As DA increases, the helicopter will require ______ power to hover.

• A. More
• B. Less
• C. The same
• D. None

Answer: (A)

Increasing density altitude means thinner air. In hover, the rotor must accelerate air downward to balance the helicopter’s weight. With lower air density, each downward thrust impulse is less efficient, so the rotor needs to move more air or do it faster to generate the same thrust. That extra airflow requires more shaft power from the engine (induced power goes up as density decreases). So, as density altitude rises, more power is required to hover. The other options would imply hover becomes easier or unchanged, which isn’t the case in thinner air.