The pilot of a Cessna Citation 501 departed in IFR conditions on a clearance that required 6,000 feet as the first level-off point. At approximately 3,000 feet the yaw damper and autopilot in heading mode were both engaged.
Air traffic controllers issued a climb to FL230 and a turn on course when the pilot sensed a problem: speed rapidly increasing and the heading indicator spinning too fast for a standard-rate turn. The Citation’s vertical-speed indicator and airspeed indicator showed a rapid descent with increasing airspeed, but the attitude indicator did not tell the same story.
The pilot disconnected the autopilot and confirmed that the attitude indicator had failed. The only instrument the pilot felt sure of was the turn indicator, which he used to stabilize the aircraft and pull out of a steep dive. Climbing once again, the pilot managed to break out on top of the clouds and regain full control of the aircraft.
The Citation then proceeded to a VFR airport recommended by controllers without injury to anyone on board.