What happened
On 17 October 2012, a Mooney M20J, registration HL1062, operated by Korea Aerospace University, experienced an engine failure while cruising at 10,000 feet. The aircraft was operating under instrument flight rules (IFR) approximately 10 nautical miles northeast of Wonju Airport when the engine began exhibiting abnormal power, significant vibration, and RPM fluctuations between 1,5 and 2,400 RPM.
The instructor pilot initially attempted engine troubleshooting procedures, including adjusting the mixture and fuel tank switches. After the initial attempts failed, the pilot declared an emergency and transitioned to visual flight rules (VFR) to approach Wonju Airport. During the descent, the engine suffered a complete shutdown. The crew performed a glide descent with the propeller windmilling and successfully executed a landing on runway 21. There were no injuries to the instructor or the two student pilots on board, and the aircraft sustained no damage.
The investigation
The ARAIB examined the aircraft's maintenance logs, which showed that the magneto had been properly inspected during recent 50-hour and 100-hour intervals. Investigators also analyzed the ignition system and the pilot's actions during the emergency. Technical examination of the magneto revealed that the right-hand breaker points had failed due to thermal damage to a plastic cam follower.
Furthermore, the investigation reviewed the cockpit configuration during the second restart attempt. It was noted that the throttle and mixture levers were left in the full forward position, which contributed to the engine's inability to restart by causing an overly rich fuel-to-air ratio.