Which statement best describes the effect of increasing density altitude on airframe performance?

• A. Higher density altitude increases engine power.
• B. Higher density altitude decreases drag.
• C. Higher density altitude reduces air density, decreasing engine power and lift, increasing takeoff and landing distances.
• D. Density altitude has no impact on performance.

Answer: (C)

Increasing density altitude means the air is thinner. With thinner air, the engine receives less oxygen and can develop less power, and the wings generate less lift for a given speed. To produce the same amount of lift, the airplane has to fly faster (true airspeed), which means more runway is needed to take off and to land safely. Drag does decrease with thinner air, but that reduction isn’t enough to compensate for the loss of power and lift, so overall performance drops and takeoff and landing distances increase.