History
Design and Development
The Bell XP-77 development was initiated by the USAAF to explore the feasibility of mass-producing an ultra-light fighter. It was envisaged to be smaller, faster, and more maneuverable than any fighter. It was to be built with non-strategic materials such as wood since the USAAF had concerns that there could be a shortage of aluminum, metals, and other alloys once the US entered the war.
On October 30, 1941, the USAAF requested Bell to study the approach to the ultra-light fighter with non-strategic materials. Bell’s Chief Designer, Robert J. Woods, designed a fighter to fulfill a 4-4-4 combination of 400 horsepower, 4,000 pounds, and 400 miles per hour. The design was given the company designation Tri-4 based on that combination specification. Six months later, Woods submitted the design proposal of the Tri-4, and on May 16, 1942, the USAAF approved and ordered the construction and testing of 25 aircraft with army designation XP-77.
The aircraft was made of almost entirely wood, except for the laminate skin, which would be fashioned with metal. It was a low-wing monoplane with a tricycle landing gear and a laminar-flow wing equipped with manually operated flaps. It was to have a bubble canopy to provide fair visibility except in the forward-downward direction due to the extended nose. It was to be powered by an air-cooled 670-hp Ranger XV-770-9 12-cylinder engine with a unique French Planiol supercharger. The armament was two 0.50-cal. machine guns and one Hispano 20-mm cannon firing through the propeller hub like P-39 Airacobra’s 37-mm cannon through the spinner. The aircraft could mount either one 300-lb bomb or 325-lb depth charge, though this required the removal of the cannon gun.
The XP-77 project, however, continued to suffer numerous delays, many related to the correction of the excess weight issues alongside concerns over structural integrity associated with the glue and its binding properties. Additionally, Bell was busy with P-39 Airacobra, P-63 Kingcobra, and P-59 Airacomet fighter productions, so it factored in multiple delays. By late 1943, Bell suggested the number of aircraft on order be reduced, so the USAAF reduced to just two prototypes. They were expected to be delivered on January 31, 1944, and March 1, 1944, respectively. Due to the unavailability of the XV-770-9 engine with a two-staged supercharger, the prototypes would be installed and powered by a 520-hp XV-770-7 with a single-stage supercharger.
Flight Testing
On April 1, 1944 (April Fool’s Day), after an 8-month delay, the first XP-77 (43-34915) finally took off for its maiden flight out of Wright Field, Ohio, for 25 minutes in flight. However, the flight tests revealed vibration problems since the engine was directly mounted to the airframe without vibration isolation. The XP-77 was found unpleasant and difficult to fly despite flying without guns or armor, and it took a too long takeoff distance into flight. The XP-77 only had achieved a speed of 330 mph at 4,000 feet, and the ailerons fluttered at higher speeds. The initial performance results were underwhelming and failed to impress somebody.
By the beginning of July 1944, the second XP-77 (43-34916) was sent to Eglin Field, Florida, for fuel consumption and operational suitability trials. During evaluations, the XP-77 was reported to have good handling characteristics but subpar performance. It was notably slower than the USAAF fighters in service, and its climb rate was too interior to be classified as an interceptor. Further trials were continued at Eglin Field with the second aircraft until it was destroyed on October 2, 1944, when it entered an inverted spin while attempting an Immelmann, and the pilot bailed out safely. The cause was likely attributed to the V-770 with reliability issues.
The XP-77 development project, plagued by technical issues and inferior performance, compelled the USAAF to terminate it effectively on December 2, 1944. Additionally, the aluminum supply was abundant, and there was never a problem presented with the aluminum shortage, which relieved the USAAF’s initial worries.
Epilogue
After the program’s cancellation, the first prototype was sent to Wilbur Wright Field, then to Eglin Field, then back to Wright. The aircraft was seen at various airshows with spurious markings and 1947-style roundels before being sent to an unknown air base as a gate guard. The aircraft remained on display for several years before deteriorating to the point where it was beginning to be so foul that it was to be burned and destroyed, forever erasing the last traces of the XP-77.
The XP-77 was the only American fighter built of wood for the USAAF.
