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Turbine engines use percent rpm indicators due to the high rpm that the engines generally operate. Each rotating assembly in an engine has its own percent rpm indicator. The 100 percent position on the indicator is the highest rpm the engine can operate. Red lines and green arcs operate the same as with reciprocating engines. 

## Cylinder Head Temperature Indicator 

During the engine test procedures, the cylinder head temperatures of various cylinders on the reciprocating engine are normally tested. Thermocouples are connected to several cylinders and, by a selector switch, any cylinder head temperature can be indicated on the indicators. 

When installed in the aircraft, there is sometimes only one thermocouple lead and indicator for each engine installed in an aircraft. 

Cylinder head temperatures are indicated by a gauge connected to a thermocouple attached to the cylinder, that tests show to be the hottest on an engine in a particular installation. The thermocouple may be placed in a special gasket located under a rear spark plug, or in a special well in the top or rear of the cylinder head. 

The temperature recorded at either of these points is merely a reference or control temperature; but as long as it is kept within the prescribed limits, the temperatures inside the cylinder dome, exhaust valve, and piston is within a satisfactory range. Since the thermocouple is attached to only one cylinder, it can do no more than give evidence of general engine temperature. While normally it can be assumed that the remaining cylinder temperatures are lower, conditions such as detonation are not indicated unless they occur in the cylinder that has the thermocouple attached. 

The cylinder head temperature gauge range marking is similar to that of the manifold pressure and tachometer indicator. The cylinder head temperature gauge is a dual gauge that incorporates two separate temperature scales. [Figure 10-39] The scales are calibrated in increments of 10°, with numerals at the 0°, 100°, 200°, and 300° graduations. The space between any two graduation marks represents 10 °C. 

## Torquemeter 

Most torque systems use an oil pressure output from a torque valve to indicate actual engine power output at various power settings. The torquemeter indicates the amount of torque being produced at the propeller shaft. A helical gear moves back and forth as the torque on the propeller shaft varies. This gear, acting on a piston, positions a valve that meters the oil pressure proportionally to the torque being produced. A change in 

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