Bell P-39 Airacobra

P-39 Airacobra
USAAF P-39F-1BE 41-7224 c/n 15-563 (7224 to RFC at Ponca City, OK, 12 December 1944)[1]
Role	Fighter
Manufacturer	Bell Aircraft
First flight	6 April 1938
Introduced	1941
Status	Retired
Primary users	United States Army Air Forces Soviet Air Force Royal Air Force
Produced	1940-May 1944
Number built	9,584
Unit cost	50,666 USD in 1944[2]
Variants	XFL Airabonita P-63 Kingcobra

The Bell P-39 Airacobra was one of the principal American fighter aircraft in service at the start of World War II. It was the first fighter in history with a tricycle undercarriage and the first to have the engine installed in the centre fuselage, behind the pilot.^[3] Although its mid-engine placement was innovative, the P-39 design was handicapped by the lack of an efficient turbo-supercharger, limiting it to low-altitude work. The P-39 was used with great success by the Soviet Air Force, who scored the highest number of individual kills attributed to any U.S. fighter type.^[4] Other important users were the Free French and co-belligerent Italian air forces.^[5] Together with the derivative P-63 Kingcobra, these aircraft became the most successful mass-produced fixed-wing aircraft manufactured by Bell.^[6]

Design and development

In February 1937, Lieutenant Benjamin S. Kelsey, Project Officer for Fighters at the United States Army Air Corps (USAAC), issued a specification for a new fighter via Circular Proposal X-609.^[7] It was a request for a single-engine high-altitude "interceptor" having "the tactical mission of interception and attack of hostile aircraft at high altitude".^[8] Despite being called an interceptor, the proposed aircraft's role was simply an extension of the traditional pursuit (fighter) role, using a heavier and more powerful aircraft at higher altitude. Specifications called for at least 1,000 lb of heavy armament including a cannon, a liquid-cooled Allison engine with a General Electric turbo-supercharger, tricycle landing gear, a level airspeed of at least 360 mph (580 km/h) at altitude, and a climb to 20,000 ft (6,100 m) within 6 minutes;^[9] the toughest set of specifications USAAC had presented to that date.^[10] Although Bell's limited fighter design work had previously resulted in the unusual Bell YFM-1 Airacuda, the Model 12^[11] proposal adopted an equally original configuration with an Allison V-12 engine mounted in the middle of the fuselage, just behind the cockpit, and a propeller driven by a shaft passing beneath the pilot's feet under the cockpit floor.^[11]

The main purpose of this configuration was to free up space for the heavy main armament, a 37 mm (1.46 in) Oldsmobile T9 cannon firing through the center of the propeller hub for optimum accuracy and stability when firing. In fact, the entire design was made to accommodate this gun in the aircraft.^[12] This happened because H.M. Poyer, designer for project leader Robert Woods, was impressed by the power of this weapon and he pressed for its incorporation though the original concept had been a 20–25 mm (.79–98 in) cannon mounted in a conventional manner in the nose. This was unusual, because fighters had previously been designed around an engine, not a weapon system. Although devastating when it worked, the T9 had very limited ammunition, a low rate of fire, and was prone to jamming.^[13]

A secondary benefit of the mid-engine arrangement was to create a smooth and streamlined nose profile. Entry to the cockpit was through side doors (mounted on both sides of the cockpit) rather than a sliding canopy. Its unusual engine location and the long driveshaft caused some pilot concern at first, but experience showed this was no more of a hazard in a crash landing than with an engine located forward of the cockpit. There were no problems with propshaft failure.

As originally designed, the XP-39 had a turbocharger with a scoop on the left side of the fuselage;^[14] both were deleted for production.^[15] The production P-39 retained a single-stage, single-speed supercharger with a critical altitude (above which performance declined) of about 12,000 ft (3,658 m).^[16]

Bell P-39 Airacobra center fuselage detail with maintenance panels open.

The XP-39 made her maiden flight on 6 April 1938^[17] at Wright Field, Ohio, achieving 390 mph (630 km/h) at 20,000 ft (6,100 m), reaching this altitude in only five minutes.^[18] The Army ordered twelve YP-39s (with only a single-stage, single-speed supercharger) for service evaluation^[17] and one YP-39A. After these trials were complete, which resulted in detail changes including deletion of the external radiator,^[17][19] and on advice from NACA,^[17] the prototype was modified as the XP-39B; after demonstrating a performance improvement,^[17] the 13 YP-39s were completed to this standard, adding two .30 in (7.62 mm) machine guns to the two existing .50 in (12.7 mm) guns.^[17] Lacking armor or self-sealing fuel tanks, the prototype was one ton (900 kg) lighter than the production fighters.^[20]

After completing service trials, and originally designated P-45, a first order for 80 aircraft was placed 10 August 1939; the designation would revert before deliveries began.^[17]

Technical details

The P-39 was an all-metal, low-wing, single-engine fighter, with a tricycle undercarriage and an Allison V-1710 liquid-cooled Vee-12 engine mounted in the central fuselage, directly behind the cockpit.

