Cessna 177B N34283 accident near Evansville, Indiana

Probable cause

The pilot’s loss of control due to an inaccurate attitude reference, which was caused by an impending (“in process”) failure of the bearing in the attitude indicator.

NTSB analysis

The pilot reported a loss of attitude reference and a subsequent loss of control during cruise flight in instrument meteorological conditions. About 15 minutes into the flight, the attitude indicator displayed a 30-degree right bank and the pilot’s control inputs did not seem to correct the banked condition. The pilot subsequently noticed a 2,000 foot-per-minute descent with increasing airspeed. The attitude indicator and turn coordinator were displaying conflicting information, and the directional gyro was indicating a rapid heading change to the left. About 5,000 feet mean sea level, the airplane broke out of the clouds, and the pilot was able to regain control and landed without further incident. The pilot observed substantial damage to the wings after landing.

A postaccident examination of the attitude indicator revealed significant noise during testing, consistent with an impending gyro bearing failure. In addition, after the gyro was allowed to reach operating speed, it did not fully stabilize again after it was disturbed from equilibrium. Postaccident examination of the vacuum pump and airframe vacuum system did not reveal any anomalies.

Text from the NTSB. Open the NTSB docket for CEN12LA532 for the full record.