350hp at 2000ft low gear or 1450hp at 1000ft in low gear depending on take-off rating.


That actually makes the R-2000 sound worse than the R-2600, which obviously wasn't a stellar option either. (though I suppose somewhat makes sense given Wright's single-stage superchargers tended to fare a bit better than P&W's even with the R-2600's development progressing less smoothly than the R-1830's)

On the note of the R-2600: the issue of larger propellers and longer landing gear (or clearance issues on existing gear) has come up in the past and looking at the P&W H81 test 'hack' a bit more closely, its propeller does appear to be a fair bit closer to ground level than the P-40's or P-36's, particularly taking the longer nose (than P-36) into account. This also might have been a bit of a bonus for the higher thrust line of the F series Allison (and Merlin) as it raised ground clearance and allowed a slightly larger propeller without making take-off or landing clearance trickier. (the P&W example looks like it may have required near 3-point landing conditions somewhat like large-prop P-47s)



> We have no data on the breakdown rate of the FN guns. There were well over a dozen attempts to develop high rate of fire US .50 guns and while the US requirements may well have been too stringent a few of the attempts failed miserably well before getting even 1/5 of the required rounds fired. Some failures were rather simple like broken extractor hook but I believe in at least one case the gun was wrecked. Placement of guns _may_ have to do with other issues than rate of fire and "concentration" of fire. Like gun heating or design of the wings, adding gun bays that will hold .50 cal Brownings and ammo to existing structures may be more than some design teams wanted to deal with. Japaneses Navy however added big Brownings in the wing of the Zero.


The Zero had been designed to carry Oerlikon FFF or FFL type guns prior to that, so the structure was there to some extent, even if API blowback made for lower recoil (more so for the FFF).

I do wonder if the P40D and E wing redesign played a significant role in the weight gain over the P-40B and C. The P-40D had only been fitted with 4 guns but had wings designed in mind for 4 20 mm hispanos while the P-40E adapted that to 6 .50s. Designing more tightly around the more balanced (especially for 1941/42) 4x .50 armament might have saved some weight and design modification complexity over the wings they ended up using. (or it wasn't a major issue and weight increase was from the fuselage structure and equipment changes instead)

The synchronization mechanism itself added weight and complexity, so in theory, deleting them might actually reduce weight in a 4-gun wing arrangement or been very close to the overall weight of the 2x 50s and 4x .30s.

Deletion of the guns and ammunition boxes should have added enough space for a small reserve fuel tank to be added too, but the P-40D seems to have re-distributed space differently. (a radial engine installation would -as I noted with the P&W testbed- left more open space for internal storage there and at a location close to CoG, good for fuel, and even if the intercooler and oil cooler(s) comprised the lower portion of that compartment, there should be significant room for fuel)






Shortround6 said:


> The installation was actually late 1938/early 1939 for the Curtiss and Seversky. While P & W got the Hawk 81 airframe in 1940 the picture above shows the plane in mid to late 1942. the engine was listed as the SSC7-G which was equivalent to the R-1830-86 used in the F4F-4 which doesn't show up until Dec of 1941, The earlier R-1830-76 had some operating troubles as the impellers/airflow had some miss matches that caused rumbling in the intake ducts (rapid pulses/shock waves as one impeller stalled or choked)


Sounds somewhat like some of the difficulties Allison was dealing with early on in their auxiliary supercharger development (and some of the problems you mentioned with mix-matched impellers and diffusers, pressure ratio, mass flow, etc).

That actually starts making the R-2600 look better than the 2-stage R-1830 too (on top of the R-2000 as mentioned above). I forget how big the weight difference is from an R-2600-3 (or -5, I know the -8 was heavier, more powerful, and later to production) and R-1830-76 is though. (if we're comparing models in production in 1940 or earlier) No intercooler to deal with either, but added diameter and drag (both from frontal area and cooling work required -ie cowling might be similar in diameter to an R-1820 Wildcat or Hawk 75, but cooling capacity would need to be greater). It might have been an interesting test-fit on the Wildcat (probably requiring yet a larger tail though) but for Curtiss in 1940 they might have more luck with a more heavily modified airframe than a Hawk 81 derivative. (the H81 airframe might have been more suitable than some discussions have concluded, but I think the best case would have been designing the XP-46 project around the R-2600 rather than the V-1710 at all ... in parallel with the XP-40D/H87 development)

The R-2600 would look even worse if Allison development/testing had been more aggressive, though. Had the V-1710-39 seen WEP ratings at introduction with the P-40D or E (particularly if emergency power RPM was raised to 3200-3400 RPM -with correspondingly higher supercharger speed and altitude performance) it wouldn't be much of a contest at all. Though I suppose Allison WER usage could have been a bit more freely implemented (or operationally tested) had there been more engines to spare relative to aircraft demanding them (more spare engines in the field to work with -particularly important compared to British engine repair/replacement.manufacturing much closer to the front lines). So in that sense, manufacturing both R-2600 and V-1710 powered Curtiss fighters might have made at least some sense.

