NTSB Identification: LAX94LA114.
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Accident occurred Sunday, February 06, 1994 in BORREGO SPRINGS, CA
Probable Cause Approval Date: 11/14/1994
Aircraft: CESSNA 150F, registration: N8855S
Injuries: 1 Serious.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

While in cruise, the pilot noticed that his engine began running roughly. He made a precautionary landing at a nearby airport, but was unable to identify the problem. A second ground run-up developed only 2,100 rpm's at full throttle. He then called the operator. After a discussion, he decided that if the engine performance improved, he would fly back. On the next run-up, the rpm improved in the 2,200-to-2,300 rpm range, and the pilot felt this was fine for takeoff. The takeoff roll seemed slower than normal, so he decided to climb over the airport in case of an emergency. On climbout at 100-to-200 feet agl, the engine again began running roughly. He began a shallow turn back toward the runway, and lost control of the aircraft. The aircraft stalled, impacted the ground, and nosed over. An inspection of the engine showed the rocker arm boss on the No. 1 cylinder had fractured due to fatigue cracking. Lab analysis showed the boss was welded during cylinder overhaul, a procedure not allowed by Continental.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

1) the pilot's decision to takeoff in an aircraft with a known, yet unresolved, engine performance deficiency, and 2) the pilot's failure to maintain an adequate airspeed while maneuvering back to the runway. A factor in the accident was the weld repair of the cylinder head rocker arm boss during overhaul, which led to a fatigue failure of the component.

Full narrative available

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