Engines of Our Ingenuity

No. 2138:
P-39, BELL AIRACOBRA

by John H. Lienhard

Today, we're given a lemon, and we make lemonade. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Any kid interested in airplanes in 1940 looked at the new Bell P-39 Airacobra in awe. It was pure streamlined menace. Its liquid-cooled engine was mounted behind the pilot, and its nose tapered into a 37-mm canon in the propeller hub. As we soaked up propaganda about American air superiority, we saw it everywhere.

America eventually achieved air superiority, but not through the P-39. No sooner did the experimental version reach the Army Air Corps, than they began modifying it. They thought the air-scoop imposed too much drag. They reduced the scoop, and changed over to a simple mechanical supercharger.

P-39

That backed up the center of gravity and made the plane hard to fly. They reduced the wingspan by two feet. When they were done, the Airacobra simply couldn't compete above 10,000 feet, which is where much of the air war was being waged. The British refused to use it; American pilots called it the Iron Dog.

We'd created our lemon. For us at home, it continued to be a glamorous icon of American air power. It was wall-paper for cigarette ads and War Bond sales. And the actual airplane was being produced in vast numbers. But no lemonade, at least not yet.

One country saw value in it -- the Soviet Union. So we sent P-39s to Iran and Fairbanks, Alaska, then flew them into the Soviet Union. Great Britain also sent hers off to Russia. In all, Russia received 5000 Airacobras. But why did they want them?

Russia had begun the war with antediluvian Polikarpov biplane fighters. Their designs continued to lag behind the west until late in the war when their Yak and Lavochkin fighters finally emerged as competitive pursuit planes. But pursuing bombers was not so important by then. Germany's bombing capacity had been seriously spent over Great Britain in 1940. She was in no position to go after the distant cities of the Soviet Union.

Germany's war with Russia was being fought on the vast expanse of Russia's western lands. And down there, nearer to the hard earth, the P-39 became Russia's lemonade. As a low level attack plane -- an anti-tank gun platform -- it was very effective. Then, with tanks out of the way, P-39s went after ground troops.

My fascination with the P-39 is less a fascination with an airplane, for it was surely one of the less memorable flying machines. Rather it is with the old myth that war drives invention. What war drives, besides production, is adaptation. It gets in the way of invention because everything moves too fast. Necessity is the mother of quick response.

In a less urgent world, post-production tinkering might've made a fine airplane of the P-39, but that was not to be. War created a kludge which was then turned into useful lemonade by resourceful fliers fighting for theirs and their country's very life.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


R. Miller, The Soviet Air Force at War. (Alexandria, VA: Time-Life Books, 1983/1985).

Some websites dealing with the Airacobra itself and with its Allison engine:
http://www.acepilots.com/planes/p39_airacobra.html
http://home.att.net/~C.C.Jordan/XP-39.html
http://en.wikipedia.org/wiki/P-39_Airacobra
http://en.wikipedia.org/wiki/Allison_V-1710


Airacobra collector's card
Cards such as these appeared in cigarette cartons ca. 1940 -- one more means for attracting kids to smoking. This one doesn't show the air-scoop behind the pilot, cannon in the nose, or engine exhaust pipes. It anticipates a 400 mph speed which was about 30 mph slower than the last versions of the air-plane. And it calls it a high-altitude interceptor, when it functioned effectively only at low altitude.

The Engines of Our Ingenuity is Copyright © 1988-2006 by John H. Lienhard.