BLUFFTON, SC, USA
N982Q
BEECH P35
DURING CRUISE FLIGHT, THE PILOT OBSERVED A LOSS OF OIL PRESSURE, ACCOMPANIED BY THE SMELL OF BURNING OIL. THE PROPELLER OVERSPED, AND THE ENGINE SUBSEQUENTLY QUIT. THE AIRPLANE WAS FORCE LANDED ON A GOLF COURSE, AND COLLIDED WITH TREES DURING THE LANDING ROLL. AN EXAMINATION OF THE ENGINE REVEALED THE THREADS ON THE OIL FILTER ADAPTER, AND THE MATING THREADS ON THE ENGINE CASE, WERE SEVERELY FRETTED, AND OIL HAD LEAKED OUT OF THE ENGINE, AROUND THE ADAPTER THREADS. THERE WAS EVIDENCE OF OIL STARVATION AND THERMAL DISTRESS ON INTERNAL ENGINE PARTS. EVIDENCE SUGGESTS THAT THE JAM NUT WHICH TIGHTENS THE ADAPTER TO THE ENGINE CASE EITHER LOST ITS PRELOAD TORQUE, OR WAS UNDERTORQUED DURING MAINTENANCE. LOGBOOK ENTRIES INDICATING THE LAST MAINTENANCE ON THE ADAPTER WERE NOT LOCATED.
On June 12, 1994, at 1200 eastern daylight time, a Beech P35, N982Q, collided with trees during a forced landing near Bluffton, South Carolina. The commercial pilot and two passengers were not injured. The aircraft was destroyed. The flight was operated under 14 CFR Part 91 by SRQ Flyers, Inc. Visual meteorological conditions existed at the time, and an instrument flight rules flight plan was in effect for the personal flight to Garner, North Carolina. The flight originated in Sarasota, Florida, at 1010. The pilot reported that during cruise flight, he smelled burning oil, and there was no oil pressure indication on the gauge. He turned toward the closest airport, and advised Air Traffic Control of the problem. The propeller oversped a few seconds later. The throttle was retarded, and the engine continued to lose power until the propeller stopped turning. The aircraft descended into clouds at about 6,000 feet mean sea level (msl), and remained in the clouds until reaching about 1,600 feet msl. As he exited the clouds, it was apparent that the aircraft could not make the closest airport. A forced landing was attempted at a nearby golf course. The aircraft touched down on a fairway, and maximum braking was applied. The aircraft could not be stopped in an open area, and it collided with trees. The engine was examined following the accident. The examination revealed oil had leaked out of the engine via the oil filter adapter. The engine was disassembled, and there was evidence of heat distress and a lack of lubrication on all main and connecting rod bearings. The number two cylinder wall and piston were scored from operation at elevated temperatures. The engine oil sump contained about one quart of oil. An examination of the threads on the oil filter adapter revealed that about 60 to 70 percent of the thread pitch diameter had been fretted away. The mating threads on the engine case were also fretted. A rubber "o" ring, which fits between a jam nut and the engine case, was damaged in several areas around its circumference. There was evidence of inadequate torque on the jam nut. It is not known whether the inadequate torque resulted from a loss of preload torque, or from insufficient torquing during installation. The oil filter adapter was not supplied with the engine by the engine manufacturer. No maintenance records were located which identified when the adapter was last installed or inspected.
A LOSS OF ENGINE POWER DUE TO OIL STARVATION. THIS RESULTED FROM AN UNDERTORQUED CONDITION OF THE OIL FILTER ADAPTER, AND THE SUBSEQUENT FRETTING OF THE ADAPTER THREADS.
Source: NTSB Aviation Accident Database
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