Narrative:

I was advised by center to verify altitude. It was noted that the aircraft was in a very slight climb - approximately 100 FPM - and that the altitude was passing through 37.4. The autoplt was disengaged and altitude reestablished at FL370. This altitude excursion probably was the result of the autoplt attitude controller wheel being inadvertently dislodged from the 'altitude hold' detent or from the wheel being slightly out of the detent after the aircraft was retrimmed and the autoplt engaged.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION - ACR DID NOT ENGAGE ALT HOLD MODE OF AUTOPLT. NIGHT OP.

Narrative: I WAS ADVISED BY CTR TO VERIFY ALT. IT WAS NOTED THAT THE ACFT WAS IN A VERY SLIGHT CLB - APPROX 100 FPM - AND THAT THE ALT WAS PASSING THROUGH 37.4. THE AUTOPLT WAS DISENGAGED AND ALT REESTABLISHED AT FL370. THIS ALT EXCURSION PROBABLY WAS THE RESULT OF THE AUTOPLT ATTITUDE CTLR WHEEL BEING INADVERTENTLY DISLODGED FROM THE 'ALT HOLD' DETENT OR FROM THE WHEEL BEING SLIGHTLY OUT OF THE DETENT AFTER THE ACFT WAS RETRIMMED AND THE AUTOPLT ENGAGED.

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.