The Airacobra was one of the first production fighters to be conceived as a "weapons system"; in this case the aircraft (known originally as the Bell Model 4) was designed around the 37mm T9 cannon.^[21] This weapon, which was designed in 1934 by the American Armament Corporation, a division of Oldsmobile, fired a 1.3 lb (610 g) projectile capable of piercing .8 in (2 cm) of armor at 500 yd (450 m) with armor piercing rounds. The 200 lb, 90 inch long weapon had to be rigidly mounted and fire parallel to and close to the centerline of the new fighter; however, it would be impossible to mount the weapon in the fuselage, firing through the propeller shaft as could be done with smaller 20mm cannon. Weight, balance and visibility problems meant that the cockpit could not be placed farther back in the fuselage, behind the engine and cannon.^[21] The solution adopted was to mount the cannon in the forward fuselage and the engine in the center fuselage, directly behind the pilot's seat. The tractor propeller was driven via a 10-foot-long (3.0 m) drive shaft which was made in two sections, incorporating a self-aligning bearing to accommodate fuselage deflection during violent maneuvers. This shaft ran through a tunnel in the cockpit floor and was connected to a gearbox in the nose of the fuselage which, in turn, drove the three or (later) four bladed propeller via a short central shaft. The gearbox was provided with its own lubrication system, separate from the engine; in later versions of the Airacobra the gearbox was provided with some armor protection.^[21] The glycol cooled radiator was fitted in the wing center section, immediately beneath the engine; this was flanked on either side by a single drum shaped oil cooler. Air for the radiator and oil coolers was drawn in through intakes formed in both wing-root leading edges and was directed via four ducts to the radiator faces. The air was then exhausted through three controllable hinged flaps near the trailing edge of the center section. Air for the carburetor was drawn in via a raised oval intake immediately aft of the rear canopy.^[22][23]

The fuselage structure was unusual and innovative, being based on a strong central keel which incorporated the armament, cockpit and engine. Two strong fuselage beams to port and starboard formed the basis of the structure. These angled upwards fore and aft to create mounting points for the T9 cannon and propeller reduction gearbox and for the engine and accessories respectively. A strong arched bulkhead provided the main structural point to which the main spar of the wing was attached. This arch incorporated a fireproof panel and an armor plate separating the engine from the cockpit. It also incorporated a turnover pylon and a pane of bullet-resistant glass behind the pilot's head. The arch also formed the basis of the cockpit housing; the pilot's seat was attached to the forward face as was the cockpit floor. Forward of the cockpit the fuselage nose was formed from large removable covers. A long nose wheel well was incorporated in the lower nose section. The engine and accessories were attached to the rear of the arch and the main structural beams; these too were covered using large removable panels. A conventional semi-monocoque rear fuselage was attached aft of the main structure.^{[22][24][25][26]}

Because the pilot was riding above the extension shaft he was placed higher in the fuselage than most contemporary fighters, which, in turn, allowed Bell to use a raised cockpit enclosure, giving the pilot a good field of view.^[21] Access to the cockpit was via sideways opening "car doors", one on either side. Both had wind-down windows; because only the right hand door had a handle both inside and outside this was used as the normal means of access. The left hand door could only be opened from the outside and was only for emergency use, although both doors could be jettisoned. In operational service, however the cockpit was difficult to escape from in an emergency because the roof was fixed.^[27]

The complete armament fit consisted of the T9 with a pair of Browning M2 .50 in (12.7 mm) machine guns mounted in the nose. This would change to two .50 in (12.7 mm) and two .30 in (7.62 mm) guns in the XP-39B (P-39C, Model 13, the first 20 delivered) and two 0.50 in/12.7 mm and four 0.30 in/7.62 mm (all four in the wings) in the P-39D (Model 15), which also introduced self-sealing tanks and shackles (and piping) for a 500 lb (227 kg) bomb or drop tank.^[17]

Because of the unconventional layout, there was no space in the fuselage to place a fuel tank. Although drop tanks were implemented to extend its range, the standard fuel load was carried in the wings, with the result that the P-39 was limited to short range tactical strikes.^[28]

In September 1940, Britain ordered 386 P-39Ds (Model 14), with a 20 mm (.79 in) Hispano-Suiza HS.404 and six .303 in (7.7 mm), instead of a 37 mm (1.46 in) cannon and six 0.30 in (7.62 in) guns. The RAF eventually ordered a total of 675 P-39s. However, after the first Airacobras arrived at 601 Squadron RAF in September 1941, they were promptly recognized as having an inadequate rate of climb and performance at altitude for Western European conditions. Only 80 were adopted, all of them with 601 Squadron. Britain transferred about 200 P-39s to the Soviet Union.

