FAA Ground School Practice Test

Detonation in an aircraft engine is more likely to occur at what power setting?

1. Low-power settings

2. Idle settings

3. High-power settings

4. Any power setting

The correct answer is: High-power settings

Detonation in an aircraft engine is a condition where fuel-air mixtures explode instead of burning smoothly during the combustion process. This phenomenon creates a sudden and uncontrolled pressure spike within the cylinders, which can lead to engine damage. At high-power settings, the engine is under significant load, and the temperature and pressure within the combustion chamber increase. This environment is conducive to detonation, particularly when high-speed fuels are used or when the engine is operating under conditions like excessive heat or inappropriate fuel octane levels. Under these circumstances, the fuel can ignite prematurely, leading to a greater risk of detonation. In contrast, lower power settings and idle conditions typically do not produce the necessary pressure and temperature for detonation to occur, making detonation far less likely in those scenarios. Therefore, while detonation can theoretically occur at any power setting, it is most strongly associated with high demand conditions where the engine is working hard, maintaining optimal thrust, and operating at elevated temperatures.