History of Flight
On February 17, 2012, at 1155 Pacific standard time, a Mooney M20J, registration N367MR, experienced a loss of engine power about 5 minutes after takeoff from Lonnie Pool Field/Weaverville Airport, Weaverville, California. The pilot initiated a forced landing on California Highway 299 near Lewiston, California. The pilot, the sole occupant, was not injured. The airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan was filed.
Aircraft Information
The four-seat, low-wing, retractable landing gear airplane, serial number 24-1437, was manufactured in 1984. It was powered by a Lycoming IO-360-A3B6D 200-hp engine equipped with a McCauley constant speed propeller. The last annual inspection was completed on October 12, 2011, at 2,063.5 hours total time and 36.4 hours since major overhaul (SMOH). On February 7, 2012, at 45.0 hours SMOH, the engine accessories were removed and the accessory case housing was sent to a machine shop for repair. After repair, the housing was reinstalled along with all removed accessories and components, including the lower sump pan, exhaust system, oil cooler, magnetos, oil filter, vacuum pump, propeller governor, fuel and oil hoses, and electrical harness. The engine logbook entry noted that all perishable seals and gaskets were replaced as required. The engine was serviced with 8 quarts of Aeroshell 15W50 and run-tested. The Hobbs time on February 7 was 1,776.3; at the accident site, it was 1,786.3.
Wreckage and Impact Information
The airplane was recovered on February 18, 2012, and transported to a storage location for examination. On March 29, 2012, the NTSB and FAA examined the engine, which had been removed from the airframe. The engine was seized and could not be rotated by hand. The propeller showed no impact damage. Oil droplets were observed on external horizontal surfaces and underside flanges. Spark plugs exhibited normal wear except for cylinder #4, which had black dust-like residue on the top plug and black deposits fouling the bottom plug. The fuel flow divider was intact with a petroleum odor and liquid on the plunger.
The oil filter was dated 1/31/2012. When opened, portions of the filter element were black, others light brown/tan, and gold and black flakes were found in the filter folds. Oil lines were secure. About 6 oz of oil drained from the oil cooler; pressure testing showed no leaks. The oil plug finger screen had some black flakes and fibrous material but did not restrict oil flow. Fuel lines and the fuel pump contained fuel. The propeller governor rotated freely, and its filter screen was clear. The governor drained approximately 2 oz of oil. The exhaust manifolds were dark brown/black; the muffler had dark vertical streaks.
The accessory case housing gasket was pliable with no evidence of oil leakage. The oil pump rotated freely and showed no damage. The oil sump contained a small amount of oil with gold and black flakes. No oil leak was found at the sump gasket. Valve rockers were lightly coated with oil. Cylinders were removed; all valves seated, no mechanical damage. Pushrods were lubricated. The No. 1 connecting rod was seized at the crankshaft bearing with red-brown discoloration. The No. 2 and No. 4 connecting rods moved freely with no discoloration; the No. 3 rod moved freely but was discolored. Crankshaft balance weights moved freely. The engine case was not split. Total oil recovered from the engine was about 1 quart, with an estimated additional 1/8 to 1/4 quart observed draining from the oil suction screen plug hole.
Engine Monitor Data
The aircraft was equipped with a JPI EDM-700 engine monitor. The unit recorded 11.2 hours of data over 21 power cycles, including the accident flight on February 17, 2012. Parameters recorded were exhaust gas temperature (EGT), cylinder head temperature (CHT), and battery voltage. For the accident flight, CHT was steady at about 386°F until a rise at 11:54:09; EGT was steady at about 1,303°F until a rise at 11:54:04. CHT began to decrease at 11:56:03, about 42 seconds after EGT began to decrease.
Maintenance and Service Information
Lycoming Service Instruction No. 1438A, dated December 9, 2005, addresses the installation of a propeller governor pad plate and two gaskets on dual magneto engines with rear-mounted propeller governor drives to prevent oil leakage. Special Airworthiness Information Bulletin NE-06-08, dated November 9, 2005, alerts operators of a potential assembly problem that could result in loss of engine oil and engine failure if a required plate is omitted. The Mooney M20J Service Manual provides a 6-step procedure for governor installation, which does not explicitly mention multiple gaskets, but the illustrated parts catalog shows three separate gasket items at the propeller governor interface.
The A&P mechanic with Inspection Authorization who installed the accessories stated that all work was done per the Lycoming and Mooney manuals. The director of the maintenance facility noted that the mechanic was unaware at the time that the propeller governor shim and gasket needed to be retained for reuse after removal.