Narrative:

I was the flight engineer on flight X from milan, italy, to new york-jfk on M/D/92. As we approached the fix-dotty-ending the oceanic portion of our flight, we were cleared to climb to FL370 from FL350 and to proceed via north america route 144 from dotty to ebony. We climbed to 370 and inserted the proper ebony coordinates in all 3 INS's. At about this time, the PF apparently put the autoplt mode selector in the heading mode. About 25 mins later, the gander controller called us to hand us over to moncton center and he asked where we were going. We told him we were proceeding on na-144. He advised us that we were 80 mi north of course. We immediately checked the coordinates in the INS and found them correct. We then saw the autoplt mode selector was still in heading mode instead of INS mode. The reason for navigation error was the autoplt mode selector had not been returned to INS mode after passing dotty. The controller advised us he would file a violation against us for gross navigation error, and handed us over to moncton. The remainder of the flight was normal. Some factors which may have contributed to this mistake were: routing via na-144 was a change from our flight plan requested routing. Crew meals for PF and flight engineer were brought to cockpit about same time as passing dotty. Although under radar control, gander controller didn't question our position until we were 80 mi off course. Supplemental information from acn 211123. Observations in the aftermath. Most countries do not predicate ATC on radar as we do in the united states but use radar primarily as a monitor. My primary concern on north american rtes has been to take navigation fixes to confirm adherence to track. The primary concern should be checking waypoints and INS/autoplt status the same as we do in mhps airspace. I have never heard of an excursion attributed to INS malfunction. It is always a programming error of some sort, usually involving a 'rerte.' I picked a poor time to 'debrief' a student. Fatigue. Put INS checking procedures ahead of navigation fix plotting. The problem does not lie in the hardware but in its programming and use. Do not debrief on chkrides until after the flight is over. Eliminate the fifth digit in en route fix coordinates. Rounding to the nearest min could not result in more than 1/2 mi change in position.

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Original NASA ASRS Text

Title: A WDB LINE CHK AIRMAN GOT 80 MI OFF COURSE WHEN HE SWITCHED THE INS COUPLED TO THE AUTOPLT FROM INS TO HDG.

Narrative: I WAS THE FE ON FLT X FROM MILAN, ITALY, TO NEW YORK-JFK ON M/D/92. AS WE APCHED THE FIX-DOTTY-ENDING THE OCEANIC PORTION OF OUR FLT, WE WERE CLRED TO CLB TO FL370 FROM FL350 AND TO PROCEED VIA N AMERICA RTE 144 FROM DOTTY TO EBONY. WE CLBED TO 370 AND INSERTED THE PROPER EBONY COORDINATES IN ALL 3 INS'S. AT ABOUT THIS TIME, THE PF APPARENTLY PUT THE AUTOPLT MODE SELECTOR IN THE HDG MODE. ABOUT 25 MINS LATER, THE GANDER CTLR CALLED US TO HAND US OVER TO MONCTON CTR AND HE ASKED WHERE WE WERE GOING. WE TOLD HIM WE WERE PROCEEDING ON NA-144. HE ADVISED US THAT WE WERE 80 MI N OF COURSE. WE IMMEDIATELY CHKED THE COORDINATES IN THE INS AND FOUND THEM CORRECT. WE THEN SAW THE AUTOPLT MODE SELECTOR WAS STILL IN HDG MODE INSTEAD OF INS MODE. THE REASON FOR NAV ERROR WAS THE AUTOPLT MODE SELECTOR HAD NOT BEEN RETURNED TO INS MODE AFTER PASSING DOTTY. THE CTLR ADVISED US HE WOULD FILE A VIOLATION AGAINST US FOR GROSS NAV ERROR, AND HANDED US OVER TO MONCTON. THE REMAINDER OF THE FLT WAS NORMAL. SOME FACTORS WHICH MAY HAVE CONTRIBUTED TO THIS MISTAKE WERE: ROUTING VIA NA-144 WAS A CHANGE FROM OUR FLT PLAN REQUESTED ROUTING. CREW MEALS FOR PF AND FLT ENGINEER WERE BROUGHT TO COCKPIT ABOUT SAME TIME AS PASSING DOTTY. ALTHOUGH UNDER RADAR CTL, GANDER CTLR DIDN'T QUESTION OUR POS UNTIL WE WERE 80 MI OFF COURSE. SUPPLEMENTAL INFO FROM ACN 211123. OBSERVATIONS IN THE AFTERMATH. MOST COUNTRIES DO NOT PREDICATE ATC ON RADAR AS WE DO IN THE UNITED STATES BUT USE RADAR PRIMARILY AS A MONITOR. MY PRIMARY CONCERN ON NORTH AMERICAN RTES HAS BEEN TO TAKE NAV FIXES TO CONFIRM ADHERENCE TO TRACK. THE PRIMARY CONCERN SHOULD BE CHKING WAYPOINTS AND INS/AUTOPLT STATUS THE SAME AS WE DO IN MHPS AIRSPACE. I HAVE NEVER HEARD OF AN EXCURSION ATTRIBUTED TO INS MALFUNCTION. IT IS ALWAYS A PROGRAMMING ERROR OF SOME SORT, USUALLY INVOLVING A 'RERTE.' I PICKED A POOR TIME TO 'DEBRIEF' A STUDENT. FATIGUE. PUT INS CHKING PROCS AHEAD OF NAV FIX PLOTTING. THE PROBLEM DOES NOT LIE IN THE HARDWARE BUT IN ITS PROGRAMMING AND USE. DO NOT DEBRIEF ON CHKRIDES UNTIL AFTER THE FLT IS OVER. ELIMINATE THE FIFTH DIGIT IN ENRTE FIX COORDINATES. ROUNDING TO THE NEAREST MIN COULD NOT RESULT IN MORE THAN 1/2 MI CHANGE IN POS.

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.