I list the 3400 RPM figure limit there given that tends to be the upper end of structural ratings for propellers coupled with 2:1 reduction gearing (1700 RPM prop rotation) with genuine risk of failure much beyond that. (though hitting supersonic tip speeds under the right altitude and forward velocity could make that speed unattractive short of clipping prop tips -as some air racers take to doing) 3400 RPM is also proportional to the overrev engine type test conditions for the E and F series V-1710 vs the older C series. (3600 vs 4100 is a 13.9% increase, and applying that to the 3000 RPM nominal take-off/military rating of the C series results in 3417 RPM ... so round down to 3400 RPM and there you go) At 3400 RPM and 8.8 supercharger ratio, the impeller is also turning faster than 9.6 ratio at 3000 engine RPM, so added precautions would need to be considered there as well. (it's equivalent to 9.97:1 supercharger ratio with the exception the cylinders will be pulling more air at 3400 RPM than 3000 RPM so manifold pressures and critical altitudes wouldn't quite relate to that alone either) It also might have been feasible to raise the maximum continuous rating to 3000 RPM (at correspondingly lower manifold pressure). I still suspect experiences with the C series engines (especially operationally) led to overly conservative official ratings though, more so than just lack of funding and considerations for spare engines. (the C series seemed far less conservatively rated relative to its absolute limits and could take far less abuse without failure or severely reduced longevity ... though likely still more tolerant to overspeeding than most or perhaps all other aircraft engines of 1940/41)



> The "exceptional altitude performance" was actually pretty mediocre. Military power was 1200hp at a whopping 1800ft in low gear and 1000hp at 13,500ft in high gear. It was the standard engine in Martlet Is and IVs. Please compare to the two speed engine in the F4F-3A or Martlet II & III. That R-1830 was good for 1200hp at 4900ft and 1000hp at 14500ft.
> 
> Edit, Lets not confuse cause and effect. The F2A-2/3 was around 900/600lb lighter than an F4F-3, difference between a Cyclone powered Martlet and a F2A is less but ammunition and fuel loads need to be taken into account.
> 
> ...



The F2A-3's empty weight was also almost identical to that of the F4F-3 from what I've seen, though loaded weights might vary more. (F2A-2 and even B.339 were lighter though -the self-sealing material added to the Buffalo Mk.I apparently not adding much compared to the F2A-3's fusealage extensions and new self-sealing tanks)

I suspect the R-1820-40's performance is closer to the R-1820-56's supercharger performance (but with engine RPM, manifold pressure, and power reduced to operating levels of the older design more like comparing a V-1710-33 to a V-1710-73). The comparison would be much easier if I had better data on the -40 to go on, particularly had there ever been a production F4F to use it.


On the note of the poorer (but still decent) performing single-stage 2-speed R-1830. It probably wouldn't have been a great option for the Hawk (at least to displace the existing Tomahawk) but might have better matched the F2A than it did the F4F given the smaller size and lower drag of the Buffalo. (the R-1830-76 or -86's added weight, length, and intercooling requirement might have compromised too much by comparison, particularly given Brewester's degrading management situation)


----------



## Shortround6 (May 8, 2016)

For cooling a "ram" intake may _not _be what is wanted. 
Airflow over the engine cooling fins or through radiator/oil cooler cores is subject to the same drag considerations as the outside of the airframe. Drag goes up with the square of the speed. _IF _you can slow the speed of the air through the cooling fins or radiator/oil cooler you can get a substantial reduction in cooling drag. Hi speed air also doesn't allow for much heat transfer. 300mph airflow is 440fps and the time the air is in contact with the cooling fins is measured in thousands of a second. Most radiators/oil cooler cores were much longer than the fins on an air cooled cylinder. air flowed through tubes in the cooler.




Granted smooth airflow is better than turbulent airflow which is why some aircraft used airflow splitters to get around using boundary air. 
P-51 had a low drag set up _NOT _because it used a ram intake or airflow splitter but because it used a whacking big radiator. 




incoming air was allowed to expand in the duct slowing it down before it hit the radiator/intercooler matrix. The large radiator allowed for a small pressure drop as the air went through it and then the converging exit duct speed the air back up. There is a lot of argument about wither or not they actually got thrust out of it but it was at the very least one of the lowest drag radiator arrangements around. A smaller radiator core and higher air speed through the core would have a much higher pressure drop (drag). 
AN air cooled engine should follow the same principle. Take in the amount of air needed ( and amount of air taken in was actually governed by the the amount of air allowed to leave through the exit doors/flaps) slow it down _before _it hits the engine cooling fins and baffles and then allow it to leave with the least turbulence and changes in air pressure. 

I would also note that "ram" air is *NOT *free. RR figured that the air intake on a Hurricane II had over 25hp worth of drag anywhere from 15,000 to 25,000ft ( peak was 32.8hp at 20,000ft at 340mph true.) This was what it took to compress the air _before_ it hit the carb and provide the ram effect and the drag in the internal duct.

Ram air intakes for combustion air make sense as you are trading drag for extra pressure at the carb (or engine intake) for higher altitude performance. Designing intakes for radiators/oil coolers/engine cooling fins that deliver higher than "normal" pressure in flight seems to be counter productive.

Cooling on the ground can be a whole different thing. Most if not all of the B-29 cooling problems were while taxing, taking off or climbing while heavily loaded. In any case when cooling loads are the most severe the plane has the least amount of airflow due to the forward motion of the plane. Ram inlets are going to nothing (or darn little) in these conditions just like many planes show differences of thousands of feet in critical altitude between level flight and climb as at climbing speed the RAM effect is not that great.


