During World War II, Bell Aircraft manufactured the Bell P-39 Airacobra as a fighter for the United States Army Air Forces.
This aircraft played a significant role as one of the primary American fighters in active service when the United States joined the combat.
Notably, the Soviet Air Force utilized the P-39, allowing individual Soviet pilots to achieve the highest number of kills credited to any U.S. fighter model operated by any air force during any conflict.
Additionally, the Free French, the Royal Air Force, and the Italian Co-Belligerent Air Force were among the other notable users of this aircraft.
The P-39 featured a unique layout, positioning the engine in the centre fuselage behind the pilot, and utilizing a tractor propeller in the nose connected by a long shaft.
Additionally, it was the first fighter to have a tricycle undercarriage.
Despite its innovative mid-engine placement, the P-39 design suffered from the lack of an efficient turbo-supercharger, limiting its high-altitude capabilities.
As a result, the RAF declined its use in western Europe, but it was embraced by the USSR due to most air combat occurring at medium and lower altitudes.
Alongside its variant, the Bell P-63 Kingcobra, the P-39 stood out as one of Bell’s most successful fixed-wing aircraft.
Variants
XP-39-BE
The Bell Model 11, a prototype 38–326, took its first flight on 6 April 1938.
Equipped with an Allison V-1710-17 engine (1,150 hp/858 kW), the aircraft featured a General Electric B-5 turbo supercharger, creating a two-stage supercharging system similar to the P-38.
This system consisted of an engine-mounted mechanical supercharger and a remote exhaust-driven turbo-supercharger as a second stage for high-altitude flights.
Although provision was made for two .50 in (12.7 mm) machine guns in the forward fuselage and one 25 mm (.98 in) cannon, the aircraft remained unarmed.
It was later converted to XP-39B.
XP-39B
The initial prototype took its maiden flight on 25th November 1939.
The XP-39 was redesigned based on NACA wind tunnel testing, resulting in modifications such as a revised canopy and wheel door shape, relocation of oil cooler/engine coolant radiator intakes from the right fuselage to the wing roots, an increase in fuselage length by 1 foot 1 inch to 29 feet 9 inches, and a decrease in wingspan by 1 foot 10 inches to 34 feet.
The turbo supercharger was eliminated, and the Allison V-1710-37 engine (1,090 hp/813 kW) remained with a single-stage, single-speed supercharger.
The carburettor air intake was repositioned behind the canopy, just above the carburettor.
YP-39
The Bell Model 12, service test version, is equipped with a V-1710-37 engine generating 1,090 hp/813 kW.
The first two aircraft were delivered with armament, while the rest were armed 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.
It features a wider vertical tail compared to the XP-39B.
The 12 aircraft were completed with the first one taking flight on September 13, 1940.
YP-39A
The initial plan was to equip it with a powerful V-1710-31 engine (1,150 hp/858 kW) suitable for high-altitude operations, but unfortunately, it was ultimately supplied with a standard YP-39 engine.
P-39C
The Bell Model 13, which took its first flight in January 1941, was the initial production variant.
It was nearly identical to the YP-39, with the only difference being the V-1710-35 engine (1,150 hp/858 kW).
This aircraft was equipped 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.
However, it lacked armour and self-sealing fuel tanks.
Out of the total order of 80 units, only twenty were produced, with the remaining aircraft being reclassified as P-39D.
P-39D-BE
The Bell Model 13 is a production variant that is derived from the P-39C.
It features an additional 245 lb (111 kg) of armour and self-sealing fuel tanks for enhanced protection.
The armament has also been upgraded, now including 1 × 37 mm/1.46 in cannon with 30 rounds, 2 × .50 in/12.7 mm machine guns with 200 rounds per gun, and 4 × wing-mounted .30 in/7.62 mm machine guns with 1,000 rounds per gun.
A total of 60 units of this variant were produced.
