Narrative:

During an experimental test flight, the autoplt failed to capture the selected altitude. Captain disconnected the autoplt and recaptured the assigned altitude manually. Postflt investigation found that a new software load had been compiled incorrectly and altitude capture was rendered inoperative. Since the descent was a steep angle at vmo, the altitude overshoot was approximately 2000 ft.

Google
 

Original NASA ASRS Text

Title: CL65 ALTDEV NEAR SLN OF 2000 FT.

Narrative: DURING AN EXPERIMENTAL TEST FLT, THE AUTOPLT FAILED TO CAPTURE THE SELECTED ALT. CAPT DISCONNECTED THE AUTOPLT AND RECAPTURED THE ASSIGNED ALT MANUALLY. POSTFLT INVESTIGATION FOUND THAT A NEW SOFTWARE LOAD HAD BEEN COMPILED INCORRECTLY AND ALT CAPTURE WAS RENDERED INOP. SINCE THE DSCNT WAS A STEEP ANGLE AT VMO, THE ALT OVERSHOOT WAS APPROX 2000 FT.

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.