The XF-84H Thunderscreech, a turboprop plane with a supersonic propeller
The video in this article post features a recording of the Republic XF-84H Thunderscreech, a turboprop plane with a supersonic propeller. When played at its original volume, this sound is said to have caused fainting, vomiting, mild hearing loss, and people reputedly soil themselves.
It was the first Ram Air Turbine (RAT)-equipped aircraft ever built in the United States. In later US aircraft, it provided emergency hydraulic and electrical power; nevertheless, the XF-84H required power for landing. A “take-off fin” or “vortex gate” aft of the cockpit was another innovative feature that helped overcome the impacts of propeller torque.
The XF-84H, a joint Air Force/Navy project, was derived from the RF-84F as a supersonic propeller test vehicle driven by an after-burning Allison XT-40 turboprop engine.
Sickening noise
Two aircraft were built and briefly tested, as the propeller’s noise, even at idle, was too severe for safe ground crew activities. The sickening noise gave the aircraft its nickname, “Thunderscreech.”
According to Military.com, ‘the XF-84H was riddled with problems from the start. For starters, the supersonic propeller created enough torque and propeller wash to destabilize the plane in flight. Even Republic Aviation referred to the engine as “a monstrosity, a mechanical nightmare.”
‘It would have been useless as a fighter aircraft because, despite its powerful acceleration, it took 30 minutes to prepare for flight. In that time, the ground crews servicing the plane would have their work cut out for them.
‘XF-84 ground crews nicknamed the plane “Thunderscreech,” a play on the nickname of the operation F-84 fighter bomber because it was so loud. The propeller tips of the XF-84 traveled at Mach 1.18, faster than the speed of sound, producing sonic booms that could be heard some 25 miles away.
‘The noise combined with the shock waves of the booms were enough to effectively cripple the area and any crewmen who might be in it. Crews would have to endure while the XF-84 was powering up for 30 minutes before takeoff.
‘One unlucky C-47 Skytrain crew chief who happened to be in the area while a Thunderscreech was powering suffered a seizure in the back of his aircraft due to the intensity coming out of the XF-84.’
The loudest aircraft ever built
The flight program lasted from June 1955 until October 1956, when it was taken over by the McDonnell XF-88B, which flew until January 1958. The XF-88B had turbojet and turboprop engines and could taxi and take off without the turboprop operating, thus avoiding the painful noise to the ground crew.
Republic’s first prototype is currently on display at the National Museum of the US Air Force (USAF). This aircraft flew 8 of the 12 test flights.
The XF-84H remains the loudest aircraft ever built.
H/T Earl Belz
Photo by U.S. Air Force
