Narrative:

Left wing aileron floated up and down with the right aileron not moving. This was a pronounced movement and could be felt in the cockpit. Left aileron would move up then abruptly move down to a center position then; move up or down and center itself again. This occurred several times. Yesterday this aircraft had the same problem; which was checked and returned to service. Movement of aileron was substantial enough to [cause us to] divert under captain's emergency authority to a nearby airport for further maintenance. Uneventful landing.

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Original NASA ASRS Text

Title: An A319 diverted to a nearby airport for an emergency landing when the left aileron made repeated uncommanded deflections.

Narrative: Left wing aileron floated up and down with the right aileron not moving. This was a pronounced movement and could be felt in the cockpit. Left aileron would move up then abruptly move down to a center position then; move up or down and center itself again. This occurred several times. Yesterday this aircraft had the same problem; which was checked and returned to service. Movement of aileron was substantial enough to [cause us to] divert under Captain's emergency authority to a nearby airport for further maintenance. Uneventful landing.

Data retrieved from NASA's ASRS site as of April 2012 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.