FAA Private Pilot Helicopter (PRH)Helicopter Aerodynamics and SystemsMedium
A single main rotor helicopter's main rotor turns counterclockwise as viewed from above. As the pilot raises the collective to climb, engine torque increases and, per Newton's third law, the fuselage tends to yaw opposite the direction of main rotor rotation. Which pilot action is required to maintain heading?
- ALower the collective slightly to reduce main rotor lift
- BApply left pedal to increase tail rotor thrust
- CApply forward cyclic to increase airspeed
- DApply right pedal to reduce tail rotor thrust
Show answer & explanationAnswer & explanation
Correct answer: B. Apply left pedal to increase tail rotor thrust
Newton's third law states that as the engine applies torque to turn the main rotor counterclockwise, an equal and opposite reaction tends to rotate the fuselage clockwise (nose right). Increasing collective increases this torque reaction, so the pilot must apply left pedal to increase tail rotor thrust and counteract the yaw.
Why the other options are wrong
- A. Lowering collective reduces power/climb performance and is not the correct antitorque correction.
- C. Forward cyclic changes airspeed, not yaw caused by torque changes.
- D. Reducing tail rotor thrust would worsen the uncommanded right yaw, not correct it.
Torque Effect (Newton's Third Law)
The tendency of the fuselage to rotate opposite the main rotor's direction of turn, caused by the equal and opposite reaction to engine torque driving the rotor.
- Increased power increases torque reaction
- Tail rotor thrust counteracts this reaction
- Pedal inputs must change whenever power/torque changes
- Distinct from translating tendency, which is a lateral drift caused by tail rotor thrust itself
Memory trick: More power up, more left pedal to keep the nose true.