----------



## Shortround6 (May 8, 2016)

kool kitty89 said:


> Compromises other than just engine design would need to be made to keep weight down though, yes, particularly in the list of changes the Hawk 87 saw (the P-40E gained nearly 1000 lbs empty over a P-40B, though the P-40C had already gained some and the D/E radiator likely added weight and drag on its own, there were other structure changes, the heavier armament, increased self-sealing fuel tank capacity over the P-40C, among other things). If they could have taken the Hawk 81 airframe and introduced a new wing with 4 .50 cal guns without substantial changes in weight, it would have been much more competitive for the time. (either with the Allison or with the 2-stage R-1830).
> 
> 
> I do wonder if the P40D and E wing redesign played a significant role in the weight gain over the P-40B and C. The P-40D had only been fitted with 4 guns but had wings designed in mind for 4 20 mm hispanos while the P-40E adapted that to 6 .50s. Designing more tightly around the more balanced (especially for 1941/42) 4x .50 armament might have saved some weight and design modification complexity over the wings they ended up using. (or it wasn't a major issue and weight increase was from the fuselage structure and equipment changes instead)



From "America's Hundred Thousand" the empty weight of the P-40E (no guns and some other stuff) was about 450lbs more than a P-40B. of which about 100lbs was in the wing structure. Difference between P-40C and P-40E was about 300lbs. Empty equipped was about 710lbs between the "B" and "E". Of course that is in part due to the 480lbs worth of .50 cal guns in the "E" (but not including ammo, that was another 423lbs) 
The "D" was designed to hold a _single _20mm cannon _under _the wing. I don't know if it was supposed to keep both .50s in the wing or only one if the 20mm was fitted. 
We have a slight problem with the "more balanced (especially for 1941/42) 4x .50 armament might have saved...." as the P-40Ds were ordered in May of 1940. I don't know when in 1940 the US got the rate of fire of un-synchronized .50 cal guns up from 600rpm to 800-850rpm. Please note that this is about 11 months before the first P-40C flies at the Curtiss factory. 
A few dates to show how much over lap was going on ( and how little time there was for other intermediate solutions).
June 10th 1940, sees the XP-46 canceled in favor of the H87A 
Last P-40B delivered April 24th 1941.
First P-40C delivered April 30th 1941.
First flight of XP-40F with Merlin engine was June 30th 1941.
First production P-40D delivered to US army July 11th of 1941.
Curtiss starts delivering P-40Es Aug 29th, 1941. 

Granted leaving a pair of the .50s out in order to combat the weight escalation might have been a good idea but designing the "new" wing around only 4 guns bays might not have given the firepower desired at the *start* of the project. 





> The synchronization mechanism itself added weight and complexity, so in theory, deleting them might actually reduce weight in a 4-gun wing arrangement or been very close to the overall weight of the 2x 50s and 4x .30s.
> 
> Deletion of the guns and ammunition boxes should have added enough space for a small reserve fuel tank to be added too, but the P-40D seems to have re-distributed space differently. (a radial engine installation would -as I noted with the P&W testbed- left more open space for internal storage there and at a location close to CoG, good for fuel, and even if the intercooler and oil cooler(s) comprised the lower portion of that compartment, there should be significant room for fuel)



The Synchronizers are rather negligible. About 3-4 lbs each on the engine. Balanced out pretty well by the hydraulic charging systems needed for the wing guns. 
weight of two .50s and four .30s was 245lbs. weight of four .50s was 314lbs. problem was in part due to ammo. P-40C carried a ridiculous 380 rounds for each fuselage .50 cal. Weight was 228lbs. Weight of the 2000 rounds in the wings for the .30s was 127.4lbs. weight of 235 rounds per gun for 4 wing guns was 282lbs. 

I would also note that you have to be a bit careful as to what you want to put where, The long nosed P-40s had the oil tank behind the pilot while the D,E,K,M,N had the oil tank in cowl ahead of the instrument panel. Perhaps the Merlin versions had it there too. 
As oil was a consumable (13 gallons was normal while 18 gallons were carried when drop tanks were used) some consideration as the CG should be taken into consideration. 



> That actually starts making the R-2600 look better than the 2-stage R-1830 too (on top of the R-2000 as mentioned above). I forget how big the weight difference is from an R-2600-3 (or -5, I know the -8 was heavier, more powerful, and later to production) and R-1830-76 is though. (if we're comparing models in production in 1940 or earlier) No intercooler to deal with either, but added diameter and drag (both from frontal area and cooling work required -ie cowling might be similar in diameter to an R-1820 Wildcat or Hawk 75, but cooling capacity would need to be greater).


R-2600 is roughly 350-400lbs heavier than the two stage R-1830 and that is for the bare engine. you have 1400hp Military at 12,700ft. By the time you fit the bigger prop and all the bits and pieces it its going to be 5-600lbs heavier. A P-40's cooling system for the V-12s weighed about 300lbs. Allison + radiators and coolant was 300lbs lighter than an R-2600. 

