USAAC/AAF being much improved in 1938-42?

Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules


Thank you. I guess I should have fleshed my question out a bit more. I knew the intercooler looks like a radiator. So if a Wildcat only has 1 intercooler intake and an XP50 has 2, I would assume the XP50 has more, maybe even double the amount of intercooler volume (which you have said several times it would need). I wonder where the turbocharger is on the XP50?
 
F4F's with two stage engines had two intercoolers, one on each side.

For an idea of what kind of intercooler was needed for 1200hp at 25,000ft for the R-1830 see;



Left hand upper duct is for the carb, left hand lower duct is for the oil cooler, entire right hand duct is for the intercooler visible below the workers arms.
perhaps the bomber needed bigger inlets due to lower speeds? however

P-40 with pretty much the same engine as the F4F, a few minor improvements and a lot better cowl and exhaust thrust. There is an intercooler (or 2?) hiding in there somewhere.
However the engine in this plane was rated at 1100hp/2700rpm/17,800ft Military and 1000hp/2550rpm/19,000ft Normal (max continuous) so obviously it is giving away quite a bit to a turbo charged engines that were rated at 1200hp/2700rpm/25,000 and could get away with a rather smaller intercooler. The air at 18,000ft being about 27% denser than the air at 25,000 it needs to be compressed less (isn't as hot) and the intercooler requires much less fewer cubic feet of air (about 79%) for the same cooling effect.

If you want the high altitude performance a turbo gives you have to pay for it at lower altitudes with increased weight and drag.
 

I understand everything you typed except one thing: I see the big toolbox looking intercooler, I understand the extra weight. I do have a problem understanding extra drag at low altitude. So, my question, if you stuff that engine, and intercooler into an F4F-3 up front, turbocharger goes behind pilot like on a P47, pipes to and from turbo are completely contained inside the aircraft, from outer appearances nothing has changed. It is flying side by side with a standard F4F-3 at 3000 feet, both aircraft are using 1100 hp. The turbocharged F4F shouldn't need any more intercooling at 3000 feet and the same hp than the real life 2 stage supercharged F4F-3.

How is there more drag?

(I'm not arguing, I'm trying to get my head around internal drag)

I understand if turbocharged F4F is at 25,000 feet and NEEDS the entire intercooler to cool the air but down low it doesn't make sense to me.
 
The extra drag comes from the large inlet duct/scoop. Just because you close off the exit and stop much of the flow through the duct doesn't mean the increase in frontal area or turbulence around the inlet goes away completely.

When Consolidated built the Navy PB4Y-2 Privateer they dropped the turbocharger installation.

AIr scoops are now the carburetor air and the oil cooler/s. two speed engines (not two stage) and giving 1350hp for take-off.
Be careful looking at internet pictures of PB4Ys as some of them that were used as water bombers got Wright R-2600 engines with the carb air scoop on top of and behind the engine like the air scoop on a B-25.

There were two attempts as putting the turbo back in the P-39, neither was particularly streamline but they figured about a 30-40mph loss of speed at low altitude depending on exact installation.
P-43 was good for about 295mph at sea level, about 310mph at 5,000ft and 325mph at 10,000ft using 1200hp, A P-36A (no wing guns) could do 313mph at 10,000ft using 1050hp.
Not as bad as the turbo installations on the P-39

Now in case people are wondering why the US wasn't jumping all over turbocharged airplanes in 1940-41 consider the P-40B vs the P-43. The P-40B could do 347mph at 15,000 using 1050hp, The P-43 did 339mph at 15,000ft using 1200hp. and 329mph at 15,000ft using 1100hp. 300mph needed 840hp at the same altitude while the P-40B needed 698hp to go 306mph. Granted the P-40 made much better use of exhaust thrust than either the P-36 or the P-43. This may have affected the P-39 installations, not only the drag but the loss of exhaust thrust.
 
Ok. That makes sense as far as air intake even if it's closed off. Of course the P39 pics we've seen were horrible "hey let's glue the turbo on the outside". P43 was a bit porky compared to P36. Wildcat was shaped about the same but as you pointed out one time the wing was much larger so comparing a P43 to a Wildcat doesn't work either.
 
