# Is hovering helicopter torque ever exactly = 0 ?

Can a helicoptor, considering its primary and secondary rotors, ever generate exactly zero torque, i. e., while hovering? The secondary compensates for the primary's torque, but what compensates for the secondary's torque? Is there such a thing as or a need for a tertiary rotor?

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brewnog
Gold Member
The helicopter will always provide torque to overcome the air resistance (which is needed anyway for the helicopter to work). If the tail rotor compensates for the turning effect of the primary rotor, nothing needs to compensate for that of the tail rotor because the "turning effects" of each rotor (and here I mean orientation of the aircraft, not of the rotor itself) cancel each other out in order for the helicopter to point forwards.

drag
Loren, is that a philosophical question ?

Averagesupernova
Gold Member
Actually I don't think that the 'turning effects' cancel each other so to speak.

Obviously, the tail rotor is used to push against the tail to counteract the torque on the machine caused by the main rotor. But what I suspect Loren wants to know why the torque caused by the tail rotor doesn't cause the whole machine to turn end over end in the opposite direction that the tail rotor is going. One reason is that the pitch is constantly changing on the main rotor blades. It is set up in such a way that in order to move in different lateral directions the main rotor is pitched to torque the body of the machine, but not torqued in the vertical axis, the other two. This so called torque causes the machine to 'slide' in the appropriate direction as well as counter the small amount of torque caused by the tail rotor. If this is not what you were getting at Loren, just ignore my ramblings....

P.S. I would also suspect gyroscopic effects come into play keeping the machine stable. Not only that, but consider that a helicopter is being 'hung' by it's top center. Gravity is probably enough to keep it from turning end over end from the torque caused by the tail rotor.

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An above-average explanation, Asn. The pitch has it!

Have any of you ever flown a helicoptor? I think I would get airsick. :yuck:

Anyone hear of a third rotor or similar device?

chroot
Staff Emeritus
Gold Member

- Warren

They're two very different beasts, from what I hear.

chroot
Staff Emeritus