FTW97LA185

While in cruise flight at 8,500 feet msl, the pilot reported that he observed his oil pressure gauge 'indicating at or near zero.' He stated that he called ATC and began looking for a place to land. He then noticed that the 'oil temperature had begun to rise and the engine was running slightly rougher.' As he approached a highway on which he planned to land, 'the prop governor ceased to regulate the engine RPM and the engine begain to smell really hot.' On landing roll, the pilot stated that 'a gust of wind caused me to depart the left side of the road and the airplane subsequently impacted several sandy knolls.' Postimpact examination of the engine revealed an aluminum ball in the number four cylinder forward piston pin bore. Investigators stated that 'this was the result of the piston pin plug working in the bore for an extended period of time.' This would account for metal particles throughout the oil system and a rub mark on the interior of the cylinder wall. The oil journal leading to the number two cylinder was found with metal particles emanating from it and the number two and number three connecting rod bearings showed significant damage.

On May 9, 1997, at approximately 1519 mountain daylight time, a Mooney M20C, N7853V, was substantially damaged during an emergency landing following the loss of engine oil pressure near Torreon, New Mexico. The private pilot was not injured and his passenger received minor injuries. The airplane was owned by the pilot and operated by the owner under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the personal cross-country flight which originated from Albuquerque, New Mexico, approximately 31 minutes before the accident. A VFR flight plan had been activated with Farmington, New Mexico, as the intended destination.

According to the pilot in his NTSB Pilot/Operator Aircraft Accident Report statement, he was in cruise flight at 8,500 feet msl when he observed his oil pressure was "indicating at or near zero." He stated that he called ATC to report his problem and began looking for an airport or other place to land. The pilot then noticed that the "oil temperature had begun to rise and the engine was running slightly rougher." The pilot "decided that it would be better to land the airplane while the engine was still running rather than wait until the engine quit."

The pilot stated that while flying the landing pattern to a paved highway, "the prop governor ceased to regulate the engine RPM and the engine began to smell really hot." He said that "I knew that the engine would not continue to run much longer and turned base before reaching a good altitude or position." After touchdown, the pilot reported that a gust of wind lifted his right wing, turned the airplane towards the left, and subsequently the airplane left the road. The pilot stated that the terrain beside the road consisted of sandy knolls which the airplane impacted.

Postimpact examination of the engine on June 16, 1997, by an FAA Inspector and a representative of the engine's manufacturer revealed the following: the oil filter and oil suction screen were contaminated with metal particles. The accessory case was removed and engine continuity was established; metal particles were found in the sump and interior compartments of the engine. The airplane recovery personnel reported to the team that approximately seven quarts of engine oil had been removed from the undamaged sump at the time of recovery.

The investigative team removed four cylinder assemblies and found in the number four cylinder forward piston pin bore a ball of aluminum which the team stated "was the remains of the piston pin plug." The manufacturer's representative stated that "this was the result of the piston pin plug working in the piston pin bore for an extended period of time creating aluminum particles that became mixed with the engine oil." The representative also noted a "significant piston pin plug rub mark on the interior of the subject cylinder."

The investigative team further noted metal particles emanating from around the connecting rod journal of the number two cylinder. Examination of the number two rod end revealed "significant heat distress." The team removed all four connecting rod bearings and "observed significant damage to the number two and number three bearings." The team found the crankshaft intact, "although damaged at the journals."