ASN Wikibase Occurrence # 361824
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| Date: | Sunday 20 June 1993 |
| Time: | 15:00 LT |
| Type: |  Rutan Long-EZ |
| Owner/operator: | Private |
| Registration: | N977ST |
| MSN: | 100ST |
| Total airframe hrs: | 484 hours |
| Engine model: | Lycoming O-235-L2C |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Lone Pine, CA -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Mammoth, CA (MMH |
| Van Nuys, CA (KVNY) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
THE PILOT STATED THAT HE WAS IN LEVEL CRUISE AT 10,500 FEET MSL WHEN THE ENGINE SUDDENLY QUIT. HE MADE A FORCED LANDING ON OWENS DRY LAKE, WHICH WAS SOFT FROM RECENT RAINS. THE NOSE GEAR COLLAPSED AND THE AIRPLANE NOSED OVER INVERTED. POST CRASH EXAMINATION OF THE ENGINE REVEALED THAT THE EXHAUST VALVE HAD FAILED IN THE NUMBER FOUR CYLINDER. THE VALVE HEAD HAD SEPARATED FROM THE VALVE STEM. EXAMINATION OF THE VALVE SPRING AREA REVEALED OVERHEAT SIGNATURES IN THE FORM OF OIL COKING AND OXIDIZATION, AND CARBON DEPOSITS. THE NTSB METALLURGY LABORATORY FOUND THAT THE VALVE STEM WAS DEVOID OF CHROME PLATING IN THE AREA OF THE FRACTURE, WAS REDUCED IN DIAMETER, AND HAD A SIGNIFICANTLY DECREASED MATERIAL HARDNESS, ALL PRINCIPALLY DUE TO HEAT EXPOSURE. POST ACCIDENT EXAMINATION OF THE LOG BOOKS AND THE FAA OPERATING LIMITATIONS REVEALED NO RECORD OF A REQUIRED CONDITION (ANNUAL EQUIVALENT) INSPECTION SINCE THE AIRCRAFT WAS PLACED INTO SERVICE. EXAMINATION OF THE ENGINE REVEALED MANY AREAS OF SUBSTANDARD MAINTENANCE PRACTICES.
Probable Cause: the failure of the number four cylinder exhaust valve due to excessive heat exposure and lack of maintenance.
Accident investigation:
 |
|
Sources:
NTSB LAX93LA263
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 17-Mar-2024 08:06 | ASN Update Bot | Added |
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