Republic XF-91 "Thunderceptor"
     The XF-91, a high-speed experimental interceptor, was America's
 first rocket-powered combat-type fighter to fly faster than the speed
 of sound. The airplane had a number of unusual design features--an
 inverse taper wing (wider at the tips than at the roots), a variable
 incidence wing that could be varied in flight (high angle of attack
 for takeoff and landing and low angle of attack for high-speed
 flight), a main landing gear that retracted outward with the tandam
 wheels being housed in the wing tips and a rocket engine that
 augmented the standard jet engine to provide an outstanding rate
 of climb.
     The airplane made its first flight on May 9, 1949. Numerous other
 test flights were made which provided valuable research data, but the
 airplane was not put into production because it did not carry
 sufficient fuel for a flight of longer than 25 minutes, and did not
 incorporate the latest type of fire control system.
 TYPE          Number built/Converted        Remarks
 XF-91                    2                Jet/Rocket Ftr.
 SPECIFICATIONS
 Span: 31 ft. 3 in.
 Length: 43 ft. 3 in.
 Height: 18 ft. 1 in.
 Weight: 28,300 lbs. loaded
 Engines: General Electric J47-GE-3 of 6,700 lbs. thrust with after-
 burner and Reaction Motors rocket of 6,000 lbs. thrust
 (four XLR11-RM-9s of 1,500 lbs. thrust each).
 Armament: Designed for four 20 mm cannons
 Crew: One
 PERFORMANCE
 Maximum speed: 984 mph
 Cruising speed: 560 mph
 Endurance: 25 minutes
 Service Ceiling: 48,700 ft
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