FAA Powerplant Written Practice Test

How does a floating control thermostat help to regulate oil temperature in some reciprocating engines?

1. By adjusting oil pressure

2. By controlling air flow through the oil cooler

3. By modifying oil viscosity

4. By directing oil to a secondary cooler

The correct answer is: By controlling air flow through the oil cooler

A floating control thermostat helps regulate oil temperature in some reciprocating engines by controlling airflow through the oil cooler. Its primary function is to maintain the oil within a specific temperature range, ensuring that the oil operates efficiently for lubrication and cooling. When the oil temperature rises above a set point, the floating control thermostat opens, allowing air to flow through the oil cooler more effectively. This increased airflow facilitates the cooling of the oil by enhancing heat exchange, resulting in lower oil temperatures. Conversely, when the oil temperature is within the ideal range, the thermostat reduces airflow, limiting cooling to maintain optimal operating temperatures. This mechanism is crucial because excessive oil temperatures can lead to decreased lubrication effectiveness and can increase the likelihood of engine wear or failure. By efficiently managing the coolant flow, the floating control thermostat plays an essential role in ensuring the engine remains within safe operational limits, promoting longevity and reliability.