To: Rameses III
Which paragraph amazed you? Paragraph (1) was a joke. Paragraph (2) is true.
They built a special test stand that had several water brake dynamometers on it. The set up was such that they could attach the main rotor shaft to one of the dynamometers and operate the engine and the tail rotor. They would then disconnect the main rotor shaft from its’ dynamometer and re installed the head and blades. In this condition they would connect the tail rotor drive to its’ dynamometer. They took noise measurements under both conditions to determine the contribution to the overall noise emanating from the helicopter. They then hooked both rotor systems to their respective dynamometers and checked the noise emanating from the skin of the helicopter and at the same time checked the noise coming from the engine. With all this information they went back to the drawing board and redesigned the main and tail rotor. They made a five blade main rotor and an X tail rotor, which significantly cut down on the noise. They added foam padding to the internal structure to dampen the noise transmitted through the fuselage skin and the crowning glory was a silencer installed on the engine exhaust.
The consensus of those not involved in the program was that the helicopter or several like it would be employed in Vietnam but that was never proven to be true. Some time later, Hughes sold a bunch of helicopters to the Customs and DEA branches. These helicopters left the factory in black paint and no N-numbers but I don’t know if any were given the silent treatment.
In any case the government research financed the five-blade system on the 500-F series as it did for the X tail rotor used on the F and the Apache.
I do not know if an official report was ever generated or, if any material is available on the Internet.
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The Cat