R-2800 for fighters: how would've you done it?

[wuzak]

Basically I can't see a simplified R-2800 fighter appearing much before the F4U-1 or P-47, unless it was based on an older airframe which would produce its own set of compromises.

 

[Shortround6]

According to Graham White, R-2800 - Pratt Whitney's Dependable Masterpiece, the first F4U-1 was delivered on June 30 1941, the first P-47B was accepted in December 1941. 171 P-47Bs were built and 688 F4U-1s. Also, the XF4U flew a year before the XF-47B (May 1940 vs May 1941).


The operational introduction for the F4U is shown as December 1942, the P-47 is just noted as 1942.

I believe the June 30, 1941 is a misprint and should be June 30, 1942. It would certainly agree more with the figures in this document.

http://www.enginehistory.org/References/WWII Eng Production.pdf

It has the production numbers of the major types of engines built in the US by month and factory (group) and a time chart for the 5th, 500th and 1000th aircraft of a number of major types. Since it took, in some cases, months to get a production rate of double digits the roll-out of "first" production engine or airframe can only be viewed with skepticism when using to refer to squadron or combat availability.

This especially true for US aircraft. Please note that VMF 124 was formed up and "commissioned" on Sept 7th 1942 but didn't receive it's first Corsair until later in the month, it was "declared" operational in Dec 1942 (on the 28?) Embarked on board ship in Jan 1943 in San Diego and sails for the Solomons. The squadron Arrives on Guadalcanal on the Feb 12th 1943. With 2-3 weeks (or longer) transit time by ship for US shore ( not factory or airbase) to a combat zone and the time needed to prep the panes after the trip it can be 1-3 months from when a plane rolls out the door to when it can be used in combat. When the "front line" is only a few hundred miles from the factory (or over it) aircraft can get into action much quicker

 

[wuzak]

You document shows 178 F4Us delivered in 1942, against 532 P-47s and 10 F6Fs.

If the F4Us were earmarked for Europe they may have been able to get into battle sooner.

 

[Shortround6]

True but how much sooner? half way through Jan instead of the middle of Feb?

Out of that 178, 68 were accepted in Dec and 54 in November and 32 in October.

It takes time to train the pilots on the new planes and time to train the mechanics. other wise you might as well unload american planes in Liverpool put them on a train to Dover and dump them in the sea for all the good they would do.

The deployment of VMF 124 was fast by US standards. As a comparison there were 5 Mustangs in England on Nov 11,1941. It took until May 10th for #2 squadron to make the first operational mission. 92 Mustang is had been completed back in December alone. Or take the P-47, 56th fighter group gets first planes in June of 1942, they are not declared "operational" in the US until Nov 1942. after sailing to England and getting new planes by the end of January they don't under take their first combat mission ( a fighter sweep over France) until April 8th. 4th Fighter Group which had converted from Spitfires, had flown an operational mission in March. The very first P-47D had rolled out the factory door in Feb, 56th fighter group gets it's first "D"s in May when squadron strength is changed from 18 to 25.

 

[tomo pauk]

(admins, I apologize for posting a picture of such a size)

A power graph for 'our' engines. R-2800s lack lines for power under their FTHs, but that's not the issue
For 801C it should be subtracted for some 170HP at max power (at take off settings, though; perhaps 120 at hi-blower FTH?).
Blue line is for two-stage R-2800 'B'.

Another pic shows a weight distribution of the Fw-190 - whole powerplant system (engine, prop, cowling, etc) weights just a tad less than two-stage R-2800 powerplant system?

The figures at the border of the graph (1325 - prior mid 1943; 1425 1600 HP - after mid 1943) are for turboed V-1710, with a remark that they should spread between 0-7750m only!

 

[tomo pauk]

An interesting issue re. 801Ds in 1942 (ie. rules applying from march 1942 to what date?): their operative manifold pressure RPMs were restricted, to avoid overheating. In other words, instead of 1460-1470 HP at 5700m, they were producing only some 1350 HP @ 5300M.

 

[Siegfried]

The F4U-5 with its huge sidewinder auxiliary stage superchargers show what could have been done with turbochargier packaging - perhaps.

SNIP

At the time the P-47 and the P-38 were being designed the NACA was recommending to the USAAF/USAAC that the turbo was to be mounted seperate from the engine with no tight bending of the ducts. This must have had the effect of nobbling the development of the compact integral turbo-supercharger where the engine, turbo-supercharger, inter cooler were tightly integrated in a single package: the BMW 801TJ being one such example.

