During the Second World War, aircraft development went into overdrive. Many, in fact most, of the new machines were at the cutting edge of aviation technology for the time. However some designs were born out of practicality and necessity. The Bell XP-77 was one such design. The brief for a simplified lightweight fighter aircraft, built using “non-strategic” materials was initiated by the USAAF in 1941. The idea was to create an interceptor aircraft which was very much modeled on the fast and agile air racers from the 1930s.
On May 16th 1942, the USAAF ordered 25 XP-77s for testing. The aircraft was to be a single engine, low-wing monoplane built primarily from wood. The neat bubble canopy provided excellent vision in all directions – except for directly forward, a fairly major error for a point-and-shoot fighter aircraft!
Originally Bell had envisaged equipping the XP-77 with an air-cooled 500 horsepower 12 cylinder supercharged engine. However due to delays with the supercharged engine, a lower performance non-supercharged version of the 12 cylinder engine was fitted. The original production run of 25 aircraft was also reduced to just seven – mainly because there were only seven engines available for the project.
In September 1942 the Bell Aircraft Corporation unveiled a mock-up of the aircraft for a USAAF inspection team. At the meeting both the USAAF and Bell voiced some concerns about the aircraft’s development. Firstly, the weight was above the 3,7oo lb (1,678 kg) limit set out in the original brief. But perhaps more troublesome were the delays in construction thanks to a sub-contractor brought in to build the wooden airframe – due to the fact Bell’s production facilities were occupied with more important aircraft. At the meeting Bell asked if they could build just two prototypes for testing. The USAAF agreed.
Originally the idea was to arm the XP-77 with one Hispano 20 mm cannon which fired through the propeller hub, and two 0.5 inch Browning machine guns. Optionally it could be equipped with either a 300 lb bomb or a 325 lb depth charge – if the extra weight of the cannon was removed.
Neither of the prototypes was ever fitted with any armaments, and the project continued to suffer from delays and setbacks throughout development – many relating from engineering problems associated with trying to reduce the aircraft’s weight. As the problems stacked up, the USAAF decided to continue with the project, but reduced its importance. Now instead of being a prototype for a possible fighter aircraft, it was merely a test bed to see how well a wooden aircraft could perform against contemporary combat aircraft.
The first flight of the Bell XP-77 was on April 1st 1944. True to the problematic character of the aircraft from the very start, the initial flight revealed that the XP-77 suffered terribly from vibration due to the fact the engine was mounted directly to the airframe. In addition the XP-77 proved to be a difficult aircraft to fly, and it was significantly underpowered.
During further tests with the second prototype in October 1944, the aircraft was destroyed after it entered into an inverted spin while attempting to perform a classic combat aircraft maneuver, the Immelmann turn. Thankfully the pilot managed to bail out. The XP-77 project wasn’t quite so lucky, and in December 1944 any further development of the sole remaining aircraft was canceled.