FAA Powerplant Written Practice Test

If a two-stroke light sport aircraft engine continues to run with the ignition off, what is a probable cause?

1. The engine has mechanical failure

2. The engine has overheated

3. The fuel system is malfunctioning

4. The ignition switch is faulty

The correct answer is: The engine has overheated

When a two-stroke light sport aircraft engine continues to run despite the ignition being turned off, one plausible explanation is overheating. Two-stroke engines rely on a mixture of fuel and oil for lubrication and combustion, and if these components are not being properly regulated, it can cause excessive heating. This overheating can lead to conditions such as pre-ignition or run-on, where the engine continues to operate even when the ignition system is deactivated. In this scenario, the engine might still be receiving enough residual fuel to continue running due to the heat being generated. This can promote combustion even in the absence of a spark from the ignition system. The characteristics of two-stroke engines make them particularly susceptible to this situation, especially if there is an obstruction or a misfueling condition that leads to improper fuel delivery, further contributing to the engine's ability to run at high temperature. Understanding the overheating phenomenon in two-stroke engines sheds light on the interaction between engine operation and temperature management, which is crucial for proper engine performance and safety in aviation.