MONITORING
During an engine run-up, it is necessary to have several indications to check the engine performances and to detect a possible faulty operation.
1. TORQUE:
The “torque” of a turbo-propeller is the ratio between the delivered power and the rotational speed of the power shaft.
This parameter is very useful because it allows to display an exact power whatever might be the flight phase, and to check the turbo-propeller performances. In this case, the real torque is often compared to the theoretical torque, given by diagrams (with respect to the pressure and the outside air temperature).
The torque measurement is generally carried out by reading an oil pressure on the level of the reducer (hydraulic torque-meter). An indicator displays in the cockpit a value expressed in unit of oil pressure (bar), or as a percentage of torque compared to the maximum torque (%).
The torque may also be read thanks to gauges which measure the power shaft torsion.
2. ROTATIONAL SPEEDS:
A tachometric generator (or alternator), connected on the accessories output shaft for example, provides more or less the current depending on the rotational speed. This current is measured in the cockpit by an indicator graduated in turns/minute or expressed as a percentage (%).
The rotational speed may also be read thanks to a phonic wheel and a sensor.