During a climb with constant MAP, RPM, and mixture, how does the power output of a piston engine change?

When a piston engine is operating during a climb with constant manifold absolute pressure (MAP), revolutions per minute (RPM), and mixture settings, the power output is primarily influenced by changes in air density and airflow. As the aircraft climbs, the altitude increases, resulting in a decrease in air density. Although the MAP is held constant, meaning the engine is trying to maintain a specific pressure in the intake manifold, the actual amount of oxygen available for combustion decreases due to the lower air density at higher altitudes.

In response, the engine may experience lower back pressure, which allows the engine to operate more efficiently. With lower back pressure, the engine works less against the exhaust and can expel exhaust gases more easily. This scenario can result in a momentary increase in power output until the decreased air density and related factors begin to significantly impact engine performance.

Therefore, stating that the power output increases due to lower back pressure, as indicated in the correct answer, recognizes the balance between maintaining constant operational parameters (like MAP and RPM) and the physical principles governing engine performance at lower densities during a climb. Thus, while the actual power output can start to increase initially, it is important to understand that prolonged climbs at altitude necessitate adjustments in mixture and MAP to compensate