The Bell P-39 Airacobra was a fighter produced for the U.S. Army Air Forces during World War II.
It was one of the principal American fighters in service when the United States entered combat.
Bell Model 11, one prototype 38–326 first flown 6 April 1938.
Powered by an Allison V-1710-17 engine (1,150 hp/858 kW), the aircraft was fitted with a General Electric B-5 turbo supercharger, creating a two stage supercharging system similar to the P-38 (engine-mounted mechanical supercharger, remote exhaust-driven turbo-supercharger as a second stage for high-altitude).
Provision was made for two .50 in (12.7 mm) machine guns in the forward fuselage and one 25 mm (.98 in) cannon but aircraft remained unarmed.
Later converted to XP-39B.
One conversion first flown 25 November 1939.
Streamlined XP-39 based on NACA wind tunnel testing resulting in revised canopy and wheel door shape, oil cooler/ engine coolant radiator intakes moved from right fuselage to wing roots, fuselage increased length (by 1 ft 1 in, to 29 ft 9 in) and decreased wingspan (by 1 ft 10 in, to 34 ft).
The turbo supercharger was removed, and the single-stage, single speed, supercharged Allison V-1710-37 engine (1,090 hp/813 kW) was left in place.
The carburettor air intake was moved behind canopy, just above the carburettor.
Bell Model 12, service test version, V-1710-37 engine (1,090 hp/813 kW).
First two aircraft delivered with armament, the remained with a M4 37 mm (1.46 in) auto cannon with 15 rounds, 2 × .50 in (12.7 mm) machine guns with 200 rpg, and 2 × .30 in (7.62 in) machine guns with 500 rpg in the nose.
Wider vertical tail than XP-39B.
12 completed with the first flying 13 September 1940.
One intended to have a high-altitude V-1710-31 engine (1,150 hp/858 kW), but was delivered as a regular YP-39.
Bell Model 13, first flown in January 1941 it was the first production version, identical to YP-39 except for V-1710-35 engine (1,150 hp/858 kW).
Armed with 1 × 37 mm (1.46 in) cannon, 2 × .50 in (12.7 mm) & 2 × .30 in (7.62 mm) machine guns in the nose.
Aircraft lacked armour and self-sealing fuel tanks.
Twenty produced out of an order of 80 the remainder were redesignated P-39D
Bell Model 13, production variant based on the P-39C with 245 lb (111 kg) of additional armour, self-sealing fuel tanks.
Armament increased to 1 × 37 mm/1.46 in cannon (30 rounds), 2 × .50 in/12.7 mm (200 rpg) and 4 × wing mounted .30 in/7.62 mm (1,000 rpg) machine guns, 60 Produced.
Bell Model 14A, production variant fitted with a 20 mm (.79 in) M1 cannon.
Specifically ordered for delivery under Lend-Lease, 336 produced, 1 sent to Soviet Union and used in combat alongside P-39D-2s.
Bell Model 14A-1, production variant with a V-1710-63 engine (1,325 hp/988 kW) restored the 37 mm (1.46 in) cannon, provisions for a single 145 gal (549 l) drop tank or maximum 500 lb (227 kg) bomb under the fuselage, 158 produced.
Some 50 at least sent to USSR and used in combat, some 15–20 used by 16th Guards Fighter Regiment.
26 conversions from P-39D-1 to Photo Reconnaissance Configuration, K-24 and K-25 camera in rear fuselage, extra armour for oil coolers
11 conversions from P-39D-2 to Photo Reconnaissance Configuration.
Same modifications as D-3 aircraft.
Bell Model 23, three P-39Ds modified for ground and flight testing first flown 21 February 1942.
Intended for Continental I-1430-1 engine with (2,100 hp/1,566 kW) actually flown with Allison V-1710-47 (1,325 hp/988 kW) engine.
Airframes were used to test various wing and different vertical tail surfaces.
Fuselage was lengthened by 1 ft 9 in (53 cm).
Used in the development of the P-63.
The production variant, with the Continental engines was to be redesignated P-76, there was no Bell XP-76 as such.
Bell Model 15B, production variant with three bladed Aeroproducts constant speed propeller, 12 exhaust stacks, 229 built.
