Accident Overview
On January 9, 2009, at 2210 Pacific standard time, a Cessna R172K (registration N758FN) sustained substantial damage during a precautionary off-airport landing near Fremont, California. The aircraft had departed from the Palo Alto Airport of Santa Clara County in Palo Alto for a local visual flight rules (VFR) personal flight under 14 CFR Part 91. Night visual meteorological conditions prevailed and no flight plan was filed. The commercial pilot, who was the sole occupant, was not injured.
Pilot's Account
According to a written report to the National Transportation Safety Board, the pilot stated that after takeoff, during a left turn, he heard a sudden change in the engine sound followed by a loss of power. He observed that the oil temperature gauge indicated a very low value. Throttle adjustments produced little engine response. The pilot decided to execute a precautionary landing onto a nearby levy. During the landing roll, the airplane veered to the right, exited the levy, and nosed over in a bog. Both wings sustained substantial damage.
Postaccident Examination
The aircraft was recovered to a storage facility in Pleasant Grove, California. During the postaccident airframe and engine examination conducted by the NTSB investigator-in-charge and an FAA representative, the engine was started. It ran at idle for approximately one minute; oil pressure and tachometer gauge readings were nil, prompting discontinuation of the run.
Engine Component Analysis
The accessory gear cover was removed and the gear assembly examined. The oil pump/tachometer drive gear (part number 653236) had separated from the base of its respective drive shaft. The drive gear and shaft were sent to Teledyne Continental Motors (TCM) in Mobile, Alabama, for further evaluation.
Examination at TCM's Materials and Processes Laboratory revealed that the gear failed at the intersection of the shaft and gear. Scanning electron microscope images showed raised and flattened areas typical of contact damage during cyclic loading. The specific reason for the fracture was not determined.
Maintenance History
Review of the engine maintenance logbook indicated that an annual inspection had been completed on July 15, 2008, at an engine total time of 4,904 hours, with 1,864 hours since major overhaul.