Incident Overview
An Avro RJ-70 was on approach at approximately 1,500 feet above ground level with the autopilot engaged. The aircraft encountered wake turbulence from a preceding Airbus A340, resulting in a left roll.
Pilot Actions
The flying pilot, occupying the right seat, reached for the yoke to disconnect the autopilot and apply corrective aileron input. Large and/or abrupt movement of the ailerons occurred before the autopilot disconnect was achieved.
Aileron Uncoupling
Following the abrupt aileron inputs, the ailerons uncoupled. In the uncoupled state, the left yoke controlled the left aileron and roll spoiler, while the right yoke controlled the right aileron and roll spoiler. The pilot continued the approach and landed without further incident.
Post-Incident Findings
A post-incident test revealed that the breakaway forces for the aileron interconnect detent strut were within the manufacturer's specification. The manufacturer reported that movement of the aileron flight controls from the side opposite of the engaged autopilot servo could result in an aileron uncoupling.
Conclusion
The incident involved wake turbulence encounter and subsequent aileron uncoupling during the approach phase. The aircraft landed safely with no additional events.