America made an aircraft that was so loud it could knock people over

An experimental US aircraft was so loud that it was capable of knocking over ground crew with its shock wave. 

Built by Republic Aviation for the US Air Force back in the 1950s, the XF-84H was a turboprop, meaning it had a turbine engine that powered a propellor. 

In this case, the XF-84H had a supersonic propeller.

That supersonic propellor was so loud that the XF-84H was given the nickname Thunderscreech or the ‘Mighty Ear Banger’. 

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The XF-84H Thunderscreech produced a continuous sonic boom

You’re probably familiar with the term ‘sonic boom’ – the noise created when an aircraft exceeds the speed of sound, which is around 1,236km/h or 768mph, according to NASA.

These sonic booms can be pretty loud on the ground, even if the plane is flying at high altitude. 

In fact, the noise was considered so loud that several countries banned supersonic flights over land, including the US – which is part of the reason we don’t see supersonic commercial flights anymore. 

On the Thunderscreech, the outer edges of its propeller blades traveled faster than the speed of sound even at idle thrust, which meant the aircraft produced a continuous and visible sonic boom that could travel for hundreds of meters. 

During one ground run-up test of the Thunderscreech’s prototype, the noise could reportedly be heard from 40km (25 miles) away. 

The aircraft was so loud it could knock people off their feet 

According to reports from the time, the shock wave produced by the XF-84H was so powerful it could – and did – knock people off their feet. 

The ultra-loud supersonic propellers were coupled with noisy T40’s dual turbine sections – meaning the whole thing was almost certainly the loudest aircraft built. 

It soon earned a reputation for inducing nausea and headaches among ground staff, and one engineer was even reported to have a seizure following ‘close range’ exposure to the noise, according to Real Engineering.

In another report, a crew chief in a C-47 was left ‘severely incapacitated’ during a half-hour ground run of the Thunderscreech. 

In September 1956, the US Air Force canceled the XF-84H program due to engine reliability problems and aerodynamic deficiency – and that was the last anyone would hear of the world’s loudest aircraft.