TYPE: Experimental swept-wing aircraft

ACCOMMODATION: Pilot only

POWER PLANT: One Allison V-1710-117 liquid-cooled engine, rated at 1,800 hp

PERFORMANCE: 410 mph at 25,000 ft

COMMENT: Two war surplus Bell P-63C Kingcobra fighter aircraft were modified by Bell under Navy contract for flight testing of low-speed and stall characteristics of high-speed wing designs. The aircraft received new wings with adjustable leading edge slats, trailing edge flaps and a pronounced sweep of 35 degrees. The wings had no wheel wells; only the nose gear was retractable. L-39-1 first flew 23 April 1946, demonstrating a need for extra tail surface and rear fuselage length to balance the aircraft in flight—the wing repositioning reduced empennage effectiveness and moved the center of lift aft. A lighter three-bladed propeller from a Bell P-38Q-10 was mounted and the necessary changes to the empennage were made. L-39-2 incorporated these adjustments from the start. L-39-1 later went to NACA at Langley for wind tunnel testing, where much valuable data were gathered. Bell L-39-2 also served as a testbed for the Bell X-2 40-degree wing design (Ref.: 24).