One P-39F converted as a two seat training version with additional cockpit added in nose, no armament.
27 conversions from P-39F-1 with additional belly armour and cameras in rear fuselage.
Bell Model 26, 1800 ordered, intended to be a P-39D-2 with an Aeroproducts propeller.
Due to modifications during production no P-39G were actually delivered.
Instead, these aircraft were re-designated P-39K, L, M and N.
Bell Model 15B, P-39F with V-1710-59 (1,100 hp/820 kW) engine with automatic boost control, 25 built.
Bell Model 26A, a P-39D-2 with Aeroproducts propeller and V-1710-63 (E6) (1,325 hp/988 kW) engine.
Vents added to nose, 210 built.
Some 50 sent to USSR and used in combat, 16th Guards Fighter Regiment were initially issued 11, 1 of which was Pokryshkin’s first Airacobra.
Six conversion from P-39K-1 with additional belly armour and cameras in rear fuselage.
One conversion with a V-1710-85 (E19) engine to serve as a P-39N prototype
Lend-Lease to USSR
Bell Model 26C, a P-39K with Curtiss Electric propeller, revised nose gear for reduced drag, provision for under wing rockets, 250 built.
Eleven conversions from P-39L-1 with additional belly armour and cameras in rear fuselage.
Bell Model 26D, variant with an 11 ft 1 in Aeroproducts propeller, V-1710-67 (1,200 hp/895 kW) engine with improved high-altitude performance at the expense of low altitude performance, 10 mph (16 km/h) faster than P-39L at 15,000 ft (4,600 m).
Some P-39M-1BE were delivered with the V-1710-83 engine, 240 built.
Bell Model 26N, originally part of the P-39G order.
V-1710-85 (E19) (1,325 hp/988 kW) engine.
Aeroproducts propeller (10 ft 4 in diameter) & different propeller reduction gear ratio.
Starting with the 167th aircraft, propeller increased to 11 ft 7 in & internal fuel reduced from 120 gal (454 l) to 87 gal (329 l), 500 built.
Variant with internal changes to adjust centre of gravity when nose guns were fired, 900 built.
128 P-39N-1 converted with additional belly armour and cameras in rear fuselage.
35 P-39N converted with additional belly armour and cameras in rear fuselage.
Variant with armour reduced from 231 lb (105 kg) to 193 lb (88 kg), armour plate replaced the bulletproof glass behind the pilot, SCR-695 radio was fitted, and a new oxygen system was installed, 695 built.
84 P-39N-5 converted with additional belly armour and cameras in rear fuselage.
The final production variant last one built in August 1944.
Bell Model 26Q, variant with wing-mounted 0.30 in (7.62 mm) machine guns replaced with a single 0.50 in (12.7 mm) with 300 rounds of ammunition in a pod under each wing.
Armour increased to the original 231 lb (105 kg) of armour of the P-39N-1BE, 150 built.
Five P-39Q-1s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.
Production variant with reduced armour (193 lb/88 kg), fuel capacity increased (110 gal/416 l).
Automatic Boost controls added and Throttle & RPM controls were coordinated.
Winterization of oil systems and rubber mounts added to the engines, 705 built.
Eight P-39Q-10s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.
Production variant with reinforced inclined deck to prevent .50 in (12.7 mm) machine gun tripod mounting cracking, bulkhead reinforcements to prevent rudder pedal wall cracking, a reinforced reduction gearbox bulkhead to prevent cowling former cracking, and repositioning of the battery solenoid.
Oxygen system reduced from four bottle to only two, 1,000 built.
Production variant with minor equipment changes.
The under wing 0.50 in (12.7 mm) machine gun pods were sometimes omitted in this version, 1,000 built.
109 P-39Q-20 fitted with a four bladed Aeroproducts propeller.
12 P-39Q-20s converted to two-seat trainers .
Production variant similar to the P-39Q-21 but with a reinforced aft fuselage and horizontal stabilizer structure, 700 built.
Production variant that reverted to the three-bladed propeller, 400 built.
Remaining examples in service, re-designated in June 1948.
The P-45 was the initial designation of the P-39C or Model 13.