When using a universal propeller protractor, how should it be calibrated?

Calibrating a universal propeller protractor at maximum aileron travel is crucial because this position represents the full extent to which the aileron can move, and it helps to accurately align the protractor with the maximum desired angle for propeller indication. In this position, the calibration can account for any variations or misalignment that may occur at the extremes of aileron movement.

Choosing maximum aileron travel ensures that the readings are obtainable across the full range of motion and maintains consistent performance during operation. This calibration contributes to achieving optimal aircraft performance and stability during flight, as it directly impacts the effectiveness of the aircraft's control surfaces.

In contrast, calibrating with the aileron in a neutral position or at minimum travel may not accurately reflect the full range of movement, potentially leading to discrepancies during actual flight conditions. Additionally, calibrating at maximum deflection does not provide a baseline reference for typical operations, making maximum travel the most practical choice for accurate and effective protractor calibration.