P-40s had trouble with stability as engine power went up requiring a 20in extension in the rear fuselage (which still wasn't a full cure) sticking a 1600hp engine for take-off and a bigger prop is really going give a beast to handle without extensive rear fuselage modifications. 



> The R-2600 would look even worse if Allison development/testing had been more aggressive, though. Had the V-1710-39 seen WEP ratings at introduction with the P-40D or E (particularly if emergency power RPM was raised to 3200-3400 RPM -with correspondingly higher supercharger speed and altitude performance) it wouldn't be much of a contest at all. Though I suppose Allison WER usage could have been a bit more freely implemented (or operationally tested) had there been more engines to spare relative to aircraft demanding them (more spare engines in the field to work with -particularly important compared to British engine repair/replacement.manufacturing much closer to the front lines). So in that sense, manufacturing both R-2600 and V-1710 powered Curtiss fighters might have made at least some sense.



While the P-40 carried a decent (but not great) amount of fuel for it's size sticking an R-2600 on it is really going to create problems. A R-2600 could suck down 2 1/2 gallons a minute at max continuous let alone at full power. Through in the fact that due to the higher drag it is going to use more fuel even at cruising speeds than the Allison. A P-36 needed more power to fly the same speeds than an early P40. 



> The comparison would be much easier if I had better data on the -40 to go on, particularly had there ever been a production F4F to use it


.
There was a production F4F that used it, it was called either a Martlet I or Martlet IV (both used Cyclone R-1820-G205 engines, and there wasn't that much to choose between the R-1820-G205 versions)


----------



## Shortround6 (May 9, 2016)

Some data from Mike Williams site concerning the P-36, the P-40B and the P-40D that may be of interest.

At 5000ft using max power
Plane..........power..................speed
P-36A...........1045...................280
P-40B...........1085...................319
P-40D...........1150...................326

At 15,000ft at about the same speed
Plane.............power...............speed
P-36A.............845..................292
P-40B.............600..................286
P-40D.............635..................290

At 15,000ft using max power
Plane.............power.............speed
P-36A.............845................292
P-40B............1090...............352
P-40D............1085...............354

Weights were normal gross (?? full gas and oil, no mention of ammo) so 5650lbs ??? for the P-36A and 6,835lbs for the P-40B and 7740lbs for the P-40D.

From this we can see the much higher drag of the radial engine _at the time in question. _
We can also see that the _chin _radiator on the P-40D and later had so little difference from the pointy nose P-40s as to be insignificant.
In fact the P-40D _might_ be just a shade cleaner than the P-40B but that could be due to the gun installation or some other factor. Or using two different P-40Bs and Ds the actual difference in speed might be reversed?

Using the cube root rule it would take a plane with the _same _drag as the P-36A 1648hp to equal the speed of the P-40D at 5,000ft.

I will grant you that the P-40B and D were getting a boost from exhaust thrust that the P-36 was not but it is going take one tricky radial engine installation to come close to the standard P-40s. Of course they were also much heavier creating more induced drag.

Adding 1000-2000lbs to the P-36 in fancier radial (two stage/turbo/R-2600) protection, armament and beefed up structure (a 7300lb plane which is splitting the difference between a P-40B and D) would have an ultimate load factor of 9.36 if not beefed up from a standard P-36 structure, is going to leave you with a plane that is not really going to perform much different than a regular P-40.
Or perhaps it trades worse performance down low for better performance at altitude depending on exact engine.

edit: I would add that a test of a P-43 (plane had 250lb of armament which means???) gave speeds at 15,000ft of 339mph using 1200hp, 328 using 1100hp and 300mph using 840hp.

Reactions: Like Like:
2 | Like List reactions


----------



## tomo pauk (May 10, 2016)

Could we arrive at some rate of climb estimates for different plausible powerplants, feturing P-36/P-40 as base?
Eg. the R-2600 powered P-40 (8100-8200 lbs?) vs. Fw 190A-1 (3780 kg clean, or ~8330 lbs) or A-2 (3855 - 3978 kg, depending whether MG FFM is installed or not, clean; 8500-8770 lbs)? Granted, the Fw 190 has less drag, but also greater wing loading, power is 1380 PS at 4.6 km (1341 HP at 15100 ft, 3 min, vs. 1300 HP at 15100 ft, 5 min). 
Also compared with historical P-40 in 1941/42?


----------



## rinkol (May 10, 2016)

kool kitty89 said:


> Turbo controls early-war were also less than satisfactory, both confusing and far from foolproof with lack of features like automatic turbo RPM limiting. (no overrev protection, and this resulted in the majority of catastrophic failures or exploding turbochargers)



Note that a multi-engine plane, such as the B-17, had a crew that was large enough to allow one of the crew members to carefully monitor the operation of the turbosuperchargers. Also, the engines in such a plane would operate under relatively constant conditions, thus simplifying the control issues.

It might also be noted that the B-17 had priority for the turbochargers - this was clearly an application where the performance of the plane was dramatically increased, even if, as was found later, it was still insufficient to provide immunity to interceptors.