In 38 (or earlier ) if the bomber will always get thru/self defending bomber idea is dropped what follows ?
 
using R-1820, R-1830 or V-1710 engines running on 91 octane fuel?

The R-1830 used the XB-15 Bomber first flight 15 October 1937 was the R-1830-11 which was rated at 1000hp for take-off at 2600rpm on 87 octane fuel, max continuous was 850hp/2450rpm at 5000ft.
The engine used in the first production P-36s was the R-1830-13 which was rated at 1050hp for take-off at 2700rpm on 91 octane fuel, max continuous was 900hp/2550rpm at 10,000ft.
This engine had "C" type cylinder heads, a new rear section, a new larger impeller supercharger, long reach spark plugs, automatic valve gear lubrication and some other improvements.
The engine used in the later P-36s was the R-1830-17 which was rated at 1200hp for take-off at 2700rpm on 100 octane fuel, max continuous was 1050hp/2550rpm at 6500ft. It got silver coated bearings and strengthened cylinders.

The Americans don't order the V-1710 in numbers until April of 1939 (the long nose engine in the P-40s)
The Americans can think about longe escorts, they don't have the engines/power plants to make them viable.
The IV-1430 was supposed to help with this

The Americans had different standards of strength and handling than the Japanese had, so unless you can change the requirements the heavier American structure stays.
 
rednev said:
In 38 (or earlier ) if the bomber will always get thru/self defending bomber idea is dropped what follows ?
Click to expand...

time travel?

Seriously, we have to look at some of this stuff through several lenses.

What were they thinking/dreaming of a number of years in the future?
What could they actually build 2-3 years in the future?
What was the state of the art at the moment?


for the last the US Army was taking delivery of Douglas B-18 bombers and ordering B-18As. the last of which would not be delivered until Jan 1940. This plane was deliverable in numbers but not really the "state of the art", it had three .30 cal guns with no power mounting. When the British came looking for aircraft after the Munich crisis they passed on the B-18 and bought Lockheed Hudsons instead.
There were only about 13 B-17s in existence and only one of them had turbochargers. The US ordered more of the turbo version but it had four-five hand held .30 cal guns and was hardly the self defending bomber of 1941-44. It was a lot faster and higher flying than most other bombers in the world though.
The USAAC could dream of turbo charged flat 12 engines buried in the wings for low drag and pressure cabins for the crew and remote gun power gun mounts but getting such things into service was going to take an awfully long time. It took five years to build the B-19 due to low funding but it does point to USAAC thinking at the time. Planned armament (never fitted) was up to two 37mm cannon, five .50 cal guns and six .30 cal guns. It's "normal" range of over 5000 miles shows why there wasn't a whole lot of interest in "escort fighters".
Between the extremes of the B-18 and the B-19 were the B-17s they were ordering in 1938/39 and these were the turbo equipped planes that could get close to 290mph at around 25,000ft. max range of 3200 miles which also shows the problem of trying to build an escort fighter. even if actual combat radius was more reasonable 7-800 miles. Defensive armament was a mere five .30 cal guns. The B-17C, ordered in 1939 but with first delivery in late 1940 (after the BoB) had four .50s and one .30, range was supposed to be 2400 miles with 4000lb bfo bombs which again shows that a 1940 fighter was going to have a lot of difficulty escorting it unless the range of the bombers was cut to match the range of the fighters. There was not experience yet to force that decision and this is two years after 1938. It was on Aug 30th 1940 that the B-17E was ordered ( BoB was only a few weeks old) with eight ,50 cal guns ( four in powered turrets although the remote control belly turret would prove to be a failure) and one .30 cal.
Germans were frantically up gunning their bombers to 5-6 7.9mm machine guns, none in powered mounts, so the US armament fit was not looking too shabby.

In 1938 there was little to indicate that the unescorted bomber would be a failure.
 
Going back to the big picture, 1942 is a difficult cutoff. It seems hard to make the actual combat USAAF in 1942 significantly better without more resources earlier.

