Prior 1942: ideal fighters for USAAC

[drgondog]

As long as it is a 'what if' based on objective judgment of an airframe potential in early 1940 to go to war with in 1942, and setting priorities around both producing the airframe/engines with an eye toward improvement....

I would select XF4U/XP-51A as the foundation and move to license the Merlin, focus on R2800 extentions - and steal the FF then the Mg 151 to arm both... or extend the M2 to 60 cal/15mm to get minimum explosive round capability.

 

[Shortround6]

The context of this thread is prior-1942, so waiting for the R-2800 and the P-47 isn't a viable solution, unless there is another what-if scenario to dramatically speed their development.

If the goal is to have a better fighter available for use in small numbers, regardless of the cost per plane and regardless of delaying better planes in 1942 then the P-44 is the way to go.

The first contract for 13 YP-43 is placed in March, 1939. First YP-43 is delivered in Sept 1940, over one year later, the 13th YP-43 is not delivered until April 1941.
A contract for 80 P-44s is placed in Sept 1939. By Sept 1940 Republic had the order for 80 P-44s plus letters of intent for a batch of 225 P-44s and a batch of 602 P-44s. Kartveli had been working on a V-1710 powered P-47 but decided that the R-2800 offered a better solution and pitched what would become the P-47 to the Army in the summer of 1940. The Army went for it and changed the contracts/letters of intent from two P-47s with Allisons to one P-47B with the R-2800 on Sept 6th 1940. By Sept 13th 1940 the P-44 was dead and the letter of intent for 225 was changed to 54 P-43s and 171 P-47Bs and the letter of intent for 602 P-44s was changed to 602 P-47Cs.
The P-43s followed the YP-43s with the first being delivered May 16 1941. First P-43A is delivered in Sept 1941. A follow up contract is placed in June for another 125 P-43A-1s with self sealing tanks and armor for leand lease to China and to help Republic expand and train workers of the up coming P-47 production.
The XP-47B prototype was rolled out the end of April 1941 and first flown May 6, 1941. First production P-47Bs were rolled out March of 1942.

You might get a few hundred P-44s squeezed in there if you cut the P-43s and delay the P-47. Considering the problems with both the P-43s and the early P-47s the likelihood of it being a somewhat trouble free fighter suitable for deployment to combat zones is slim. All P-47Bs stayed in the United States to be used as trainers for the pilots going to units that would be equipped with P-47Cs
While the R-2180 and the R-2800 used the same cylinders and pistons they would use different crankcases, crankshafts, engine mounted superchargers and have different vibration problems. Working on the R-2180 is going to delay the R-2800.

 

[Shortround6]

Tomo, installing the turbo there is going to some serious things to the CG. Maybe we can add 300lbs of lead in the space right behind the gear box

In the XP-39 the turbo was mounted under the engine, about where item 18 or 19 is, the radiator/oil cooler. Inter cooler may have been behind engine.

Bell used a P-39D for two experimental turbo mock ups. One was a saddle pack behind cockpit about were the rear of canopy and air intake is, the other was a belly pod about where the drop tank goes. These were not active units but were tested for drag. As I have said before they took 40-45mph of the speed of the plane. Photos are in "US Experimental Prototype aircraft projects, fighters 1939-1945" by Bill Norton, Page 89.

 

[tomo pauk]

Thanks for further info. Glad to know that turbo unit was so compact that it could've been mounted at even smaller space than I've suggested

For my proposal CoG issues to be solved, we'll relocate the oil tank under pilot's seat (much smaller coolant expansion tank remains aft the engine now). That way we can also place aft armor plate (previously located just aft the oil tank) more forward too.

For that belly pod installation, was it supposed to contain just an inter cooler, of even the turbo?

 

[Shortround6]

Not really, you would have to see the pictures.

Both the saddle pack (which replaced all the rear canopy in back of the metal framing and covered the original intake, and bulged out to the sides considerably--really ugly) and the belly pod (it looks like a jet booster pod, big hole in the front end) contained both turbo and intercooler. As I have said before, speed below rated altitude was cut by 40-45mph.
They look like "add-ons". a plan to make a pack to modify existing aircraft rather than build it in?

