Narrative:

Altitude alerter deferred. Neither pilot noticed that assigned altitude had come and gone. ATC asked for our 'assigned altitude.' we then became aware of the mistake and advised center that we were descending back to 24000 ft. We were then handed off to the next center. A traffic conflict did not exist. Although the MEL (that I helped write) called for 'increased altitude vigilance,' saying it is easier than doing it. I have modified my procedures to include not getting involved in non essential tasks/conversations until the final altitude is reached, when the altitude alerter is deferred. I fly a fairly old model turbojet without the benefit of modern instrumentation but I have often thought that the altitude selected in the altitude alerter should be repeated and displayed within or immediately adjacent to the altimeter. The alerter that we use is located elsewhere on our instrument panel and not really visible unless looking directly at it. I had been scanning the altimeter during the climb but I had been expecting a climb clearance to 28000 ft and I guess that I had mentally decided that I had already received it.

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Original NASA ASRS Text

Title: FK28 FLC OVERSHOT ATC ASSIGNED ALT, ALT ALERTER EQUIP DEFERRED. PIC AWARE THE COCKPIT PROCS WERE NOT ADHERED TO. ACFT RETURNED TO ASSIGNED ALT AND PROCEEDED TO DEST WITHOUT FURTHER INCIDENT. PIC STATES NON ESSENTIAL CONVERSATION TASKS A DISTR.

Narrative: ALT ALERTER DEFERRED. NEITHER PLT NOTICED THAT ASSIGNED ALT HAD COME AND GONE. ATC ASKED FOR OUR 'ASSIGNED ALT.' WE THEN BECAME AWARE OF THE MISTAKE AND ADVISED CTR THAT WE WERE DSNDING BACK TO 24000 FT. WE WERE THEN HANDED OFF TO THE NEXT CTR. A TFC CONFLICT DID NOT EXIST. ALTHOUGH THE MEL (THAT I HELPED WRITE) CALLED FOR 'INCREASED ALT VIGILANCE,' SAYING IT IS EASIER THAN DOING IT. I HAVE MODIFIED MY PROCS TO INCLUDE NOT GETTING INVOLVED IN NON ESSENTIAL TASKS/CONVERSATIONS UNTIL THE FINAL ALT IS REACHED, WHEN THE ALT ALERTER IS DEFERRED. I FLY A FAIRLY OLD MODEL TURBOJET WITHOUT THE BENEFIT OF MODERN INSTRUMENTATION BUT I HAVE OFTEN THOUGHT THAT THE ALT SELECTED IN THE ALT ALERTER SHOULD BE REPEATED AND DISPLAYED WITHIN OR IMMEDIATELY ADJACENT TO THE ALTIMETER. THE ALERTER THAT WE USE IS LOCATED ELSEWHERE ON OUR INST PANEL AND NOT REALLY VISIBLE UNLESS LOOKING DIRECTLY AT IT. I HAD BEEN SCANNING THE ALTIMETER DURING THE CLB BUT I HAD BEEN EXPECTING A CLB CLRNC TO 28000 FT AND I GUESS THAT I HAD MENTALLY DECIDED THAT I HAD ALREADY RECEIVED IT.

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.