Is hovering helicopter torque ever exactly = 0 ?

Click For Summary

Discussion Overview

The discussion revolves around whether a helicopter can generate exactly zero torque while hovering, considering the roles of its primary and secondary rotors. Participants explore the mechanics of torque compensation and the potential need for additional rotors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if a helicopter can achieve zero torque while hovering, noting that the secondary rotor compensates for the primary's torque but raises the issue of the secondary's torque compensation.
  • Another participant argues that the helicopter must always provide torque to overcome air resistance and suggests that the tail rotor's torque cancels out the primary rotor's torque, eliminating the need for further compensation.
  • A different viewpoint suggests that the tail rotor's torque does not lead to the helicopter turning end over end due to the changing pitch of the main rotor blades and the influence of gyroscopic effects.
  • One participant expresses curiosity about the existence of a third rotor or similar device to assist with torque compensation.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics of torque compensation in helicopters, with no consensus reached on whether zero torque can be achieved while hovering.

Contextual Notes

Participants mention various factors affecting torque, including rotor pitch and gyroscopic effects, but do not resolve the implications of these factors on the overall question of torque management.

Loren Booda
Messages
3,115
Reaction score
4
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?
 
Physics news on Phys.org
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.
 
Loren, is that a philosophical question ? :wink:
 
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.
 
Last edited:
An above-average explanation, Asn. The pitch has it!

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

Anyone hear of a third rotor or similar device?
 
I've been thinking about getting a helicopter license after I finish my single-engine land aircraft license.

- Warren
 
I've been thinking about getting a helicopter license after I finish my single-engine land aircraft license.
They're two very different beasts, from what I hear.
 
Totally different. The only things common to both licenses are the FAA regulations concerning e.g. speed limits at altitudes and flight path separation distances and so on.

- Warren
 
I passed the FAA ground school test in 1974 when I was 15, but never pursued my pilot's license due to vestibular hypersensitivity. I remember studying weather, instruments and regulations.
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 18 ·
Replies
18
Views
4K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 3 ·
Replies
3
Views
4K