If they could have stuffed a turbo into the P-39, why didn't they?
Please look at the P-39E and P-63 for what Bell engineers though was needed for a two stage supercharger and they still didn't have an intercooler (they wanted one but the sub contractor couldn't deliver).
Why build long fuselages and bigger wings if you could get the engines in a P-39?

 

[davparlr]

As long as it is a 'what if' based on objective judgment of an airframe potential in early 1940 to go to war with in 1942, and setting priorities around both producing the airframe/engines with an eye toward improvement....

I would select XF4U/XP-51A as the foundation and move to license the Merlin, focus on R2800 extentions - and steal the FF then the Mg 151 to arm both... or extend the M2 to 60 cal/15mm to get minimum explosive round capability.

Exactly. The P-51 could easily perform all low level activity including tactical support. While not the best tactical support aircraft it performed quite well in this role. And, if the AF had been willing, just about any Merlin could have been inserted to allow the P-51 to outperform all ETO aircraft at whatever time the engine was installed. Delaying the second aircraft to allow development of the 2800 provides all the aircraft you would need to partner with the P-51. The Allied war machine would suffer in '42, but really start to get its legs under it in '43.

 

[Shortround6]

and steal the FF then the Mg 151 to arm both... or extend the M2 to 60 cal/15mm to get minimum explosive round capability.

Just build the Hispano to British specifications.

Or neck the .50 up to about 20mm (ok the case needs to be slightly bigger) for a rimless 20mm Shvak/Japanese Ho 105?

 

[parsifal]

Did a little further checking of the Luft. Ju87bs were not armoured, and there is no evidence i can find of retrofitting. Main type deplyed to the med against the RN until September was Ju87B, but more often the Ju87r, long range version. This most definately was never armoured.

Neither can i find any evidence of retrofitting armour to the he-111. There is some evidence of armouring from mid 1941, however the h-6 concentrated on increased defensive arment. it was not until the end of 1942, with the introduction of the h-11 subtype, that the he-111 began to be extensively armoured.

i am unsure about the Ju88. I will keep checking

 

[tomo pauk]

Yep, it was Ju-87D that received proper armor. More precise specs were stated @ our forum previously.

 

[tomo pauk]

Not really, you would have to see the pictures.

Is the comment about strap-on turbos (mock-ups) or about the real XP-39 installation?

Both the saddle pack (which replaced all the rear canopy in back of the metal framing and covered the original intake, and bulged out to the sides considerably--really ugly) and the belly pod (it looks like a jet booster pod, big hole in the front end) contained both turbo and intercooler. As I have said before, speed below rated altitude was cut by 40-45mph.
They look like "add-ons". a plan to make a pack to modify existing aircraft rather than build it in?

Thanks for the description

If they could have stuffed a turbo into the P-39, why didn't they?
Please look at the P-39E and P-63 for what Bell engineers though was needed for a two stage supercharger and they still didn't have an intercooler (they wanted one but the sub contractor couldn't deliver).
Why build long fuselages and bigger wings if you could get the engines in a P-39?

People at Bell have had the chance to address the combat range issue - but they did not.
They designed new wing, yet a single gun must go in pod - pathetic when compared with what batteries were carried in (also thin wing) Spitfire or P-51.
They were hampered by a sub-contractor - couldn't Bell built the intercooler themselves?
With all that said, think I wouldn't be far off the mark when stating they've made a lousy job when developing P-63. Should I've expected them to install the turbo without issues?

 

[Glider]

He 111's did reveive armour before the BOB as it was reported from the examination of crashed aircraft. It was noted that one of the first He111 shot down during the war was the result of the pilot being killed by 2 rounds that went through the back of his seat. By the BOB the pilots had been given armoured seats so some retrofitting was undertaken.
As for the Ju87, in the book Hitlers Stuka Squadrons page 109 you are correct they didn't have armour during the BOB but this was quickly fitted by ground crews who stripped the armour from French planes and fitted it to the Ju87B. The book also says that the manufcturer responded to aircrews apeals increased passive protection for the pilot and armour for the gunner on the production line but infuriatingly doesn't say what the passive protection was. As for the use in the Med the same book states that Ju87B and Ju87R were issued during 1940 to the Italian forces but later they received the Ju87D.
Either way it is clear that the Ju87 was fitted with protection after the BOB and before the battles in the Med.

