Final answer:
Piston-powered aircraft are more efficient at high altitudes compared to low altitudes at the same power setting. The reduced air density and cooler air temperature contribute to this increased efficiency.
Step-by-step explanation:
In high-altitude flight, a piston-powered aircraft is more efficient compared to low altitudes at the same power setting. This is because the air density at higher altitudes is lower, which reduces the amount of drag experienced by the aircraft. With less drag, the aircraft can maintain its speed more easily, resulting in a higher overall efficiency.
Additionally, at higher altitudes, the engine can operate more efficiently due to the cooler air temperature. Cooler air allows the engine to achieve better combustion, resulting in improved fuel efficiency.
Overall, the combination of reduced drag and improved engine efficiency at high altitudes makes piston-powered aircraft more efficient in terms of fuel consumption.