When rotor RPM is below 70%, mast moment indication is shown on which type of scale?

• A. Logarithmic
• B. Circular
• C. Linear
• D. Bar graph

Answer: (C)

At low rotor speeds (below 70%), the mast moment indicator uses a linear scale because readings stay directly proportional across the range. This gives consistent, precise sensitivity to small changes in mast moment when the rotor isn’t turning fast, which is important for careful control. A linear scale shows equal increments everywhere, so a small change near the bottom of the scale is as noticeable as a small change higher up. Other scale types would distort or obscure those small changes: a logarithmic scale would compress higher values and stretch lower ones nonlinearly, making precise low-end readings harder; a circular dial mainly shows position but isn’t as easy to read precisely for small differences; a bar graph conveys magnitude but not the same continuous proportional reading. Therefore, the indication is shown on a linear scale.