Republic XF-84H Thunderscreech

The Republic Aviation Company XF-84H Thunderscreech was an American-built turboprop experimental fighter. Part of the F-84 Thunderjet series of planes. It is unique among them in that it was driven by a supersonic propellor rather than a straight jet engine.

It was originally designated the XF-106.

Design and Development

The design of the XF-84H was based on the swept wing F-84F, and both prototypes were converted F-84F Thunderstreaks.

It was powered by an Allison XT-40 jet engine with afterburner, capable of 5850 horsepower, without afterburner. The afterburner was never lit.

The propellor was a square blade, constant speed supersonic propellor, turning at 3000 rpm, with the tips of the blades travelling at approximately mach 1.18, Thrust was adjusted by changing the blade pitch.

The Tail was a true "T-Tail" to avoid turbulent airflow flow over the horizontal stabilizer/elevator surfaces from propeller wash.

It was the first plane to carry a Ram Air Turbine. This turbine would automatically swing out into the air stream to provide extra hydraulic and electrical power.

Testing

Due to the nature of the massive torque from the propellor, as well as inherent problems with a propellor at high speeds, it was plagued with excessive drive shaft vibrations. Handling was reportedly "very difficult".

It flew a total of 12 test flights.

One test pilot flew in it once and refused to ever fly in it again. Another encountered 10 "emergencies" of varying degrees during his 11 test flights in it.

Historical Significance

It appears in the Guinness book of records as the fastest propellor driven plane ever built, with a design top speed of 670 m/ph, it is unofficially reported to have reached 623 m/ph.

As a postscript to that record, it is almost always also refered to as possibly the loudest propellor plane ever built. They were extremely loud, hence the nickname thunderscreech, and were reportedly audible 25 miles away. Ground crew reported that nearby, standard ear protectors "made no difference".

It was only ever flown by the Republic test pilots, making it possibly the only USAF plane to be never flown by a USAF pilot.

Surviving Plane

Two prototypes were built (FS-059 and FS-060) were ever made and only the FS-059 ever flew, logging only 10 hours.

FS-059 (pictured) was retired and spent many years mounted on a pole outside Meadows Field Airport, Bakersfield, California. In 199x the plane was taken to the 178th Fighter Wing of the Ohio Air National Guard whose volunteers spent over 3000 hours bringing the Thunderscreech back into display condition. It is now on show at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio.

FS-060 (currently unknown). Assumed scrapped when the project was decommissioned in 1956, along with the plans.

Specifications (XF-84H)

General characteristics

• Crew: 1

Performance

• Thrust/weight: 0.66

Armament
3 x g16mm

External links

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