Rotor RPM (RRPM)

Rotor RPM during flight is not constant. It naturally increases or decreases depending on the load being carried by the rotor.

Put simply, the greater the load on the rotor, the faster it tends to rotate. The lighter the load, the slower it tends to rotate.

For example, rotor RPM will generally increase when:

• Aircraft weight increases, such as carrying additional passengers or fuel.

• G-loading increases, such as during steep turns or a flare at the bottom of a descent.

Conversely, rotor RPM will generally decrease when:

• G-loading reduces, such as when abruptly pushing the nose forward at the top of a climb.

• Turbulence causes a temporary reduction in rotor loading.

An increase in airspeed alone does not necessarily produce a significant increase in rotor RPM. The main influence is the load being supported by the rotor.

Key point

Rotor RPM increases with increased rotor loading and decreases with reduced rotor loading. Low-G or negative-G conditions are particularly dangerous because they can cause a rapid loss of rotor RPM and control.

Rotor Blade Coning

Coning is the upward bending of the rotor blades during flight, caused by the combined effects of lift and centrifugal force.