Which concept governs the need for a helicopter to have a proper center of gravity?

The concept that governs the need for a helicopter to have a proper center of gravity is stability and control. The center of gravity (CG) is the point where the weight of the helicopter is evenly distributed. If the CG is too far forward, backward, or off-center, it can lead to handling difficulties, making the helicopter unstable during flight.

A helicopter with a properly balanced center of gravity will respond more predictably to pilot inputs, allowing for smoother maneuvers and a more controlled flight environment. This stability is crucial for maintaining altitude, executing turns, and managing adverse weather conditions. Furthermore, if the CG is not within the manufacturer's specified limits, it can affect the rotorcraft's ability to maintain lift, potentially leading to dangerous flight situations.

While other concepts like thrust and drag balance, energy efficiency, and fuel consumption optimization are important in aviation, they are secondary to the fundamental requirement of stability and control, which ensures that the helicopter operates safely and effectively in various flight conditions.