This plane was the Army's fastest and most heavily armed fighter in World War II. The concentration of firepower in the nose was so effective that a one-second burst could destroy an enemy plane. In the Pacific Theater, pilots downed more Japanese aircraft than pilots flying any other Allied airplane.
This plane, designed by engineer Clarence "Kelly" Johnson and his team of designers, represented one of the most radical departures from tradition in American fighter development. This plane was a complete break-away from conventional airframe design, power, and at long last, armament. Not only did it have twice the power and almost twice the size of its predecessors, but with no less than four .50 cal. machine guns plus a 20 mm cannon, it had enough firepower to sink a ship--and sometimes did. Concentrated in the central fuselage pod, the guns fired parallel which eliminated a need for a propeller synchronizer.
The tricycle landing gear and twin-boom configuration completed the list of major deviations from what might he considered conventional Army fighters. In this respect, it was very unusual that the design progressed beyond the testing stage; such radical concepts seldom achieved production status. But the simple fact was that the design worked and the Army seemed to have found its dream plane in this 400 mph fighter.
The XP-38, 37-457, was
built under tight secrecy and made its maiden flight on January 27,
1939, with Air Corps test pilot and project officer, Lt. Benjamin S.
Kelsey, at the controls. The performance justified manufacturer's
investment of nearly $6,000,000 of its own funds to complete the
prototype. The Army was so delighted with the big new fighter, it lifted
the wraps of secrecy from the plane for a transcontinental speed dash on
February 11, 1939. This event was marred by a crash when Kelsey
undershot the runway at Mitchell Field, NY. Kelsey survived the crash
and remained an important part of the program. The airplane was written
off, but the manufacturer received a contract for thirteen YP-38s
along with the usual list of improvements.
A major problem surfaced with the loss of control in a dive caused by aerodynamic compressibility. During late spring 1941, Air Corps Major Signa A. Gilke encountered serious trouble while diving his plane at high-speed from an altitude of 30,000 ft (9,120 m). When he reached an indicated airspeed of about 320 mph (515 kph), the airplane's tail began to shake violently and the nose dropped until the dive was almost vertical. Signa recovered and landed safely and the tail buffet problem was soon resolved after the manufacturer installed new fillets to improve airflow where the cockpit gondola joined the wing center section. Seventeen months passed before engineers began to determine what caused the nose to drop. They tested a scale model in the Ames Laboratory wind tunnel operated by the NACA (National Advisory Committee for Aeronautics) and found that shock waves formed when airflow over the wing reached transonic speeds and became turbulent. The manufacturer never remedied this problem but the firm did install dive recovery flaps under each wing in 1944 to restore lift and smooth the airflow enough to maintain control when diving at high-speed.
The fastest of these planes had a top
speed of 420 mph, and the version produced in the greatest quantity was
the "L", of which 3,735 were built by the original manufacturer and 113
by Vultee. The plane was powered by two 1,475 hp Allison
V1710-111 engines. As with any long-term production aircraft, the
plane underwent many modifications. The intakes under the engines were
enlarged to house core-type intercoolers. The curved windscreen was
replaced by a flat panel, and the boom mounted radiators were enlarged.
Some were fitted with bombardier type noses, and were used to lead
formations of bomb-laden planes to their targets. One version of the
plane was a two-seat radar-equipped night fighter, a few of which had
become operational before the war ended. One interesting variation had
an elevated tail assembly on upswept booms; another one had an elongated
center pod and was used for airfoil evaluation.