Narrative:

Both my first officer and I were reserve and called at the last minute to fly an md-11 flight from mem to fll on jun/xx/94. It should be noted that both of us had only approximately 2 hours of sleep prior to departure. After the flight was airborne from mem, ZME cleared the flight direct fll at FL370. My first officer was at the controls on the leg from mem to fll. Upon being handed over to ZMA after approximately 5 minutes on the 180 heading, center cleared the flight to fortl for the fortl to arrival into fll. My first officer 'inadvertently' turned the altitude selector thinking it was the heading selector, then realized what he had done and continued his hand along the gcp (glare shield control panel), selected the heading bug to put the aircraft going to fortl and then put his head down so he had to get into the secondary flight plan on the FMS. The aircraft was in profile at the time all this was taking place. When the secondary flight plan page on the FMS was activated, the aircraft started a profile descent to the altitude the first officer had inadvertently selected, which was part of the fortal 2 arrival already selected in the FMS computer. The aircraft descended to approximately 35500 ft before I realized what had happened and told my first officer we had not been cleared to a lower altitude. He then disconnected the autoplt, climbed back to FL370. We told ZMA and they were very understanding and professional. A combination of lack of sleep, a high tech airplane and a busy environment led to this altitude deviation. We should have corrected the inadvertent altitude setting right away, because the computer in profile will do exactly what the pilot asked for when in the profile mode. Also, I think the cockpit crew must be very careful before using the secondary flight plan page on the FMS. Supplemental information from acn 272817: contributing factors: both pilots had been called out on reserve at XX30 left. I was not as sharp as I hope I would have been with more rest. Distraction from multiple flight plan changes at the same time the captain was busy with arrival calls. On reserve for nearly a yr, my proficiency and recent experience is not at the level I desire.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION FROM ASSIGNED.

Narrative: BOTH MY FO AND I WERE RESERVE AND CALLED AT THE LAST MINUTE TO FLY AN MD-11 FLT FROM MEM TO FLL ON JUN/XX/94. IT SHOULD BE NOTED THAT BOTH OF US HAD ONLY APPROX 2 HRS OF SLEEP PRIOR TO DEP. AFTER THE FLT WAS AIRBORNE FROM MEM, ZME CLRED THE FLT DIRECT FLL AT FL370. MY FO WAS AT THE CTLS ON THE LEG FROM MEM TO FLL. UPON BEING HANDED OVER TO ZMA AFTER APPROX 5 MINUTES ON THE 180 HDG, CTR CLRED THE FLT TO FORTL FOR THE FORTL TO ARR INTO FLL. MY FO 'INADVERTENTLY' TURNED THE ALT SELECTOR THINKING IT WAS THE HDG SELECTOR, THEN REALIZED WHAT HE HAD DONE AND CONTINUED HIS HAND ALONG THE GCP (GLARE SHIELD CTL PANEL), SELECTED THE HDG BUG TO PUT THE ACFT GOING TO FORTL AND THEN PUT HIS HEAD DOWN SO HE HAD TO GET INTO THE SECONDARY FLT PLAN ON THE FMS. THE ACFT WAS IN PROFILE AT THE TIME ALL THIS WAS TAKING PLACE. WHEN THE SECONDARY FLT PLAN PAGE ON THE FMS WAS ACTIVATED, THE ACFT STARTED A PROFILE DSCNT TO THE ALT THE FO HAD INADVERTENTLY SELECTED, WHICH WAS PART OF THE FORTAL 2 ARR ALREADY SELECTED IN THE FMS COMPUTER. THE ACFT DSNDED TO APPROX 35500 FT BEFORE I REALIZED WHAT HAD HAPPENED AND TOLD MY FO WE HAD NOT BEEN CLRED TO A LOWER ALT. HE THEN DISCONNECTED THE AUTOPLT, CLBED BACK TO FL370. WE TOLD ZMA AND THEY WERE VERY UNDERSTANDING AND PROFESSIONAL. A COMBINATION OF LACK OF SLEEP, A HIGH TECH AIRPLANE AND A BUSY ENVIRONMENT LED TO THIS ALTDEV. WE SHOULD HAVE CORRECTED THE INADVERTENT ALT SETTING RIGHT AWAY, BECAUSE THE COMPUTER IN PROFILE WILL DO EXACTLY WHAT THE PLT ASKED FOR WHEN IN THE PROFILE MODE. ALSO, I THINK THE COCKPIT CREW MUST BE VERY CAREFUL BEFORE USING THE SECONDARY FLT PLAN PAGE ON THE FMS. SUPPLEMENTAL INFO FROM ACN 272817: CONTRIBUTING FACTORS: BOTH PLTS HAD BEEN CALLED OUT ON RESERVE AT XX30 L. I WAS NOT AS SHARP AS I HOPE I WOULD HAVE BEEN WITH MORE REST. DISTR FROM MULTIPLE FLT PLAN CHANGES AT THE SAME TIME THE CAPT WAS BUSY WITH ARR CALLS. ON RESERVE FOR NEARLY A YR, MY PROFICIENCY AND RECENT EXPERIENCE IS NOT AT THE LEVEL I DESIRE.

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.