What type of scale is used to depict the mast moment indication when rotor RPM is below 70%?

• A. Exponential
• B. Logarithmic
• C. Linear
• D. Circular

Answer: (C)

The correct choice is the linear scale, which is used for mast moment indication when rotor RPM is below 70%. A linear scale represents values in equal increments, making it easier for the operator to gauge variations in the mast moment directly as the rotor speed decreases. This is crucial for ensuring stability and safety, allowing users to quickly understand how changes in the rotor RPM affect the mast moment.

In contrast, other types of scales would not be as effective for this purpose. An exponential scale would depict values that increase or decrease rapidly, which could obscure subtle changes in low RPM readings that are critical for safety. A logarithmic scale compresses the data in such a way that small changes may not be effectively communicated, particularly at lower RPMs. Lastly, a circular scale, while useful in specific applications, does not provide the straightforward linear relationship needed for precise mast moment readings in this context. Because of these factors, a linear scale is the most appropriate choice for this specific operational scenario.