Citation I/SP (C501)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 61; Flight Crew Total 10150; Flight Crew Type 830
Human-Machine Interface
Aircraft Equipment Problem Critical; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Became Reoriented; Flight Crew Regained Aircraft Control; Flight Crew Diverted
Aircraft
[I] received clearance via cell phone while on ramp. Completed checklist and took-off on Runway 31 and initiated climb to 6;000 FT. At approximately 3;000 FT engaged yaw dampener and autopilot in heading mode. Contacted Center and received clearance to 'turn on-course' and climb to flight level 230. Initiated left turn with heading bug of approximately 100 degrees toward final 'on course' heading and proceeded to change the altitude pre-select (located just right of panel center) from 6;000 FT to FL230 and re-arm. Sensed problem; speed was rapidly increasing and DG was spinning too fast for a standard rate turn; VSI indicated rapid descent airspeed rapidly increasing and attitude indicator abnormal. Confirmed autopilot was still engaged and continuing to roll aircraft. Disconnected autopilot and assumed manual control. Attitude indicator did not correspond to input. [I] confirmed left turn with turn needle. Rolled aircraft right until turn needle moved right and DG stabilized and pulled aircraft from dive to prevent ground impact. [I] continued climbing to top of cloud layer. Notified Center of failed attitude indicator and asked for clearance to nearest VFR airport. Proceeded to VFR airport and landed. No injuries to any passengers onboard.
A CE501 pilot reported attitude indicator failure with auto pilot engaged in IMC. Recovery from the steep turning descent was initiated using the turn needle and the aircraft was climbed to VMC before diverting to a VMC airport.