Narrative:

After crossing a flight planned fix, I turned the aircraft to the outbound heading for direct navigation to the next VOR. The captain advised he was going to the back to use the facility. At this time I referred to my high altitude chart to reference our flight planned route. Before the captain returned, center questioned me about my heading. I looked up and noticed that the aircraft was in a slight turn and was not holding in the heading mode of the autoplt. The aircraft had turned a sizeable degree off the original heading and a correction was made back to the original heading. Before turning the aircraft I checked to make sure that the turn knob on the autoplt was centered. It was in fact and the aircraft should not have turned at all, but it did. A big lesson was learned from this event. First of all when a crew member leaves his position on the flight deck, constant vigilance must be maintained in his absence. This is not the time to be referring to charts etc. Even though I had been glancing up periodically to check my altitude for deviation it never occurred to me that the aircraft was turning off heading. You just can't maintain the high level of concentration needed unless you focus yourself solely on the operation of the aircraft. The absence of a crew member on the flight deck demands a constant and undivided attention for the safe operation of the aircraft.

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Original NASA ASRS Text

Title: ACR LGT FLT TRACK HDG DEV.

Narrative: AFTER XING A FLT PLANNED FIX, I TURNED THE ACFT TO THE OUTBOUND HDG FOR DIRECT NAV TO THE NEXT VOR. THE CAPT ADVISED HE WAS GOING TO THE BACK TO USE THE FACILITY. AT THIS TIME I REFERRED TO MY HIGH ALT CHART TO REF OUR FLT PLANNED RTE. BEFORE THE CAPT RETURNED, CENTER QUESTIONED ME ABOUT MY HDG. I LOOKED UP AND NOTICED THAT THE ACFT WAS IN A SLIGHT TURN AND WAS NOT HOLDING IN THE HDG MODE OF THE AUTOPLT. THE ACFT HAD TURNED A SIZEABLE DEG OFF THE ORIGINAL HDG AND A CORRECTION WAS MADE BACK TO THE ORIGINAL HDG. BEFORE TURNING THE ACFT I CHKED TO MAKE SURE THAT THE TURN KNOB ON THE AUTOPLT WAS CENTERED. IT WAS IN FACT AND THE ACFT SHOULD NOT HAVE TURNED AT ALL, BUT IT DID. A BIG LESSON WAS LEARNED FROM THIS EVENT. FIRST OF ALL WHEN A CREW MEMBER LEAVES HIS POS ON THE FLT DECK, CONSTANT VIGILANCE MUST BE MAINTAINED IN HIS ABSENCE. THIS IS NOT THE TIME TO BE REFERRING TO CHARTS ETC. EVEN THOUGH I HAD BEEN GLANCING UP PERIODICALLY TO CHK MY ALT FOR DEV IT NEVER OCCURRED TO ME THAT THE ACFT WAS TURNING OFF HDG. YOU JUST CAN'T MAINTAIN THE HIGH LEVEL OF CONCENTRATION NEEDED UNLESS YOU FOCUS YOURSELF SOLELY ON THE OP OF THE ACFT. THE ABSENCE OF A CREW MEMBER ON THE FLT DECK DEMANDS A CONSTANT AND UNDIVIDED ATTN FOR THE SAFE OP OF THE ACFT.

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.