What if the P-39...

Salim · 12-11-2006, 05:20 PM

Well, I've been doing some thinking, and in all honesty I should have made a thread like this months ago, but I never got to it. Regardless, I'll start.

As we know, the P-39 was scorned by many for it's lack of high altitude performance, a dangerous tendancy to spin and a myraid of other problems, but when I decided to take a look at the original design of the airplane, one could actually see a rather interesting design that could have been a top notch airplane in 1941, equal or better than anything else the Axis could have had.

The Bell P-39

So here's my question... what if the USAAC didn't mess up the design and kept it as it was intended by Bell? I know that the performance of the production model wouldn't have matched the prototype (the proto had no weapons or armor) but it would have still been very considerable as far as I can see.

Well, any answers?

Marshall_Stack · 12-11-2006, 05:29 PM

With a functioning turbocharger and a better cannon, it could have been a good interceptor. The limitation of this plane is that it had a really short range of operation (not much fuel capacity init's small wings).

delcyros · 12-11-2006, 05:35 PM

I would rather remove the 3.7cm gun and replace it with a state of the art 20mm gun. Together with four wing mounted 0.50 cal M2 this would benefit anything in the plane and turn it into a decent air superiority fighter. Turbocharger is no must in this plane. Keep it simple and lightweighted. High alt performance is a necessarity for long range escorts or recon but not for air superiority over the battlefield. Early turbochargers tended to be complicated and prone to multiple failures. And they added a lot of weight.

Glider · 12-12-2006, 06:57 AM

The British did replace the 37mm with the 20mm giving it 1 x 20 and 6 x LMG which was more than sufficient for a fighter but it didn't make it a decent air superiority fighter. For than reason the turbo charger was a requirement to give it a chance.

That said, would a turbo charger have turned it into a silk purse? I think not.

Armour, Bullet proof glass, self sealing fuel tanks were needed and add weight. The aerofoil was flawed and would have taken time to sort and the vertical stabilizer needed work but that would be fairly quick to address.

Weight would always have been a problem. A cleaned up prototype aircraft (without armour, guns and protected tanks) was always going to be fast. Equiping it would and did, have a significant impact on performance. The basic design imposed an additional weight in the form of the link between the engine and the propeller.

Not everyone was fooled by the headline performance figures of the XP-39. The english magazine Flight I believe, pointed out that it was supposed to weigh about the same as a Spitfire, carry more fuel, have an armament that weighed a lot more than the 8 x LMG, had an engine of similar power, have a mid mounted engine with built in additional weight re the distance between the prop and the engine, whilst going 30-40mph faster. Frankly they simply didn't believe the claims and urged the RAF not to consider it.

I also wonder about the amount of testing that had been undertaken. To leave it to the RAF to find out that firing the guns knocked out the compass, let alone the cockpit filling with fumes, is a little late in the process.

Vassili Zaitzev · 12-12-2006, 07:25 AM

it probaly wouldn't be a good fighter, but it could intercept bombers.

twoeagles · 12-12-2006, 08:17 AM

It did become a fine fighter with the flaws removed, they called it the
P-63. It was just too late.

Glider · 12-12-2006, 10:24 AM

I understood that it was still limited to low level due to problems at altitude and was deemed unsuitable for action with the USAAF only being used for training.

Twitch · 12-12-2006, 11:23 AM

Yes, the P-63 was all the P-39 was not vindicating the concept somewhat.

DerAdlerIstGelandet · 12-12-2006, 11:49 AM

I dont know. I still dont think it would have been that great of an aircraft. Atleast not when compared to the P-47, P-51, Spitfire, Bf-109 and Fw-190s.

My main dislike of the aircraft is sitting on the damn shaft! I would hate that!

Matt308 · 12-12-2006, 11:57 AM

Maybe that's the problem. It was a woman's airplane!

twoeagles · 12-12-2006, 12:09 PM

And a shaft that vibrated, at that...

I did watch a P-63 race in heats against the usual pack of P-51's,
and up until it burned out some sparkplugs, it was holding its own.
After it made it back to the ramp and shut down a very rough engine, the
loudspeakers blasted "will the Champion representative please report to
the P-63!" I think Frank Borman owns that bird today.

twoeagles · 12-12-2006, 12:56 PM

Listen to the P-39 gearbox whine..This can be found via a link
on the Aircraft Engine Historical Society page, a group many of
you will find interesting. AEHS Home

Matt308 · 12-12-2006, 02:10 PM

Way cool.

Salim · 12-12-2006, 05:53 PM

Yeah, the production model would have probably have been slower, but still. That airplane had a lot of potential. If given a chance, the guys at Bell would have probably made it perform like the P-63 by the time America entered the war, and this would have given the US a decent advantage in the air war... with the Zeroes and Oscars around, a decent fighter always a good thing.

Tony Williams · 12-12-2006, 06:11 PM

It would have been interesting if the designers had taken an even more radical route - kept the central engine location, but transferred the power to two small props just ahead of the wing leading edge. I doubt that the gearing and structural stiffening would have been much worse than it was. Then move the cockpit to the nose, with the guns running underneath and the magazines installed behind it.

On paper, this achieves a number of advantages:
- puts the ammo weight closer to the centre of lift, so the trim isn't affected as it's used up.
- increases the firepower of the .50s which no longer need to be synchronised
- improves the pilot's forwards/downwards view
- improves the low-speed lift due to propwash being spread over the wings.

Whether it would reallly have been better I don't know, but it would have been interesting.

I agree that the 37mm was a suboptimal gun for most purposes: too slow-firing, and with a rainbow trajectory. The US should have done a deal with the Russians to make their 23mm VYa-23 cannon for it; much harder hitting than the 20mm Hispano and almost as fast-firing, for not a lot more weight. The trajectory would have been a close match for the .50 as well.

Tony Williams: Military gun and ammunition website and discussion forum