ASN Wikibase Occurrence # 297263
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| Date: | Friday 24 May 2002 |
| Time: | 05:45 LT |
| Type: |  Cessna 172K |
| Owner/operator: | Bell Sky Pilots Inc. |
| Registration: | N79944 |
| MSN: | 17258271 |
| Year of manufacture: | 1969 |
| Total airframe hrs: | 3676 hours |
| Engine model: | Lycoming O-320-E2D |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Lake Thomas A., California -
 United States of America
|
| Phase: | Unknown |
| Nature: | Private |
| Departure airport: | Reedley, CA (O32) |
| Milford Municipal-Ben and Judy Briscoe Field, UT (KMLF) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The airplane experienced a partial loss of engine power and collided with a tree stump during a precautionary landing on a beach. While climbing through 9,000 feet mean sea level (msl) the pilot leaned the airplane by relying solely on the exhaust gas temperature gauge. When reaching about 9,500 feet msl, about 1,500 feet above ground level over mountainous terrain, the pilot reported that the engine lost partial power. The propeller continued to turn, and the tachometer showed about 2,450 to 2,500 rpm, but the engine failed to produce enough power to sustain level flight. The pilot adjusted the mixture control, while also turning the carburetor heat to the on position, and applying full throttle. The engine failed to respond and the pilot made an approach to a sandy beach. The pilot flared the airplane about 2 feet above ground level, and the left wing collided with a tree stump, veering the airplane to the right. The elevation at the crash site was about 7,600 feet msl. A post accident investigation revealed that the left magneto exhibited excessive play at the cam end (points) of the main shaft. The subject magneto was later functionally tested, which revealed an intermittent spark on ignition lead T1. According to Textron Lycoming Mandatory Service Bulletin 515 the magnetos must be inspected every 500 hours. At the time of the accident, the magneto had accumulated a total time in service of 1,540.23 hours, and there was no maintenance entry indicating that the Service Bulletin had been complied with. While post accident tests showed that the left magneto was working only on an intermittent basis, information provided by Lycoming suggests that in and of itself the complete loss of one magneto would only result in a 3 to 5 percent loss of power. It is likely that the combined effects of the magneto malfunction, the high density altitude, and the pilot's manipulation of the mixture and carburetor heat all played roles in the engine's decreased performance capability.
Probable Cause: a partial loss of engine power due to the partial malfunction of the left magneto and leakage of the ignition leads for that magneto, due to inadequate maintenance inspections. Factors in the accident include the high density altitude, the maintenance personnel's failure to accomplish a service bulletin, and the effects of the pilot's manipulation of the mixture and carburetor heat controls.
Accident investigation:
 |
|
Sources:
NTSB LAX02LA172
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Oct-2022 16:27 | ASN Update Bot | Added |
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