Another 200 examples intended for the RAF were taken up by the USAAF after the attack on Pearl Harbor as the P-400, and were sent to the Fifth Air Force in Australia, for service in the South West Pacific Theatre.^[29]

A heavy structure, and around 265 lb (120 kg) of armor were characteristic of this aircraft as well. The production P-39's heavier weight combined with the Allison engine having only a single-stage, single-speed supercharger, limited the high-altitude capabilities of the fighter. The P-39's altitude performance was markedly inferior to the contemporary European fighters and, as a result, the first USAAF fighter units in the European Theater were equipped with the Spitfire V. However, the P-39D's roll rate was 75°/s at 235 mph (378 km/h)– better than the A6M2, F4F, F6F, or P-38 up to 265 mph (426 km/h). (see NACA chart).^[30]

Above the supercharger's critical altitude of about 12,000 ft (3,658 m), an early P-39's performance dropped off rapidly. This limited its usefulness in traditional fighter missions in Europe as well as in the Pacific, where it was not uncommon for Japanese bombers to attack at altitudes above the P-39's operational ceiling (which in the tropical hot air inevitably was lower than in moderate climates). However the late production N and Q models, making up 75% of all Aircobras, could maintain a top speed of approximately 375 mph (604 km/h) up to 20,000 ft (6,100 m).

The weight distribution of the P-39 was supposedly the reason for its tendency to enter a dangerous flat spin, a characteristic Soviet test pilots were able to demonstrate to the skeptical manufacturer who had been unable to reproduce the effect. After extensive tests, it was determined the spin could only be induced if the aircraft was improperly loaded, with no ammunition in the front compartment. The flight manual specifically noted a need to ballast the front ammunition compartment with the appropriate weight of shell casings to achieve a reasonable center of gravity. High speed controls were light, consequently, high speed turns and pull-outs were possible. However, the P-39 had to be held in a dive since it tended to level out, reminiscent of the Spitfire. Recommended dive speed limit (Vne) was 475 mph (764 km/h) for the P-39.^[31]

The rear-mounted engine made the aircraft ideal for ground attack since fire would be coming from the front-bottom quarter and was less likely to hit the engine and its cooling systems. However, the arrangement proved to be very vulnerable to attacks from above and behind and nearly any hit on the fuselage from an attacking enemy fighter was virtually guaranteed to disable the cooling system and lead to the prompt demise of the engine and thus the airplane. Coupled with lack of high-altitude performance, the Airacobra was extremely vulnerable to any enemy fighter with decent high altitude performance.^[32]

By the time of the Pearl Harbor attack, nearly 600 had been built. When P-39 production ended in August 1944, Bell had built 9,558^[17][19] Airacobras, of which 4,773 (mostly -39N and -39Q^[17]) were sent to the Soviet Union through the Lend-Lease program. There were numerous minor variations in engine, propeller, and armament, but no major structural changes in production types, excepting a few two-seat TP-39F and RP-39Q trainers.^[33] In addition, seven went to the U.S. Navy as radio-controlled drones.

Trials of a laminar flow wing (in the XP-39E) and Continental IV-1430 engine (the P-76) were unsuccessful.^[17] The mid-engine, gun-through-hub concept was developed further in the Bell P-63 Kingcobra.

A naval version with tail-dragger landing gear, the XFL-1 Airabonita, was ordered as a competitor to the F4U Corsair and XF5F Skyrocket. It first flew 13 May 1940,^[17] but after a troublesome and protracted development and testing period, it was rejected.

Operational history

The Airacobra saw combat throughout the world, particularly in the Southwest Pacific, Mediterranean and Russian theaters. Because its engine was not equipped with a supercharger, the P-39 performed best below 17,000 feet (5,200 m) altitude. In both Europe and the Pacific, the Airacobra found itself outclassed as an interceptor, its earliest proposed role, and the type was gradually relegated to other duties.^[3] It often was used at lower altitudes for such missions as ground strafing.

United Kingdom

P-39Q-1BE 42-19447, Saga Boy II of Lt. Col. Edwin S. Chickering, CO 357th Fighter Group, July 1943.

In 1940, the British Direct Purchase Commission in the US was looking for combat aircraft; they ordered 675 of the export version Bell Model 14 as the "Caribou" on the strength of the company's representations on 13 April 1940. The performance of the Bell P-39 prototype and 13 test aircraft which were able to achieve a speed of 390 mph (630 km/h) at altitude was due to the installation of turbo-supercharging. The British armament was two nose mounted 0.50 in (12.7 mm) machine guns, and four 0.30 in (7.62 mm) machine guns in the wings, the 37 mm gun was replaced by a 20 mm (.79 in) Hispano-Suiza.

The British export models were renamed "Airacobra" in 1941. A further 150 were specified for delivery under Lend-lease in 1941 but these were not supplied. The Royal Air Force (RAF) took delivery in mid 1941 and found that actual performance of the non-turbo-supercharged production aircraft differed markedly from what they were expecting.^[34] In some areas, the Airacobra was inferior to existing aircraft such as the Hawker Hurricane and Supermarine Spitfire and its performance at altitude suffered drastically. On the other hand it was considered effective for low level fighter and ground attack work. Problems with gun and exhaust flash suppression and compass were fixable.

