Engine Failure During Cruise Leads to Ditching; Loose Magneto Lugs Found (N2476Y)

Accident Overview

During cruise flight, the engine suddenly quit. The pilot was unable to reach land and ditched the aircraft in the ocean. After recovery, investigators observed oil streaks inside the engine cowling that extended along the underside of the aircraft to the empennage.

Examination Findings

Examination of the engine revealed a separation of the magneto housing from the accessory case, along with oil residue. The magneto housing showed wear on the contact surfaces of the hold down lugs, indicating that both lugs were loose prior to the accident. The looseness of the lugs would have allowed the magneto to vibrate, resulting in fatigue cracking through the mounting flange.

Maintenance History

The magneto had been recently installed during the last inspection. The mechanic who performed the work did not hold an inspection authorization.