P-39D-1
The Bell Model 14A, a production version equipped with a 20 mm (.79 in) M1 cannon, was specially requested for delivery under Lend-Lease.
A total of 336 units were manufactured, with one being sent to the Soviet Union where it saw combat action alongside P-39D-2s.
P-39D-2
The Bell Model 14A-1, a production variant equipped with a V-1710-63 engine generating 1,325 hp (988 kW), featured the restoration of the 37 mm (1.46 in) cannon.
It also had provisions for a single 145 gal (549 l) drop tank or a maximum 500 lb (227 kg) bomb under the fuselage.
A total of 158 units were produced.
Approximately 50 units were sent to the USSR for combat purposes, with around 15 to 20 being utilized by the 16th Guards Fighter Regiment.
P-39D-3
26 P-39D-1 aircraft have been converted into a Photo Reconnaissance Configuration, with the installation of K-24 and K-25 cameras in the rear fuselage.
Additionally, extra armour has been added to protect the oil coolers.
P-39D-4
Conversion of 11 P-39D-2 aircraft to a Photo Reconnaissance Configuration, with the same modifications as the D-3 aircraft.
XP-39E
The Bell Model 23, which consisted of three P-39Ds that were modified for ground and flight testing, took its first flight on 21 February 1942.
Originally intended for the Continental I-1430-1 engine with 2,100 hp (1,566 kW), it ended up being flown with the Allison V-1710-47 engine, which had 1,325 hp (988 kW).
These airframes were utilized to experiment with various wing and vertical tail surfaces.
The fuselage was extended by 1 ft 9 in (53 cm).
This aircraft played a crucial role in the development of the P-63.
The production version, which was supposed to have the Continental engines, was planned to be renamed as the P-76, as there was no specific Bell XP-76 model.
P-39F
P-39F-1
The Bell Model 15B is a production variant equipped with a three-bladed Aeroproducts constant speed propeller, 12 exhaust stacks, and a total of 229 units built.
A P-39F was modified into a two-seat training version by adding an extra cockpit in the nose and removing the armament.
P-39F-2
Bell completed 27 modifications on the P-39F-1 aircraft, which now includes extra belly armour and rear fuselage cameras.
P-39G
The Bell Model 26, with 1800 units ordered, was originally planned to be a P-39D-2 featuring an Aeroproducts propeller.
However, due to changes made during production, no P-39G aircraft were ultimately produced.
Instead, these planes were re-designated as P-39K, L, M, and N models.
P-39J
The Bell Model 15B, also known as the P-39F, was equipped with a V-1710-59 engine capable of 1,100 hp (820 kW) and featured automatic boost control.
A total of 25 units were produced.
P-39K
P-39K-1
The Bell Model 26A, a P-39D-2 aircraft equipped with an Aeroproducts propeller and a V-1710-63 (E6) engine, boasted a power of 1,325 hp/988 kW.
Notably, vents were incorporated into the nose of this model, and a total of 210 units were manufactured.
Out of these, approximately 50 were dispatched to the USSR and actively employed in combat.
The 16th Guards Fighter Regiment initially received 11 of these aircraft, with the distinction of one being the first Airacobra flown by Hero of the Soviet Union Ace Alexander Pokryshkin.
P-39K-2
Six P-39K-1s were converted with additional belly armour and cameras in the rear fuselage.
P-39K-5
One unit was converted with a V-1710-85 (E19) engine to serve as the prototype for the P-39N.
P-39L-1BE
Lend-Lease to USSR
P-39L
P-39L-1
The Bell Model 26C is a variant of the P-39K equipped with a Curtiss Electric propeller, an updated nose gear for decreased drag, and the capability to carry underwing rockets, with a total of 250 units produced.
P-39L-2
Eleven P-39L-1 aircraft were converted to include additional belly armour and cameras in the rear fuselage.
P-39M
P-39M-1
The Bell Model 26D features an 11 ft 1 in Aeroproducts propeller, V-1710-67 engine producing 1,200 hp/895 kW, offering enhanced high-altitude capabilities while sacrificing performance at lower altitudes.