Robert


----------



## Shortround6 (May 10, 2016)

tomo pauk said:


> Could we arrive at some rate of climb estimates for different plausible powerplants, feturing P-36/P-40 as base?
> Eg. the R-2600 powered P-40 (8100-8200 lbs?) vs. Fw 190A-1 (3780 kg clean, or ~8330 lbs) or A-2 (3855 - 3978 kg, depending whether MG FFM is installed or not, clean; 8500-8770 lbs)? Granted, the Fw 190 has less drag, but also greater wing loading, power is 1380 PS at 4.6 km (1341 HP at 15100 ft, 3 min, vs. 1300 HP at 15100 ft, 5 min).
> Also compared with historical P-40 in 1941/42?



A few things make this much more complicated.
One is figuring out the surplus power available for climb after figuring out the power needed for flying level at best climb speed and then figuring the extra drag after the plane points it's nose high for the climb, flight path is NOT in line with the wing but the wing is operating at several degrees higher angle of attack (or more than several) than flying level at the same speed. A simple comparison of wing loading takes none of this into account and in fact sometimes a higher wing loading plane with less drag can out climb a low wing loading (but high drag) airplane. 

Getting a 8100-8200 lbs R-2600 powered P-40 airframe is going to be quite a trick also. The R-2600 weighed around 300lbs more than an Allison engine *plus *radiators and coolant. I dare say you might need a larger oil system for the R-2600 and of course the larger prop. 

What can you leave out of the P-40 to get the weight back down to 81-8200lbs? 

BTW the gross weights for the P-40 _without_ center drop tank were 8250-60lb for an E, 8570lbs for an F, 8520lbs for a K, 8120lbs for an L and 8350lbs for a late model N. The *L* was a stripper model with only 4 guns, a fuel tank taken out (saved about 100lbs just in tank weight + 168lbs of fuel) and a few other things. Production planes could vary some what (government would take planes about over 100lbs overweight but charge penalties). 

Finding performance numbers for the L version would be a good start.


----------



## tomo pauk (May 10, 2016)

Indeed, I've took a peek in The Book, and listed P-40s with 6 HMGs are heavy beasts. So we'd probaby have the R-2600 powered P-40, 6 HMGs, at 8500-8600 lbs, or thereabout as with Fw 190A-2/A-3.


----------



## Shortround6 (May 10, 2016)

And then you have a higher weight plane, with more drag than the Fw-190 and with arguably less range. Range is going to be real problem as while the P-40 was no long range escort it did have around 25% more internal capacity than a Spitfire or Hurricane (and around 20% more than a P-39) which may have been important in the Med or in the Pacific. Sticking the high drag radial on it is going use more fuel at cruising speeds. 

Just what mission/s is this modified P-40 supposed to fulfill?
Most people criticize the P-40 for lack of altitude performance and the R-2600 conversion isn't going to solve that.


----------



## tomo pauk (May 10, 2016)

Vs. the Fw 190, the weight is in ballpark, and it carries more fuel. Should be good on intercepting - climb rate on max continuous is improved vs. P-40?


----------



## Shortround6 (May 10, 2016)

Not a lot more fuel, Fw 190 carried 114 Imp gallons? P-40 E carried 123 imp gallons? P-40F carried 130 imp gallons If drag at cruising speed/s is 10% worse than the FW 190 than range/endurance is no better. 
First four Fw-190A-1s are delivered in June of 1941 or within a week or two of the XP-40F with Merlin first flying. Obviously work on the Merlin P-40 had started months before that. Work on the R-2600 P-40 would have to begin in late 1940 in order for it show up in the middle of 1942. Can't wait for the FW 190 to show up, that is too late.


----------



## Shortround6 (May 10, 2016)

A few notes concerning weight and balance between the P-40E and the P-40F and engine availability. Both planes started and took off on the forward wing tank and switched to the belly (external tank) if carried as soon as possible. The difference is that with the E the next tank to be used is the fuselage tank (the one behind the pilot) followed by the main tank (rear wing tank) with the forward wing tank being the "reserve" tank.
The sequence changed on the F, after taking off on the forward wing tank and using the belly tank, if carried, the next tank was the fuselage tank behind the pilot _but *only* until 35 US gallons were *left*. _at that point the forward wing tank was selected again followed by the rear wing tank leaving the approximately 35 gallons in the fuselage tank as the reserve.
Basically they were using about 210lbs worth of fuel in the fuselage tank behind the pilot as a counter weight for the heavier Merlin engine installation.

Please remember that the three internal tanks (and some of the piping) were a legacy from the P-36 even if actual size varied a bit.
The Forward wing tank never changed from being the tank to start on as it received the return vapors and any excess fuel returned from the carb so using it first for a short period of time created space for the returned fuel to go to. On long flights this returned fuel could be used by going back to the forward wing tank near the end of the flight.

The Flight manuals do say both planes had the same sized fuel tanks unlike Americas Hundred Thousand. And that was 157-158 US gallons.

Please note that the Oil tank bounced around. It started behind the engine and forward of the firewall on the P-36 and was shifted to behind the pilot and on top of the fuselage fuel tank on the pointy Nose P-40s and then back to the engine compartment on the P-40E/F and later.

