Incident
Approximately ten minutes after departure, the airplane's engine started running rough. During the attempt to level off at 6,500 feet for cruise, the engine began to run rough and backfire. The engine's operation would sporadically become rough then smooth out. The pilot executed emergency procedures, including switching fuel tanks and activating the boost pump, but the rough-running condition persisted. Deciding to return to the airport, the pilot configured the airplane for best glide and set up for a 2-mile final approach to runway 34. Upon determining that the runway could not be reached, the pilot force-landed the airplane in a clear area near a river bed. The airplane collided with terrain during this forced landing.
Examination
An examination of the engine revealed that the right magneto contained engine oil. The seal between the engine accessory drive and the magneto was found to be hard, loose fitting, and covered with engine oil. This condition was identified during the post-accident inspection.
Maintenance History
Review of the engine maintenance logbook showed that the engine was manufactured new on February 8, 1979, and installed on the airplane on April 13, 1979. A 9-year gap in maintenance records was noted between October 1992 (when the engine had 1,302.9 hours total time) and July 2002 (when the engine had 1,322.39 hours total time). A 100-hour inspection was recorded on July 2, 2002. The most recent 100-hour inspection was performed on June 22, 2006, at 1,439.1 hours total time. There was no record of an engine or magneto overhaul.
Lycoming Service Instruction No. 1009AS states that for engines that do not accumulate the specified hourly period between overhauls (2,000 hours for the O-360-A1D), an overhaul is recommended in the twelfth year. Teledyne Continental Ignition Systems Service Bulletin SB643B specifies that for all TCM and Bendix magnetos, the magnetos must be overhauled or replaced at the expiration of 5 years since the date of original manufacture or last overhaul, or 4 years since the date the magneto was placed in service, whichever occurs first, regardless of accumulated operating hours.