Republic XF-84H
| XF-84H "Thunderscreech" | |
|---|---|
 |
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| XF-84H serial number 51-17060 in flight | |
| Role | Experimental fighter |
| Manufacturer | Republic Aviation |
| First flight | 22 July 1955 |
| Primary user | United States Air Force |
| Number built | 2 |
| Developed from | Republic F-84F Thunderstreak |
The Republic XF-84H "Thunderscreech" was an experimental turboprop aircraft derived from the F-84F Thunderstreak. Powered by a turbine engine that was mated to a supersonic propeller, the XF-84H had the potential of setting the unofficial air speed record for propeller-driven aircraft, but was unable to overcome teething aerodynamic deficiencies, resulting in the cancellation of the program.
Although the USAF Wright Air Development Center was the key sponsor of the Republic Project 3347 turboprop fighter, the initial inception came from a U.S. Navy requirement for a carrier fighter not requiring catapult assistance. Originally known as XF-106, the project and its resultant prototype aircraft were redesignated XF-84H, closely identifying the program as an F-84 variant, rather than an entirely new type. With a projected contract for three prototypes, when the US Navy cancelled its order, ultimately, the remaining XF-84H prototypes became pure research aircraft built for the Air Force’s Propeller Laboratory at Wright-Patterson AFB to test supersonic propellers in exploring the combination of propeller responsiveness at jet speeds.
The XF-84H was created by modifying a F-84F airframe, installing a 5,850 hp (4,360 kW) Allison XT40-A-1 turboprop engine in a centrally-located housing behind the cockpit with a long extension shaft to the nose-mounted propeller. The turbine engine also provided thrust through its exhaust; an afterburner which could further increase power to 7,230 hp (5,390 kW), was installed but never used. Thrust was adjusted by changing the blade pitch of the 12 ft (3.7 m)-diameter Aeroproducts propeller, consisting of three steel, square-tipped blades turning at a constant speed, with the tips traveling at approximately Mach 1.18 (1,446 km/h). To counter the propeller's torque and "P-factor", the XF-84H was fitted with a fixed dorsal yaw vane. The tail was changed to a T-tail to avoid turbulent airflow flow over the horizontal stabilizer/elevator surfaces from propeller wash.
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