 

[Shortround6]

The P-39/P-63 concept has a problem. The engine is just in back of the CG with the pilot on the CG with the guns in front (and nose wheel) there is no place for fuel in the fuselage without doing something silly like sticking it the tail. The wing center section and wing roots were full of radiator and oil cooler and landing gear. This pretty much leaves the wing lading edge and middle for fuel. You want the fuel tanks centered on about 25-30% of the wing cord. other locations lead to handling changes as the fuel burns off. Many aircraft had instructions as to which fuel tanks should be used first. P-39 already had a CG problem with the ammo, the plane handled differently with full ammo and empty.

You can have a lot of unused volume in an airplane. that doesn't mean you can stick what ever you want where ever you want.

As far as the intercooler goes, it may have been a sub contractor to Allison that failed to provide a satisfactory unit. The subcontractor was a radiator company. I don't know who designed the intercooler on the XP-39 but that was obviously fouled up.
The P-39 was a small , well streamlined aircraft. It's drag figures are second best next to the Mustang of all US fighters. Anything you do to it that increases frontal area or increases the amount of air that flows through ducts is going to increase the drag. NACA thought that the original XP-39 needed as much as 7000cu ft of air per minute for the intercooler, and that is for a 1150 hp engine. Over 8000 cu ft per minute for the 1325 engines used in later P-39s? Actually you don't need cu ft of air per minute, you pounds of air per minute which means you need twice the cu ft of air at 20,000ft or so than you do at sea level. Fixed ducts won't do it, you need an adjustable duct.
This was the problem with all turbo charged planes (and planes with two stage superchargers) they were slower at low altitudes where a single stage super charger could provide the air needed by the engine and only got faster than the single stage planes when they reached an altitude at which the single stage couldn't provide the same (or close) total boost. The two stage supercharged plane always had more drag.
A P-51A pulling 1480hp (WER) was about 20mph faster than a P-5B using 1450-1485hp at 5,000 to 10,000ft. It is only above 11,000-12,000 that the P-51 B starts to out run the A.
Now those Bell mock ups may have been higher drag than a more integrated installation may have been but but a turbo P-39 was going to be slower (20-30mph?) than the non turbo version up until 12,000-15,000ft.

 

[gjs238]

Then how much of the P-47's missions were at altitudes requiring the turbocharger?
Theoretically, might a non-turbo aircraft been more suitable?

 

[Shortround6]

A lot of it's mission didn't require the turbo and for a lot of it's mission a non-turbo plane would have been better. It is just going to take 2 1/2 to 3 years to to design, build, and issue to units the non-turbo plane. If you realize in 1943 that you don't need the turbo the new plane may not make combat until the spring /summer of 1945.

 

[tomo pauk]

The P-39/P-63 concept has a problem. The engine is just in back of the CG with the pilot on the CG with the guns in front (and nose wheel) there is no place for fuel in the fuselage without doing something silly like sticking it the tail. The wing center section and wing roots were full of radiator and oil cooler and landing gear. This pretty much leaves the wing lading edge and middle for fuel. You want the fuel tanks centered on about 25-30% of the wing cord. other locations lead to handling changes as the fuel burns off. Many aircraft had instructions as to which fuel tanks should be used first. P-39 already had a CG problem with the ammo, the plane handled differently with full ammo and empty.

Indeed, the coolers their ducting take away a lot of internal volume that could've been used for fuel tankage. Again a minus for people designing P-63 - despite known low fuel supply, they've neither increased wing fuel tankage (despite bigger wing), neither relocated coolers to a less volume-consuming place (eg. oil coolers placed akin to F4U, with exit louvers just after coolers themselves).

