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Not lovingly known as "The loudest aircraft ever built": Republic XF-84H "ThunderScreech. The propellor spun at faster than the speed of sound, causing a shock wave that could knock men over and caused ground crew to become nauseous and incapacitated. From Wikipedia:
Noise
The XF-84H was almost certainly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as the "Mighty Ear Banger".[16] On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away.[17] Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run.[17] Coupled with the already considerable noise from the subsonic aspect of the propeller and the T40's dual turbine sections, the aircraft was notorious for inducing severe nausea and headaches among ground crews.[11] In one report, a Republic engineer suffered a seizure after close range exposure to the shock waves emanating from a powered-up XF-84H.[18]
The pervasive noise also severely disrupted operations in the Edwards AFB control tower by risking vibration damage to sensitive components and forcing air traffic personnel to communicate with the XF-84H's crew on the flight line by light signals. After numerous complaints, the Air Force Flight Test Center directed Republic to tow the aircraft out on Rogers Dry Lake, far from the flight line, before running up its engine.[14] The test program did not proceed further than the manufacturer's Phase I proving flights; consequently, no USAF test pilots flew the XF-84H. With the likelihood that the engine and equipment failures coupled with the inability to reach design speeds and subsequent instability experienced were insurmountable problems, the USAF canceled the program in September 1956.[19]
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