C210 pilot reported a temporary loss of control due to the failure of the autopilot roll servo.

Attributes
ACN	1623276
Time
Date	201902
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Cessna 210 Centurion / Turbo Centurion 210C 210D
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Aileron Control System
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Instrument Flight Crew Private
Experience	Flight Crew Last 90 Days 35 Flight Crew Total 1750 Flight Crew Type 1400
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

While flying the initial part of the arrival in mild turbulence and IMC; my autopilot failed. The failure resulted in a full and hard left bank. The roll servo locked in a complete hard left bank and required pilot override. While struggling with controlling the aircraft and trying to prevent inversion; I had significant altitude and course deviations. Once I was able to diagnose the condition (locked roll servo) and pull the correct autopilot circuit breaker; I was able to regain proper control of the aircraft and shoot an RNAV approach to the closest airport. During this time; I informed center; asked for a delay vector; and was given the same. ATC helped me identify the closest airport with a published approach.

Original NASA ASRS Text

Title: C210 pilot reported a temporary loss of control due to the failure of the autopilot roll servo.

Narrative: While flying the initial part of the arrival in mild turbulence and IMC; my autopilot failed. The failure resulted in a full and hard left bank. The roll servo locked in a complete hard left bank and required pilot override. While struggling with controlling the aircraft and trying to prevent inversion; I had significant altitude and course deviations. Once I was able to diagnose the condition (locked roll servo) and pull the correct autopilot circuit breaker; I was able to regain proper control of the aircraft and shoot an RNAV approach to the closest airport. During this time; I informed Center; asked for a delay vector; and was given the same. ATC helped me identify the closest airport with a published approach.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.