What is the result of reduced rotor efficiency at high density altitudes?

Reduced rotor efficiency at high density altitudes results in longer takeoff distances due to the decreased lift generated by the rotor system. At higher elevations, the air density is lower, which directly impacts the rotor blades' ability to generate sufficient lift. As a result, helicopters require a longer distance to reach the speed necessary for effective lifting off the ground.

In addition to this, the overall performance of the aircraft is affected, leading to potential limitations in weight carrying capacity and an increase in power requirements, which all contribute to the extended distances needed for takeoff. The other options do not accurately represent the consequences of reduced rotor efficiency; for example, higher fuel efficiency or increased maneuverability are often not achievable under conditions of decreased rotor performance, and lower engine temperature is not a direct result of this aerodynamic change.