P-39 Airacobra – An Unconventional Fighter

The P-39 Airacobra, produced by Bell Aircraft, holds a unique place in the history of World War II aviation.

Unlike conventional fighter designs of the time, the Airacobra featured a tricycle landing gear and a centrally mounted engine, behind the pilot, driving the propeller via a long drive shaft.

With its unique characteristics and variable performance at different altitudes, the P-39 was subject to mixed opinions among pilots and saw varied success in different theatres of the war.


Proposal X-609

The story of the P-39 began with Proposal X-609, submitted by Bell Aircraft to the U.S. Army in February 1937.

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The innovative proposal outlined a fighter plane design equipped with a 1,150 horsepower Allison V-1710-37 engine, located in the centre of the fuselage, behind the pilot.

The Allison engine that powered the P-39. Despite not having a super charger, for low level operations it performed admirably.
The Allison engine that powered the P-39. Despite not having a supercharger, for low-level operations, it performed admirably.

The engine layout was one of the most radical departures from conventional designs, intended to allow for a larger, more powerful cannon to be mounted in the nose of the aircraft.

The experimental prototype, dubbed XP-39, first took to the skies on April 6, 1938. The XP-39 featured a streamlined design with a tricycle landing gear and a car-like side-opening door for the cockpit.

Initially, the XP-39 was equipped with a turbo-supercharger, allowing it to achieve excellent high-altitude performance.

However, due to a variety of factors, including the Army’s decision to simplify the design for mass production, the supercharger was removed from production models, affecting the P-39’s high-altitude performance.

The prototype XP-39.
The prototype XP-39.

The Airacobra

The production version of the P-39 was 30 feet long, with a wingspan of 34 feet. It had a top speed of approximately 375 mph at 15,000 feet, powered by a 1,200-horsepower Allison V-1710-83 engine.

The V-1710-83 was a twelve-cylinder, liquid-cooled, V-engine widely used in American aircraft during the Second World War.

One of the main features of the Allison engines was the absence of a supercharger, which was a device used to increase the density of the air supplied to the engine, improving its performance at high altitudes.

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

This absence is often attributed to the P-39’s limited high-altitude performance. However, at low to medium altitudes, the engine performed adequately.

The most distinguished feature of the Airacobra was the 37mm M4 cannon, a powerful weapon that gave the aircraft significant punch in air-to-air and air-to-ground engagements.

This cannon was a standout feature of the Airacobra and was possible thanks to the aircraft’s unique engine placement behind the pilot, which allowed the cannon to be mounted to fire directly through the propeller hub.

The 37mm cannon on display in the nose of a P-39Q. Photo credit - Kogo GFDL.
The 37mm cannon on display in the nose of a P-39Q. Photo credit – Kogo GFDL.

The M4 cannon, developed by the American company Oldsmobile, was known for its high muzzle velocity and large explosive shells.

It fired a 1.34 lb (610 gram) shell at a muzzle velocity of about 2,000 feet per second (610 meters per second).

The gun had a relatively slow rate of fire, typically around 120-150 rounds per minute, but the substantial impact of each shell more than compensated for this.

The cannon was fed by a 30-round magazine located in the nose of the aircraft, and its large calibre made it a formidable weapon against both airborne and ground targets.

Against enemy aircraft, a single hit could often be enough to cause serious damage or destroy the target outright, while against ground targets, it could penetrate light armour and cause considerable blast damage.

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In the context of the Eastern Front, where the P-39 saw extensive service in the hands of Soviet pilots, the M4 cannon was especially valued for its effectiveness against German tanks and armoured vehicles.

A P-39N of the 357th Fighter Group.
A P-39N of the 357th Fighter Group.

In air-to-air engagements, Soviet aces used the cannon to great effect, often aiming to score a single decisive hit on enemy aircraft.

But not only was there a 37mm cannon, but also two .50 calibre machine guns in the nose, and four .30 calibre machine guns in the wings. The weight of fire from this machine would shred anything in front of the nose.

The P-39 could also carry a bomb load of up to 500 pounds.

There were numerous variants of the P-39, including the P-39N and P-39Q, which were the most common.

Changes across variants generally included improved engines, different armament load-outs, and minor tweaks to the aircraft’s systems and structure.

One variant, the P-39K, was even equipped with wing-mounted rocket launchers.

A P-39 firing all weapons at night.
A P-39 firing all weapons at night.

Service History

In the Pacific Theater, the P-39 was among the first U.S. fighter planes to be engaged in combat following the entry of the U.S. into World War II.

It was initially deployed in the defence of Australia in 1942 with the 8th Pursuit Group, participating in several crucial early campaigns.

During the Guadalcanal Campaign in the Solomon Islands, USAAF P-39s played a critical role in supporting the Marines’ ground operations. Their primary tasks were close air support, escort missions, and interdiction of enemy shipping.

