The Bell P-39 Airacobra was one of America’s unique piston engine fighters of World War 2

Referring to World War II fighter aircraft, many people will think of the ME-109, P-51 Mustang or the Japanese Zero. In fact, there was a very controversial American fighter that achieved impressive results in the Soviet Union. It was the famous P-39 Airacobra. The Bell P-39 Airacobra was one of America’s unique piston engine fighters of World War 2 – putting the engine behind the pilot while driving the propeller unit in the nose.

The P-39 was developed by Bell in 1937 and officially entered service in 1941. In total, more than 9,500 units were produced. It was one of the principal American fighters in service when the United States entered combat. The P-39 was used by the Soviet Air Force, and enabled individual Soviet pilots to collect the highest number of kills attributed to any U.S. fighter type flown by any air force in any conflict. Other major users of the type included the Free French, the Royal Air Force, and the Italian Co-Belligerent Air Force.

It had an unusual layout, with the engine installed in the center fuselage, behind the pilot, and driving a tractor propeller in the nose with a long shaft. It was also the first fighter fitted with a tricycle undercarriage. Although its mid-engine placement was innovative, the P-39 design was handicapped by the absence of an efficient turbo-supercharger, preventing it from performing high-altitude work. For this reason it was rejected by the RAF for use over western Europe but adopted by the USSR, where most air combat took place at medium and lower altitudes.

The main purpose of this configuration was to free up space for a 37 mm Browning Arms Company T9 cannon, later produced by Oldsmobile, firing through the center of the propeller hub for optimum accuracy and stability. This was unusual, because fighter design had previously been driven by the intended engine, not the weapon system. Although devastating when it worked, the T9 had very limited ammunition, a low rate of fire, and was prone to jamming.

A secondary benefit of the mid-engine arrangement was that it created a smooth and streamlined nose profile. Much was made of the fact that this resulted in a configuration “with as trim and clean a fuselage nose as the snout of a high velocity bullet”. Entry to the cockpit was through side doors rather than a sliding canopy. Its unusual engine location and the long drive shaft caused some concern to pilots 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.

Bell P-39 Airacobra center fuselage detail with maintenance panels open. (U.S. Air Force photo)

The Allison V-1710 liquid-cooled V-12 engine was mounted in the center fuselage, just behind the cockpit, delivering 1,200 hp. The aircraft could reach a top speed of 389 mph, a range of 525 mi, a service ceiling of 35,000 ft, and a Rate of climb of 3,805 ft/min.

The Airacobra was one of the first production fighters to be conceived as a “weapons system”; in this case the aircraft was designed to provide a platform for the 37 mm T9 cannon. This weapon fired a 1.3 lb projectile capable of piercing 20 mm of armor at 460 m with armor-piercing rounds. It was attached to the forward fuselage behind the propeller. The rear-mounted engine was less likely to be hit when attacking ground targets, but was vulnerable to attacks from above and behind. At its upper altitude limits, the Airacobra was out-performed by many enemy aircraft.

The Airacobra saw combat throughout the world, particularly in the Southwest Pacific, Mediterranean and Soviet theaters. Because its engine was equipped with only a single-stage, single-speed supercharger, the P-39 performed poorly above 17,000 feet altitude. In both western Europe and the Pacific, the Airacobra found itself outclassed as an interceptor and the type was gradually relegated to other duties. It often was used at lower altitudes for such missions as ground strafing.

It should be noted that the aircraft could provide a fair fight in the hands of a skilled pilot knowing the limitations of his system. If the Airacobra could drag an opponent down below 10,000 feet, it stood a definitive chance to overtake an enemy through ingenuity and firepower. However, the P-39 made many-an ace for the Soviet Air Force where air-to-air battles along the East Front typically unfolded under the optimal 10,000 feet ceiling limit of the Airacobra.

Soviet pilots appreciated the cannon-armed P-39 primarily for its air-to-air capability. The Soviets developed successful group aerial fighting tactics for the Bell fighters and scored a surprising number of aerial victories over a variety of German aircraft. Soviet P-39s had no trouble dispatching Junkers Ju 87 Stukas or German twin-engine bombers and matched, and in some areas surpassed, early and mid-war Messerschmitt Bf 109s.

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 Red Air Force, and nearly half of all P-39 production. Soviet Airacobra losses totalled 1,030 aircraft.

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