To:212 Man
“Does it not depend where the centre of pressure acts relative to the feathering axis and hence how the centripetal turning moment moves the pitch”?
Hopefully this does not start another international incident due to semantics but I believe you are talking about “Centrifugal twisting moment”. The centrifugal twisting moment coupled with the aerodynamic forces are what you feel when you move the pedals during flight, or in other words, you experience the associated feed back. Propellers on aircraft have the same condition. If say on a Hydromatic propeller you lose oil pressure the centrifugal twisting moment will return the blades to low pitch and if you don’t catch it quick enough you can have a runaway engine.
To: Imlanphere
“I believe I read somewhere that if the pitch control mechanism were to be severed somehow the tail rotor blades would work themselves back to zero pitch automatically, but maybe that’s type dependent.”
You are correct in stating that the return to low pitch is type dependent. Some helicopters that do not incorporate compensating weight would return to flat pitch if the control were severed. Many helicopters incorporate dynamic or static counterweights. The static weights are incorporated as a part of the blade on the Bell 407. Helicopters like the Sikorsky S-58 incorporate dynamic counter weights that move when the tail rotor pitch is changed. The purpose of these weights is to counter the centrifugal twisting moment so that the pilot only experiences the aerodynamic forces if he has to fly with the tail rotor boost shut off. On this type of tail rotor the dynamic or static weights will under ideal conditions maintain the blade pitch in the last commanded position when control is severed.
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The Cat