ASN Wikibase Occurrence # 354249
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| Date: | Saturday 27 June 1998 |
| Time: | 07:30 LT |
| Type: |  Grumman G-164B Ag-Cat |
| Owner/operator: | Private |
| Registration: | N7502C |
| MSN: | 817-B |
| Year of manufacture: | 1989 |
| Total airframe hrs: | 4048 hours |
| Engine model: | P&W 1340 |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Oakdale, WA -
 United States of America
|
| Phase: | Initial climb |
| Nature: | Agricultural |
| Departure airport: | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
According to the pilot, during takeoff, approximately 10 feet above the ground, the aircraft started backfiring and losing power. He aborted the takeoff, but was unable to get the aircraft stopped before impacting a ditch just off the departure end of the airstrip. A post-accident inspection of the engine by an FAA Airworthiness Inspector found that a portion of the number three cylinder head casting through which the exhaust valve rocker pin passes had fractured. This allowed the number three cylinder exhaust valve to remain in the closed position during the time that it should have been open, resulting in a loss of power. The rocker box casting was sent to the NTSB metallurgical laboratory for further analysis. That examination revealed that the fracture in the casting was the result of a fatigue crack that originated in the wall of the hole in the casting through which the rocker arm pivot bolt passed. It could not be determined what caused the fatigue crack to initiate.
Probable Cause: A fatigue failure of the number three cylinder exhaust rocker box assembly, compromising the ability of the exhaust valve to operate. Factors include a ditch at the end of the runway.
Accident investigation:
 |
|
Sources:
NTSB SEA98LA106
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 11-Mar-2024 06:06 | ASN Update Bot | Added |
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