Science Fair Project Encyclopedia
The Hughes XF-11 was a prototype military reconnaissance aircraft designed by millionaire Howard Hughes for the United States Army. It was a tricycle-gear, twin-engine, twin-fuselage, all-metal monoplane with a pressurized central crew nacelle. In general appearance, it was similar to the Lockheed P-38 Lightning made famous in World War II, though the XF-11's wing had a much larger span and much higher aspect ratio.
The XF-11 used Pratt & Whitney R-4360-31 28-cylinder radial engines with twin four-bladed, controllable-pitch propellers at the front of each engine. The propeller design was very unusual in that the front and rear propellers on each engine were counter-rotating.
The aircraft was designed to be very fast and have long range, and the Army originally ordered 100 of them for the purposes of photo reconnaissance. The order was cancelled following the end of World War II, leaving Hughes with two prototypes.
The first prototype crashed on July 7, 1946, on its maiden flight. An oil leak caused the right engine propeller controls to lose their effectiveness, and the rear propeller reversed its pitch, making the aircraft yaw hard to the right and making it extraordinarily difficult to control. Hughes elected to make an emergency landing on the Los Angeles Country Club 's golf course, but about 300 yards short of the course, the aircraft suddenly lost altitude and clipped three houses. The third house was completely destroyed by the fire that resulted from the crash, and Hughes was nearly killed. 
The second prototype was fitted with conventional propellers and flown on April 5, 1947, after Hughes had recuperated from his injuries. The test flight was uneventful, and the aircraft proved to be stable and controllable at high speed. Its low-speed stability, however, was lacking, and the Air Force didn't want to spend the money for the XF-11 when the Boeing RB-50, which had similar long-range photo-reconnaissance capability, was available for much less.
- Crew: two, pilot and navigator/photographer
- Length: 65 ft 5 in (19.94 m)
- Wingspan: 101 ft 4 in (30.89 m)
- Height: 23 ft 2 in (7.06 m)
- Wing area: 983 ft² (91.4 m²)
- Empty: 37,100 lb (16,864 kg)
- Loaded: lb ( kg)
- Maximum takeoff: 58,300 lb (26,500 kg)
- Powerplant: 2x Pratt & Whitney R-4360-31 radials, 3,000 hp (2,238 kW) each
- Maximum speed: 450 mph (720 km/h)
- Range: 5,000 miles (8,000 km)
- Service ceiling: 44,000 ft (13,415 m)
- Rate of climb: ft/min ( m/min)
- Wing loading: lb/ft² ( kg/m²)
- Power/Mass: hp/lb ( kW/kg)
Related development: Hughes XP-73 - Hughes A-37
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