It boasts a speed of 10 mph (16 km/h) faster than the P-39L at 15,000 ft (4,600 m).
A total of 240 P-39M-1BE aircraft were equipped with the V-1710-83 engine upon delivery.
P-39N
The Bell Model 26N was initially included in the P-39G order, featuring the V-1710-85 (E19) engine with 1,325 hp/988 kW.
It was equipped with an Aeroproducts propeller measuring 10 ft 4 in in diameter and a unique propeller reduction gear ratio.
From the 167th aircraft onwards, the propeller size was upgraded to 11 ft 7 in, while the internal fuel capacity was decreased from 120 gal (454 l) to 87 gal (329 l).
A total of 500 units were manufactured.
P-39N-1
A variant underwent internal modifications to balance the centre of gravity when the nose guns were deployed, with a total of 900 units constructed.
P-39N-2
A total of 128 P-39N-1 aircraft were modified to include additional belly armour and cameras in the rear fuselage.
P-39N-3B
Thirty-five P-39N aircraft were converted with additional belly armour and cameras in the rear fuselage.
P-39N-5
The armour has been decreased from 231 lb (105 kg) to 193 lb (88 kg), with the bulletproof glass behind the pilot being replaced by an armour plate.
Additionally, the SCR-695 radio has been installed, along with a new oxygen system.
A total of 695 units have been constructed.
P-39N-6
Eighty-four P-39N-5 aircraft were modified with additional belly armour and cameras in the rear fuselage.
P-39Q
The final production variant, the last one was built in August 1944.
P-39Q-1
The Bell Model 26Q has been modified to include a single 0.50 in (12.7 mm) machine gun with 300 rounds of ammunition mounted under each wing, replacing the previous 0.30 in (7.62 mm) machine guns.
Additionally, the armour has been upgraded to match the original 231 lb (105 kg) armour of the P-39N-1BE.
A total of 150 of these modified aircraft were built.
P-39Q-2
Five P-39Q-1 aircraft were modified for photographic reconnaissance by installing K-24 and K-25 cameras in the rear fuselage.
P-39Q-5
Production variant featured reduced armour (193 lb/88 kg) and increased fuel capacity (110 gal/416 l).
Type A-1 bombsight adapters were added, with a total of 950 units built.
The modification involved converting to a two-seat training variant by adding an extra cockpit in the nose and removing the armament.
Additionally, an enlarged tail fillet and a shallow ventral fin were incorporated.
P-39Q-6
A total of 148 P-39Q-5 aircraft were modified to include K-24 and K-25 cameras in the aft fuselage for photographic reconnaissance purposes.
P-39Q-10
The upgraded version features enhanced armour, weighing in at 228 lb/103 kg, along with increased fuel capacity of 120 gal/454 l.
Additionally, automatic boost controls have been incorporated, ensuring optimal performance, while the coordination of throttle and RPM controls further enhances efficiency.
To withstand harsh winter conditions, oil systems have been winterized and rubber mounts have been added to the engines.
A total of 705 units have been built, showcasing the advancements in this variant.
P-39Q-11
Eight P-39Q-10 aircraft were modified for photographic reconnaissance by installing K-24 and K-25 cameras in the rear fuselage.
P-39Q-15
The production variant features an inclined deck that has been reinforced to effectively prevent any cracking in the .50 in (12.7 mm) machine gun tripod mounting.
Additionally, bulkhead reinforcements have been implemented to ensure that there is no cracking in the rudder pedal wall.
Furthermore, a reinforced reduction gearbox bulkhead has been incorporated to prevent any cracking in the cowling former.
Lastly, the battery solenoid has been repositioned for enhanced functionality.
The oxygen system has been downsized from four bottles to just two, with 1,000 units manufactured.
P-39Q-20
Modified production version with slight equipment adjustments.
