FAA Powerplant Written Practice Test

Where is damage likely to occur if small metal filings are found in the oil screen after a sudden engine speed reduction due to a prop strike?

1. Oil filter

2. Crankshaft bearings

3. Cylinder head

4. Fuel injectors

The correct answer is: Crankshaft bearings

When small metal filings are found in the oil screen after a sudden engine speed reduction caused by a prop strike, it indicates that there may have been metal particles generated from wear or damage within the engine. The crankshaft bearings are critical components that endure significant stress and are designed to support the crankshaft while allowing it to rotate smoothly. In a situation like a prop strike, the sudden change in speed can create shock loads that may lead to localized damage or excessive wear of the bearings. These events can produce metal particles that are subsequently filtered out by the oil screen. The presence of filings in the oil is a strong indicator that the crankshaft bearings have suffered some form of damage, because the bearings typically carry the most load and experience the highest amount of friction in the engine. Therefore, finding small metal filings is most indicative of issues related to the crankshaft bearings, as they are the components most likely to fail or wear prematurely due to the sudden stresses experienced during an abrupt change in engine speed.