P 39 questions

[MacArther]

I have often read that our (USAAF) pilots deplored using the P 39 against enemy fighters in the European and North African theatres. I have also heard that on the flight debut (of the P 39) with the British, the plane was immediately given a bad reputation, leading to only one squadron being equipped with the fighter. What made the P 39 so bad in running dogfights? I am aware of the lack of supercharger, but were there other limitations in the design? On top of all of this, how were the Russians able to use the fighter (not to meant be condescending in any way) and have pilots enjoy the aircraft and request it?

 

[delcyros]

They have modified it a bit.
Usual russian field conversion included the removal of most of it´s armor, partly also the replacement of the heavy centerline gun by a lighter soviet 20 or 23 mm gun (don´t recall correctly). The weight reduction greatly improved the low speed handling, increasing the turn rate and acceleration considerably. The stall speed also was little lower, but it remained worrisome stall charackteristics. However, the best advantages for the VVS flyers were reliable radio communication and reflection gunsights. Just from what I read.

 

[lesofprimus]

From what I know and recall, many a young Russian pilot died while stalling out his P-39...

 

[FLYBOYJ]

Mac if you go into some of the older threads we've had a whole bunch of P-39 discussions, but I'll throw some info in here...

The P-39 had a very small center of gravity and actually had 2 CG envelopes that had to be maintained. The aircraft could be a bit unstable but that is actually a positive trait in a fighter. Check Yeager has said on several occasions it was his favorite WW2 aircraft.

The 39th FS began to score against the Japanese using the P-39 and P-400 (the export version of the P-39 with a 20mm cannon in the nose) to the point were they were actually gaining air superiority over New Guinea in late summer 1942. The P-39 was fast but easily outmaneuvered by the Japanese, and it had poor high altitude performance. A big plus was its tri-cycle landing gear which makes it easier to land than say a P-40.

One thing for sure - one hit from its 37mm cannon and any Japanese fighter was turned to small pieces of aluminum....

 

[plan_D]

The Airacobra's lack of supercharger made it unsuitable for the ETO where combat took place at anywhere up to 30,000 feet and beyond. When flying a P-39 it was always best to keep it below 15,000 feet, and this suited the Russian front perfectly. Combat on that front took place anywhere between 0 - 15,000 feet, and mostly at 4,000 - 6,000 feet which was ideal for the P-39. This is why the VVS had some decent success in the P-39. It could certainly fight against the best of the Germans in 1942-'43 but I'd always much prefer the German fighters.

The P-39 got an awful name in the RAF, correct. But that wasn't true throughout. Some pilots of the RAF admitted that the P-39 could, in fact, get the better of the Bf-109E if handled properly and kept in it's heights of combat. It must be remembered that the RAF operated the P-39 in the ETO at heights of 20,000 + feet, where the lack of a supercharger was felt.

The XP-39 was the greatest fighter of the day it rolled out on to the pan.

 

[Jabberwocky]

The P-39 had a supercharger, it was just a single stage, single speed supercharger tuned for low altitude operations, while Merlins had a two speed supercharger, giving better performance at height.

The V-1710 family had excellent performance below 14,000 feet. In fact, in many respects it was a superior engine to the Merlin for low altitude operations, being a touch heavier built and able to absorb more power at low level.

However, in 1940-43 most fights in the ETO BEGAN at 18,000 feet and upwards. Spitfires used to do stacked patrol beginning at 22,000 feet and finishing at 28,000 feet.

The P-39 didn't offer the RAF anything that it didn't already have apart from a good top speed below 10,000 feet. The Spitfire I/II/V already in service climbed better at all heights, were more nimble in the vertical and horizontal, and were faster at all heights above 15,000 feet. The 'B' wing armament of 2 Hispanos and 4 .303s was judged superior for aerial combat to the mixed .50, .303 and 37mm armament of the P-39. The instability of the P-39 in certain manouvers as well as its tendency to fall into a flat spin also meant that pilots weren't especially well predisposed to it.

The initial promises of the Bell Aircraft Corportation to the British Purchasing Comissions also went unmet. Bell promised to deliver a plane capable of 400 mph, with a 1000 mile range and a 36,000 foot flight ceiling. What it delivered was a 365 mph plane with a 600 mile range and a effective flight ceiling of far less than 30,000 feet. The British felt that the P-39 wasn't really useful above 15,000. It was judged against a Spitfire and a Hurricane, and testing revealed that while in some respects it was a more advanced fighter, it was actually less capable than either of the RAF birds. Furthermore, its long take off run made it unsuitable to the small grass airfields that some RAF bases still operated.

 

[DaveB.inVa]

The P-39 had a supercharger, it was just a single stage, single speed supercharger tuned for low altitude operations, while Merlins had a two speed supercharger, giving better performance at height.

The V-1710 family had excellent performance below 14,000 feet. In fact, in many respects it was a superior engine to the Merlin for low altitude operations, being a touch heavier built and able to absorb more power at low level.

Thank you!! My thoughts exactly!!

 

[Twitch]

I had the pleasure of spending a day with a bunch of pilots that flew P-39s together before being assigned some decent fighters later. Without a doubt, unanimously they rated the P-39 as very poor, below the P-40 even.

