FAA Private Pilot Helicopter (PRH)Helicopter Aerodynamics and SystemsHard
A pilot is flying at very low airspeed, just above effective translational lift, and needs to reduce airspeed slightly to maintain obstacle clearance. According to the power-required curve, operating in this 'region of reverse command' means that to slow down further while maintaining altitude, the pilot must:
- Aincrease power, since more power is required as airspeed decreases in this region
- Bdecrease power, since less airspeed always requires less power
- Cmaintain the same power setting, since power required is constant at low airspeed
- Dreduce collective pitch to trade rotor RPM for additional lift
Show answer & explanationAnswer & explanation
Correct answer: A. increase power, since more power is required as airspeed decreases in this region
In the region of reverse command (low-speed end of the power-required curve), power required increases as airspeed decreases due to rising induced drag; this is the opposite of normal cruise flight, where power decreases as speed decreases.
Why the other options are wrong
- B. This is only true in the normal flight regime above minimum-power airspeed, not at very low airspeeds.
- C. Power required varies significantly with airspeed in this regime; it is not constant.
- D. Reducing collective decreases lift and RPM management is unrelated to the region of reverse command concept.
Region of Reverse Command
The portion of the power-required curve at low airspeeds where power required increases as airspeed decreases, opposite to the normal relationship at higher speeds.
- Occurs below the speed for minimum power required
- Induced drag/power dominates at low airspeed
- Requires more power to slow down or hover, not less
- Important for understanding low-speed flight and approach-to-hover power management
Memory trick: Below minimum-power speed, slower means you must push harder—reverse of normal.