Also please note that Allison had built and was testing engines using 9.60 supercharger gears in the late fall of 1941. (engine for P-40 started testing Dec 5th 1941) A batch of 25 engines had been built for the P-39 and another batch of 25 was built (or was building) for the P-40. These were the first engines with the nitrided crankshaft and some other improvements. The engines failed the 150 test and most were rebuilt using 8.80 gears, These tests and planned power ratings were done using 100 octane or 100/125 fuel and take-off power was limited to 1100-1125hp unlike the later engines using 9.60 gears that were developed and rated using 100/130 fuel and allowed 1200hp for take-off. There was almost a year delay in actually delivering engines with the 9.60 gears. I would also note that using WEP settings on Allisons using the older non-nitrided crankshafts (engines built during 1941 and earlier) might not have been a very good idea. The engines may have stood up to the higher power settings the first few times it was used but the crankshaft had a much lower fatigue life than the later crankshaft. At some point higher engine failure rates ( or more frequent engine replacement/overhaul) would have had to been dealt with. 
Supplies of 100/130 fuel may not have been universal (in all theaters) in late 1941 or early 1942 either.


----------



## Shortround6 (May 13, 2016)

A few further notes. 
The original Curtiss Hawk 75 used an experimental Curtiss two row 14 cylinder radial of 1670 cu in that weighed 1170-1230lbs (depending on exact model) and weighed 3760 lbs empty, 4843 lbs gross. 
Later experimental engines installed were a P & W R-1535 of about 1100lbs and then a Wright Cyclone 9 R-1820G-5 of 1205lbs. 
The P-36A got a P & W R-1830-13 that weighed about 1370lbs however empty and loaded weights had gone to 4567 lb and 5470 lbs respectively so something else was going on. 

And the P-36A didn't weigh quite enough. From Joe Baugher's web site 
" However, the new Curtiss fighters began to encounter an extensive series of teething troubles almost as soon as they reached the field. Severe skin buckling in the vicinity of the landing gear wells had appeared, dictating increased skin thicknesses and reinforcing webs. Engine exhaust difficulties and some weaknesses in the fuselage structure were also encountered. Despite both production line and field fixes, the P-36As were grounded again and again. At one time, the 20th Pursuit Group was down to six serviceable P-36As, and even these planes had to be flown under severe limitations on their speed, aerobatics, and combat maneuvers."

Curtiss did fix it and eventually the Basic airframe was turned into a sturdy fighter that went over 8000lbs and used powerplants (including radiators) that went 1700-1800lbs but how much further could it be pushed?


----------



## kool kitty89 (Dec 2, 2016)

With all the discussion that's gone on regarding fitting some model of R-2600 to some modification of the Curtiss model 75, 81, or 87 airframe, I think it's at least fair to argue that investing in developing such an aircraft would have been more worthwhile than the XP-46 project, and a more viable parallel development with the XP-40D and likely initiated significantly earlier than the Merlin P-40 project.

Even down-rating take-off power to better comply with toque and related stability limitations seems like it would've been acceptable if overall performance proved promising once in the air. Though with take-off and low-altitude power being overkill in general, a lighter simplified single-speed R-2600 running only in the high gear ratio may have been worth pursuing. (yes, more complicated logistics initially, and not worth doing unless such an aircraft actually showed promise, but in full-scale production, such an engine should be slightly cheaper to manufacture than the contemporary 2-stage variants on top of being shorter and lighter and at least potentially available sooner than either the 9.6 ratio V-1710 or V-1650-1) All that really depends on how early things get started, though. (it's also somewhat akin to the arguments in favor of the lighter, earlier single-speed BMW 139 over the heavier 801) 

I'm also not sure, but with the lower power range in mind, the lighter early models using aluminum crankcases might have had more long-term (or larger scale) production adapted into fighter engines rather than phased out. (and yes I also remember that development of the R-2600 slowed down/became troubled once the US entered the war and its chief designer was barred from the project due to German citizenship, though this is less directly relevant for pre-1940 developments)


Aside from that, the issue of prop clearance and prop RPM is something that was in question (in several other threads as well), and going by the 16:9 reduction gearing of the common 'bomber' R-2600s, you really wouldn't want faster prop speeds than that on a fighter either given the tip-speeds of an 11' prop (akin to that of the P-40D) would already be higher at max continuous 2400 RPM with 16:9 reduction than at 2600 RPM with 2:1 reduction on a V-1710, while take-off RPM ratings would push the V-1710 prop speeds a bit higher (1/2 of 3000 RPM vs 9/16 of 2600 RPM, or 1500 vs 1462.5 RPM at the prop) but still quite close.

Additionally, the props used on the Model 75 appear to have been smaller than the 11' of the P-40D given this document:
http://www.wwiiaircraftperformance.org/P-36/Curtiss_Hawk_75-A_Detail_Specifications.pdf

For the R-1820 Cyclone 9 powered variant:
10 ft 6 in propeller and 1616 rpm rotation rate (16:11 ratio, 2350 rpm R-1820)

10 ft 1 1/2 in prop and 1519 rpm rotation (16:9 reduction, 2700 rpm R-1830)

I did some simple geometry calculations regarding tip speed in flight conditions (taking net velocity of the angular motion from the rotation + perpendicular flight velocity, simple 90 degree pathagorean theorem type stuff), and while those props and rotation rates really wouldn't be cutting it close (except in dives at fairly high altitudes, mostly >400 mph and >20,000 ft) you wouldn't be getting supersonic tip speeds, though cold climates would narrow this margin.