The under wing 0.50 in (12.7 mm) machine gun pods were occasionally left out in this iteration, with a total of 1,000 units manufactured.
P-39Q-21
The P-39Q-20 aircraft is equipped with a four-bladed Aeroproducts propeller.
RP-39Q-22
Twelve P-39Q-20 aircraft were modified into two-seat trainers.
P-39Q-25
A production version resembling the P-39Q-21, featuring a strengthened rear fuselage and horizontal stabilizer structure, with a total of 700 units manufactured.
P-39Q-30
The production variant returned to using a three-bladed propeller, with 400 units manufactured.
ZF-39
The remaining units in service were re-designated in June 1948.
P-45
The initial designation for the P-39C, also known as Model 13, was P-45.
A prototype carrier fighter with a tail-wheel undercarriage was developed for the USN.
XTDL-1
Two P-39Q aircraft were designated by the United States Navy (USN) for use as target drones.
They were assigned to NAS Cape May for testing purposes.
Subsequently, they were redesignated as F2L-1K.
F2L-1K
XTDL-1 drones re-designated
P-400
The P-39 export variant featured a 20 mm Hispano cannon instead of the standard 37 mm cannon, resulting in reduced firepower.
Additionally, it was equipped with two .50 calibre machine guns in the nose and two .30 calibre machine guns in each wing.
Airacobra I
The Bell Model 13 was the Royal Air Force (RAF) designation assigned to three P-39C Airacobras that were delivered to the Aeroplane and Armament Experimental Establishment (A&AEE) at Boscombe Down for evaluation.
Airacobra IA
The Bell Model 14, also known as the ‘Caribou’, was equipped with a V-1710-E4 engine producing 1,150 hp (858 kW).
It featured 1 × 20 mm (.79 in) cannon with 60 rounds, 2 × 0.50 in (12.7 mm) machine guns mounted in the nose, and four 0.303 in (7.7 mm) machine guns mounted in the wings.
The IFF set was relocated from behind the pilot.
The IA designation signifies aircraft that were directly purchased, rather than acquired through the Lend-Lease program.
A total of 675 aircraft were built under this designation.
The USAAF operated 128 aircraft that were previously used by the RAF, which were designated as P-400.
1,200 hp (890 kW) at 9,000 ft (2,743 m) (Emergency power)
Propellers
3 bladed constant speed propellers
Performance
Maximum speed
389 mph (626 km/h, 338 kn)
Stall speed
95 mph (153 km/h, 83 kn) power off,
Flaps and undercarriage down
Never exceed speed
525 mph (845 km/h, 456 kn)
Range
525 mi (845 km, 456 nmi) on internal fuel
Service ceiling
35,000 ft (11,000 m)
Rate of climb
3,805 ft/min (19.33 m/s) at 7,400 ft (2,300 m)
(Using emergency power)
Time to altitude
15,000 ft (4,600 m) in 4 minutes 30 seconds at 160 mph (260 km/h)
Wing loading
34.6 lb/sq ft (169 kg/m2)
Power/mass
0.16 hp/lb (0.26 kW/kg).
Sources
P-39 Airacobra Aces of World War 2-J Stanaway & G Mellinger.
Bell P-39 Airacobra, MMP Books-A Juszczak & R Pęczkowski.
Bell P-39 Airacobra: Profile Publications No.165.
P-39 Airacobra In Detail-B Kinzey.
Bell P-39/P-63 Airacobra & Kingcobra-F A. Johnsen.
P-39 Airacobra in action No. 43, Squadron Signal.
Bell P-39 Airacobra, Mushroom Models 6106-A Juszczak & Peczkowski.
The Bell P-39 Airacobra-Profile Publications 165.
The Bell P-39 Airacobra and P-63 Kingcobra Fighters: Soviet Service during World War II-Y Gordon, D Komissarov & S Komissarov.
Bell P-39 Airacobra, Crowood Aviation-R F. Dorr & Jerry C Scutts.
