Which tool is commonly used to measure control surface travel in aircraft rigging?

A protractor or a specialized control travel gauge is commonly used to measure control surface travel in aircraft rigging because these tools provide the precision needed to determine the angle of deflection of control surfaces such as ailerons, elevators, and rudders. Accurate measurement of this travel is crucial for ensuring that the control surfaces operate within the specified limits as defined by the aircraft manufacturer. This ensures proper aerodynamic performance and safety during flight.

Using a protractor allows for a visual and numerical assessment of the angle, while specialized gauges may provide more advanced features tailored specifically to the rigging process, including ease of setup and measurement.

Other tools mentioned, such as an altimeter, air pressure gauge, and torque wrench, serve very different functions—measuring altitude, evaluating pressure, and applying a specific amount of torque, respectively. They do not provide the necessary measurements for control surface travel, which revolves around angle and deflection measurements.