Going up to the 11 ft prop and the higher rotation rates of either the V-1710 or (most) R-2600s could be more problematic though and cutting it somewhat closer, so going with bomber-sized props (or P-47/Corsair sized ones) really wouldn't be an option even aside from problems with torque or (especially) ground clearance.



Also note this issue of supersonic prop speeds would also create some problems with V-1710 overreving, though mostly at high altitude and using 3,400 RPM engine speeds in level flight. (for high alt emergency climb, it might be plausible, but in level flight at 17,000 ft with Mach 1 at around 1050 fps, you'd be hitting supersonic tip speeds at 259 mph) 3200 RPM gives much more practical leeway for boosting top speed, but still runs it fairly close for practical purposes. (just some food for thought in line with Allison potentially performing sufficient testing to allow more regular use of overrev on the E/F series engines, particular with more moderate loads at higher altitudes, somewhat like certain DB 601 models were allowed: though the V-1710 seems to have had a much wider margin for safety in general than the DB engines, or Merlin for that matter; the C-series V-1710 being abused by the AVG and possibly some Colonial units may have also set an additionally conservative president for Allison with their later series engines on top of their limited funding and resource allotment)



Also note that document lists wing guns loading from the top of the wings, with internal ammunition boxes. (it also mentions link and shell retention boxes that may be installed below the ejection chutes of the fuselage guns, so some internet article references to external amunition boxes are likely incorrect, but could be misidentification of detachable link retention boxes for training purposes, retaining spend cartridge cases and belt links: which would better fit the 'cartridge case retainer box' description used on Baugher's website) There's mo mention of external ammo boxes ever being used on the P-36 (or other Hawk models) that I've managed to find on official documents, and this document seems to point to both the single-gun and 2-gun installations in wings used ammunition boxes fitted within the wings and loaded through panels on the upper section of the wing, nothing underneath. 

However, in as far as things actually mounted underwing: note alternate armament installation provisions:
1 .50 cal gun below each wing (200 rpg), 1 20 mm oerlikon cannon below each wing (75 rpg), 1 23 mm Madsen cannon below each wing (100 rpg).

The .50 cal option seems most appealing, and might have been a viable trade-off for some speed loss on the P-40B/C/Tomohawk for the added firepower (matching the F2A) prior to the modified 4-gun wings of the Model 87. (and deletion of nose guns entirely) Additionally, the drag added to a radial engine powered fighter would be proportionally smaller than the P-40 itself, and perhaps a more valuable trade-off for relatively limited performance change. (especially for the bulkier R-1820 or a hypothetical R-2600) Incidentally, a 4x .50 cal armed 2-speed Cyclone powered variant might have fared the best in British use as BoB era interceptor, of the Hawk variants available at that time. (fast enough to chase bombers at most altitude in that conflict, much better at damaging fuel tanks and armor, even with ball ammo, thanks to massive hydrostatic shock, and superior roll-rate to anything else in the sky at the time, allowing a totally different sort of out-maneuvering than the simple level turning ability the Hurricane showed; plus all-around lighter controls at high speeds, even if this was curtailed by the higher drag of the engine installation slowing dive acceleration ... perhaps less so when weighed down with armor and tanks wrapped with sealing material; plus good all-around visibility)

Also oddly, there appears to be a substantial weight gain on the R-1830 powered model and I can't work out particular reasons for this.


----------



## Shortround6 (Dec 2, 2016)

In reverse order, a 185lb increase in powerplant weight is responsible for most of the weight difference between the Cyclone model and the Twin Wasp.
Drag is not the big the problem with using .50 cal guns in the wings (or under). weight is. 400 rounds of .50 cal ammo weighs about 120lbs or as much as 2000 rounds of .30 cal ammo. weight of the guns is about 150lbs for a pair of .50 cal. it is about 95lbs for FOUR . 30 cal guns. _IF _you are using the Higher cycle rate .50s then you have about 15-16 seconds of firing time. Navy pilots didn't like 240rpg on 6 gun Wildcats.
In the BoB you would have had the 600rpm guns, four 50.s would have been putting out about 36 bullets a second (at best), a four gun WIldcat in the Pacific was putting out about 52 bullets per second. Wildcat not having to put up with synchronized guns in addition to having the faster firing guns.
The guns are not a problem in themselves, they do add to the weight problem .

AS in "A pilot's protective shield of 1/4" armor plate may be installed to the rear of the pilots seat" in the " optional equipment section. Weight of armor is not included in base figures. Neither are protected fuel tanks.
I would also note that the *radio* is also an extra as is an electric starter.

Bringing a Hawk 75 up to the standards of even a P-40B is going to add around 260-270lbs just for protection, radio and electric starter. Now throw in the added guns/ammo. Your 12G load rating just went in the toilet, requiring a bit of extra weight to get back.
Turning ability may suffer only a little bit but climb is starting to take it in the neck. And climb is related to _sustained _turn.