It is mainly fighting in the SW Pacific and Med (building up in England but not really doing much yet). The bombers are pretty good (as mentioned so are the transports) but they are struggling for air superiority. So focusing on show pony fighters is justified. The F5F/XP-50 and Packard Merlins have already been discussed so some other thoughts:
  • Applying "boom and zoom" and Thatch weave sooner is probably as useful as plausible technical improvements in the Pacific.
  • The big beef is the altitude performance of the Allison. If you're not putting a turbo on everything (and IMO it's only worth it for big high-altitude bombers and maybe their escorts), want something in between it and the single-stage single-speed versions. But
    • Don't know how much a 2-speed would have disrupted production given the 1-speed was integral to the engine?
    • Reliable production 2-stage may be too much to ask at this time (and it won't fit in existing designs).
  • US fighters were much heavier than other countries' and climb rate was inadequate, particularly against the Japanese.
    • The P-51H was able to save about 10% of empty weight by a systematic weight comparison with the Spitfire and building to British standards. Similar savings should be possible with other planes. But this needed mostly new parts and the advantage of the P-40 was it was just the P-36 with a new engine (and the P-36 was in service in 1938). So might be too late in this case?
    • Initially design armour & self-sealing tanks against .30 rather than .50 cal?
  • The P-39 with hindsight is mainly useful for lend-lease to the Soviets, and they seemed to like it, so no need for drastic changes.
  • P-38: Dive flaps obviously. Work on turbo reliability. Or even an economy non-turbo version (esp. if supercharging improved)? Lower aspect ratio (shorter but wider) wing?
    • The bean counter in me is tempted to kill it entirely given its cost, turbo unreliability, and dive speed limits, although this works against the stated goal of improving the USAAF by 1942. (Unless the XP-50 works as a replacement.)
  • Order the Allison Mustang (P-51A) as a fighter ASAP. Even the historical version is better than a P-40 and any supercharger improvement or weight reduction would be a bonus. (Probably can't move the initial prototype earlier, or it wouldn't be the Mustang.)
  • A R-2600 engined fighter could be in service quicker than the R-2800, but might sacrifice development potential.
  • The P-43 had its problems but was better at altitude than the P-39 or -40. Build a few more for the Pacific. Or some F4F-3s even if it is a Navy plane!
  • Make the 20mm cannon work, if you build it at all! Modifications and Attempts at Standardization
  • [Edit: also train in skip instead of medium level bombing for antishipping.]
Now if you are considering changes in that period that really pay off in 1943 and later, that opens up more options. The main game switches to high altitude bomber escort in the ETO.
  • Disposable paper drop tanks.
  • Anything possible to expedite the Mustang, displacing literally anything else where necessary.
    • Possibly try a turbo or 2-stage Allison in parallel with Packard Merlin (would need a bigger fuselage - P-52 Kingmustang?). If it worked it would allow production to displace P-38s and -40s.
    • Could P-51As (with rear fuel tanks) be used flying ahead of and below the bombers to attack enemy fighters while climbing?
  • IMO the Hellcat would make a good enough and cheaper fighter bomber than the P-47 (and Corsair, and probably XP-50). Especially if it could be tweaked halfway to a Bearcat.
  • If you bother with the P-47 at all, aim for a lightweight P-47N i.e. maximum fuel capacity including in wings from beginning to match the Mustang for range with superior high altitude performance and survivability on strafing runs (more Mustangs were lost to flak than fighters IIRC).
  • Prepare for strategic bombing in bad weather!
  • A tankbuster plane with 40mm or 57mm AT gun for the big cats (rockets were inaccurate). XP-50 minus the turbos might be good here.
  • Could the B-29 have been ready sooner with six R-2600s instead of four R-3350s?
Looking at the above I feel the 2-stage superchargers on the Twin & Double Wasps are wasted. But I'm not sure what to do with them given the P-43, -47, and Merlin Mustang have high altitude pretty well covered.
 
Last edited:
hobbes154 said:
Going back to the big picture, 1942 is a difficult cutoff. It seems hard to make the actual combat USAAF in 1942 significantly better without more resources earlier.
Click to expand...

Mostly true.
A two speed won't buy much as the engine was already using what would be near to the high altitude gear, Over boosting at low altitudes gave close (or better) power than a low altitude gear would (although less maintenance or engine life problems?)
It is not only a question of reliability but getting the airflow right, two impellers of the same size won't work. A big problem with fit is the intercooler, more so than fitting the 2nd stage itself. Part of the problem is also timing, the fuel that allowed some of the higher boosts/power levels of 1942 didn't exist (at least in the US) in 1940 making plans for certain engines a bit uncertain.