 

[Shortround6]

any idea why the NACA was making those recommendations?

 

[Rivet]

"Basically I can't see a simplified R-2800 fighter appearing much before the F4U-1 or P-47, unless it was based on an older airframe which would produce its own set of compromises. "


I can visualize the R-2800 used for a limited production run of P-36's until the P-47 production was established.

Thanks for the link to the engine production stats link, Shortround. Some holes in the timeline covered with it.

Regards

 

[Shortround6]

Here is a link to a manual/sales brochure for the Curtiss Hawk 75/P-36, it has a small weight beak down. Weight of wings, fuselage, powerplant and such. it also gives stress factors for both Wright Cyclone and P&W Twin Wasp engines. Chances of sticking a P&W R-2800 into this aircraft and ending up with a useable airplane are about like sticking an iron blocked 7 liter V-8 into a Mazda Miata and expecting it to still go around corners.

 

[Rivet]

I still believe the R-2800 in a P-36, more or less, a good idea. Keep the materials flowing and adhere to war department wishes that the line be kept going until the P-47 was in production.Yes, a 350 Chevrolet engine will fit inside a Toyota Corolla body. You're on the money as to steering.Regards

I'd picked up on the P-36 manual some time back, might go copy it. They were some of the few to get into the air when the attack came on December 7. Regards

 

[Shortround6]

By the time you get the R-2800 into a P-36 you don't have much P-36 left. The engine alone is about 1/2 ton heavier not counting all the extra "bits" like the much bigger propeller, and then we are back to the 1 to 1 1/2 foot longer landing gear, the heavier wing, the bigger fuel tanks and so on. In fact the "powerplant" of an F4U-1 weighed about 3900lbs including engine mounts and cowling but not including fuel tanks but including fuel piping. A Curtiss 75A Hawk when powered by a 9 cylinder Cyclone engine weighed
4483lbs empty and 5692lbs normal loaded. Pilot, 105 gallons fuel , 10 gals oil, guns (one .50 and one .30) and ammo, radio even oxygen and signal pistol. Granted the FU4-1 used the two stage supercharger and intercoolers but this is more like sticking a 1000lb engine in one end of a 1970s Corolla. Or sticking a 8V-92 Detroit diesel into a 1970 Chevelle. or in aircraft terms, sticking a P&W R-1340 from a T-6 onto the nose of Beechcraft Bonanza.

 

[Siegfried]

any idea why the NACA was making those recommendations?

My recollection, sorry I can't find my sources, was that they wanted the turbo itself external and in the slipstream and that they also wanted to avoid corrosion or hot spots at the ducting bends.

 

[davparlr]

An engine swap is not just the weight of the engine and radiators, the R-2800 needs bigger oil tanks, bigger oil coolers, a heavier exhaust system, a bigger starting system and a bigger propeller. Prop on an a F4U weighed 494lbs compared to the 337lb prop on a P-40C.

Of course.

Fine, a 16% increase in landing gear weight.

Remember this weight is for a landing gear built for a carrier landing of a 12000+ lb airplane not 9000+lb land plane, so, your probably talking about an 8% increase. I don't think a landing gear is a big challenge.

Was the Fw 190 designed to the same "G" limits as the American planes? The 109 was not.

Lot of discussion on this and other forums that have claimed that both the Bf-109 and Fw-190 was stressed to an ultimate load of 12 gs, which I think is similar to the US requirements.

"My" American engineers are just as good, they just can't change the laws of physics.

To know that the Germans could design and field a fighter with an empty weight of 6380 lbs with a capacity of 138 gal. and claim the US could not field a similar fighter with the capacity of 180 gallons of fuel in the 7000 lb class implies incompetence of the engineers. I have no idea of what physical law must be violated to do this.

Actually the P-51D was NOT stressed to 12 Gs at 9600lbs. It was stress for 8 Gs at 8000lbs with a 1.5 safety factor which is were the 12Gs comes from. All flight maneuvers required the actual weight of the plane to divided into 64,000 (8,000lbs X 8 Gs) to get the actual "G" limit. At 9600lbs a P-51D was rated for 6.66Gs plus the 1.5 safety factor or 10 "G"s.

Okay? I am not modifying an existing airframe, I am building a ground up aircraft.

