FAA Powerplant Written Practice Test

After an engine overhaul, what key element must be checked as part of the run-in procedure?

1. Carburetor synchronization

2. Fuel tank integrity

3. Piston ring seating

4. Oil level verification

The correct answer is: Piston ring seating

After an engine overhaul, one of the most critical aspects to consider during the run-in procedure is the seating of the piston rings. This process is essential because properly seated piston rings ensure effective sealing of the combustion chamber, which in turn optimizes engine performance and efficiency. The run-in procedure involves operating the engine under specific conditions that allow the piston rings to wear slightly against the cylinder walls, forming a proper fit. Successful piston ring seating minimizes oil consumption, reduces exhaust emissions, and enhances overall engine longevity. If the rings do not seat correctly, it can lead to excessive blow-by, where combustion gases escape past the rings, resulting in a significant decrease in engine power and efficiency. While elements like carburetor synchronization, fuel tank integrity, and oil level verification are important for overall engine operation, they do not have the same immediate impact on the engine's performance post-overhaul as piston ring seating does. Ensuring the piston rings are correctly seated is crucial for the long-term reliability and performance of the engine.