No. 601 Squadron RAF was the only British unit to use the Airacobra operationally, receiving their first two examples on 6 August 1941. On 9 October, four Airacobras attacked enemy barges near Dunkirk, in the type's only operational action with the RAF. The squadron continued to train with the Airacobra during the winter, but a combination of poor serviceability and deep distrust of this unfamiliar fighter resulted in the RAF rejecting the type after one combat mission.^[5] In March 1942, the unit re-equipped with Spitfires.

The Airacobras already in the UK, along with the remainder of the first batch being built in the US, were sent to the Soviet Air force, the sole exception being AH574, which was passed to the Royal Navy and used for experimental work, including the first carrier landing by a tricycle undercarriage aircraft on 4 April 1945 on HMS Pretoria Castle,^[35] until it was scrapped on the recommendation of a visiting Bell test pilot in March 1946.^[36]

U.S.

Bell P-39 Airacobra firing all weapons at night.

The United States requisitioned 200 of the next part of the order as the P-400. The P-400 designation came from advertised top speed of 400 mph (644 km/h). After Pearl Harbor, the P-400 was deployed to training units, but some saw combat in the Southwest Pacific including with the Cactus Air Force in the Battle of Guadalcanal.^[37] Though outclassed by Japanese fighter planes, it performed well in strafing and bombing runs, often proving deadly in ground attacks on Japanese forces trying to retake Henderson Field. Guns salvaged from P-39s were sometimes fitted to Navy PT boats to increase firepower.^[38]

From September to November 1942 pilots of the 57th Fighter Squadron flew P-39s and P-38s from an airfield built on land bulldozed into Kuluk Bay on the barren island of Adak in Alaska's Aleutian Islands. They attacked the Japanese forces which had invaded Attu and Kiska islands in the Aleutians in June 1942. The number one foe that claimed the most lives, however, was not the Japanese but the weather. The low clouds, heavy mist and fog, driving rain, snow and high winds made flying dangerous and lives miserable. The 57th remained in Alaska until November 1942 and then returned to the United States.

In North Africa, the Tuskegee Airmen were assigned P-39s in February 1944. They successfully transitioned and carried out their duties including supporting Operation Shingle over Anzio as well as missions over the Gulf of Naples in the Airacobra but achieved few aerial victories.^[39] By June they had transitioned to P-47 Thunderbolts and then P-51 Mustangs in July 1944.

While only one U.S. pilot, Lt. Bill Fiedler, became an ace in a P-39, many U.S. aces scored one or two of their victories in the aircraft.^[40]

USSR

P-39Q-15BE 44-2664
Aviation Museum of Central Finland

The most successful use of the P-39 was in the hands of the Soviet Air Force (VVS). The tactical environment of the Eastern Front did not demand the extreme high-altitude operations that the RAF and United States Army Air Forces (USAAF) employed with their big bombers. The low-speed, low-altitude turning nature of most air combat on the Russian Front suited the P-39's strengths: sturdy construction, reliable radio gear, and adequate firepower. Russian pilots appreciated the cannon-armed P-39 primarily for its air-to-air attack capability.

The usual nickname for the well-loved Airacobra in the VVS was Kobrushka, "little cobra", or Kobrastochka, a portmanteau of Kobra and Lastochka (swallow), "dear little cobra".^[41][42]

Soviet pilot Nikolai G. Golodnikov, in an interview with Andrei Sukhrukov, recalled:

"I liked the Cobra, especially the Q-5 version. It was the lightest version of all Cobras and was the best fighter I ever flew. The cockpit was very comfortable, and visibility was outstanding. The instrument panel was very ergonomic, with the entire complement of instruments right up to an artificial horizon and radio compass. It even had a relief tube in the shape of a funnel. The armored glass was very strong, extremely thick. The armor on the back was also thick. The oxygen equipment was reliable, although the mask was quite small, only covering the nose and mouth. We wore that mask only at high altitude. The HF radio set was powerful, reliable and clear."

^[43]

The first “Soviet” Cobras had a 20 mm Hispano-Suiza cannon and two heavy Browning machine guns, synchronized and mounted in the nose. Later, Cobras arrived with the M-4 37 mm cannon and four machine guns, two synchronized and two wing-mounted. "We immediately removed the wing machine guns, leaving one cannon and two machine guns," Golodnikov recalled later.^[43] That modification improved roll rate by reducing rotational inertia. Soviet airmen appreciated the M-4 cannon with its powerful rounds and the reliable action but complained about the low rate of fire (three rounds per second) and inadequate ammunition storage (only 30 rounds).^[43] The Soviets used the Airacobra primarily for air-to-air combat^[44] against a variety of German aircraft, including Messerschmitt Bf 109s, Focke-Wulf Fw 190s, Junkers Ju 87s, and Ju 88s.