By the way, if you can call splicing in a 7in high horizontal section for a good part of the length of the fuselage "no Change in structure" what else are you glossing over? Do you have the weight of the wing of a P-51A?

Somehow I don't think an increase in the area of the vertical stabilizer to improve lateral stability helped improve the load carrying limits of the structure.

A Hawk 75a (P-36 had wing that weighed 842lbs, the P-40C had wing that weighed 1002 and the P-40E-N had a wing that weighed about 1120lbs.

Okay

Standard load in what? the P-39 with CG problems when it fired off the ammo?
Standard load in an early P-40, soon changed to 380rpg. Not the brightest move, the sychro-ed guns fired at under 500rpm. wing guns fired at about 800rpg giving you 15 seconds of firing time. Navy pilots preferred 4 guns with 400rpg to 6 guns with 240 for the longer firing time.
P-40s with 6 guns were often loaded with 200-235rpg in an effort to save weight for performance even though the ammo spaces would hold more. But 6 .50cal P-40s are pretty thin in 1941 aren't they?

It is designed as a light weight fighter. Anyway I included 250 rds/gun for six guns in weight chart.

Well that is the trick isn't it? finding space on the center of gravity (or tanks space for and aft 9or side to side) to balance on the center of gravity, plus the weight of the tanks, plus the piping (fuel piping on a F4U-1 was over 100lbs) without making the fuselage or wing any bigger and adding weight that way.

This is only parametric. Okay, let's add only 70 gallons and 200 extra lbs for tanks and plumbing. It still beats the F8F.

There just aren't many R-2800s of any type available until the fall of 1941, and I as noted in the Post to Tomo the "A" series goes out of production rather quickly, being replace by the "B" series single stage engine.

The article you posted indicated that one of the main reasons there were so low a production of engines was because there were no airframes requiring them.

A P-66 would be much simpler than a P-47 but then sicking an 1800-2000hp engine in/on a jumped up basic trainer is going to lead to all sorts of problems.

According to wikipedia, the BT-13 was adapted from a design of a fighter being designed by Vultee, like the F-5/T-38, not vise versa. No reason here to believe it was particularly weak. But again, it was just a parametric comparison.

I know, you are only using the P-66 as an indicator of size. But with that big R-2800 you are going to need bigger tail surfaces or move them back (longer fuselage). We are back to the landing gear problem, you can't use the same diameter prop as the R-1830 engine.

This landing gear issue is over blown. I believe swinging a 6 -6.5ft gear with a similar design to the P-51, is not particularly problematic. This would clear a 13' prop a distance similar to the P-51D. Some outboard movement of the machine guns ala F8F may be required. The Fw-190 had a landing gear height (ground to wing) of about 6' but a gear length of 6.5' (it leans inboard and juts forward). Both the Ta-152H and C both having about 6' gear length.

The armament of the P-66 was barely adequate for 1941 and not at all what the customers wanted if given any choice at all. And 220-240 gallon capacity seems rather suspect given the empty and loaded weights quoted for the plane. Maybe the tanks would hold that much but what else had to be left out of the plane in order to fill them? You can find weights for US Navy planes in "ferry" condition. Lots of fuel but they actually pulled the guns out let alone the ammo in order to get to that weight.

240 gallons available would be nice with 60 gallons used as extended range fuel like the P-51B/D. I like it but I would not calculate fighter performance with the extra fuel weight. I'll put that in my spec.

It is if you don't want the prop plowing ground. Remember you are designing in 1939-40, what kind of propeller do you KNOW you can get in Jan of 1942, not what kind of propeller do you HOPE to get.

A six foot gear swing should clear a vertical plane 13 ft F4U prop by about foot, probably better than the F4U. The F4U prop will do just fine.

Engine availability is certainly an issue. Maybe with a proper airframe, AAF and RAF pressure, and money, would encourage better delivery performance. Initial aircraft, 1942, would require only the A engine to outperform the Fw-190A1, or 2.

Weight breakdown of light weight R-2800 powered fighter.

This is probably conservative. This looks close to the F8F but with more machine guns. However, if you built the F8F to much less stress levels for land based only, I would think you would come out with less weight overall, even with the added guns. Gear weight could be reduced.

Parameters used. P-40C except where noted, P-40F (gross weight 8676 lbs), P-47. F6F.

