Super King Air 300
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 50; Flight Crew Total 5600; Flight Crew Type 65
Workload; Training / Qualification
Aircraft Equipment Problem Critical; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Flight Crew Took Evasive Action; Flight Crew Regained Aircraft Control; Flight Crew Overcame Equipment Problem; Flight Crew FLC Overrode Automation
Aircraft
Approach had the BE-30 descend to 4;000 then continue to 2;000. Approaching 2;000 feet I tried to disconnect the autopilot. The autopilot lights went out; but the yoke and trim wheel were still locked. I had the co-pilot pull the AP servo breaker and it took over 20 seconds for the servo to release the yoke and trim. While this was happening we descended to approximately 1;800 feet and ATC advised us of low altitude warning.
A BE-30 autopilot failed to disengage by the normal means so the Captain had the First Officer pull the autopilot servo circuit breaker which allowed the servo to release 20 seconds or more later.