NTSB Identification: FTW98LA062.
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Accident occurred Saturday, December 13, 1997 in HOUSTON, TX
Probable Cause Approval Date: 11/10/1998
Aircraft: Cessna 175A, registration: N6846E
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.

During cruise flight at full throttle and engine rpm at 2,700 to 2,800 (maximum 3,200 rpm), the engine ran rough. As the engine rpm and oil pressure decreased, emergency procedures performed by the flight instructor did not restore engine power. During the forced landing in a wet field, the nose gear collapsed and the airplane nosed over to an inverted position. This was the flight instructor's first flight in this make and model of aircraft. Before takeoff, the left magneto drop was beyond the 125 rpm maximum drop allowable. The last annual inspection was conducted in April 1997 at a tachometer reading of 1,956.59 hours. The tachometer reading at the time of the accident was 1,995.61 hours. A teardown of the engine revealed a hole in the #6 cylinder piston, and separation of the rod cap and bolts for the #3 cylinder connecting rod. The components of the #3 connecting rod exhibited overload features. The #6 cylinder piston exhibited physical evidence of detonation or preignition.

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

The total loss of engine power resulting from detonation and the ensuing failure of the engine piston and connecting rod components. Factors were: the instructor's decision to take off with a known deficiency (magneto drop over limit), the flight instructor's lack of familiarity with the aircraft, and the lack of suitable terrain for the forced landing.

Full narrative available

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