During the battle of Kuban River, the Soviet air force relied on P-39s much more than Spitfires and P-40s. Aleksandr Pokryshkin, from 16.Gv.IAP, claimed 20 air victories in that campaign.^[45] Pokryshkin, the third-highest scoring Allied ace (with a score of 53 air victories plus six shared)^[46] flew the P-39 from late 1942 until the end of the war (though rumors exist that he changed in late 1944 to a P-63 Kingcobra).

Grigoriy Rechkalov, second Soviet top-scoring ace (56 individual air victories plus 5 shared), occasionally his wingman while both in 16.Gv.IAP,^[47] scored 44 victories flying Airacobras. The majority of his kills were achieved on P-39N-0 number 42-8747 and P-39Q-15 number 44-2547. During the Great Patriotic War, he was awarded with the Order of Lenin, the Order of the Red Banner (four times), the Order of Alexandr Nievskii, the Order of Patriotic War 1st Class and the Order of the Red Star (twice).^[48] This is the highest score ever attained by any pilot with any American-made aircraft.

The United States did not supply M80 armor-piercing rounds for the autocannons of Soviet P-39s—instead, approximately 1,200,000 M54 high-explosive rounds were supplied, which the Soviets used for air-to-air combat and against soft ground targets. The VVS did not use the P-39 for tank-busting duties.^[49]

A total of 4,719 P-39s were sent to the Soviet Union, accounting for more than one-third of all U.S. and UK-supplied fighter aircraft in the VVS, and nearly half of all P-39 production.^[50]

Australia

In early 1942, the Royal Australian Air Force (RAAF), experiencing Japanese air raids on towns in northern Australia, found itself unable to obtain British-designed interceptors or sufficient numbers of P-40s. US Fifth Air Force squadrons in Australia were already receiving the brand new P-39D-1.^[51] Consequently, in July 1942, older USAAF P-39s, which had been repaired at Australian workshops, were adopted by the RAAF as a stop-gap interceptor.

Seven P-39Ds were sent to No. 23 Squadron RAAF at Lowood, Queensland. Later, seven P-39Fs were operated by No. 24 Squadron RAAF at Townsville. In the absence of adequate supplies of P-39s, both squadrons also operated Wirraway armed trainers. However, neither squadron received a full complement of Airacobras, or saw combat with them. The home air defence role was filled first by P-40s, followed by Spitfires. Plans to equip two more squadrons with P-39s were also abandoned. 23 and 24 Squadrons converted to the Vultee Vengeance in 1943.

France

In 1940, France ordered numerous P-39s to Bell, but because of the armistice with Germany they were not delivered. However, after Operation Torch, French forces in North Africa sided with the Allies, and were re-equipped with Allied equipment including P-39Ns. From mid-1943 on, three fighter squadrons, the GC 3/6 Roussillon, GC 1/4 Navarre and GC 1/5 Champagne, flew these P-39s in combat over the Mediterranean, Italy and Southern France. A batch of P-39Qs was delivered later, but Airacobras, which were never popular with French pilots, had been replaced by P-47 Thunderbolts in front line units by late 1944.

Italy

In June 1944, the Italian Co-Belligerent Air Force (ICAF) received 170 P-39s, most of them -Qs, and a few -Ns (15th USAAF surplus aircraft stored in Napoli-Capodichino airfield) and also at least one -L and five -Ms. The P-39 N (without the underwing fairing for 12.7 machine guns) had engines with about 200 hours; a little newer than the P-39Q engines with 30–150 hours. A total of 149 P-39s would be used: the P-39N for training, while more modern Qs were used in the front line.

In June–July 1944, Gruppi 12°, 9° and 10° of 4° Stormo, moved to Campo Vesuvio airstrip to re-equip with the P-39s. The site was not suitable and, in three months of training, 11 accidents occurred, due to engine failures and poor maintenance of the base. Three pilots died and two were seriously injured. One of the victims, on 25 August 1944, was the "ace of aces", Sergente Maggiore Teresio Martinoli.^[52]

The three groups of 4° Stormo were first sent to Leverano (Lecce) airstrip, then in mid-October, to Galatina airfield. At the end of the training, eight more accidents occurred. Almost 70 aircraft were operational, and on 18 September 1944, 12° Group's P-39s flew their first mission over Albania. Concentrating on ground attack, the Italian P-39s proved to be suitable in this role, losing 10 aircraft to German flak in over 3,000 hours of combat.^[53]

By 8 May 1945, at the end of the war, 89 P-39s were still at the Canne airport and 13 at the Scuola Addestramento Bombardamento e Caccia (Training School for Bombers and Fighters), on Frosinone airfield. In 10 months of operational service, the 4° Stormo had been awarded with three Medaglia d'Oro al Valore Militare "alla memoria".^[54]

