FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceMedium
A pilot is flying an airplane that is in the region of reverse command. What characteristic describes the relationship between airspeed and power in this flight regime?
- APower requirements are independent of airspeed.
- BAn increase in airspeed requires an increase in power.
- CA decrease in airspeed requires an increase in power.
- DAn increase in airspeed requires a decrease in power.
Show answer & explanationAnswer & explanation
Correct answer: C. A decrease in airspeed requires an increase in power.
In the region of reverse command (speeds below L/D max), to fly at a slower airspeed, an airplane requires a higher angle of attack, which significantly increases induced drag. To overcome this increased drag and maintain altitude (or slow down further), more power is needed.
Why the other options are wrong
- A. Power requirements are always dependent on airspeed to maintain level flight.
- B. This describes flight in the normal region of command (above L/D max).
- D. This is true in the normal region of command, not reverse command.
Region of Reverse Command
The flight regime where an airplane requires more power to fly at a slower airspeed, due to the rapid increase in induced drag at high angles of attack. It occurs at airspeeds below L/D max (minimum drag speed).
- Occurs at speeds below L/D max.
- Induced drag dominates and increases significantly at lower speeds.
- More power is needed to overcome increased drag and maintain level flight at slower speeds.
- Associated with slow flight, landing approach, and climbing at Vx.
Memory trick: In reverse command, slowing down means powering up, like trying to walk slowly up a steep hill.