The Mast Moment Indicator measures what parameter?

• A. Measures rotor speed
• B. Measures bending moments on the rotor mast
• C. Measures oil temperature
• D. Displays flight altitude

Answer: (B)

The Mast Moment Indicator focuses on the bending moment that the rotor mast experiences. When the rotor produces lift, those aerodynamic forces push and bend the mast as it transmits power from the engine to the rotor. Measuring this bending moment in real time lets the pilot see how close the mast is to its structural limits, so they can adjust controls (like collective) to keep loads within safe levels and prevent overstress or failure. This is different from rotor speed, oil temperature, or altitude readings, which are provided by other instruments.