Accident Description
According to the pilot, while on the downwind leg for landing on runway 18, the engine experienced a backfire, ran roughly, and then ceased operation. During the ensuing forced landing, the airplane collided with trees and terrain short of the runway. The left outer wing sustained structural damage.
Engine Examination
Following the accident, an attempted engine run was unsuccessful; the engine could not be started. Examination determined that both sets of magneto points were not opening. Further inspection of the single-drive dual magneto revealed that the nylon cam followers on both sets of points had worn to the extent that they could no longer open the contacts. The cam followers appeared burned and discolored, attributed to a lack of lubrication. The felt pads mounted on the cam followers, which are normally saturated with lubricating oil, were found to be very dry.
Maintenance History
The magneto manufacturer's recommended maintenance instructions specify that the cam follower felt pads should be inspected for adequate lubricating oil every 100 hours of time in service. According to the airplane's maintenance records, the ignition points had accumulated 372.9 hours since their installation on January 1, 2001. No entries were found in the engine logbook indicating that the points had been inspected since installation.