Portugal

Between December 1942 and February 1943, the Aeronáutica Militar (Army Military Aviation) obtained aircraft operated by the 81st and the 350th Fighter Groups originally dispatched to North Africa as part of Operation Torch. Due to several problems en route, some of the aircraft were forced to land in Portugal and Spain. Of the 19 fighter aircraft that landed in Portugal, all were interned and entered service that year with the Portuguese Army Military Aviation.^[55]

Though unnecessary, the Portuguese Government paid the United States US$20,000 for each of these interned aircraft as well as for one interned P-38 Lightning.^[56] The US accepted the payment, and gave as a gift four additional crates of aircraft, two of which were not badly damaged, without supplying spares, flight manuals or service manuals.^[56] Lacking proper training, incorporation of the aircraft into service was plagued with problems, and the last six Portuguese Airacobras that remained in 1950 were sold for scrap.

Postwar

In 1945, Italy purchased the 46 surviving P-39s at 1% of their cost but in summer 1946 many accidents occurred, including fatal ones. By 1947, 4 Stormo re-equipped with P-38s, with P-39s sent to training units until the type's retirement in 1951. Only a T9 cannon survives today at Vigna di Valle Museum.^[53]

Racing Airacobras

The Airacobra was raced at the National Air Races in the United States after World War II. Famous versions used for racing included the twin aircraft known as "Cobra I" and "Cobra II," owned jointly between three Bell Aircraft test pilots, Chalmers "Slick" Goodlin, Alvin M. "Tex" Johnston, and Jack Woolams. These craft were extensively modified to use the more powerful P-63 Kingcobra engine and had prototype propeller blades from the Bell factory. "Cobra I" with its pilot, Jack Woolams, was lost in 1946, over the Great Lakes while he was flying from the National Air Races in Cleveland, Ohio back to the factory to get a fresh engine.

The "Cobra II" (Race #84) flown by famed test pilot "Tex" Johnston, beat out P-51 Mustangs and other P-39 racers, which were the favorites, to win the 1946 Thompson Trophy race. Cobra II raced again in the 1947 Thompson Trophy race, finishing 3rd. It raced yet again in the 1948 Thompson trophy race, but was unable to finish due to engine difficulties. Cobra II did not race again and was destroyed on 10 August 1968 during a test flight prior to a run on the world piston-engine speed record, when owner-pilot Mike Carroll lost control and crashed. Carroll perished and the highly-modified P-39 was destroyed.

Mira Slovak's "Mr. Mennen" (Race #21) P-39Q Airacobra was a very fast unlimited racer; a late arrival in 1972 kept this little 2,000 hp (1,491 kW) racer out of the Reno races, and it was never entered again. Its color scheme was all white with "Mennen" green and bronze trim. It is now owned and displayed by the Kalamazoo Air Zoo. The P-39Q (former USAAC serial no. 44-3908/NX40A), is painted as a P-400, "Whistlin' Britches."

Variants

XP-39

XP-39-BE

Bell Model 11, one prototype 38-326 first flown 6 April 1939 . Powered by an Allison V-1710-17 (E2) engine (1,150 hp/858 kW) fitted with a B-5 two-stage turbosupercharger. 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.

YP-39

YP-39

Bell Model 12, service test version, V-1710-37 (E5) engine (1,090 hp/813 kW). First two aircraft delivered with armament, the remained with a M4 37 mm (1.46 in) autocannon 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.

YP-39A

One intended to have a high-altitude V-1710-31 engine (1,150 hp/858 kW), but was delivered as a regular YP-39.

XP-39B

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 and 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). Turbosupercharger replaced with single-stage geared supercharger, Allison V-1710-37 (E5) engine (1,090 hp/813 kW), carburetor air intake moved to fuselage behind canopy.

P-39C

P-39C-BE assigned to the 40th PS / 31st PG at Selfridge Field

P-39C

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 armor and self-sealing fuel tanks. Twenty produced out of an order of 80 the remainder were redesignated P-39D

Airacobra I

Airacobra I

Bell Model 13, Royal Air Force designation for three P-39Cs sent to United Kingdom England for testing.

Airacobra IA

Bell Model 14. Briefly named Caribou. V-1710-E4 (1,150 hp/858 kW) engine, 1 × 20 mm (.79 in) cannon with 60 rounds & 2 × 0.50 in (12.7 mm) machine guns were mounted nose and four 0.303 in (7.7 mm) machine guns were mounted in the wings. IFF set removed from behind pilot. note: the designation IA indicates direct purchase aircraft;, 675 built. The USAAF operated 128 former RAF aircraft with the designation P-400.

P-39D

P-39D-BE

Bell Model 13, production variant based on the P-39C with 245 lb (111 kg) of additional armor, self-sealing fuel tanks. Armament increased to 1 × 37 mm/1.46 mm 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.

