The Bell L-39 was the designation given to two P-63 Kingcobras when they were given experimental swept wings.
The project was originally funded by the US Navy, which wanted more date on the handling performance of swept wings and low speeds. Two airframes were chosen for the project. The first aircraft used a standard P-63A, while the second used a P-63N, but without the V-tail used on that version.
Both were originally given the same wing, which had the standard wing roots, and a P-36E outer panel swept back at 35 degrees, and with new tips. Ballast was added to the tail to compensate for the change in centre of gravity. The undercarriage had to be modified, and was no longer retractable. During their short lifespan the L-39s were also given a lighter three blade propeller in an attempt to balance the aircraft, a ventral fin was added and the fuselage was lengthened by four feet.
L-39-1 made its maiden flight on 23 April 1946. It was used for experiments with wing slats, which revealed some problems, including the potential to go into an unexpected snap roll.
L-39-2 had an automatic fuel equalizer, designed to make sure that the centre of gravity didn’t change as fuel was used up. In August 1946 it was fitted with a circular arc aerofoil developed for the Grumman XS-2F Tracker. The second aircraft was later given wings based on those developed for the Bell X-2 - swept wings with a sharp leading edge, and mounted close to the nose.
On 26 August 1946 the first aircraft went to Langley, where it was used for tests in the wind tunnel. The second aircraft was retained for the tests with the X-2 wing.
Both aircraft moved to the NACA Lewis Research Centre on 12 December 1949.
Both were sold as scrap in 1955.
Engine: Allison V-1710-93
Span: 33ft 6in
Length: 36ft 8 3/8in