What happened
Shortly after liftoff, the aircraft appeared to stop climbing at an altitude of approximately 90 to 100 feet AGL. During this phase of flight, the wings began rocking from side to side, and the aircraft subsequently pitched nose down into the ground. The engine remained audible until the moment of impact.
The investigation
Investigators examined the engine and found several mechanical discrepancies. At the time of the accident, the density altitude was approximately 5,000 feet, and the mixture control was in the full rich position. An oil stain was discovered near the propeller governor; notably, AD 90-04-06 and Lycoming SB No. 488 addressed the propeller governor line and elbow fitting.
A teardown of the engine revealed that the propeller governor screen was blocked with numerous contaminants. Metallic flakes were present on the oil filter, the carburetor body was dirty, and the carburetor float attach pin was worn. The spark plugs indicated a rich fuel condition, and the magneto timing was 3 degrees off.
Further internal inspection showed that the intake and exhaust rocker arms were improperly installed. Additionally, the piston rings were worn beyond life limits, and the top ring on the number two cylinder was broken. Significant assembly errors were also identified, including numerous rod caps and bearings installed backwards. All crank pins and all main bearings were found to be worn beyond service limits. Finally, the serial number on the data plate did not match the engine case number.