What if the P-39...

[Salim]

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]

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]

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]

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]

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

 

[twoeagles]

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

 

[Glider]

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]

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

 

[DerAdlerIstGelandet]

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]

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

 

[twoeagles]

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]

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]

Way cool.

 

[Salim]

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]

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

 

[delcyros]

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.

Interesting idea. But there are tradeoffs as well:
*The cockpit in the front would mean to expose the pilot more to pitch forces.
*The twin prop layout would add more weight to the wings. This is suspect to negatively affect it´s initial roll rate
However,
*with the guns under the fuselage, it takes away almost all blinding issues and most convergence issues as well!

Anyway a nice display.

I also think that the YVa-23 is excellent altough a domestic US cannon in the area of 25mm should work best. Perhaps remove the big gun for 3-4 fuselage mounted 15mm high velocity Cal.60´s?

 

[Tony Williams]

I also think that the YVa-23 is excellent altough a domestic US cannon in the area of 25mm should work best. Perhaps remove the big gun for 3-4 fuselage mounted 15mm high velocity Cal.60´s?

The problem the USA had at that time was that, due to the lack of funds for gun development between the two world wars, they did not have much in the way of design expertise in automatic weapons, especially large-calibre ones. The 37mm M4 had actually been designed by the great master, John Browning, years before.

The US did try to come up with better aircraft guns. There was the 23mm T1 to T4 programme of the late 1930s and early 40s, which produced nothing worthwhile and was scrapped. Then they tried to adapt the excellent Mauser MG 151 to their own .60 calibre cartridge, as you mention, but that never got anywhere either. Incidentally, they tried to adapt the MG 42 to .30-06 calibre, and made a mess of that as well. And of course, they made another mess of producing the 20mm Hispano, even though all they had to do was copy what the British were doing. Not until well after WW2, with the M61 Vulcan programme, were they able to produce anything worth having. It's just as well that the .30 and .50 Brownings had been perfected before the war.

In contrast, the Russians had an entire college set up in the 1920s to train engineers in gun design. No wonder they came up with such good weapons. And the Germans and the Swiss, of course, seemed to have a natural talent, presumably fostered by a thriving and competitive gun-making industry. The Japanese also producing some interesting designs, considering their lack of resources, although they were mainly based on Oerlikons or Brownings.

Tony Williams: Military gun and ammunition website and discussion forum

 

[Jabberwocky]

That the USAAF neutered the P-39 is to no small extent true. However, you have to remember that, due to many reasons, the performance of the XP-39 couldn't really have been replicated on production machines and that the philisophy of the USAAF at the time didn't really favour high altitude interceptors.

The quite excellent 390 mph top speed and 5 minutes to 20,000 feet climb figures that the XP-39 achieved in testing were for an unarmed, polished prototype without any military equipment. The XP-39 that achieved them weighed just 3,995 lbs empty (only 200lbs heavier than an empty A6M Zero and more than 1,400lbs lighter than P-40 protoypes). If you add military equipment, like self sealing fuel tanks, military radios, antenna, armour, guns, gunsights, gun heaters, ammunition, IFF and all the other stuff necessary to make the plane a workable fighter, performance is going to take a nose dive.

Just to give an idea of how much weight creep there would be, the empty weight of the YP-39 was 5,040 lbs, up just over a 1,000 lbs from the 3,995 lbs of the XP-39. That's a weight gain of just over 25% on the empty weight AFTER stripping out the heavy turbosupercharger. Loaded weight shot up from 5,550 lbs for the unarmed XP-39 prototype to 7,070 lbs for the armed YP-39, and it was still without internal or cockpit armour and had no self sealing fuel tanks. When these, and more guns and ammunition were added, combat weight climbed by another 500lbs.

So, a fully loaded, combat capable P-39D circa September 1941, weighted around 7,650 lbs, almost a full 2,100lb heavier than its turbosupercharged XP-39 ancestor. Its empty weight was 1,400lbs higher than that of the XP-39 prototype. That increase would markedly effect handling, speed and climb performance.

Would the P-39 have been better a better fighter in the ETO and Pacific if the USAAF had left it alone? Yes, but probably not by much. It would of been marginally slower and less manouverable down low, but progressively faster above 15,000 feet. Its problems with CoG and cannon reliability would of still existed.

To turn the P-39 into a fighter it needed all that equipment. So, the weight creep that was allways going to happen meant that the performace exhibited by the prototype wouldn't of been achievable in real life unless there was a serious jump in power in the military models.

 

[Tony Williams]

To be fair, the cannon reliability issue seems to have been a short-term problem. The M4 kept jamming after the first shot or two, and it was discovered that it wasn't really the gun's fault - the slot for ejecting spent cartridge cases was too small, or not the right shape (I forget which) so the cases kept getting stuck in it. Once the slot was modified, that problem went away and the gun was then quite reliable I believe.

Tony Williams: Military gun and ammunition website and discussion forum

 

[Salim]

OK fellas, one quick question.

What if the engine powering the P-39 was powered by an engine 15% stronger? As in, a 1350 hp powerplant? Since the additional power would probably help offset some of the performance degradation of the added armor and weapons. What do you think would have happened?

Just a hypothetical question... OK, I'll be totally serious as to why I'm asking all these question (as I did in most previous threads). I'm planning to write a series of 'modern fantasy' novels and the P-39 and Buffalo are going to make 'modified' appearances, if you take my meaning. I've even begun writing the first story... about time, too, I should have started months ago!

The biggest problem in my stories is creating a realistic 'fantasy airforce', hence the reason why I research so much about the topic.