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I don't think it didWhy did the P-39 perform, or seem to perform, so much more poorly than the P-40 - particularly in the early war years?
Spinning is about the worst possible problem to have when you are flying at low altitude. I suspect some pilots were afraid to fly the P-39 at max ability for fear of a low altitude spin.It had handling problems, I think spinning was one of them.
Never doubted it for a minuteSpinning is about the worst possible problem to have when you are flying at low altitude.
I suspect some pilots were afraid to fly the P-39 at max ability for fear of a low altitude spin.
Low endurance is a huge problem, as the Luftwaffe discovered during the Battle of Britain.
The problemTurbocharger:
Mounting the turbocharger close to the engine, as was done on the P-38 and bombers, makes for a clean, simple and compact package. The P-39 seemed to provide a great opportunity for this.
I always read about how the mid-engine placement was ideal for the nose mounted cannon and a streamlined profile, but I can't help but feel that turbocharger placement was a great beneficiary of this layout
The problem
with turbocharger arrangements is the hefty volume of ducting to and from the engine and the double problem is where would you put it all in the P-39? It sat behind the pilot in the P-47 (a substantially bigger bird than the P-39) but with the engine behind the pilot in the P-39, it clearly can't go there; Bell needed to weigh up the pros and cons of their lower-profile canopy vs the choice of single or two-stage supercharging, it might have had a different history altogether with the western Allied airforces.
My apologiesThe prototype XP-39 flew with the turbocharger and performed well.
The P-38 mounted the turbo behind the engine in the nacelle nicely.
Extensive ducting is not required.
IIRC there was capacity promlem in turbocharger production, bombers needed it also. At least part of USAAF hierarcy saw the main function of US fighters as protection of USA beaches against invasition, so low altitude work, so no need to put turbo into all fighters.
Juha
The P-38 and P-47 cost twice as much as many other fighter aircraft. Which suggests to me that turbochargers and their associated ducting were very expensive. Not even the U.S. can afford to turbocharge the entire fighter force.
Throughout its service life, many considered the P-39 to be a maintenance nightmare, largely owing to...the biggest differance was in reliability. He said that the some part of the P-39 electrical system failed on every mission, and everything was electric...
The XP-39B was flown on 25Nov39 and was the XP-39 prototype rebuilt with considerable modification.I doubt this is why NACA removed the turbo from the XP-39
The XP-39B was flown on 25Nov39 and was the XP-39 prototype rebuilt with considerable modification.
Gone was the 1,150hp V-1710-17(E2) B-5 turbocharged powerplant and in came the 'improved' 1,090hp V-1710-37(E5) unit with single-stage intregral mechanical supercharger.
The removal of the turbocharger was recorded as necessary for two reasons, firstly, when the P-39 was being designed, US turbochargers weren't that reliable and secondly, NACA noted that the original Airacobra design had numerous lift and drag problems.
The changes made by NACA were done in stages, most were put in place at Langley Field, Virginia and the wind-tunnel tests determined a need for the improvements that were incorporated into the XP-39B. These included:
streamlining and reducing the size of the wheel doors
lowering and streamlining the canopy
moving the carburettor air scoop from the left side of the cockpit to directly behind the cockpit and
moving radiators from the fuselage sides to the central wing-root leading edges
along with a slightly altered fin and an all-up weight increased by about 15%
Top photo: The prototype P-39 (38-326), progenitor of all Airacobras to follow, poses at Wright Field around the time of its 06Apr39 maiden flight. The P-39 had a radiator and oil cooler on its starboard side behind the exhaust outlets and a three-bladed Curtiss-Wright propeller. The details of the cockpit underwent numerous changes from the drawing board to the flight line. via Dave Ostrowski
Lower photo: The XP-39B in its initial configuration at the Buffalo plant on 05Dec39. Bell via Truman Partridge
Why did the P-39 perform, or seem to perform, so much more poorly than the P-40 - particularly in the early war years?
Both were V-1710 powered, sans turbocharger with single stage/single speed supercharger.
I know the P-39 had short endurance.
But what else?