Narrative:

After takeoff we engaged the RNAV to the autoplt. Almost immediately we got the 'where are you going?' from departure control. According to our map display, we were proceeding correctly, but departure gave us vectors in almost the opposite direction. It took quite awhile to decipher the problem, what with workload, loss of positional awareness, etc, but it appeared that I misentered the coords on the ramp and had a 2 degree longitude error. I thought the captain had crosschecked it but apparently he never did. We had other IRS problems during alignment, so we didn't catch the position error and the IRS accepted it. It didn't at first, but due to the other problems, we missed the position problem. Apparently, the large transport IRS system will accept a gross error after a few tries. In any event, we navigated the rest of the trip the old-fashioned way -- thankfully, we were not headed over the ocean. Also, fortunately, although we strayed off course, and had a traffic conflict, there was no loss of separation, thinks to a sharp controller. All of this could have been prevented if: I had been more careful, the captain had crosschecked, or we had backed up the departure with VOR, all of which we normally do! Guess it all boils down to complacency. Also, it would help if the IRS system would tell you if your position was way off from the last position, so that the error would not be masked by other alignment problems. Last but not least, an update feature would be very helpful. If we had been launching on an oceanic crossing, we would have had to land and realign.

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Original NASA ASRS Text

Title: HDG TRACK DEV ON DEP WHICH WAS CAUGHT BY ALERT DEP CTLR VIGILANCE.

Narrative: AFTER TKOF WE ENGAGED THE RNAV TO THE AUTOPLT. ALMOST IMMEDIATELY WE GOT THE 'WHERE ARE YOU GOING?' FROM DEP CTL. ACCORDING TO OUR MAP DISPLAY, WE WERE PROCEEDING CORRECTLY, BUT DEP GAVE US VECTORS IN ALMOST THE OPPOSITE DIRECTION. IT TOOK QUITE AWHILE TO DECIPHER THE PROBLEM, WHAT WITH WORKLOAD, LOSS OF POSITIONAL AWARENESS, ETC, BUT IT APPEARED THAT I MISENTERED THE COORDS ON THE RAMP AND HAD A 2 DEG LONGITUDE ERROR. I THOUGHT THE CAPT HAD XCHKED IT BUT APPARENTLY HE NEVER DID. WE HAD OTHER IRS PROBLEMS DURING ALIGNMENT, SO WE DIDN'T CATCH THE POS ERROR AND THE IRS ACCEPTED IT. IT DIDN'T AT FIRST, BUT DUE TO THE OTHER PROBLEMS, WE MISSED THE POS PROBLEM. APPARENTLY, THE LGT IRS SYS WILL ACCEPT A GROSS ERROR AFTER A FEW TRIES. IN ANY EVENT, WE NAVIGATED THE REST OF THE TRIP THE OLD-FASHIONED WAY -- THANKFULLY, WE WERE NOT HEADED OVER THE OCEAN. ALSO, FORTUNATELY, ALTHOUGH WE STRAYED OFF COURSE, AND HAD A TFC CONFLICT, THERE WAS NO LOSS OF SEPARATION, THINKS TO A SHARP CTLR. ALL OF THIS COULD HAVE BEEN PREVENTED IF: I HAD BEEN MORE CAREFUL, THE CAPT HAD XCHKED, OR WE HAD BACKED UP THE DEP WITH VOR, ALL OF WHICH WE NORMALLY DO! GUESS IT ALL BOILS DOWN TO COMPLACENCY. ALSO, IT WOULD HELP IF THE IRS SYS WOULD TELL YOU IF YOUR POS WAS WAY OFF FROM THE LAST POS, SO THAT THE ERROR WOULD NOT BE MASKED BY OTHER ALIGNMENT PROBLEMS. LAST BUT NOT LEAST, AN UPDATE FEATURE WOULD BE VERY HELPFUL. IF WE HAD BEEN LAUNCHING ON AN OCEANIC XING, WE WOULD HAVE HAD TO LAND AND REALIGN.

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.