I think the P-39 could have benefited from the installation of a turbo-supercharger if a few changes to the airplanes' design had been implemented. There was adequate room to the rear of the engine if space had been freed up by getting rid of useless accessories like landing flares, tool kit and lastly the first aid kit which should be in the pilots' bail out package.
To fit a P-38 size turbo-supercharger in the P-39's rear fuselage that is not as bulky and draggy as Bells' first attempt will necessitate a more compact method of charge cooling. Why not liquid cool the hot compressed air from the turbo-supercharger? In all the USAAF airplanes including bombers and fighters flown in WW2 that used turbo-superchargers (TSC) charge temperature control was done by directing the compressed air from the TSC through a heat exchanger that was cooled by outside air being ducted to the heat exchanger and than the cooled down air was ducted to the carburetors.
This system was simple, adequate and robust but bulky because of all the ducting that was used. Not a big drawback for bombers or a spacious airplane like the P-47. It was a difficulty for a leaner airplane like the P-38 which could have benefited from my suggested innovations and an absolute necessity for a smaller plane like the P-39 especially in view of the botch job Bell Aircraft did in trying to install a TSC in the P-39 albeit they were hampered by existing Air Corps requirements for outdated ideas like landing flares and toolkits using up valuable space.
To reduce the bulky OTL intercooler installation have the ducting run from the TSC directly to the carburetors. In that ducting just before its connection to the carbs is placed a heat exchanger that is connected by tubing to a small radiator. A liquid (namely Glycol and water) system is used for removing excess heat from the TSC compressed air.
The small radiator would be located on the inside skin of the fuselage and would be exposed to the slipstream through a forward facing opening and rearward adjustable door. This and a variable pump (electric, mechanical, hydraulic?) would permit with well designed thermostats a precise control of the charge temperature. I think the P-38 would have benefited from a similar system.
Does this arrangement sound familiar? It is very similar to the method used in the two stage mechanically supercharged Merlin engines to control the charge temperature in the later Spitfire versions and the Mustangs as well. Regardless of how the compressor is driven the compressed air has to be within the temperature limits to ensure reliable engine performance.
Now since we have been able to fit a properly working turbo-supercharger into the P-39 giving it a much improved high altitude performance how else can we improve the Bell Airacobra?
First off remove the .30 guns from the wings so as to add extra fuel tankage thereby increasing the internal fuel capacity and thus overall range of the P-39.
Because the turbo-supercharger is installed in a similar way to the P-38 with the turbine level with the top of the rear fuselage 2 feet behind where the OTL air scoop is located the supercharger air intake is now positioned on the right side of the fuselage beside the TSC location. There is no ingestion of exhaust gasses as these would be now piped back to the TSC.
The entire cockpit canopy is redesigned to a 3 piece fixture consisting of a forward windshield using a built in armoured glass. And a sliding one piece canopy cover. And a one piece rearward facing windshield. This would greatly improve the visibility from the OTL P-39 by removing the cockpit framing.
The 37mm cannon should be replaced by the 20mm AN2 cannon. The 20mm would have a larger ammunition supply than the 37mm and with the higher muzzle velocity and higher rate of fire it would be a better suited weapon for our new ATL interceptor/fighter P-39. With a smaller cannon up front would there be room for another .50 HMG and its ammunition? What a punch that would be for our hotted up little Airacobra. 3 .50s and a 20mm.
Just imagine Bell Aircraft churning out these planes in quantity in 1941. Once the Air Corp pilots figured out how best to utilize them (bigger boom and a little more zoom) they would have been clearing the skies over New Guinea and the Solomons months earlier and hammering the Luftwaffe harder in the Med.
And in an America stands alone scenario our ATL P-39 would be a lot cheaper than the P-38 and more easily mass produced and still a very capable airplane instead of some death trap like an XP-77 and its ilk.
To fit a P-38 size turbo-supercharger in the P-39's rear fuselage that is not as bulky and draggy as Bells' first attempt will necessitate a more compact method of charge cooling. Why not liquid cool the hot compressed air from the turbo-supercharger? In all the USAAF airplanes including bombers and fighters flown in WW2 that used turbo-superchargers (TSC) charge temperature control was done by directing the compressed air from the TSC through a heat exchanger that was cooled by outside air being ducted to the heat exchanger and than the cooled down air was ducted to the carburetors.
This system was simple, adequate and robust but bulky because of all the ducting that was used. Not a big drawback for bombers or a spacious airplane like the P-47. It was a difficulty for a leaner airplane like the P-38 which could have benefited from my suggested innovations and an absolute necessity for a smaller plane like the P-39 especially in view of the botch job Bell Aircraft did in trying to install a TSC in the P-39 albeit they were hampered by existing Air Corps requirements for outdated ideas like landing flares and toolkits using up valuable space.
To reduce the bulky OTL intercooler installation have the ducting run from the TSC directly to the carburetors. In that ducting just before its connection to the carbs is placed a heat exchanger that is connected by tubing to a small radiator. A liquid (namely Glycol and water) system is used for removing excess heat from the TSC compressed air.
The small radiator would be located on the inside skin of the fuselage and would be exposed to the slipstream through a forward facing opening and rearward adjustable door. This and a variable pump (electric, mechanical, hydraulic?) would permit with well designed thermostats a precise control of the charge temperature. I think the P-38 would have benefited from a similar system.
Does this arrangement sound familiar? It is very similar to the method used in the two stage mechanically supercharged Merlin engines to control the charge temperature in the later Spitfire versions and the Mustangs as well. Regardless of how the compressor is driven the compressed air has to be within the temperature limits to ensure reliable engine performance.
Now since we have been able to fit a properly working turbo-supercharger into the P-39 giving it a much improved high altitude performance how else can we improve the Bell Airacobra?
First off remove the .30 guns from the wings so as to add extra fuel tankage thereby increasing the internal fuel capacity and thus overall range of the P-39.
Because the turbo-supercharger is installed in a similar way to the P-38 with the turbine level with the top of the rear fuselage 2 feet behind where the OTL air scoop is located the supercharger air intake is now positioned on the right side of the fuselage beside the TSC location. There is no ingestion of exhaust gasses as these would be now piped back to the TSC.
The entire cockpit canopy is redesigned to a 3 piece fixture consisting of a forward windshield using a built in armoured glass. And a sliding one piece canopy cover. And a one piece rearward facing windshield. This would greatly improve the visibility from the OTL P-39 by removing the cockpit framing.
The 37mm cannon should be replaced by the 20mm AN2 cannon. The 20mm would have a larger ammunition supply than the 37mm and with the higher muzzle velocity and higher rate of fire it would be a better suited weapon for our new ATL interceptor/fighter P-39. With a smaller cannon up front would there be room for another .50 HMG and its ammunition? What a punch that would be for our hotted up little Airacobra. 3 .50s and a 20mm.
Just imagine Bell Aircraft churning out these planes in quantity in 1941. Once the Air Corp pilots figured out how best to utilize them (bigger boom and a little more zoom) they would have been clearing the skies over New Guinea and the Solomons months earlier and hammering the Luftwaffe harder in the Med.
And in an America stands alone scenario our ATL P-39 would be a lot cheaper than the P-38 and more easily mass produced and still a very capable airplane instead of some death trap like an XP-77 and its ilk.
