FAA Ground School Practice Test

When a pilot suspects engine detonation during climb-out after takeoff with a fixed pitch propeller, what is the recommended initial corrective action?

1. Increase the throttle

2. Lower the nose slightly to increase airspeed

3. Enrich the fuel mixture

4. Engage the propeller governor

The correct answer is: Lower the nose slightly to increase airspeed

When a pilot suspects engine detonation during climb-out after takeoff with a fixed pitch propeller, lowering the nose slightly to increase airspeed is a recommended initial corrective action. This maneuver helps to alleviate detonation by increasing airflow over the engine’s cooling surfaces and promoting better combustion characteristics. Detonation occurs when the fuel-air mixture ignites prematurely within the cylinder, which can lead to excessively high temperatures and pressures. By increasing airspeed, the pilot can ensure that the engine receives adequate cooling and that the fuel-air mixture remains stable, reducing the likelihood of knock. While other actions like enriching the fuel mixture could also mitigate detonation by cooling the combustion chamber, the immediate response to enhance airflow and decrease cylinder temperatures through increased speed is often more effective to address the overheating condition, especially during initial climb-out when the aircraft is still at a relatively low altitude and experiencing high power settings.