P-39D-1

Bell Model 14A, production variant fitted with a M1 20 mm (.79 in) M1 cannon. Specifically ordered for delivery under Lend-Lease; 336 produced

P-39D-2

Bell Model 14A-1, production variant with a V-1710-63 (E6) 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.

P-39D-3

26 conversions from P-39D-1 to Photo Reconnaissance Configuration; K-24 and K-25 camera in rear fuselage, extra armor for oil coolers

P-39D-4

11 conversions from P-39D-2 to Photo Reconnaissance Configuration. Same modifications as D-3 aircraft.

XP-39E

XP-39E

Bell Model 23. three P-39Ds modified for ground and flight testing first flown 21 February 1942.^[57] 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 variants, with the Continental engines were to be redesignated as P-76; there was no Bell XP-76 as such.^[57]

P-39F

P-39F-1

Bell Model 15B, production variant with three-bladed Aeroproducts constant speed propeller, 12 exhaust stacks; 229 built.

TP-39F-1

One P-39F converted as a two-seat training version with additional cockpit added in nose— no armament.

P-39F-2

27 conversions from P-39F-1 with additional belly armor and cameras in rear fuselage.

P-39G

P-39G

Bell Model 26, 1800 order and 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 designated P-39K, L, M and N.

P-39H

• Designation not used

P-39J

P-39J

Bell Model 15B, a P-39F with V-1710-59 (1,100 hp/820 kW) engine with automatic boost control,; 25 built.

P-39K

P-39K-1

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.

P-39K-2

Six conversion from P-39K-1 with additional belly armor and cameras in rear fuselage.

P-39K-5

One conversion with a V-1710-85 (E19) engine to serve as a P-39N prototype

P-39L

P-39L-1BE 44-4673
Lend-Lease to USSR

P-39L-1

Bell Model 26C, a P-39K with Curtiss Electric propeller, revised nose gear for reduced drag, provision for underwing rockets; 250 built.

P-39L-2

Eleven conversion from P-39L-1 with additional belly armor and cameras in rear fuselage.

P-39M

P-39M-1

Bell Model 26D, variant with a 11 ft 1 in Aeroproducts propeller, V-1710-67 (E8) (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). Note: some P-39M-1BE were delivered with the V-1710-83 (E18) engine; 240 built.

P-39N

P-39N

Bell Model 26N, originally part of the P-39G order. V-1710-85 (E19) (1,200 hp/895 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.

P-39N-1

Variant with internal changes to adjust center of gravity when nose guns were fired; 900 built.

P-39N-2

128 P-39N-1 converted with additional belly armor and cameras in rear fuselage.

P-39N-3B

35 P-39N converted with additional belly armor and cameras in rear fuselage.

P-39N-5

Variant with armor reduced from 231 lb (105 kg) to 193 lb (88 kg), Armor plate replaced the bulletproof glass behind the pilot, SCR-695 radio was fitted, and a new oxygen system was installed; 695 built.

P-39N-6

84 P-39N-5 converted with additional belly armor and cameras in rear fuselage.

P-39P

• Not used

P-39Q

• The final production variant last one built in August 1944.

P-39Q-1

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. Armor increased to the original 231 lb (105 kg) of armor of the P-39N-1BE; 150 built.

P-39Q-2

Five P-39Q-1s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

P-39Q-6BE 42-19993
Brooklyn Bum
8th FG, 36th FS
The Fighter Collection

P-39Q-5

Production variant with reduced armor (193 lb/88 kg), fuel capacity increased (110 gal/l). Type A-1 bombsight adapters added; 950 built.

TP-39Q-5

One conversions to a two-seat training variant with additional cockpit added in nose - no armament. Enlarged tail fillet and a shallow ventral fin added.

P-39Q-6

148 P-39Q-5s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

P-39Q-10

Variant with increased armor (228 lb/103 kg), fuel capacity increased (120 gal/454 l). Automatic Boost controls added and Throttle & RPM controls were coordinated. Winterization of oil systems and rubber mounts added to the engines; 705 built.

P-39Q-11

Eight P-39Q-10s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

P-39Q-15

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.

P-39Q-20

Production variant with minor equipment changes. The underwing 0.50 in (12.7 mm) machine gun pods were sometimes omitted in this version; 1,000 built.

P-39Q-21

109 P-39Q-20 fitted with a four-bladed Aeroproducts propeller.

RP-39Q-22

12 P-39Q-20s converted to two-seat trainers .

P-39Q-25

Production variant similar to the P-39Q-21 but with a reinforced aft-fuselage and horizontal stabilizer structure; 700 built.

P-39Q-30

Production variant that reverted back to the three-bladed propellor; 400 built.

XTDL-1

United States Navy designation for two P-39Qs used as target drones. Assigned to NAS Cape May for test work. Later redesignated F2L-1K.

Other

P-45

The P-45 was the initial designation of the P-39C or Model 13.

XFL-1 Airabonita

One prototype for the United States Navy.

