Narrative:

Upon reaching assigned FL290 and simultaneously crossing tys VOR, I roughly leveled aircraft with the pitch trim button and selected altitude hold. In my previous 9 mo experience with this aircraft, occasionally the altitude hold will not engage on the first attempt and under certain light conditions the engage light is difficult to see. At this time the captain and I were both busy in light to moderate turbulence making small horizontal deviations to avoid buildups and checking charts and the STAR and setting up the radios for the arrival. Neither the captain nor I noticed the deviation until the 'chime' alerted us 420' above FL290 whereupon I made an immediate correction (total deviation 450'). The autoplt had not engaged. Since this incident I have checked other alerters in the same aircraft type and have discovered that the average alert is approximately 400'! I consider an alert of 400' totally unsafe. To allow the crew sufficient time to react and avoid a serious situation, the chime should be set to alert at no more than 250'. Supplemental information from acn 137599. Climbing through 28000' the first officer reached away to tune VOR radio, and climbed through 29000' to approximately 29400'. ATC controller made no mention of deviation.

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Original NASA ASRS Text

Title: ACR MLG OVERSHOOTS ASSIGNED ALT IN CLIMB.

Narrative: UPON REACHING ASSIGNED FL290 AND SIMULTANEOUSLY XING TYS VOR, I ROUGHLY LEVELED ACFT WITH THE PITCH TRIM BUTTON AND SELECTED ALT HOLD. IN MY PREVIOUS 9 MO EXPERIENCE WITH THIS ACFT, OCCASIONALLY THE ALT HOLD WILL NOT ENGAGE ON THE FIRST ATTEMPT AND UNDER CERTAIN LIGHT CONDITIONS THE ENGAGE LIGHT IS DIFFICULT TO SEE. AT THIS TIME THE CAPT AND I WERE BOTH BUSY IN LIGHT TO MODERATE TURB MAKING SMALL HORIZONTAL DEVIATIONS TO AVOID BUILDUPS AND CHKING CHARTS AND THE STAR AND SETTING UP THE RADIOS FOR THE ARR. NEITHER THE CAPT NOR I NOTICED THE DEVIATION UNTIL THE 'CHIME' ALERTED US 420' ABOVE FL290 WHEREUPON I MADE AN IMMEDIATE CORRECTION (TOTAL DEVIATION 450'). THE AUTOPLT HAD NOT ENGAGED. SINCE THIS INCIDENT I HAVE CHKED OTHER ALERTERS IN THE SAME ACFT TYPE AND HAVE DISCOVERED THAT THE AVERAGE ALERT IS APPROX 400'! I CONSIDER AN ALERT OF 400' TOTALLY UNSAFE. TO ALLOW THE CREW SUFFICIENT TIME TO REACT AND AVOID A SERIOUS SITUATION, THE CHIME SHOULD BE SET TO ALERT AT NO MORE THAN 250'. SUPPLEMENTAL INFO FROM ACN 137599. CLBING THROUGH 28000' THE F/O REACHED AWAY TO TUNE VOR RADIO, AND CLBED THROUGH 29000' TO APPROX 29400'. ATC CTLR MADE NO MENTION OF DEVIATION.

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.