US fighters were much heavier than other countries' and climb rate was inadequate, particularly against the Japanese.
Click to expand...

In part because the US was specifying some ridiculously heavy armament loads. A P-40E (or F4F-4) carried well over twice the weight in guns and ammo that an A6M2 did.
A P-40E with 235rpg was carrying over 900lbs of guns, ammo and armament miscellaneous equipment (and that is not the full armament load)


It actually works against you until at least the 2nd 1/2 of 1943 if not the end of 1943. ANd if you can't get the P-38 to work the chances of the XP-50 working are about zero.

A R-2600 engined fighter could be in service quicker than the R-2800, but might sacrifice development potential.
Click to expand...

It also sacrifices performance. We have been over this a bunch of times, A nearly one ton engine that is actually bigger in diameter than the R-2800 and gives you a whopping 1400hp at 11,500ft is not going to give a very impressive fighter, The "B" series R-2600 was good for 1450hp at 12,000ft.
Stopping the USAAC from stuffing even more guns and ammo into such a plane than they stuffed in the P-40E and P-39 was going to be a real challenge.
 
Shortround6 said:
ANd if you can't get the P-38 to work the chances of the XP-50 working are about zero.
Click to expand...

Well the P-38 did "work", just not as well as hoped. And for whatever reason turbos worked better on the R-1820 and -1830 (which I'd prefer due to its smaller diameter) than the V-1710. Though some of that may be the installation rather than the engine per se. ('Supercharged' in Wings & Airpower 2001 says the P-38 problem, aside from disintegrating turbine wheels, was the intercooler working poorly then too well.) But I'd be happy to ditch the turbos if you could fit a 2-stage -1830. Plus the XP-50 has a smaller wingspan which might help dive performance? Not fixated on this plane though - a P-43 is the quick and available altitude fix, and an Allison P-51 with rear tank should get most of the range of the P-38 if not altitude performance.

Shortround6 said:
It also sacrifices performance.
Click to expand...

Sure, relative to an engine that wasn't available yet! I agree the R-2600 doesn't offer much over the V-1710 on a pure fighter but might be useful for a fighter-bomber (especially given those ridiculous US armament loads ). Though possibly more for a carrier than land-based. Given the -1820 and -1830 were swapped on several planes maybe it could take the R-2800 later like the Hellcat prototype.

And speaking of armament, if US industry is determined to fuck up the Hispano then maybe a Ho-5 style 20mm Browning derivative as others have suggested somewhere? Lighter than the Hispano and you could even get away with 2 early war.

Shortround6 said:
A two speed won't buy much
Click to expand...

Was every other country and company wasting their time then?
 
The XF5F was dived vertically to 505 mph, so I would imagine there should be no problem with the XP50 diving. I agree with you as well that the turbocharged 1820 and 1830 seemed to have fewer problems than the turbocharged Allison, as well as being less complicated so keeping them in service in primitive conditions should have been much easier. The XF5F was 10 feet shorter, 10 feet less wingspan and even adding the extra weight of armor, a selfsealing tank and 500 pounds for turbochargers it would have weighed about 3,000 pounds less so climb should have been outstanding.
 

There were two different intercooler set ups on the P-38, the wing leading edge used up until the J model and the under engine core type intercoolers used on the J and later. Yes,as engine power grew the wing leading version was increasingly inadequate.
One reason the turbos worked so well on the R-1820 and R-1830 was that the bombers didn't change altitude all that quickly and often had a flight engineer monitoring engines, including exhaust gas temperature, Turbo RPM and other things. SInce the P-38 used the same turbine wheels as the B-17 and B-24 I don't see why the P-38, if flown to the same limits, should have suffered any higher turbine wheel failure rate. Wingspan has got nothing to do with dive performance. Wing thickness does.

Allison powered Mustang with a rear tank is going to be squirrel city without a major redesign. The Two stage Merlin was around 300lbs heavier than the Allison and the 4 bladed prop went about 100lbs more than the prop used on the Allisons. Amazing what you can stuff in the rear fuselage when you have another 400lbs in the nose.




