FAA Powerplant Written Practice Test

If small filings of metal are found in the oil screen after a sudden reduction in engine speed due to a prop strike, where is the damage most likely located?

1. Crankshaft bearings

2. Piston rings

3. Connecting rods

4. Camshaft

The correct answer is: Crankshaft bearings

The presence of small filings of metal in the oil screen following a prop strike, which causes a sudden reduction in engine speed, strongly indicates that the damage is most likely located in the crankshaft bearings. When an engine experiences a sudden shock, like a prop strike, it can lead to intense, localized forces that may cause wear or failure in the bearings that support the crankshaft. Crankshaft bearings are critical components that allow for the smooth rotation of the crankshaft while supporting its weight and managing the forces generated during engine operation. If the bearings are damaged or compromised, pieces of metal can become dislodged and circulate through the oil, resulting in metal filings accumulating in the oil screen. The other potential locations of damage, such as piston rings, connecting rods, or the camshaft, typically do not produce metal filings in the same manner when subject to such impact. Piston rings are more likely to wear and produce carbon deposits or scuffing rather than filings. Connecting rods, while critical, often exhibit bending or fracture under extreme conditions rather than generate metal debris. The camshaft, typically operating in a different part of the engine and under varying stresses, is less prone to produce metal filings from a sudden prop strike compared to the bearings directly