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DC10 crew descends below assigned altitude when autoflt, although engaged to capture altitude, does not.
| Attributes | |
| ACN | 472550 |
| Time | |
| Date | 200005 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : dtw.airport |
| State Reference | MI |
| Altitude | msl bound lower : 2600 msl bound upper : 3000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : d21.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | DC-10 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 3r |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : cfi pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 220 flight time total : 15000 flight time type : 3000 |
| ASRS Report | 472550 |
| Person 2 | |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : instrument pilot : commercial |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance non adherence : far |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to assigned altitude |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Aircraft |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were given a clearance to maintain 3000 ft until established and cleared for an ILS to runway 3R. Autoplt was on with altitude capture mode engaged. Some how, some way, the altitude failed to capture and all 3 pilots missed that it hadn't captured and we descended to approximately 2600 ft MSL before catching it. I immediately climbed back to 3000 ft. We were around 4-5 mi from the FAF and 3000 ft was the minimum for our position. The first officer was somewhat distracted at the same time this occurred due to the GS flag appearing on the right (first officer side) instruments. Deviation was only brief and ATC never stated any problem or that it was a conflict. Fatigue also may have been a factor. It was the end of about a 9 hour flight from milan, italy. I did not feel fatigued and had a lot of sleep before departure, but did get up about XA00 'body' time.
Original NASA ASRS Text
Title: DC10 CREW DSNDS BELOW ASSIGNED ALT WHEN AUTOFLT, ALTHOUGH ENGAGED TO CAPTURE ALT, DOES NOT.
Narrative: WE WERE GIVEN A CLRNC TO MAINTAIN 3000 FT UNTIL ESTABLISHED AND CLRED FOR AN ILS TO RWY 3R. AUTOPLT WAS ON WITH ALT CAPTURE MODE ENGAGED. SOME HOW, SOME WAY, THE ALT FAILED TO CAPTURE AND ALL 3 PLTS MISSED THAT IT HADN'T CAPTURED AND WE DSNDED TO APPROX 2600 FT MSL BEFORE CATCHING IT. I IMMEDIATELY CLBED BACK TO 3000 FT. WE WERE AROUND 4-5 MI FROM THE FAF AND 3000 FT WAS THE MINIMUM FOR OUR POS. THE FO WAS SOMEWHAT DISTRACTED AT THE SAME TIME THIS OCCURRED DUE TO THE GS FLAG APPEARING ON THE R (FO SIDE) INSTS. DEV WAS ONLY BRIEF AND ATC NEVER STATED ANY PROB OR THAT IT WAS A CONFLICT. FATIGUE ALSO MAY HAVE BEEN A FACTOR. IT WAS THE END OF ABOUT A 9 HR FLT FROM MILAN, ITALY. I DID NOT FEEL FATIGUED AND HAD A LOT OF SLEEP BEFORE DEP, BUT DID GET UP ABOUT XA00 'BODY' TIME.
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.