Narrative:

During climb out, passing FL180, a routine check of systems idented right engine generator constant speed drive rise temperature to be off scale high and out of limits. APU was immediately started in anticipation of impending right CSD and consequent right generator failure requiring an irreversible CSD disconnect. During power transfer from right generator to APU, flight director failed, autoplt disconnected, omega coupling disengaged, altitude arming annunciator went blank and altitude capture via flight director became disabled. All above failures took place moments before leveloff procedure was commenced to level at FL250. While climbing through 24800 ft the altitude warning sounded. It was at that point we noted the flight director altitude arming window had rearmed itself at 25000 ft. We attributed the altitude warning to a software malfunction associated with the power source interruption as the system is designed to only provide altitude warnings, during a climb, when exceeding a set altitude by 300 plus ft. Although the flight director indicated 25000 ft after re- initializing, and crew believed the assigned altitude had been FL250 crew could not recall if FL240 or FL250 had actually been assigned. Simultaneously with the level off at FL250 ATC announced 'amend your clearance to maintain FL270.' no TCASII targets were displayed above or below within 40 NM. No conflicts were idented by ATC. Abnormal electrical procedures were accomplished with flight continuing to destination. It is unknown if an altitude deviation occurred during incident.

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Original NASA ASRS Text

Title: ACFT EQUIP PROB. CONSTANT SPD DRIVE -- GENERATOR FAILURE.

Narrative: DURING CLB OUT, PASSING FL180, A ROUTINE CHK OF SYSTEMS IDENTED R ENG GENERATOR CONSTANT SPD DRIVE RISE TEMP TO BE OFF SCALE HIGH AND OUT OF LIMITS. APU WAS IMMEDIATELY STARTED IN ANTICIPATION OF IMPENDING R CSD AND CONSEQUENT R GENERATOR FAILURE REQUIRING AN IRREVERSIBLE CSD DISCONNECT. DURING PWR TRANSFER FROM R GENERATOR TO APU, FLT DIRECTOR FAILED, AUTOPLT DISCONNECTED, OMEGA COUPLING DISENGAGED, ALT ARMING ANNUNCIATOR WENT BLANK AND ALT CAPTURE VIA FLT DIRECTOR BECAME DISABLED. ALL ABOVE FAILURES TOOK PLACE MOMENTS BEFORE LEVELOFF PROC WAS COMMENCED TO LEVEL AT FL250. WHILE CLBING THROUGH 24800 FT THE ALT WARNING SOUNDED. IT WAS AT THAT POINT WE NOTED THE FLT DIRECTOR ALT ARMING WINDOW HAD REARMED ITSELF AT 25000 FT. WE ATTRIBUTED THE ALT WARNING TO A SOFTWARE MALFUNCTION ASSOCIATED WITH THE PWR SOURCE INTERRUPTION AS THE SYS IS DESIGNED TO ONLY PROVIDE ALT WARNINGS, DURING A CLB, WHEN EXCEEDING A SET ALT BY 300 PLUS FT. ALTHOUGH THE FLT DIRECTOR INDICATED 25000 FT AFTER RE- INITIALIZING, AND CREW BELIEVED THE ASSIGNED ALT HAD BEEN FL250 CREW COULD NOT RECALL IF FL240 OR FL250 HAD ACTUALLY BEEN ASSIGNED. SIMULTANEOUSLY WITH THE LEVEL OFF AT FL250 ATC ANNOUNCED 'AMEND YOUR CLRNC TO MAINTAIN FL270.' NO TCASII TARGETS WERE DISPLAYED ABOVE OR BELOW WITHIN 40 NM. NO CONFLICTS WERE IDENTED BY ATC. ABNORMAL ELECTRICAL PROCS WERE ACCOMPLISHED WITH FLT CONTINUING TO DEST. IT IS UNKNOWN IF AN ALTDEV OCCURRED DURING INCIDENT.

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.