On July 28, 2005, approximately 1215 Pacific daylight time, a Mooney M20J airplane, N110MP, sustained substantial damage during a forced landing following a loss of engine power in the traffic pattern at Sunriver Airport, Sunriver, Oregon. The commercial pilot and his two passengers were not injured. The airplane was registered to and operated by the pilot. Visual meteorological conditions prevailed and no flight plan was filed for the personal cross country flight conducted under 14 CFR Part 91. The airplane departed from Sacramento, California, at 1000 with an intended destination of Sunriver. According to the pilot, while on the downwind leg for landing on runway 18, the engine "backfired, ran rough and quit." During the ensuing forced landing, the airplane collided with trees and terrain short of the runway. The outboard section of the left wing sustained structural damage. During an attempted engine run following the accident, conducted at the request of the owner's insurance company, the engine could not be started, and it was determined that both sets of magneto points were not opening. The single-drive dual magneto, an Electrosystems-rebuilt TCM/Bendix D4LN-3000, P/N 10-682555-11, S/N 4082075, was removed from the engine and shipped to the NTSB investigator-in-charge (IIC) for further examination. The magneto was examined under the supervision of the IIC at Galvin Flying Service in Seattle, Washington, on October 24, 2005. The mechanic who performed the inspection found that the nylon cam followers on both sets of points were worn to the point that they could no longer open the contacts. The mechanic noted that the cam followers appeared to be burned and discolored due to a lack of lubrication. The felt pads mounted on the cam followers appeared to be very dry. According to the mechanic, these pads are normally saturated with oil to lubricate the cam followers. The TCM Ignition Service Support Manual for the D-3000 magneto, Recommended Maintenance and Overhaul Periods section, dated July 1989, states, in part: "After the first 50 hour and 100 hour periods in service and every 100 hours thereafter, the contact assemblies should be checked as specified in paragraph 6.2.1 of Periodic Maintenance." The Periodic Maintenance section, Paragraph 6.2.1 Contact Assemblies, dated July 1989, states, in part: "Check condition of cam follower felt. Squeeze felt between thumb and forefinger. If fingers are not moistened with oil, re-oil using 2 or 3 drops of 10-86527 Lubricant." According to the airplane's maintenance records, the magneto was delivered with a Textron Lycoming factory rebuilt engine that was installed in the airplane on October 1, 1994, at a tachometer reading of 0.0 hours. New points were installed in the magneto on January 1, 2001, at a tachometer reading of 737.4 hours. The most recent engine 100-hour inspection was performed on May 3, 2005, at a tachometer reading of 1,086.1 hours. The engine had accumulated 24.2 hours since the most recent inspection when the accident occurred. A review of the engine logbook found no entries found indicating the points had been inspected since their installation.