| XP-77 | |
|---|---|
 | |
| General information | |
| Type | Fighter aircraft |
| Manufacturer | Bell Aircraft Corporation |
| Primary user | U.S. Army Air Forces |
| Number built | 2 prototypes |
| History | |
| First flight | 1 April 1944 |
| Retired | December 1944 |
TheBell XP-77 development was initiated by theUnited States Army Air Forces duringWorld War II to produce a simplified "lightweight"fighter aircraft usingnon-strategic materials. Despite being innovative, the diminutiveprototype proved tricky to handle and the project was canceled when the XP-77 did not deliver its projected performance.
TheTri-4 (Company designations, later changed toD-6[1]) project with theBell Aircraft Corporation was initiated in October 1941. Originally a design study to meet the USAAF specifications for a "very light" interceptor, the XP-77 was intended to be a small, light fighter much in the mold of the 1930sThompson Trophy air racers.
On 16 May 1942, the USAAF recommended the construction and testing of 25 XP-77s.[1] The aircraft featured a single-engine, low-wingmonoplane with mainly wood construction, equipped withtricycle landing gear, a typical Bell feature that bestowed good ground handling. Abubble canopy also provided fair visibility except in the forward-downward direction due to the extended nose.[2]
While originally conceived using an air-cooled 500 hp (370 kW)RangerXV-770-9 12-cylinder engine with asupercharger, the prototypes were delivered with the non-superchargedXV-770-7 engine due to engine development delays. With the anticipated delivery time of the original engine delayed for one and a half years, Bell proposed that seven XP-77s be built using the seven XV-770-7 engines then available.[1] The planned armament was oneHispano 20 mm cannon firing through the propeller hub (much like the larger caliber 37 mm cannon of theP-39 Airacobra) and two 0.5 inch (12.7 mm)M2 Browning machine guns, with the option of either a 300 lb (140 kg) bomb or 325 lb (147 kg) depth charge with the deletion of the cannon armament.
The mock-up inspection on 21–22 September 1942 produced some concerns from both the manufacturer and the USAAF inspection team. Weight had crept up beyond the 3,700 lb (1,700 kg) design limit but delays in the program were experienced when the company resorted to sub-contracting the wooden construction while the ongoing production at the Bell facilities did not allow for the XP-77 to take priority for research and development. Bell asked and received permission to reduce the production run of aircraft to two prototypes.[3]
The XP-77 project continued to suffer numerous delays, many related to correction of the excess weight issues. A change in subcontractor for the wing assembly also caused headaches as the first subcontractor refused to release necessary parts. Concerns over structural integrity relating to the glue and its binding properties were also difficult to resolve. With the anticipation that contract costs would soon be exceeded, and no hope that the supercharged engine would become available, the USAAF would only continue the project as an experiment to evaluate the use of wooden construction and materials in combat aircraft.[4] The first XP-77 flew 1 April 1944 atWright Field but the flight tests revealed vibration problems due to directly mounting the engine to the airframe, without vibration isolation. The long nose and rear-mounted cockpit also inhibited visibility relative to operational aircraft of the time.
The XP-77 proved to be difficult to fly and despite flying without guns or armor, it did not come up to the expected performance estimates mainly because it was woefully underpowered.[5] Further trials were conducted at the USAAF Proving Ground atEglin Field with the second aircraft, which was destroyed on 2 October 1944 when it entered an invertedspin while attempting anImmelmann, and the pilot bailed out. All development was terminated in December 1944.[6]
After the program's cancellation, the first prototype was sent toWilbur Wright Field, then to Eglin Field, then back to Wright. The aircraft was seen at various airshows before being sent to an unknown air base as agate guard. The aircraft remained on display for several years before deteriorating, after which it was burned.[6]
Data from Jane's Fighting Aircraft of World War II[7] and[8]
General characteristics
Performance
Armament
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