NTSB Identification: LAX99LA295.
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Accident occurred Sunday, September 05, 1999 in MENLO PARK, CA
Probable Cause Approval Date: 08/14/2001
Aircraft: Cessna 150M, registration: N8135U
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot had just departed the airport and was over the San Francisco Bay when the engine suddenly lost power. He attempted to make an emergency landing on a nearby bridge but had insufficient altitude and landed in the water on the shore short of the area. The airplane nosed over when the nose wheel plowed into the mud. Postaccident examination of the engine revealed that the spark plugs were not producing any spark. The 'P-leads' were grounded at a short in a tie-wrapped wire bundle under a grommet at the firewall. The insulation was melted and the inside conductor was contacting the radio shielding of the wire where it was attached to the airframe. Additional examination of the engine found that the rear wall section of the left muffler was missing, with the remaining edges eroded. With the muffler wall missing, hot exhaust gases were directed towards the firewall where the shorted section of the 'P-leads' were located. Maintenance actions had been performed in the engine compartment three times in the past 2 months, with the last maintenance activity 3 days prior to the accident when a cylinder was replaced. The loss of power event occurred on the first flight following return of the airplane to service.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fatigue failure of the left muffler rear wall, which resulted in hot exhaust gasses being ported onto, and shorting, the magneto p-lead wires. The failure of maintenance personnel to detect the impending failure of the muffler during the recent engine maintenance activity is also causal. Full narrative available
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