Besides the props, what are the diferences between the P-39 and P-63?

[warbird51]

Far as I know all the ones used on fixed-wing, heavier-than-air aircraft employed them, those that were proposed for airships seemed the exception to the rule. I just used the term "auxiliary" stage for the second stage.
It's not about the P-39/P-63, it's about the V-1710 design.
Was this the early or later V-1710's?

A great book is "Vee's For Victory". A definitive history on the development of the Allison engine

 

[Zipper730]

A great book is "Vee's For Victory". A definitive history on the development of the Allison engine

I should put it into the queue, but I have about four or five books I plan to buy already so that might have to wait

 

[P-39 Expert]

Excellent book, and lots of information on the RR Merlin in it also.

 

[ktank]

The P-39 and P-63 both use the same extension shafts. What they did in the P-63 was move the wing back in relation to the fuselage about 15in.

Was this to overcome the COG problems of the P39?

 

[P-39 Expert]

And balance the CG problems of the P-63.

 

[Reluctant Poster]

NACA devoted a lot of effort to improving the Allison induction system. See the attached papers, one of which shows an experimental aftercooler.

 

[Reluctant Poster]

Another paper on improving the Allison supercharger

 

[Reluctant Poster]

Another two reports on Allison ADI and V-3420 cooling

 

[tomo pauk]

Thanks for the pdfs.
Unfortunately, NACA tried to improve supercharger system on the V-1710 too late - post-war.

 

[Reluctant Poster]

I would imagine the tests were conducted during the war with the results being passed to Allison in real time. In my experience results of studies are often incorporated in a design long before a report goes through the tedious process of approval and is finally issued.

 

[P-39 Expert]

NACA devoted a lot of effort to improving the Allison induction system. See the attached papers, one of which shows an experimental aftercooler.

Fantastic information. The Allison Induction paper showed an aftercooler mounted on top of the induction manifold. Since the V-1710-93 was a P-63 engine, I wonder if the aftercooler would have fit underneath the P-63 rear canopy? Also, would the backfire screens (eliminated from V-1710s in mid '42 with the introduction of the aluminum induction manifold) be eliminated in a production model? Maybe another 10HP added to the 25HP increase with the backfire screens?

I'm pretty sure I have seen photos of Wright radials (I think an R-3350 for the B-29) with parabolic inlet guide vanes, did Wright have this before Allison?

Great stuff. Wonder why the NACA inlet elbow/interstage duct couldn't have been implemented on the production -93. Looks like at least a 25HP increase from just the elbow/duct which should have been easy to implement. And moving the carb from the auxiliary stage to the engine stage would have improved manifold pressure a couple of inches of mercury.

 

[Zipper730]

Unfortunately, NACA tried to improve supercharger system on the V-1710 too late - post-war.

When was the final improvements made?

When did the engine finally get the liquid cooled intercooler to finally work? This isn't about the P-63 but the XP-40Q and F-82 in general

 

[P-39 Expert]

When was the final improvements made?

When did the engine finally get the liquid cooled intercooler to finally work? This isn't about the P-63 but the XP-40Q and F-82 in general

The liquid cooled intercooler never worked properly and wasn't used in production planes. Without the intercooler in the way the carbueretor was moved from the auxiliary stage to the normal position on the engine stage supercharger resulting in a little more manifold pressure. This was late in the war and used on the experimantal P-40Q. A better arrangement that in hindsight should have been used on all the V-1710s with the mechanical second stage. Water injection provided cooling for war emergency power. Not sure about the F-82.

 

[drgondog]

My apologies I misread what you said. I largely agree with you. I believe the claim that NAA installed backfire screens originated with Schmued. He wasn't actually involved with the F-82 project at that time. He claimed Forrestal intervened on GM's behalf. Regardless of the details backfire screens will only prevent backfires from damaging the intake. They will not prevent the actual backfires or othe mechanical problems they can cause..
Why do you think that Schmued 'wasn't actually involved' with the F-82 project. True the F-86 was in full bore when the XP-82 first flew but he was involved.

The simple and cheap interim solution was to limit the G6 to power levels (60in @ 3200rpm) that the intake manifold could safely tolerate backfiring and research why the F-82 specifically. It's important to point out that this backfire problem was exclusive to the F-82. No other aircraft fitted with a two-stage Allison experienced this problem.
NAA had so many issues with the XP-51J that they quit testing it. The only reason they agreed to build one was a AAF/NAA/Allison conference at Wright in which Allison practically begged AAF to fund the project.

Your simple 'solution' re: Allison limitations to Boost, eliminated the performance envelope top half and emasculated the Merlin driven P-82. Equivalent to Steve Hinton deciding to use 110/LL in Voodoo.

This includes the Allison's XP-51J test mules that were refitted with G6 prototypes. It took about two years to sort out and remedy the problem.

Wow, now there is a solution - take an airframe with 470+mph top speed and reduce it to 440 because you (Allison) once again can't meet performance specifications tied to the contract. Dramatically reduce the performance - and by definition its combat potential - because your design and executive team can't deliver?
The truth is that the F-82 was largely obsolescent the moment it entered production and the USAF did not want to spend more than the minimum necessary.

The P-82B, reduced to F-82 performance via piddly Allison engine was still the Only game in town to escort B-29 and then B-36 to Moscow for nuclear mission. It was the only viable long range Night Fighter interceptor in comparison with the P-61.

In closing, it was amusing to trace the long trail (documented) of abysmal delivery and support issues by Allison to NAA for the NA-73X, NA-73, NA-83, NA-91, NA97, NA-99 with Kindelberger desperately trying to 'escape' Allison, beginning in fall 1941 and finally reaching conclusion in May 1942 when XP-78 was approved to proceed and AAF allocated the first two post test 1650-3 to NAA in July 1942.

PD studies began in July 1941 for Continental, then two stage Allison, Packard Merlin and Griffon by mid 1942. The Continental and Allison would have resulted in a complete re-design of the base NA-73 airframe and was never a consideration.