As for:

" .....Though with take-off and low-altitude power being overkill in general, a lighter simplified single-speed R-2600 running only in the high gear ratio may have been worth pursuing. (yes, more complicated logistics initially, and not worth doing unless such an aircraft actually showed promise, but in full-scale production, such an engine should be slightly cheaper to manufacture than the contemporary *2-stage variants* on top of being shorter and lighter and at least potentially available sooner than either the 9.6 ratio V-1710 or V-1650-1) All that really depends on how early things get started, though. (it's also somewhat akin to the arguments in favor of the lighter, earlier single-speed BMW 139 over the heavier 801)

I'm also not sure, but with the lower power range in mind, the lighter early models using aluminum crankcases might have had more long-term (or larger scale) production adapted into fighter engines rather than phased out. (and yes I also remember that development of the R-2600 slowed down/became troubled once the US entered the war and its chief designer was barred from the project due to German citizenship, though this is less directly relevant for pre-1940 developments)"

Not at all sure where this came from, ie the bolded part. There was NEVER an 2 stage production version of the R-2600. There were a total of 12 experimental/development engines with 2 stage superchargers. 9 of one model , one of another and 2 of a 3rd type. Plus a few experimental turbos. The two speed drive to the single stage supercharger was worth about 15-20lbs and had a negligible impact (if any) on engine length.
I would also note that the steel crankcase was actually lighter than the aluminum crankcase in addition to being stronger. the difference of 30-60lbs between the aluminium crankcase engines and steel crankcase engines was due to other changes.

An Allison went around 1350-1310lbs (the long nose ones were heavier) and the cooling system was about 300lbs (varies a bit depending on model). The R-2600 went about 1935lbs for the lightest version. You are really going to have to do a LOT of work to take out several hundred pounds. Plus the weight of the bigger prop and oil systems.

Without a low drag cowling comparable to the FW 190s sticking an R-2600 on a P-40 airframe wasn't really going to get you anything. The early P-40 had 22% less drag than a P-36 (R-1830 engine). The early R-2600 (1600hp take-off) had 1400hp at 11700ft in high gear or about 21-22% more than the Allison in the P-40D/E. (1150hp at 12,000ft)


----------



## GregP (Dec 5, 2016)

Shortround, 

Out of curiosity only, with regard to post 163, can you quote any actually higher failure rate data for any particular crankshaft? I have not seen these data. If not, where does this statement come from?

We have run both 6 and 12-counterweight crankshafts at VERY high rpm levels with regard to WWII levels, all with no failures, even in tractors running 4,600 rpm for a tractor pull, sometimes for years before rebuilds. Not one single crank failure of either 6 or 12-counterweight variety. A few other things HAVE failed, but not cranks, even one that was bent by .050 inches, was straightened with a hydraulic press... and is still running in a boat.


----------



## Shortround6 (Dec 5, 2016)

I can't give you any figures because that is a supposition on my part. However it has nothing to do with the 12 counter weight crankshaft and a lot to do with a chart on page 409 of Vees for Victory showing the difference in endurance of the 3 different 6 counter weight crankshafts.

The original "plain" crankshafts were good for around 93 X10*3 lbs per sq in stress for very short term (100,000?)cycles falling to 70 X10*3 by 0.7 million cycles after which the line flattens out and the crankshaft can run 70 X10*3 lbs per sq in stress pretty much forever (10 million cycles)

The Shot peened Crankshaft started at about 112-113 X10*3 lbs per sq in and fell off much more slowly to 90 x10*3 by 3 million cycles and then stayed flat to 10 million cycles.

The Nitrided crankshaft started at 150 x10*3 lbs per sq in and fell to 120 X10*3 by 3 million cycles and then stayed flat to 10 million.

The Nitrided crankshaft was introduced to production in very early 1942.

This means roughly 64,000+ engines were produced with the nitrided crankshaft (minus the 12 counter weight engines) and any spare cranks manufactured from early 1942 on were the nitrided version. There may have been 8300 to 9000 engines built with the two versions of the earlier crankshafts in 1939-41 and a good number of them went overseas in combat aircraft and were lost.

On shear numbers alone the nitrided crankshafts out number the early cranks about 8 to 1 and in numbers available to engine restorers the the number of early crankshafts is probably much, much lower. Not a problem as the nitrided crank will drop right into an early engine. 

Post 163 was in part an answer to people who think you can abuse an early model Allison the same way you can abuse the later versions ( official WEP ratings and such) and get the same results/life out of the engine.

The 1942 and later crankshafts will operate essential forever at a stress level almost 30% higher than the stress level that would cause failure in plain steel crank in about a hundred thousand cycles.

Reactions: Bacon Bacon:
2 | Like Like:
2 | Like List reactions


----------



## Zipper730 (Feb 12, 2018)

kool kitty89 said:


> Do remember the long nose of the YP-37 wasn't primarily to accommodate the turbocharger, but to cram the radiators, main fuel tank and a bunch of other equipment all behind the engine. . . The radiator, intercooler, and aux fuel tank take up most of the space. (that nose-mounted turbo installation would be OK if the radiators had been moved to the wings


Okay, so they'd be in the roots, and the turbo would stay down below?







Would it be possible to shift the battery/radio behind the cockpit & shift the cockpit?


> Turbo controls early-war were also less than satisfactory, both confusing and far from foolproof with lack of features like automatic turbo RPM limiting. (no overrev protection, and this resulted in the majority of catastrophic failures or exploding turbochargers)


Was this a problem with the P-38?



> This has already come up in this thread:
> Drag of radial-engined fighters


I'll give it a read...


----------

