NTSB Identification: LAX98LA182.
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Accident occurred Thursday, June 04, 1998 in LIVERMORE, CA
Probable Cause Approval Date: 03/30/2000
Aircraft: Cessna 150M, registration: N704ZA
Injuries: 2 Minor.

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

After performing air work, the instructor and student were returning to base. The instructor noted a loss of rpm's from 2,300 to 1,100. He took over the aircraft controls from the student and attempted to correct the problem. The instructor noted that the rpm's remained constant at 1,100. He conducted the emergency checklist and informed the tower of the situation. The instructor then landed the aircraft in an open field of high grass during which the aircraft came to rest inverted after the nose wheel struck a hole. The aircraft was examined on-scene and it was noted that the bolt was in place, but that the nut and cotter pin were missing from the carburetor throttle attachment assembly. It was also noted that the aircraft had flown approximately 15 hours since the last annual inspection and maintenance had been performed.

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

The missing nut/cotter pin on the throttle attachment assembly which resulted in the pilot's inability to control engine power, and the hidden obstruction (hole) in the landing area. A factor was the high vegetation.

Full narrative available

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