An instrument used with some of the larger reciprocating engines and turboprop or turboshaft engines to measure the reaction between the propeller reduction gears and the engine case is called a:

• A. Time And Speed Table
• B. Torquemeter
• C. Thrust
• D. Thrust Line

Answer: (B)

Measuring the twist produced in the drivetrain tells you the torque the engine side must resist when turning the propeller through the reduction gears. The device that does this is a torquemeter, designed to sense the reaction torque that develops between the propeller reduction gears and the engine case. It often detects torsional strain in a shaft or gear housing, using strain gauges or a similar sensing method, and converts that into a torque reading.

This information is crucial because it shows how much load the gearbox and propeller are placing on the engine. You can use it to verify the engine is producing power within the gearbox’s limits, detect overloads or misalignment, monitor propeller condition indirectly, and prevent over-torque conditions that could damage the engine or drivetrain.

Other terms listed don’t describe an instrument for measuring this reaction torque. Time and speed tables are data references, thrust measures forward force, and thrust line refers to where the thrust acts rather than a torque-measuring instrument.