The 37mm gun would always jam after a couple rounds so it was worthless weight in the nose. The trajectory was sad when it did fire. The P-400 export version with the 20mm was OK but make no mistake, American pilots disliked this plane's inferior performance most of which has already been described.

 

[FLYBOYJ]

Everyone Sing,

"Don't give me a P-39,

The one with the engine behind,

She'll tumble and roll

and make a big hole,

Don't give me a P-39!"

 

[Dogwalker]

Many people may not be aware that the Airacobra flew in Italian service after the Armistice.
Indeed, 170 P-39s were handed over to Italy. These aircraft were in such poor condition that 21 never again took to the air.
It is a credit to the Italian ground crews and pilots that they managed to get 149 Airacobras airworthy and flew them to good effect over the Balkans.

Glen Porter


Marco Mattioli, "Bell P-39 Airacobra in Italian service", a poor translation of mine:

"in three monts (beginning 18/07/1944) of intense training (at Campo Vesuvio, near Naples) with P39N, 77 pilots of 4°stormo made 1702 flighs for a total of 1000 h, there were 11 accidents, that caused the death of 3 pilots and 2 badly injured.
The first of the fatal accidents was that of lt. Armando Moresi, on 20/07/1944, while flying in couple with lt. Giorgio Bertolaso (after, general of the Air Force). Moresi was a very good acrobatic pilot and tried to do a looping with his P39, loosing control he decided not to bail out, but tried to regain control without success and finally hit the ground.
Moresi's death convincted lt. Bertolaso to not try acrobatics with the P39, he remembered the only conseil that the American chief pilot that delivered the aircrafts to the Italians, a major wich name he couldn't recall, gave to them: the P39 is a meravillious aircraft, but don't do acrobatics with it. I flew more than 500 hours with it and, if I'm still alive, its due to the fact that I resisted to do acrobatics with it.
For many Italians, convincted that a good fighter had to be a goot acrobat, this was like a challenge and, for this, some died.
P39 was effectively an ideal aircraft for ground suport, but not for acrobatics. Gen. Bertolaso remember: the orizontal stabilizer of Airacobra was simply too close to the wings for the way the pound was disposed, in tight turn it entred in the shadow of the wings (the zone of unclean air generated by the wings) and stall suddenly, before the wings themself, so the aircraft began to rotate around his transversal axis and there was nothing to do to recover it. Someone, nobody know how, succeded to exit from this situation, but it was only a case, the major part had simply to bail out.
Another source of problems was the engine. While ours, or DB, engines had the fuel injection and an idraulically driven supercharger, the Allison V-1710 had the carburetor and a mechanically driven supercharger. The difference was that the first solution provided a very stable air-fuel mixture and a certain elasticity in the functioning of the supercharger. The Allison instead, under certain flight conditions, suffered of suddenly leaning of the mixture, that provoked big "returns of fire" (I don't know the translation, they are the explosions in the exaust caused by a too lean mixture) that were very violent shocks for the too rigidly driven supercharger. In those conditions the gears of the supercharger easily broken off, the pieces were swallowed from the engine and destroyed the cylinder heads.
I personally had this terrible experience, during a tonneau at low altitude. Fortunately, apart of the supercharger, the Allison was a rugged unit, and, even with some smashed cylindres, it carryed me back to the airfield..
Two engine failures at takeoff caused the other two deaths of the training unit, that of sgt. Teresio Martinoli (the third leading Italian ace, with 22 individual victories) on 22/08/1944 and that of lt. Guerniero Silvestrini (in the opinion of lt. Bertolaso, that viewed the accident, it was caused by the overheating of the engine, cause Silvestrini's aircraft rest for a too long time at the end of the airstrip with the engine switched on) killed by the explosion of the auxiliary fuel tank on 27/09/1944.
Another engine failure was that of the aircraft of lt. Rizzitelli on 07/09/1944. In this case, it was caused by the vulcanic powder aspired by the engine (there was an eruption of mount Vesuvio in the summer 1944), but Rizzitelli succeded to land at very high speed without the undercarriage. In the hit the Airacobra lost his nose, and the pilot lost his shoes too! But finally the plane stopped, leaving the pilot barefoot, but completely unharmed".

DogW

 

[Jabberwocky]

"returns of fire" would probably be 'backfires'. Backfires and rough running were a problem that RAF Mustang I/II pilots noted as well.

 

[Dogwalker]

Yeah. "Backfires" is the right word!

DogW

 

[FLYBOYJ]

Yep - common occurance when running too lean, out of timing, or bad exhaust valves.....

 

[KraziKanuK]

How long will this myth that the Allison V-1710 did not have a supercharger persist?

The specs told to the Brits were for the turbo-supercharged engine. Naturally when it lost the tc it could not perform to the given specs.

Did the Allisons use a float carb or an injection 'carb'?

 

[FLYBOYJ]

How long will this myth that the Allison V-1710 did not have a supercharger persist?

The specs told to the Brits were for the turbo-supercharged engine. Naturally when it lost the tc it could not perform to the given specs.

Did the Allisons use a float carb or an injection 'carb'?

I believe they used a "Pressure Carb."