The window of opportunity is thin.
The 5th R-2600 A series engine (1500-1600hp) was accepted March of 1938
The 5th R-2800 A series engine (1850hp) was accepted March of 1940
The 5th R-2600 BA series engine (1700hp) was accepted June of 1941
The 5th R-2800 B series engine (2000hp) was accepted Oct of 1941

Granted the last engine was the 2 speed version and not the 2 stage engine used in the F4U and F6F but the experimental two stage engine was flying in 1940.
Designing and building a plane that used an inferior engine to gain only a few months of timing seems like a waste of resources. XP-47B first flew in May 1941, just as the first few R-2600 BA engines with 1450hp at 12,000ft trickled off the production line.


Was every other country and company wasting their time then?
Click to expand...
that depends on what they after.
Somehow the notion that 2 speed superchargers conferred much greater altitude ability than single speed superchargers has gained widespread acceptance.
In truth a single speed supercharger can only be set up for one altitude and all other altitudes are a compromise. As a result many times the altitude picked for the single speed supercharger was in itself a compromise. A single speed supercharger could be set up (gear ratio chosen) for high altitude work (or high as it was known/understood at the time)
The Merlin III being a prime example. However this severely handicapped such an engine a low altitude. The Merlin III having just 880hp at sea level. Adding a 2nd speed (low gear) allowed for several hundred extra horsepower at take-off and low altitude, and a slightly higher gear allowed for an extra 1500ft of altitude in high gear.
Please note that had they desired they could have used the higher gear ratio on the Merlin III single speed but only at the cost of even less power for take-off and lower altitudes.

Much more often than not 2 speed superchargers were used to increase take-off power and low altitude performance by substantial amounts without sacrificing high altitude performance. SO no, the other countries and companies were NOT wasting their time. There is a limit to how fast you can drive the impeller tips before gross inefficiency sets in.
 
Upgrade P-66 with F4F engines and solve other issues. P-66 was fast, 340 mph at 15k, and apparently a delight to fly and was good at aerobatics (important for dogfighting?). Installing the F4F engine the P-66 top speed should be around 350 mph at 19k, and, based on F4F performance, 340 mph at 25k, 40 mph faster than the Zero. With that advantage it could engage and disengage at will.

Provide more rigorous pilot training. The AAC sent 100 pilots fresh out of pilot training to the Philippines, only to be diverted to Australia, unprepared to confront seasoned and well trained Japanese pilots.

The AAC had state of the art bombers and attack aircraft in the B-17 and B-24 (which would soon be marginable and close to obsolete) and the B-25, B-26, which were good bombers but excellent attack aircraft, and the A-20 which was an excellent attack aircraft.

Train pilots in anti-shipping tactics and develop skip and mast-height bombing.

Both the short wing B-26 and the A-20 was near as fast, if not as fast as the Zero below 20k, making them formidable low altitude attack aircraft. Imagine the four Midway B-26s with well-trained crews, loaded with four 500lb bombs coming in at 250 - 280 mph (none of this 110 mph torpedo drop stuff) which approaches the max speed of a Zero at this altitude, and then dropping two skip bombs followed by two mast-height bombs. Remember, three B-26s at midway did make it to weapon release point and they were going at torpedo drop speed (wellll, maybe not). A four bomb strike like that would probably sink a Japanese carrier.

Build the P-47 with more internal fuel and/or work with the Navy in procuring F4U-1s, maybe lightening them up in order to provide long range bomber protection (which the AAC did not think they needed). The P-47C only had 305 gallons of internal fuel, the F4U-1 had 351. 1943 bombers would have had protection deeper into Germany.

As I have rattled on before, I would like to have an unpressurized B-33A type bomber replacing B-17/24 by the 1943 bombing offensive. I believe 50 mph increase in cruise and dash speed would have substantially reduced losses and lives and made it more efficient for fighter protection when it became available in '44. Of course, the B-29 absorbed all the oxygen of bomber development. I am sure the AAF was expecting the B-29 to be available for Europe. Unfortunately, it sucked up a lot of money and time and was a problem child.

Develop or buy a decent 20 mm cannon. Cancel the 23 mm cannon.

Recognize the potential of jet engine development and start research and fact finding.

