FAA Powerplant Written Practice Test

How are cylinder head temperatures measured?

1. Using a mechanical gauge

2. With a pressure sensing device

3. By means of an indicator and thermocouple sensing device

4. Using an infrared thermometer

The correct answer is: By means of an indicator and thermocouple sensing device

Cylinder head temperatures are typically measured using an indicator and thermocouple sensing device because this method provides accurate and real-time measurements of the temperature at the cylinder head. The thermocouple is a temperature sensing instrument that works based on the principle of measuring the electromotive force generated at the junction of two different metals, known as the thermoelectric effect. When placed against the cylinder head, it can accurately detect the temperature changes due to the combustion process. The indicator serves to display the temperature readings in a format that can be easily monitored by pilots or technicians. This combination allows for effective monitoring of engine performance, which is crucial for maintaining optimal operating conditions and avoiding overheating that can lead to engine damage. In the context of measuring cylinder head temperatures, the other options have limitations. Mechanical gauges may not provide the precision needed for high-performance engines, while pressure sensing devices measure pressure rather than temperature. Infrared thermometers can give surface temperature readings but may not accurately reflect the internal temperatures critical for engine operation. Thus, the use of an indicator and thermocouple is the most reliable and widely accepted method for this application.