XF-84H Thunderscreech

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XF-84H "Thunderscreech"

Prototype FS-059 underwent 10 hours of flight testing.
Type Experimental fighter
Manufacturer Republic Aviation
Maiden flight 22 July 1955
Primary users Republic Aviation Company
United States Air Force
Number built 2 prototypes
Developed from F-84F Thunderstreak

The Republic XF-84H "Thunderscreech" was an experimental American-built turboprop aircraft based on the F-84F Thunderstreak. Its turbine engine drove the aircraft with a supersonic propeller as well as its exhaust. Although only one ever flew, it reputedly was capable of setting the unofficial air speed record for propeller-driven craft.[1]

Contents

[edit] Design and development

Originally designated XF-106,[2] the project and its resultant prototype aircraft were renamed XF-84H, suggesting it was a mere F-84 variant,[3] rather than an entirely new type. The initial inception for the program came from a U.S. Navy requirement for a carrier fighter not requiring catapult assistance, although the USAF Wright Air Development Center was the key sponsor of the project.

The XF-84H was created by modifying F-84F Thunderstreak aircraft. The engine was changed to an Allison XT-40-A-1,[4] capable of 5,850 horsepower. An afterburner was installed but never used, which could increase power to 7,230 hp. The propeller consisted of three square-tipped blades turning at a constant 3,000 rpm, with the tips travelling at approximately Mach 1.18. Thrust was adjusted by changing the blade pitch. The tail was modified to a T-tail to avoid turbulent airflow flow over the horizontal stabilizer/elevator surfaces from propeller wash.[5] The XF-84H was the first aircraft to carry a ram air turbine. In the event of failure of the engine, it would automatically swing out into the airstream to provide extra hydraulic and electrical power.

[edit] Testing

The XF-84H was destabilized by the powerful torque from the propeller, as well as inherent problems with supersonic propeller blades. It was plagued with engine related problems that affected other aircraft of the time with similar Allison T40 engines such as the Douglas XA2D Skyshark and the North American A2J Super Savage attack aircraft.

It flew a total of 12 test flights. One test pilot flew in it once and refused to ever fly in it again. Test pilot Hank Baird took the craft up 11 times with 10 of these flights ending in forced landings.

[edit] Noise

The XF-84H was possibly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as "Mighty Ear Banger"[6][7] On the ground, they were reportedly audible 25 miles away.

Sounds produced by the aircraft’s turboprop engine caused nausea and headaches among ground crews.[8]

In short order, the Air Force Flight Test Center directed Republic to tow the XF-84H out on Rogers Dry Lake, far from the flight line, before running up its engine.[citation needed]

[edit] Historical significance

Touted as the fastest propeller-driven aircraft ever built,[9] with a design top speed of 670 mph (Mach 0.9), it is reported to have reached 623 mph (Mach 0.83), but this has been disputed.[1] This record speed is also inconsistent with data from the National Museum of the United States Air Force, which gives a top speed of 520 mph (Mach 0.70), making the XF-84H the fastest single-engine propeller-driven aircraft[5] until 1989 when a highly modified F8F Bearcat reached 528 mph (Mach 0.71).[10] See Fastest propeller-driven aircraft for a more complete discussion of speed records.

The XF-84H was only ever flown by the Republic test pilots, making it possibly the only USAF aircraft never to be flown by a USAF pilot.

[edit] Survivors

Two prototypes were built (51-17059 and 51-17060), with buzz number FS-059 and FS-060.[11] Only the first airframe FS-059 flew, taking to the air on 22 July 1955, and logged only 10 hours.[12]

FS-059 (pictured) was retired and spent many years mounted on a pole outside Meadows Field Airport, Bakersfield, California. It was taken to the 178th Fighter Wing of the Ohio Air National Guard whose volunteers spent over 3,000 hours returning the Thunderscreech to 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) is assumed to have been scrapped, along with the plans, when the project was cancelled in 1956.

[edit] Operators

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[edit] Specifications

General characteristics

  • Crew: 1
  • Length: 51 ft 5 in (15.67 m)
  • Wingspan: 33 ft 5 in (10.18 m)
  • Height: 15 ft 4 in (4.67 m)
  • Wing area: 30.75 m ()
  • Empty weight: 17,892 lb (8,132 kg)
  • Loaded weight: 27,046 lb (12,293 kg)
  • Powerplant: 1× Allison XT-40a-1 turboprop, 5,850 hp (4,365 kw)

Performance

[edit] See also

Related development

Comparable aircraft

Related lists

[edit] References

[edit] Notes

  1. ^ a b Hendrix 1977, p. 408. "The XF-84H never achieved its designer's dreams of being the first propeller-driven aircraft to attain supersonic flight. In fact, it never flew over 450 kt indicated, since at that speed, it developed an unhappy practice of 'snaking', apparently losing longitudinal stability." In Hendrix, Test Pilot: XF-84H.
  2. ^ designations systems
  3. ^ Keaveney 1987, pp.19 & 27.
  4. ^ ALLISON T-40-A-10 Fact sheet
  5. ^ a b XF-84H Fact sheet
  6. ^ Hendrix 1977, p. 406.
  7. ^ Knaack, Marcelle Size. Encyclopedia of U.S. Air Force Aircraft and Missile Systems: Volume 1 Post-World War II Fighters 1945–1973. Washington, D.C.: Office of Air Force History, 1978. ISBN 0-912799-59-5.
  8. ^ National Museum of the USAF. Fact sheets. REPUBLIC XF-84H
  9. ^ Young 1997, p. 137.
  10. ^ Performance
  11. ^ Andrade 1979, p. 103.
  12. ^ Bridgman 1956, p. 333.

[edit] Bibliography

  • Andrade, John M. U.S. Military Aircraft Designations and Serials Since 1909. Earl Shilton, Leicester, UK: Midland Counties Publications, 1979. ISBN 0-904597-22-9.
  • Bowers, Peter M. and Angellucci, Enzo. The American Fighter. New York: Orion Books, 1987. ISBN 0-517-56588-9.
  • Bridgman, Leonard, ed.Jane's All The World's Aircraft 1956-1957. New York: McGraw-Hill Book Company, 1956.
  • Hendrix, Lin. "Thunderscreech." Aeroplane Monthly Vol. 5, no. 8 August 1977.
  • Keaveney, Kevin. Republic F-84 (Swept-Wing Variants). Arlington, Texas: Aerofax Inc., 1987. ISBN 0-942548-20-5.
  • Young, Mark C., ed.The Guinness Book of Records 1997. North Sakem, New York: Mint Publishers Group, 1997. ISBN 0-85112-014-8.

[edit] External links

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