Accident Overview
On March 29, 2008, at 1654 mountain daylight time, a Cessna P210N single-engine airplane, registration N4839P, sustained substantial damage during a forced landing after a loss of engine power near Elizabeth, Colorado. The commercial pilot and two passengers were not injured. The airplane was registered to Cure Trucking LLC, Bethune, Colorado, and operated by the pilot. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. The flight departed Lamar, Colorado, at 1600 and was en route to Denver, Colorado.
Flight History
Approximately 25 nautical miles southeast of Centennial Airport (APA) in Englewood, Colorado, the pilot was instructed by the APA air traffic control tower to report a 3-mile final. While descending at 8,500 feet mean sea level (msl), the engine "let go/popped into a higher pitch sound, and the power dropped off." The pilot checked the fuel flow and attempted to regain power with the throttle but received no response. He then attempted a forced landing to a gravel road with the landing gear extended. The airplane impacted the side of the gravel road, traveled across the road, struck a ditch, and skidded on the fuselage bottom for approximately 75 feet before coming to rest upright in a residential yard. Examination revealed the fuselage was buckled.
Engine Examination
A review of aircraft records showed the engine underwent a major overhaul on May 7, 1993, at a total engine time of 1,331.0 hours. The most recent 100-hour inspection was performed on July 20, 2007, at a total time since major overhaul of 1,203.9 hours and a tachometer time of 2,534.9 hours. On September 9, 2007, the alternator was removed and replaced at a tachometer time of 2,538.9. At the time of the accident, the engine had accumulated 1,221 hours since major overhaul, and the tachometer time was 2,562.0 hours.
On June 3 and 4, 2008, at Beegles Aircraft Services in Greeley, Colorado, the engine was examined by an NTSB investigator and a representative of Teledyne Continental Motors (TCM). Visual examination showed the lower pivot bolt on the alternator was missing, the upper bolt was extruded 3/4 inches, and the alternator belt lacked tension. Safety wire was missing and not secured on several fuel system components. The engine was disassembled for further examination. Disassembly revealed fretting on all six cylinder decks and the main bearing case half sections. The number 2 main bearing support bearing tang lock-slot was elongated. Various degrees of wear were noted on all crankshaft main bearings, with additional wear on the number 2 bearing. The crankshaft number 2 main journal exhibited thermal discoloration. All oil transfer galleries were free of debris. The camshaft was intact, but the camshaft gear had a semi-circular section with seven gear teeth separated, found in the gearbox.
On June 19, 2008, at the TCM metallurgical laboratory, the camshaft gear was examined by a TCM metallurgist and an NTSB investigator. According to TCM, the fracture initiated at the surface and progressed in fatigue from left to right on the gear. The initiation site was damaged, but the approximate location was identified by crack arrest lines. Two gear teeth were removed for additional analysis. The case depth, surface hardness, and core hardness met specifications, and no anomalies were noted with the microstructure. The reason for the fracture initiation could not be determined.