*** Final Report ***
N5895Q Mooney M20E Stillwater Oklahoma 18 JUN 2022
2 No Injuries
Pilot Flight Time: 22545 hours (Total, all aircraft), 21 hours (Total, this make and model)
The pilot reported that, about 20 to 25 minutes after departure and while in cruise flight at an altitude of about 4,500 ft mean sea level, the airplane lost partial engine power. The power had been set to 2,400 rpm and 24 inches of manifold pressure, which decreased to 2,000 rpm and between 11 and 12 inches of manifold pressure. The pilot manipulated the throttle control, but the engine did not respond. He moved the fuel selector through all positions while also moving the throttle, but the engine still did not respond. Because the airplane was unable to maintain level flight, the pilot elected to conduct a forced landing to a highway. As the airplane was about to land, the pilot became focused on avoiding a vehicle and failed to extend the landing gear. The airplane touched down “very softly” with the gear up, and the pilot turned the airplane slightly to the left to keep the propeller from impacting the vehicle, which resulted in the left wing impacting a road barrier and substantial damage to the wing.
A postaccident examination revealed no anomalies with the engine control system, and throttle control continuity was established from the cockpit controls to the engine. The engine cowling was removed, and the induction air coupling was found wrapped in gray tape. When the tape was removed, separations were visible on the top and bottom at the flange on the inboard side. The inside of the coupling was examined, and the lower portion appeared to be permanently deformed in a manner consistent with compression.
The pilot reported that the airplane’s tachometer time at the time of the accident was about 4,489 hours. According to the maintenance logbooks, the airplane’s most recent annual inspection, in accordance with Title 14 CFR Part 43 Appendix D, was performed on June 11, 2021, at a tachometer time of about 4,429 hours.
The airframe and powerplant mechanic with inspection authorization who completed that annual inspection also completed the airplane’s two previous annual inspections. Those inspections were performed on November 11, 2018, and December 7, 2019, when the airplane’s tachometer time was about 4,380 and 4,396 hours, respectively.
The maintenance entry dated November 11, 2018, noted “installed new Brackett induction air filter.” No other entries in the maintenance logbooks were associated with the induction air filter or coupling. Multiple attempts to contact the mechanic were made with no success. As a result, the investigation could not determine when the tape was applied to the induction coupling.
According to Title 14 Part 43 Appendix D, during an annual inspection, lines, hoses, and clamps should be checked “for leaks, improper condition and looseness” and all systems should be checked for “improper installation, poor general condition, defects, and insecure attachment.”
Probable Cause and Findings:
The inadequate maintenance and inspection of the engine induction air coupling, which impeded airflow to the engine and resulted in the subsequent partial loss of engine power.