Write P-59 requirements to emphasize speed, perhaps using P-63 wings.
 
Train pilots in anti-shipping tactics and develop skip and mast-height bombing.

Both the short wing B-26 and the A-20 was near as fast, if not as fast as the Zero below 20k, making them formidable low altitude attack aircraft. Imagine the four Midway B-26s with well-trained crews, loaded with four 500lb bombs coming in at 250 - 280 mph (none of this 110 mph torpedo drop stuff) which approaches the max speed of a Zero at this altitude, and then dropping two skip bombs followed by two mast-height bombs. Remember, three B-26s at midway did make it to weapon release point and they were going at torpedo drop speed (wellll, maybe not). A four bomb strike like that would probably sink a Japanese carrier..[/QUOTE]

I agree 100% with the Midway scenario above. I would change out the 4 500 pounders for either 2 1000 pounders or better yet, 1 2000 pound bomb. A20 is even faster than a B26, 20 of either plane with crews trained to skip bomb could have ended the Midway battle before it started, the US Navy just there to mop up the rest of the Japanese fleet
 
"Designing and building a plane that used an inferior engine to gain only a few months of timing seems like a waste of resources. "

If you use A-series engines that is a 2-year advantage, not a few months. But looks like a R-2800 fighter in combat in 1942 is a plausible goal considering the B-26 did its first mission in April. I suppose that should have been the Corsair but the Navy wasted time trying to land it on carriers before giving it to the Marines. Maybe if they were ordered for the Army in the first place they would have been in service faster.

"SInce the P-38 used the same turbine wheels as the B-17 and B-24 ..."

The turbine wheel was not intrinsically faulty, but it seemed to overspeed more in the P-38 (Wings & Airpower Nov 2001, p.39):

The earliest models of the Lightning had lower gear ratios for the
mechanical supercharger on the Allison, requiring the turbos to
work harder and leading to disintegration of the turbine wheel
due to overspeeding. ...
On later models the engine's mechanical blower gear ratios were
raised somewhat to slow the turbos down. However, even on the
later Lightnings, applying too much power above 30,000 ft. could
also produce a disintegrating turbine wheel;

"2 speed superchargers were used to increase take-off power and low altitude performance by substantial amounts without sacrificing high altitude performance."
You make a pretty good case for a 2-speed Allison yourself! Plus it would have added a bit of weight forward
 
Last edited:
davparlr said:
I would like to have an unpressurized B-33A type bomber replacing B-17/24 by the 1943 bombing offensive.
Click to expand...

This would require working out the turbo bugs for the R-2600. And it wouldn't carry the A-bomb when that was ready (at least not a useful distance) so you still need the B-29. Possibly too much even for American industry.

I've also pondered the missing generation of heavy bombers using R-2600 or -2800. But unless you get B-29 level performance by using 6 engines this might be one gap that doesn't need filling.
 
The big radials did not offer the performance at altitude over the Allison that the take-off power figures suggest. Not without using cowlings and exhaust set ups that were not used historically until later in the war.
Using a late 30s (P-36) state of the art cowling the P-36 had either a 22% increase in drag over the P-40 or a 22% loss due to drag and poorer exhaust thrust.
Take 22% away from the R-2600 A series at 12,000ft and you wind up with just a bit less power than the Allison -39 engine.
The R-2800 A series does a bit better (and is smaller in diameter) but is over 350lbs heavier than the Wright engine. Which is almost 600lbs heavier than than Allison (of course the Allison needs nearly 300lbs worth of radiator and coolant).
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 1 (members: 0, guests: 1)

Similar threads

SMGs in ww2 with much smaller cartridges?
2 3
Replies
53
Views
2K
Admiral Beez
A
FG 42, but designed around a non-German cartridge from day 1
2
Replies
20
Views
1K
tomo pauk
"Jumo 222" and "DB 606/610" made in H16 form instead of being 24 cyl types - what gives?
3 4 5
Replies
86
Views
6K
peceed
P
Can we make a slightly smaller Fulmar as an improved carrier fighter?
18 19 20
Replies
391
Views
20K
z42
Z
Kurt Tank FW 187/ Grumman XP5F 1935/1938 et al.
2
Replies
24
Views
2K
tomo pauk
Menu
Log in
Register