Rotorshaft Torquemeter

This paper discusses the performance benefits and limitations of a rotorshaft torquemeter, surveys some methods of measuring rotorshaft torque and presents some thoughts on using the rotorshaft torque measurement. The performance benefits follow from removing the power penalty imposed by using engine torque measurement to limit rotor torque. Engine torque measurement provides no information on power diversion to accessories or the tail rotor. The greatest performance benefits occur during high-power high-gross-weight hover situations, such as pickup and delivery of heavy sling loads. Four currently-used methods of torque measurement in helicopters are reviewed including hydraulic pressure, toothed wheel phase displacement, material property change and telemetered strain gage systems. The pilots' workload and skill requirement can be reduced by using a rotorshaft torquemeter to produce an audible warning signal, to provide maximum continuous power to the rotor, to accumulate torque/time events and to limit the maximum torque that can be applied.