CEN12LA532

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.

On August 7, 2012, about 1016 central daylight time, a Cessna 177B, N34283, was substantially damaged during recovery after a loss of control while en route to Evansville Regional Airport (EVV), Evansville, Indiana. The pilot and passenger were not injured. The airplane was registered to and operated by private individuals under the provisions of 14 Code of Federal Regulations Part 91 as personal flight. Instrument meteorological conditions prevailed for the flight, which was operated on an instrument flight rules flight plan. The flight originated from Stuart Powell Field Airport (DVK), Danville, Kentucky, about 0956. The intended destination was EVV. The pilot reported a loss of attitude reference and a subsequent loss of control during cruise flight in instrument meteorological conditions (IMC). About 15 minutes into the flight, the attitude indicator displayed a 30-degree right bank and his control inputs did not appear to be correcting 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 (msl), the airplane broke out of the clouds and the pilot was able to regain control. The airspeed indications did exceed the airplane limitations during the event. The pilot reported that there did not appear to be structural damage and he elected to continue the flight in visual meteorological conditions (VMC). The indications of the flight instruments were normal until the flight was on final approach. At that time, the attitude indicator again displayed a 30-degree right bank, which continued for the remainder of the approach, landing, and taxi. The pilot reported observing substantial damage to the wings after landing. Radar track data indicated that the airplane was established in cruise flight about 8,000 feet mean sea level (msl) in the vicinity of Bardstown, Kentucky, at the time of the loss of control. About 1016, the airplane reversed course briefly, before it entered a right turn and subsequently returned to a westerly course toward the intended destination. The airplane descended to about 5,000 feet msl during the event. A postaccident examination of the airplane revealed damage to both wings. The upper wing skins were wrinkled beginning about 3 feet from the wing root and extending outboard and aft. The damage extended to and included 3 wing stringers. The left and right forward fuel tank bulkheads were also damaged. Testing of the airframe vacuum system did not reveal any anomalies. The attitude indicator was removed from the airplane. It exhibited 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. Examination of the vacuumpump did not reveal any anomalies. The pilot noted that the presence of a backup attitude indicator might have prevented the loss of control event and the subsequent accident. However, regulations did not require a secondary attitude indicator or indicating system for the accident flight.