Which will give you less thrust on takeoff?

• A. High density altitude
• B. High outside air pressure
• C. Low density altitude
• D. Increased engine RPM

Answer: (A)

Air density determines how much thrust an aircraft can produce on takeoff. When density altitude is high, the air is thinner, so engines and propellers move less air and generate less thrust. That reduction in air density means slower acceleration and a longer takeoff roll. In contrast, higher outside air pressure or a lower density altitude makes the air denser and increases thrust, while higher engine RPM generally increases thrust if the engine can deliver it. So the condition that will give you less thrust on takeoff is high density altitude.