Narrative:

At FL280, while in cruise flight, the autoplt engaged, the aircraft entered an uncommanded 20 degree right bank. I disengaged the autoplt (including altitude hold). In doing so, I inadvertently gained 400 ft. I immediately corrected back to the assigned altitude of FL280.

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Original NASA ASRS Text

Title: B727 CREW HAD ALT EXCURSION.

Narrative: AT FL280, WHILE IN CRUISE FLT, THE AUTOPLT ENGAGED, THE ACFT ENTERED AN UNCOMMANDED 20 DEG R BANK. I DISENGAGED THE AUTOPLT (INCLUDING ALT HOLD). IN DOING SO, I INADVERTENTLY GAINED 400 FT. I IMMEDIATELY CORRECTED BACK TO THE ASSIGNED ALT OF FL280.

Data retrieved from NASA's ASRS site as of July 2007 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.