Soar to New Heights with the 2026 Commercial Pilot License (CPL) Practice Exam – Ready for Takeoff!

Detonation in an aircraft engine is primarily caused by the premature ignition of the fuel-air mixture within the combustion chamber, which can be influenced by multiple factors. Using low-grade fuel is particularly significant because lower octane fuels have a higher likelihood of causing detonation when subjected to the pressures and temperatures typical in an aircraft engine during operation. High-octane fuels are designed to withstand such conditions without igniting prematurely, thus preventing detonation.

While operating at high altitudes can affect engine performance due to lower air pressure and temperature, it is not the primary cause of detonation. Instead, detonation is more directly related to the characteristics of the fuel used and the operating conditions of the engine.

Using a high power setting with a rich mixture typically helps cool the engine, reducing the likelihood of detonation rather than causing it. Similarly, excessive enrichment of the fuel mixture can also serve to cool the combustion temperature and mitigate the chances of detonation by reducing the combustion pressure.

Therefore, the correct identification of low-grade fuel as a cause of detonation highlights the importance of using fuel with an appropriate octane rating for safe and effective engine operation.