Republic XF-84H
1955
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Republic XF-84H

Even in the mid-1950s the superiority of the jet powerplant for combat aircraft was questioned by some. A modern technology propeller driven by a turbine (a turboprop) offered high speeds, long endurance and low landing speeds. To test this concept the USAF commissioned two XF-84Hs from Republic. Powered by the troublesome T-40 turboprop, the noise the F-84H made has been described as an 'unholy shriek', leading to the nickname 'Thunderscreech'. Resonance off the ground made groundcrew physically sick. The two aircraft only made a dozen test flights, all but two of which resulted in emergency landings and the USAF refused to accept it for their own tests, cancelling the programme in 1956.

The first XF-84H spent 40 years on a pole at Bakersfield Airport, California, its propeller slowly (and quietly) rotated by an electric motor.

Republic XF-84H


Specification 
 CREW1
 ENGINE1 x 585Ohp Allison XT40-A-1 turboprop
 WEIGHTS
    Take-off weight8123 kg17908 lb
 DIMENSIONS
    Wingspan10.18 m33 ft 5 in
    Length15.67 m51 ft 5 in
    Height4.67 m15 ft 4 in
 PERFORMANCE
    Max. speed837 km/h520 mph

Comments
Barry, 14.05.2013

Costas I can not comment on the noise of the XF84H, but the noise of the T6 Texan is due to the propellor being direct drive,i.e. not going through a gear box. Also,if the propellor tips are in excess of Mach they would fold back.

Timothy Boles, 29.06.2010

This plane is at Wright Patterson Air Museum, in the 'X-planes' hanger

asda, 29.04.2010

135 dB? that's CRAP!
this aircraft is too noisy...

Doug Rodrigues, 13.03.2010

I remember seeing an example of this plane on that pole at the enterance to Bakersfield Airport back in 1969. There was a placard saying that the Air National Guard flew a squadron of this model there in earlier years. A few years ago, I located it again using the GoogleEarth photos. Last month I went looking for it once again on GoogleEarth program, but it appears that the plane has been removed.

Steve, 17.02.2010

The British invented the angle deck, steam catapult, and mirror landing sight just in time - else this might have been the future of carrier aviation!

Costas Tsaganas, 22.08.2008

The noise because most of each propeller blade was supersonic when spinning (e.g. the T-6 Texan makes a distinctive buzzsaw noise because the prop tips are supersonic). Even with the engine idling and the prop feathered the noise was awful, as it is a constant speed unit and thrust variations are made by pitch change. IT would cause extreme discomfort and nausea to anyone near it, and there is at least one instance of a man collapsing to the ground with (epileptic?) convulsions a fair distance from the Thunderscreech.

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FACTS AND FIGURES

The turboprop engine was mounted behind the cockpit and drove the propeller through a long extension shaft.

A small auxiliary fin behind the cockpit helped yaw control.

The XF-84H had a T-tail arrangement rather than a mid-set tailplane as on the F-84F Thunderstreak. This kept it out of the propwash.

Various changes were needed to counteract the massive torque from the propeller. The left engine intake was mounted a foot further forward than the right and the flaps had differential operation.



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