Accident Cessna 150M N8135U,
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ASN Wikibase Occurrence # 352675
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Date:Sunday 5 September 1999
Time:14:22 LT
Type:Silhouette image of generic C150 model; specific model in this crash may look slightly different    
Cessna 150M
Owner/operator:ISBA, Inc.
Registration: N8135U
MSN: 15077898
Year of manufacture:1976
Total airframe hrs:8000 hours
Engine model:Continental O-200-A48B
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Location:Menlo Park, CA -   United States of America
Phase: En route
Departure airport:Palo Alto, CA (KPAO)
Destination airport:Oakland, CA (KOAK)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
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.

Probable Cause: 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.

Accident investigation:
Investigating agency: NTSB
Report number: LAX99LA295
Status: Investigation completed
Duration: 1 year and 11 months
Download report: Final report




Revision history:

08-Mar-2024 13:12 ASN Update Bot Added

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