Underpower means what?

• A. Using more power than required for a slower rate of airspeed change
• B. Using less power than required for the purpose of achieving a faster rate of airspeed change
• C. Engine failure
• D. Operating at maximum continuous power

Answer: (B)

Underpower means not providing enough engine power to achieve the intended rate of airspeed change. In level flight or during maneuvers, the speed at which your airspeed changes depends on the thrust available relative to drag. If you aim for a faster rate of change but you don’t supply enough power to meet that goal, the airspeed will increase or decrease more slowly than planned. So, using less power than what’s required for the desired rate of airspeed change describes being underpowered. The other ideas—engine failure or operating at maximum continuous power—don’t fit this situation, as they imply either a loss of power or excess power, not a deficiency relative to the goal.