Military Aircraft
Beautiful Bell P-39 Airacobra
A beautiful-looking and innovative US WWII fighter which despite design issues was highly successful with the Soviet air force in Europe and the Allies in SE Asia
The Bell P-39 Airacobra was one of the primary American fighter aircraft in service at the start of World War II. The P-39 was widely used by the Soviet Air Force, and saw action in a number of other theatres as well, including use by the RAF.
The first time I saw one
It was on a beach in Australia, September 2022. An oyster-encrusted wreck, discovered when I was researching Australia’s role in WWII and ended up in the bomb bay of a B52.
The wreck was reportedly the result of a below bingo fuel episode as the plane made its way back to base at Lockhart River, Queensland.
During World War II, Lockhart River Airport was constructed as a large American bomber base with three airstrips operating. The US bombers flew to Papua New Guinea and were met by their fighter escorts based at Bamaga and Horn Island further north. — Wikipedia
Unusual Design
But what caught my eye amongst all the oysters was the very unusual design. The V12 engine was situated behind the pilot. This gave the pilot exceptional all round visibility.
I later discovered that this plane was innovative in many other aspects.
Designed around a weapons system
Other than Hitler’s train mounted guns, this was arguably the first machine designed around a weapons system, the M4 auto cannon. And it was the first warplane NOT designed around the engine.
The P-39 was designed to be a high-altitude interceptor, and was armed with a 37mm cannon in the nose. The cannon fired through the propeller nose (visible in the cover picture), and had a limited rate of fire of three rounds per second from a magazine of 30. The P-39 also had two .50 caliber machine guns in the wings. Other weapons configurations were also used, but the autocannon was always at the core.
I’m still trying to work out how they could arrange the gun to fire through the nose cone.
Performance
The 601 Squadron of the RAF was the only British unit to allow the P-39 to see operational use. In October 1941, four planes arrived over Dunkirk to attack some barges, but the pilots found issues with the lack of altitude.
It became clear that air combat would regularly occur at 30,000 feet, well above the P-39’s maximum operational ceiling.
Range was limited due to fuel capacity constraints — there was tankage only in the wings in the standard version, with no space for a fuselage tank. So, a short strike range only.
- Maximum speed: 414 mph (667 km/h) at 25,000 ft (7,620 m)
- Cruising speed: 275 mph (443 km/h) Range: 1,000 mi (1,609 km)
- Service ceiling: 42,000 ft (12,800 m)
- Rate of climb: 2,700 ft/min (13.7 m/s)
- Power/mass ratio : 0.18 hp/lb (0.30 kW/kg)
Faults
The P-39 was not without its faults, however. It was under-powered, and its performance at high altitude was poor. In addition, the placement of the engine behind the pilot made it difficult to bail out in an emergency.
It had a tendency to enter a flat spin at high power and to tumble end over end (only proven many years after the war in a NASA wind tunnel).
According to Wikipedia:
Weight distribution could result in it entering a dangerous flat spin, a characteristic Soviet test pilots demonstrated to the skeptical manufacturer, which had been unable to reproduce the effect. It was determined the spin could only be induced if the aircraft was flown with no ammunition in the nose. The flight manual noted a need to ballast the front ammunition compartment to achieve a reasonable center of gravity. High-speed controls were light, consequently high-speed turns and pull-outs were possible. The P-39 had to be held in a dive since it tended to level out and the recommended never-exceed dive speed limit (Vne) was 475 mph (764 km/h).
Soon after entering service, pilots began to report that “during flights of the P-39 in certain maneuvers, it tumbled end over end.” Most of these events happened after the aircraft was stalled in a nose high attitude with considerable power applied. Bell pilots made 86 separate efforts to reproduce the reported tumbling characteristics. In no case were they able to tumble it.
Other innovations
The novel fuselage construction was based on two beams to support the engine and autocannon. It was also heavily armoured. These features made it a relatively heavy aircraft.
Clearly visible in the cover picture, the tricycle carriage was innovative, but I couldn’t find any traces of it in the beach wreck I examined…
The engine
The engine was an Allison V-1710–63 liquid-cooled V12 engine, 1,325 hp (984 kW) at 2,600 rpm from 28 litres (1,710 cu in.) driving a 3-bladed Hamilton Standard Hydromatic propeller.
If you love engines as I do (though not a fetish), you’ll see it as a thing of beauty not as an oyster-encrusted heap of junk as I did.
The engine drove the 3-bladed propeller via a 3 metre long shaft passing beneath the pilot’s feet under the cockpit floor. A universal joint in the shaft allowed compensation for fuselage distortion during high G manoeuvres.
I couldn’t find any trace of the shaft in the beach wreck I examined, although the joystick remained.
Production
9,588 units were reported to have been built. Most were supplied to the Soviet Union via the Alaska ferry link across the Bering Strait. How times have changed. Nowadays ICBMs face each other there.
Importance
Despite its shortcomings, the P-39 was an important aircraft in World War II. It saw action in a number of theatres, and was flown by some of the most famous aces of the war, including Soviet ace Alexander Pokryshkin.
It was not suitable for widespread use in Western Europe where fighter cover for bombers was important and its operational ceiling a serious limitation.
However the Soviets used it as a low level attack plane and as an interceptor.
Five of the 10 highest scoring Soviet aces logged the majority of their kills in P-39s. Grigoriy Rechkalov scored 44 victories in Airacobras. Pokryshkin scored 47 of his 59 victories in P-39s, making him the highest scoring P-39 fighter pilot of any nation, and the highest scoring Allied fighter pilot using an American fighter. — Wikipedia
The US did not supply the Soviets with M80 armour-piercing shells for the T9 cannon, so it was never seriously used as a tank-buster. 1.2 million M54 explosive shells were instead provided for air to air combat and soft ground targets.
KingCobra
The P-63 KingCobra was a much-improved version of the P-39 AiraCobra. Although larger and superior in all respects to the P-39 it was not accepted into service by the USAF in World War II. Almost all production (3,303) went to the Soviet Union.
So, was the wreck I saw an Airacobra or Kingcobra? The clue is in the wreck propeller — it’s three-bladed with one blade vertical. A four-bladed prop (Kingcobra) would have been wrecked with 2 blades in a V formation, I believe.
I was saddened to hear of the recent accident in which a KingCobra collided with a B17 at an air show near Dallas, Texas and several lives were lost
Related content and sources:
https://en.wikipedia.org/wiki/Bell_P-39_Airacobra https://www.warbirdregistry.org/p39registry/p39registry.html https://www.warhistoryonline.com/war-articles/bell-p-39-airacobra.htmhttp://www.j-aircraft.com/research/_pdfs_by_author/dave_donald_-_bell_p-39_airacobra.pdf
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