Narrative:

La center cleared our flight to climb to FL260. 26;000 was properly set in the MCP altitude window and both pilots verbalized settings. I started getting my approach charts out of my flight bag and heard ATC ask what altitude we were climbing to. I replied FL260 and at the same time looked over at the MCP altitude window and saw 29;500 in the window. I started leveling the aircraft passing FL270 and ATC replied that's ok; continue climbing to FL330. The first officer (pilot flying) was initially surprised that the altitude window showed 29;500; and then replied he must have mistakenly turned the altitude knob when he meant to adjust the heading selector. The aircraft was light and we were climbing fast and my distraction with the approach charts was too long under that condition and I missed the 25 to 26 callout that would have alerted us to the problem with the MCP altitude before it became a deviation.

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Original NASA ASRS Text

Title: Wishing to align the PFD heading bug to the aircraft heading of 295 degrees; the pilot not flying of a B737NG mistakenly reset the MCP altitude alert from the cleared 27;000 to 29;500. An altitude deviation ensued.

Narrative: LA Center cleared our flight to climb to FL260. 26;000 was properly set in the MCP altitude window and both pilots verbalized settings. I started getting my approach charts out of my flight bag and heard ATC ask what altitude we were climbing to. I replied FL260 and at the same time looked over at the MCP altitude window and saw 29;500 in the window. I started leveling the aircraft passing FL270 and ATC replied that's OK; continue climbing to FL330. The First Officer (pilot flying) was initially surprised that the altitude window showed 29;500; and then replied he must have mistakenly turned the altitude knob when he meant to adjust the heading selector. The aircraft was light and we were climbing fast and my distraction with the approach charts was too long under that condition and I missed the 25 to 26 callout that would have alerted us to the problem with the MCP altitude before it became a deviation.

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.