History of Flight
On July 22, 2009, at 1447 Pacific daylight time, a Mooney M20C, registration N6422U, was destroyed following a collision with terrain and post-crash fire approximately 3 miles northwest of Elma, Washington. The commercial pilot, the sole occupant, was killed. The airplane was registered to the pilot and operated as a visual flight rules (VFR) private fire patrol flight under 14 CFR Part 91. The flight departed Olympia, Washington, at 1417; no flight plan was filed. Visual meteorological conditions prevailed at both Olympia and the accident location.
A witness observed the airplane flying over her home at an estimated altitude of 100 to 150 feet above ground level. She reported a distinctive "clattering noise" from the airplane, likening it to a sound of running out of oil. The airplane turned right toward Elma and eventually disappeared from her view.
A second witness saw the airplane enter the tree canopy and then collide with power transmission lines. The witness estimated the airplane's speed at 60–70 miles per hour and noted that it "exploded" upon impact with terrain.
Personnel Information
The pilot, aged 77, held a commercial pilot certificate with an airplane single-engine land rating. His most recent second-class medical certificate was issued on April 16, 2009, with no limitations or waivers. On the medical application, he reported total aeronautical experience of about 6,000 hours, with 300 hours accrued in the previous 6 months. No personal flight time records were found.
Aircraft Information
The Mooney M20C, serial number 2169, was a 4-place, low-wing, single-engine airplane manufactured in 1962. It was powered by a four-cylinder Lycoming O-360 engine rated at 180 horsepower. Maintenance records showed an annual inspection of the airframe and engine was completed on May 1, 2009. At that time, the engine had accumulated approximately 2,606 total hours and 1,050.6 hours since major overhaul. The airframe total time was 3,261 hours. The engine had received a major overhaul on September 5, 1980, but detailed build records were not located. Damage precluded determining the current tachometer and Hobbs hour-meter readings.
Medical and Pathological Information
The FAA's Bioaeronautical Sciences Research Laboratory conducted toxicological testing on the pilot, which was negative for ethanol and controlled substances. An autopsy performed by the Grays Harbor County Coroner attributed the cause of death to multiple blunt trauma injuries.
Engine Examination
The wreckage was recovered and transported to a storage facility in Maple Valley, Washington, where the engine was examined and disassembled under NTSB and FAA supervision. The engine case, cylinders, and accessories exhibited extensive thermal and impact damage. The engine had separated from the airframe, but the engine mounts remained intact and attached to the engine. The propeller assembly remained attached to the crankshaft with nominal damage. All four cylinders remained attached to the crankcase, and the oil filler cap was secure.
A large hole was observed in the engine crankcase above the number four cylinder bay, with mechanical damage to the surrounding area. The number four cylinder was removed and examined. The intake and exhaust rocker arms were intact but thermally damaged. The piston and associated cylinder showed extensive mechanical and thermal damage. The number four connecting rod remained attached to the piston but had separated from the crankshaft at the base of the yoke. Fragments of the connecting rod cap, bolt, and nut were found in the oil sump. The main bearings exhibited wear, thermal discoloration, and in some cases, exposure of the copper layer.
Residual oil (less than one quart) was observed in the sump along with debris consistent with bearing, piston, crankcase, and connecting rod material. The oil pickup screen was partially obstructed by debris. The oil sump was intact.
The number four connecting rod and debris were sent to the NTSB Materials Laboratory. A metallurgist found two fractures near the end of the connecting rod. One fracture was identified as fatigue, initiating at the crankshaft end connecting rod journal surface just below the boss for the connecting rod bolt/nut. The opposing side fracture was the result of mechanical overload. Examination of the connecting rod bolt showed about 80 percent of the fracture face was damaged; the remaining area exhibited features consistent with mechanical overload.