Narrative:

Crew was tired after flight arrived over rud NDB to hold for spacing into eddf. After several dscnts, radar vectors and an additional descent clearance was issued for our flight. During a descent to 8000 ft, our attention was momentarily distraction and no crew member noticed the 'altitude armed' light (which is needed for the approach in use to capture the selected altitude) was not illuminated. Aircraft descended approximately 300 ft below the assigned altitude. A gentle but firm recovery was immediately initiated. The controller called for our flight to continue descent to 7000 ft. Nothing else was said about the altitude deviation by the controller. At least 1 crew member had been awake for about 18 hours. All were tired. It's obvious that tired or fatigued crews are not as sharp as those that are more rested, but constant attention to details are the only answer to avoiding similar events from recurring. It was the PF's responsibility to monitor the aircraft at all times, and the momentary lapse of attention allowed the aircraft to descend below the assigned altitude. It was, however, the CRM training and total crew coordination that idented the error, and initiated an immediate response to the problem.

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Original NASA ASRS Text

Title: APCHING EDFF AFTER A VERY LONG FLT, FLC WAS INSTRUCTED TO DSND TO 8000 FT AND OVERSHOT THE ALT. BEFORE A CORRECTION COULD BE MADE, THE CTLR ISSUED A CLRNC TO 7000 FT.

Narrative: CREW WAS TIRED AFTER FLT ARRIVED OVER RUD NDB TO HOLD FOR SPACING INTO EDDF. AFTER SEVERAL DSCNTS, RADAR VECTORS AND AN ADDITIONAL DSCNT CLRNC WAS ISSUED FOR OUR FLT. DURING A DSCNT TO 8000 FT, OUR ATTN WAS MOMENTARILY DISTR AND NO CREW MEMBER NOTICED THE 'ALT ARMED' LIGHT (WHICH IS NEEDED FOR THE APCH IN USE TO CAPTURE THE SELECTED ALT) WAS NOT ILLUMINATED. ACFT DSNDED APPROX 300 FT BELOW THE ASSIGNED ALT. A GENTLE BUT FIRM RECOVERY WAS IMMEDIATELY INITIATED. THE CTLR CALLED FOR OUR FLT TO CONTINUE DSCNT TO 7000 FT. NOTHING ELSE WAS SAID ABOUT THE ALTDEV BY THE CTLR. AT LEAST 1 CREW MEMBER HAD BEEN AWAKE FOR ABOUT 18 HRS. ALL WERE TIRED. IT'S OBVIOUS THAT TIRED OR FATIGUED CREWS ARE NOT AS SHARP AS THOSE THAT ARE MORE RESTED, BUT CONSTANT ATTN TO DETAILS ARE THE ONLY ANSWER TO AVOIDING SIMILAR EVENTS FROM RECURRING. IT WAS THE PF'S RESPONSIBILITY TO MONITOR THE ACFT AT ALL TIMES, AND THE MOMENTARY LAPSE OF ATTN ALLOWED THE ACFT TO DSND BELOW THE ASSIGNED ALT. IT WAS, HOWEVER, THE CRM TRAINING AND TOTAL CREW COORD THAT IDENTED THE ERROR, AND INITIATED AN IMMEDIATE RESPONSE TO THE PROB.

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.