Wing 1132 (P-40F)
Tail 154 (P-40F)
Fuselage 420
Landing Gear 733 (F6F-3)
Engine section 379 (P-47)
Engine 2469 (F6F)
Engine Acessories 314 (F6F)
Engine Controls 36 (F6F)
Propeller 485 (F6F)
Starting 56 (P-47)
Lubricating 117 (P-47)
Fuel System 332 (P-47)
Instruments 38
Surface controls 104
Hydraulic 120 (P-47)
Electrical 233
Communication 71
Furnishings 137
Empty Weight 7330 lbs.
Trapped oil 74 (P-47
Cal .50 installation (6) 450
Gun sight 4
Armor 111
Oxygen 20
Basic Weight 7989
Pilot 200
Useable Oil 143 (P-47)
Cal .50 Ammo 350 (1500 rds)
Internal Fuel 1080 (180 gallons) (240 gallons max)
Gross Weight 9762

Gross weight of F8F-3 9386
Gross weight of P-51B 9800
Gross weight of Fw-190A-3 8751
Gross weight of F4U-1 12,039

 

[Shortround6]

My recollection, sorry I can't find my sources, was that they wanted the turbo itself external and in the slipstream and that they also wanted to avoid corrosion or hot spots at the ducting bends.

They seem like somewhat valid concerns, The USAAF by 1940, has built and flown around 100 turbo charged aircraft going back to the late 20s, with varying degrees of success. One of the re-occurring problems was keeping the turbine cool, or rather, one of the re-occurring problems was the over heating of the turbine and the subsequent failure of the turbine, at times catastrophically. P-38s and other aircraft had scatter shields to keep turbine parts from entering the cockpit or crew areas in case of failure. Providing the turbine and it's housing with cooling air was important. Spacing the turbo away from the engine also allowed for the exhaust to cool a bit and lowered the entry temperature to the turbo. As WW II went on better materials and techniques were used and later model turbos could withstand both higher rpm and higher inlet temperatures. Sharp bends decrease pressure but don't do much for exhaust gas cooling in the exhaust ducts while sharp bends in the intake ducts also reduce pressure to the engine, it may only be a few percent though.

 

[davparlr]

It is interesting to see all this advanced work being done on turbines by the American industry and military, but the jet turbine engine just did not occur to them.

 

[wuzak]

Lockheed J37 - Wikipedia, the free encyclopedia

 

[wuzak]

The Wiki article says:

In 1930 Nathan C. Price joined Doble Steam Motors, a manufacturer of steam engines for cars and other uses. Over the next few years he worked on a number of projects and starting in autumn 1933 began working on a steam turbine for aircraft use. The engine featured a centrifugal compressor that fed air to a combustion chamber, which in turn fed steam into a turbine before exiting through a nozzle, powering the compressor and a propeller. The engine was fitted to a test aircraft in early 1934, where it demonstrated performance on par with existing piston engines but maintaining power to higher altitudes due to the compressor. Work on the design ended in 1936 after Doble found little interest in the design from aircraft manufacturers or the Army.

I knew that there were a few steam turbine projects in Germany, one from Junkers which was cancelled early in the war, as was another competitor's, plus another proposed for the Me264 which was to give 6000hp.

I hadn't realised that steam turbines were proposed in other countries, and in the US one actually flew!

 

[renrich]

The F4U was designed to be the smallest possible air frame able to accomodate the R2800 engine. The F8F was a smaller airframe but there were a lot of compromises in the design to enable it to be smaller. One handicap to designing a smaller airframe in 1940 -41 for a R2800 would be that the R2800 in that time period was far from a reliable engine. Engine and prop problems plagued the Corsair program and were one factor behind the long gestation period of the Corsair.

According to Dean, "America's Hundred Thousand" the first two production F4U1s were accepted by July 31,1942. There were 178 Corsairs delivered in 1942, 2298 in 1943.

 

[davparlr]

The F4U was certainly a superb design. A simpler, ground up land based version would have been happy with the A, 1850 hp, engine, the one already flying in the B-26, and in fact flew at Midway. I still think that a simpler, lighter F4U/P-66 land based designed, type aircraft, with the A engine, could have been operational by Pearl Harbor. Certainly there needed to be a more attention paid by the Navy and AAF in developing engines and aircraft in the years leading up to the war and that would have needed to change. The efforts by both in developing the excellent F4U, P-38 Lightening (which tended to be a bit too late for the need), and P-47 was good, only their delay in development left a performance gap between them and the F4F, P-40 et al., when the enemy was met. I guess what I propose is trying to fill that gap with the only US engine really capable of doing that.