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DC10 captain cites fatigue in slow reaction to altitude hold disengagement and resultant altitude deviation.
| Attributes | |
| ACN | 636265 |
| Time | |
| Date | 200411 |
| Day | Sat |
| Local Time Of Day | 0001 To 0600 |
| Place | |
| Locale Reference | airport : okc.airport |
| State Reference | OK |
| Altitude | msl bound lower : 31000 msl bound upper : 32000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zfw.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | DC-10 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 17000 flight time type : 9000 |
| ASRS Report | 636265 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | aircraft equipment : altitude alert |
| Resolutory Action | flight crew : returned to assigned altitude |
| Consequence | faa : reviewed incident with flight crew |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
This flight was the last leg of a week of flying. The previous 2 days saw the crew transition from day to night flying. Sleep patterns were disrupted as a result. Flight was in level cruise with autoplt engaged. We had been level for about 1 hour. I reached into my chart bag (below and to my left), then, upon sitting upright again, I noticed a flashing amber light that indicates we were off our assigned altitude. The flight guidance no longer indicated altitude hold but, instead, vertical speed. Because I was so sleepy, the exact problem (above or below correct altitude) didn't register. My eyes saw the instruments but the brain wasn't interpreting. I moved the vertical speed control and brought us back to FL310 and observed altitude hold once again. Some points of interest are: 1) I looked over at the first officer and noted he had fallen asleep. 2) I have no idea whether the autoplt did this on its own or whether the first officer bumped the vertical speed control (maybe to correct off altitude by 50 ft or so) and then fell asleep. I'll never know how this happened. We got up near FL320 before the trend was reversed. ATC asked us to 'say altitude' approximately 4 mins after returning to FL310. I responded 'FL310' and he replied, 'roger.' nothing else was said.
Original NASA ASRS Text
Title: DC10 CAPT CITES FATIGUE IN SLOW REACTION TO ALT HOLD DISENGAGEMENT AND RESULTANT ALTDEV.
Narrative: THIS FLT WAS THE LAST LEG OF A WK OF FLYING. THE PREVIOUS 2 DAYS SAW THE CREW TRANSITION FROM DAY TO NIGHT FLYING. SLEEP PATTERNS WERE DISRUPTED AS A RESULT. FLT WAS IN LEVEL CRUISE WITH AUTOPLT ENGAGED. WE HAD BEEN LEVEL FOR ABOUT 1 HR. I REACHED INTO MY CHART BAG (BELOW AND TO MY L), THEN, UPON SITTING UPRIGHT AGAIN, I NOTICED A FLASHING AMBER LIGHT THAT INDICATES WE WERE OFF OUR ASSIGNED ALT. THE FLT GUIDANCE NO LONGER INDICATED ALT HOLD BUT, INSTEAD, VERT SPD. BECAUSE I WAS SO SLEEPY, THE EXACT PROB (ABOVE OR BELOW CORRECT ALT) DIDN'T REGISTER. MY EYES SAW THE INSTS BUT THE BRAIN WASN'T INTERPRETING. I MOVED THE VERT SPD CTL AND BROUGHT US BACK TO FL310 AND OBSERVED ALT HOLD ONCE AGAIN. SOME POINTS OF INTEREST ARE: 1) I LOOKED OVER AT THE FO AND NOTED HE HAD FALLEN ASLEEP. 2) I HAVE NO IDEA WHETHER THE AUTOPLT DID THIS ON ITS OWN OR WHETHER THE FO BUMPED THE VERT SPD CTL (MAYBE TO CORRECT OFF ALT BY 50 FT OR SO) AND THEN FELL ASLEEP. I'LL NEVER KNOW HOW THIS HAPPENED. WE GOT UP NEAR FL320 BEFORE THE TREND WAS REVERSED. ATC ASKED US TO 'SAY ALT' APPROX 4 MINS AFTER RETURNING TO FL310. I RESPONDED 'FL310' AND HE REPLIED, 'ROGER.' NOTHING ELSE WAS SAID.
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.