FAA Powerplant Written Practice Test

What is a common sign of exhaust leaks in a reciprocating engine?

1. Soot accumulation under the aircraft

2. Unusual engine vibrations

3. Exhaust soot inside the cowling

4. Unresponsive throttle control

The correct answer is: Exhaust soot inside the cowling

A common sign of exhaust leaks in a reciprocating engine is the presence of exhaust soot inside the cowling. This occurs because when there is a leak in the exhaust system, combustion gases escape before they can be properly vented out of the exhaust pipe. This leakage allows soot and other combustion byproducts to enter the engine compartment, resulting in visible deposits on the engine components and inside the cowling. Identifying this soot is crucial, as it can indicate a potential failure in the exhaust system, which could lead to more severe engine performance issues or hazards if not addressed promptly. Other signs of exhaust leaks, though they may occur, do not pinpoint the issue as directly as the presence of soot inside the cowling.