Operators

 Australia

• Royal Australian Air Force

 France

• Armée de l'Air

 Italy

• Italian Co-Belligerent Air Force

 Italy

• Aeronautica Militare

 Portugal

• Esquadrilha Airacobra (Airacobra Squadron), later renamed Esquadrilha 4 (Squadron No. 4) — Aeronáutica Militar (Army Military Aviation)

 Soviet Union

• Soviet Air Forces

 United Kingdom

• Royal Air Force
• Royal Navy (Airacobra Mk 1 - test flight)

 United States

• United States Army Air Corps / United States Army Air Forces

Survivors

A number of P-39s are still in existence of which three are still flying. The Commemorative Air Force flies a Bell P-39 Airacobra painted in the markings and colors of the 350th Fighter Group, which consisted of the 345th, 346th and 347th Fighter Squadrons operating P-39s in North Africa and Italy. At one time, the Airacobra was painted in Russian colors and markings.

Keski-Suomen Ilmailumuseo at Tikkakoski, Finland, has one restored P-39Q Airacobra, "White 26", on static display, restored in original wartime camouflage and markings. The P-39 is originally a Soviet lend-lease aircraft captured by Finnish troops in World War II that landed in Finnish held territory after its pilot became lost and was forced to land because he was running out of fuel.

On 22 April 1942, P-39F 41-7104 assigned to the 13th AF / 347th FG / 70th FS (Pilot: 1st Lt James W. Blose) crashed in Fiji, but was not found until a local pig farmer discovered the wreck in 2004. The pilot's body was also found and sent to Hawaii for identification. Personal items were recovered at the site.^[58]

Other Airacobras on display include:

• P-39Q-6BE 42-19993, "Brooklyn Bum– 2nd" is now at the Fighter Collection in Duxford, UK.

• The Smithsonian's National Air and Space Museum has P-39Q-15BE 44-2433 on display.

• P-39Q-30 44-3887 is on display at the National Museum of the United States Air Force in Dayton, Ohio. The aircraft was obtained by the Air force Museum Foundation from the Hardwick Aircraft Company of El Monte, California in July 1966. It is painted as a P-39K flown by Lt. Leslie Spoonts of the 57th Fighter Squadron on Adak Island during the Aleutians Campaign, and displayed in the Museum's Air Power gallery.^[59]

Specifications (P-39Q)

Bell P-39Q Airacobra at the National Museum of the United States Air Force.

General characteristics

• Crew: One
• Length: 30 ft 2 in (9.2 m)
• Wingspan: 34 ft 0 in (10.4 m)
• Height: 12 ft 5 in (3.8 m)
• Wing area: 213 sq ft (19.8 m²)
• Empty weight: 5,347 lb (2,425 kg)
• Loaded weight: 7,379 lb (3,347 kg)
• Max takeoff weight: 8,400 lb (3,800 kg)
• Powerplant: 1× Allison V-1710-85 liquid-cooled V-12, 1,200 hp (895 kW)

Performance

• Maximum speed: 376 mph (605 km/h) (Redline dive speed was 525 mph)
• Range: 525 miles on internal fuel (840 km)
• Service ceiling: 35,000 ft (10,700 m)
• Rate of climb: 3,750 ft/min (19 m/s)
• Wing loading: 34.6 lb/sq ft (169 kg/m²)
• Power/mass: 0.16 hp/lb (0.27 kW/kg)
• Time to climb: 15,000 in 4.5 min at 160 mph (260 km/h).

Armament

• Guns:
  
  • 1 x 37 mm M4 cannon with 30 rounds of HE ammo.
  • 2 x .50 cal (12.7 mm) machine guns. 200 rounds per nose-gun
  • 4 x .30 cal machine guns, wing mounted. 300 per wing-pod
• Bombs: Up to 500 lb (230 kg) of bombs externally

Notable appearances in media

• The P-39 Airacobra is featured in the Russian movie Peregon (Transit) (2006) dealing with Lend Lease aircraft in transit to Russia.^[60]
• The P-39 is also featured in numerous shots in the wartime American movie "Air Force" (124 Min.), an Oscar-winning, propaganda-oriented movie directed by Howard Hawks, released by Warner Brothers in 1943.

See also

Related development

• XFL Airabonita
• P-63 Kingcobra
  

Comparable aircraft

• Curtiss P-40
• Messerschmitt Bf 109
• Supermarine Spitfire
• Yakovlev Yak-1
• Yakovlev Yak-9
  

Related lists

• List of military aircraft of the United States
• List of fighter aircraft
  

References

Notes

Bibliography

External links

• P-39 Airacobra by J Baugher
• XFL-1 Airabonita
• Bell P-39 Airacobra at acepilots.com
• acepilots.com Soviet use more description of the Loza reference and use of P-39 for air superiority
• Aircraft guns of WWII nildram.co.uk
• article on technical and operational faults of P-39
• A film clip Flying The P-39, demonstrating techniques for piloting the P-39 Airacobra is available for free download at the Internet Archive [more]

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