The development of the Bell XP-77 was initiated by the United States Army Air Forces during World War II to create a simplified, lightweight fighter aircraft using non-strategic materials.
Although innovative, the small prototype was difficult to handle, leading to the cancellation of the project when the XP-77 failed to meet its expected performance.
The project, initially known as Tri-4 and later renamed to D-6 by the Bell Aircraft Corporation, began in October 1941.
Designed to fulfil USAAF requirements for an ultra-light interceptor, the XP-77 aimed to emulate the small, agile fighters of the 1930s Thompson Trophy air races.
On May 16, 1942, the USAAF authorised the construction and testing of 25 XP-77s.
The design featured a single-engine, low-wing monoplane primarily made of wood, with tricycle landing gear—a characteristic Bell innovation that provided excellent ground handling.
The aircraft had a bubble canopy offering decent visibility, except forward-downward due to the protruding nose.
Initially planned with a supercharged 500 hp (370 kW) Ranger XV-770-9 12-cylinder engine, the prototypes were instead fitted with the non-supercharged XV-770-7 engine because of delays in engine development.
With the delivery of the original engine postponed by one and a half years, Bell suggested constructing seven XP-77s using the available XV-770-7 engines.
The intended armament included a Hispano 20 mm cannon firing through the propeller hub and two 0.5 inch (12.7 mm) M2 Browning machine guns, with an alternative loadout of either a 300 lb (140 kg) bomb or a 325 lb (147 kg) depth charge, omitting the cannon.
Concerns arose during the mock-up inspection on September 21–22, 1942, from both the manufacturer and the USAAF team, as the weight exceeded the 3,700 lb (1,700 kg) design threshold, causing further delays when the company turned to subcontracting.
Specifications
Crew
1
Length
22 ft 10 in (6.96 m)
Wingspan
27 ft 6 in (8.38 m)
Height
8 ft 2 in (2.49 m)
Wing area
100 sq ft (9.3 m2)
Empty weight
2,855 lb (1,295 kg)
Max take-off weight
4,028 lb (1,827 kg)
Powerplant
1 × Ranger V-770-7 inverted V12 engine,
520 hp (388 kW)
Propellers
2 bladed
Performance
Maximum speed
330 mph (530 km/h, 290 kn)
Range
550 mi (890 km, 480 nmi)
Service ceiling
30,100 ft (9,180 m)
Rate of climb
3,600 ft/min (18.3 m/s)
Wing loading
40.28 lb/sq ft (196.5 kg/m2)
Power/mass
13 hp/lb (213 W/kg)
Armament
Guns
1 × 20 mm (0.787 in) Hispano-Suiza HS.404 cannon, firing through the propeller hub.
2 × .50 in (12.7 mm) M2 machine guns with 200 rounds each.
Bombs
1 × 300 lb (136 kg) bomb
Or
1 × 325 lb (147 kg) depth charge
Sources
U.S. Experimental & Prototype Aircraft Projects: Fighters 1939–1945-B Norton.
The American Fighter from 1917 to the present – E Angelucci.
