Powered by a turbo-supercharged 2,300 hp Lycoming XH-2470-1 24-cylinder liquid-cooled engine, the XP-54 embodied a number of novel features, including a "ducted wing section" embodying the oil and coolant radiators and intercoolers. A pivoting (ie +3° to -6°) nose section contained two 1.46 in (37 mm) T-12/T-13 cannon mounted rigidly and two 0.50 in (12.7 mm) M2 machine guns on movable mountings, different elevations being adopted to compensate for the differing trajectories of the two types of weapon.
An electrically-operated pilot's seat also served as a lift to provide cockpit access and egress, and the XP-54 was also one of the first single-seat fighters designed for cabin pressurization. In an emergency, the elevator seat would be catapulted downward clear of the propeller, making the XP-54 the first American fighter to be fitted with an ejector seat.
Four months before the planned first flight date, the USAAC ordered a second prototype under the same contract and allotted the s/n 42-108994 on March 17, 1942. The first flight of the first prototype was delayed however till January 15, 1943, when it was flown by test pilot Frank Davis from Muroc Dry Lake (now known as Edwards AFB). The aircraft was finished in an olive-green color scheme with the exception of the rudders being painted in a lighter color. Later the rudders were also finished in green, while also fin fillets had been placed.
The second XP-54 made its first flight on May 24, 1944, when it was flown from Downey to Norton AFB, California, however the performance of the XP-54 fell appreciably below specification and, in consequence, further development was discontinued. The XP-54 was nicknamed Swoose Goose.
Span: 33 ft 10 in (16.41 m)
Length: 54 ft 8.75 in (16.68 m)
Height: 14 ft 6 in (4.42 m)
Wing area: 455.5 sq.ft (42.32 sq.m)
Weight empty: 15,262 lb (6,923 kg)
Loaded weight: 18,233 lb (8,271 kg)
Max speed at sea level: 290 mph (467 kmh)
Max speed at 28,500 ft (8,685 m): 90 mph (145 kmh)
Cruise speed: 75 mph (120 kmh) at 29,527 ft (9,000 m)
Landing speed: 37 mph (60 kmh)
Climb to 26,000 ft (7,925 m) 17 min 18 sec
Climb to 32,100 ft (9,784 m) 27 min 42 sec
Service ceiling: 37,000 ft (11,278 m)
Endurance: 1 hr