The P-39’s performance at low to medium altitudes and its heavy nose armament were well-suited to these tasks.

Airacobras were also involved in the New Guinea campaign.

An Airacobra of the RAAF in 1942.
An Airacobra of the RAAF in 1942.

Flying from makeshift airstrips, P-39s fought against Japanese aircraft and attacked ground targets, providing valuable air cover and ground support to Allied forces during the hard-fought campaign.

The P-39 was also deployed in the Mediterranean Theater, where it was used in various roles, including fighter-bomber missions, strike missions, and tactical reconnaissance.

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A notable unit was the 99th Fighter Squadron, also known as the Tuskegee Airmen, which flew the type in the North African campaign and later in the invasion of Sicily in 1943.

One significant operation involving P-39s in the Mediterranean was Operation Strangle in 1943-44, an attempt to cut off German supply lines in Italy.

There, they were used to perform ground attack missions against enemy rail and road traffic.

The RAF also usesd the P-39. Known as the Airacobra. Instead of the 37mm cannon, it had a 20mm in the nose and .303 machine guns.
The RAF also used the P-39. Known as the Airacobra. Instead of the 37mm cannon, it had a 20mm in the nose and .303 machine guns.

While the Airacobra might not have been the best high-altitude interceptor, it was an effective and versatile aircraft in roles that played to its strengths.

The USAAF made good use of the P-39’s unique capabilities in various theatres during the Second World War, and it played a significant part in many critical campaigns.

Russian Service

The P-39 Airacobra found considerable success in the Soviet Union, which received more P-39s than any other Allied nation through the Lend-Lease program.

The Soviets valued the P-39 for its robustness, firepower, and decent low-to-medium altitude performance, which was suited to the type of air combat typically encountered on the Eastern Front.

The P-39 was used extensively by the Soviet Air Force in various roles, primarily for tactical air superiority and ground-attack missions.

In fact, the Airacobra was the most common American aircraft flown by Soviet forces during World War II.

A P-39 in Soviet colours.
A P-39 in Soviet colours.

Contrary to the high-altitude air battles over Western Europe, air combat on the Eastern Front was primarily fought at lower altitudes, often under 15,000 feet, where the P-39 excelled.

The Airacobra’s powerful 37mm cannon was particularly effective against enemy aircraft, and several Soviet aces scored a significant portion of their victories in P-39s.

Notable among them were Alexander Pokryshkin, one of the highest-scoring Allied aces of the war, and Lydia Litvyak, known as “The White Rose of Stalingrad,” who was one of the world’s only female fighter aces and remains a figure of considerable fascination and respect.

Aside from air superiority roles, the P-39 was also effectively employed in ground-attack missions.

Its solid armour, sturdy airframe, and heavy nose-mounted weaponry made the Airacobra an efficient tank buster and a platform for close air support.

The 37mm cannon and machine guns could deliver devastating firepower against enemy ground targets, including vehicles, artillery positions, and infantry formations.

A P-39L on Lend-Lease to the USSR.
A P-39L on Lend-Lease to the USSR.

The P-39’s ability to operate from makeshift airstrips, along with its durability, meant that it could be deployed close to the front lines, allowing for quick response times and higher sortie rates.

These qualities further endeared the P-39 to Soviet pilots and ground crew.

In conclusion, the P-39 Airacobra proved to be a valuable asset to the Soviet Union during the Second World War, demonstrating that an aircraft’s success often depends on how well it fits into a specific operational context.

The Airacobra might not have been a universally acclaimed aircraft, but in the right hands and the right conditions, it was a formidable tool of war.


The P-39 Airacobra might not have been the most celebrated fighter of World War II, but its unique design and versatility made it an important tool in the hands of those who understood its strengths and weaknesses.

From the skies of the Pacific to the bitter cold of the Eastern Front, the P-39 proved itself to be a formidable aircraft in the right conditions.

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The P-39 Airacobra’s story serves as a reminder that innovation can create unexpected success stories and that every tool, when applied correctly, can have a profound impact on the course of history.

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  • Crew: One
  • Length: 30 ft 2 in (9.19 m)
  • Wingspan: 34 ft 0 in (10.36 m)
  • Height: 12 ft 5 in (3.78 m)
  • Empty weight: 6,516 lb (2,956 kg)
  • Gross weight: 7,570 lb (3,434 kg)
  • Max takeoff weight: 8,400 lb (3,810 kg)
  • Powerplant: 1 × Allison V-1710-85 V-12 liquid-cooled piston engine, 1,200 hp (890 kW) at 9,000 ft (2,743 m) (emergency power)
  • Maximum speed: 389 mph (626 km/h, 338 kn)
  • Stall speed: 95 mph (153 km/h, 83 kn) power off, flaps and undercarriage down
  • 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)