How does high density altitude affect settling with power?

High density altitude negatively affects helicopter performance, and one of the critical areas influenced is the efficiency of engine and rotor systems. As density altitude increases, the air becomes less dense. This reduction in air density leads to a decrease in engine performance and a loss of lift produced by the rotor blades.

At higher density altitudes, the helicopter's engines may produce less power because the thinner air means there are fewer air molecules available for combustion. Consequently, the overall efficiency of the helicopter is decreased, which can result in the helicopter having to exert more effort to maintain hovering or climb performance. This scenario can lead to a phenomenon known as "settling with power," where the helicopter may begin to descend instead of hover or climb, even when power is applied because it cannot generate enough lift to counteract the weight effectively.

This understanding illustrates why high density altitude decreases helicopter efficiency, making it significantly more challenging for pilots to manage hovering and other flight operations.