The Republic XF-84H, a joint Navy/Air Force project, was planned to combine jet-like speed with propeller-driven aircraft’s extended range, low fuel consumption, and low landing speed. The XF-84H’s altered F-84F airframe featured a T-tail and a triangular fin behind the cockpit to minimize torque from the propellers.
The XF-84H also featured a propeller that spun faster than the speed of sound, making it the loudest aircraft ever built.
The video in this post features the Republic XF-84H Thunderscreech, a turboprop plane with a supersonic propeller. This sound (when heard at its original level) caused those listening to faint, vomit, get partially deaf, and allegedly soil themselves.
The Navy eventually canceled its order, leaving the Air Force with an experimental aircraft that produced a constant stream of sonic booms from its propeller. As previously stated, the loud noises caused the ground crews who worked on the aircraft to vomit and experience convulsions.
The XF-84H was plagued with issues from the start. For starters, the supersonic propeller generated enough torque and propeller wash to unbalance the plane in flight. Even Republic Aviation described the engine as “a monstrosity, a mechanical nightmare.”
It would have been unsuccessful as a fighter aircraft because, despite its potent acceleration, it required 30 minutes to prepare for flight. The ground crews who were servicing the plane at the time would have had their hands full.
Because the plane was so loud, XF-84 ground crews nicknamed it “Thunderscreech”. The XF-84’s propeller tips moved at Mach 1.18, faster than sound, resulting in sonic booms that could be heard twenty-five miles away.
The noise, along with the shock waves from the booms, effectively crippled any crewmen who may have been present. Crews would have to last 30 minutes for the XF-84 to power up before taking off.
One unfortunate C-47 Skytrain crew chief who happened to be in the vicinity while a Thunderscreech was starting up, had a seizure in the back of his plane as a result of the intensity originating from the XF-84.
Between July 1955 and October 1956, two XF-84Hs conducted 12 test flights, 11 of which ended in emergency landings. The XF-84H was one of the fastest single-engine, propeller-driven aircraft ever built, but it never reached supersonic speeds. Due to inadequate performance and significant maintenance requirements, the XF-84H was never operational.
The XF-84H remains the loudest aircraft ever produced.