You can have a lot of unused volume in an airplane. that doesn't mean you can stick what ever you want where ever you want.

Hope I'm not doing that

As far as the intercooler goes, it may have been a sub contractor to Allison that failed to provide a satisfactory unit. The subcontractor was a radiator company. I don't know who designed the intercooler on the XP-39 but that was obviously fouled up.
The P-39 was a small , well streamlined aircraft. It's drag figures are second best next to the Mustang of all US fighters. Anything you do to it that increases frontal area or increases the amount of air that flows through ducts is going to increase the drag. NACA thought that the original XP-39 needed as much as 7000cu ft of air per minute for the intercooler, and that is for a 1150 hp engine. Over 8000 cu ft per minute for the 1325 engines used in later P-39s? Actually you don't need cu ft of air per minute, you pounds of air per minute which means you need twice the cu ft of air at 20,000ft or so than you do at sea level. Fixed ducts won't do it, you need an adjustable duct.
This was the problem with all turbo charged planes (and planes with two stage superchargers) they were slower at low altitudes where a single stage super charger could provide the air needed by the engine and only got faster than the single stage planes when they reached an altitude at which the single stage couldn't provide the same (or close) total boost. The two stage supercharged plane always had more drag.

The drag increase was a price to pay, no quarrels about that. In the USA the production of 'under 15K' planes was just fine - the hi-alt planes were needed, and P-38 could not meet the demand.

A P-51A pulling 1480hp (WER) was about 20mph faster than a P-5B using 1450-1485hp at 5,000 to 10,000ft. It is only above 11,000-12,000 that the P-51 B starts to out run the A.

I've looked at P-51A figures at ww2performance last night (being intrigued by perf figures at US 100K book - 400mph at 18K?) - the plane was roughly as good as Spit VIII. Missed opportunity those two for ETO?

Now those Bell mock ups may have been higher drag than a more integrated installation may have been but but a turbo P-39 was going to be slower (20-30mph?) than the non turbo version up until 12,000-15,000ft.

No problems with your estimates. Again, it's the good numbers of good performers @ 20K that 'we' are lacking prior (mid?) 1943.

added: How about P-39(N?, Q?) with the -81 engine (the one from P-51A). Feasible for mid 1943. Or the P-40 with that, along with some weight drag reduction - in hindsight makes more sense than Curtiss producing P-47s that weren't used

added 2: interesting article, esp regarding P-39 vs. Japanese bombers
http://yarchive.net/mil/p39.html

 

[drgondog]

All good alternatives SR - but wouldn't it more fun to break the German patents?

 

[gjs238]

Eventually the war ends and companies come looking for their patent royalties.

 

[Shortround6]

No problems with your estimates. Again, it's the good numbers of good performers @ 20K that 'we' are lacking prior (mid?) 1943.

added: How about P-39(N?, Q?) with the -81 engine (the one from P-51A). Feasible for mid 1943. Or the P-40 with that, along with some weight drag reduction - in hindsight makes more sense than Curtiss producing P-47s that weren't used

The P-39 M, N and Q used basically the same engine as the P-51A. They all used the same supercharger gear, they were all rated for 1200hp take-off and 1125hp at 15,500ft military power and 1420hp at 9,500ft WER. The altitudes are without RAM. Critical altitudes varied from climb to level speed because at the higher level speeds the was more air pressure in the intake duct leading to the carburetor. The P-40 M and N used the same basic engine. the -99 and -115 engines used different controls or accessories but had the same power ratings.

 

[Shortround6]

All good alternatives SR - but wouldn't it more fun to break the German patents?

It might be more fun but the British looked at the MG 151 and thought it was too complicated or needed too much machining for them to build. If the Americans didn't get their act together and classify the MG as a machine gun instead of a cannon (cannon could be built to looser tolerances than a MG) I don't think we would have had much luck with the result

 

[tomo pauk]

Found it; P-39 with 'bolted-on' turbo unit mock-up (exhausts are like on normal 'Cobras, not feeding the turbo):