A decent article:

America’s Worst World War II Fighter Was the Star of the Russian Air Force
Sebastien Roblin

September 3, 2017
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The P-39 Airacobra may be the least loved American fighter plane of World War II, deemed inadequate by military planners at the outset of hostilities and written off as nearly useless by many historians. Certainly, the P-39 could not match the high-altitude performance of classic American warbirds such as the dapper and agile P-51 Mustang, nor the hard-charging, hard-hitting P-47 Thunderbolt.

And yet it was pilots of the Airacobra, not the Thunderbolt or Mustang, that achieved the highest scores of any aviators flying an American war plane during World War II. That this fact is not better known maybe because those Airacobra pilots flew with red Soviet stars on their wings.

Founded in 1935, the Bell Aircraft Corporation was known for unconventional designs such as the Airacuda bomber-destroyer which would have been at home on the cover of a science fiction magazine. In 1939, Bell approached the designs of its prototype XP-39 single-engine interceptor from a revolutionary perspective: instead of designing guns to fit the airplane, Bell designed a plane to fit around its gun—an enormous Oldsmobile T9 37-millimeter automatic cannon shooting throw the propeller hub. This had a caliber commonly found on early World War II tank guns. It would only take a single direct hit to down an enemy airplane, and the P-39 also carried two additional .50 caliber machine guns in the nose and four .30 caliber weapons in the wings for a good measure.

To make room for the nose-mounted cannon and thirty rounds of ammunition, the P-39’s Allison 12-cylinder V-1710 inline engine was mounted behind the cockpit—you can even see the exhaust just below the rear canopy—with the propeller shaft passing between the pilot’s legs. The design was also the first single-seat fighter to boast a third extending landing gear under the nose in addition to one on each side of the fuselage in a more stable “tricycle” configuration which is now standard. A raised bubble canopy that opened from a side door offered the pilot excellent visibility, and self-sealing fuel tanks and around 200 pounds of armor plating added to initial P-39D production models improved the Airacobra’s survivability.

The XP-39 prototype exhibited a very decent top speed of 380 miles per hour in 1938. However, the Army Air Corps demanded that Bell increase speed even further by trimming away drag-producing elements. Ultimately, the designers settled on eliminating the Airacobra’s turbo-charger air scoop under the fuselage to deal with the drag problem.

This decision proved fatal to the Airacobra’s prospects as a frontline fighter, as aircraft without the turbochargers handled like a brick above altitudes over 15,000 feet. In a few years, the U.S. bombers would sally forth on raids against Nazi Germany conducted at altitudes of 25,000 feet, and German fighters would climb even higher to ambush them. Furthermore, the Airacobra’s slow climb rate made it terrible at its original role of intercepting high flying enemy bombers. The P-39 centrally-mounted engine also pushed the center of gravity to the rear, making it prone to vicious spins once cannon ammunition was expended from the nose. Though the P-39 was not generally disliked by its pilots, it would also never have its own pilot’s association, unlike the four other major fighter types of the Army Air Corps.

Prior to the U.S. entry in World War II, the United Kingdom received more than 200 export-model Airacobras known as P-400s, which were downgraded to a 20-millimeter cannon in the propeller hub. But Royal Air Force pilots had fought many high-altitude battles with the Luftwaffe, and hated the Airacobra. Only 601 Squadron operated the Airacobra, flying the American fighters on a single combat mission before the type was withdrawn from British service. When the first two U.S. Army Air Force fighter groups arrived in England in the summer of 1942, the RAF persuaded the Americans to leave their P-39s behind and use British Spitfires Mark Vs instead!

A few P-39 Army Air Force squadrons did eventually see action in North Africa and Italy. There, they rendered decent service largely in a ground attack role capitalizing on their hefty firepower and good low-altitude handling providing air support for the Allied force in North Africa and Italy, and amphibious landing at Anzio and Southern France. However, the Airacobra’s initial entry into action proved inauspicious as nearly a score of fighters of the 350th and 81st Fighter Group went off course while transiting from England to Morocco and made forced landings in Portugal. The Portuguese duly confiscated the planes for their own air force, though they were so courteous as to pay the U.S. government $20,000 for each airplane!

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