GROSS NAV ERROR.

Narrative

FLT WAS APCHING SSM VOR UNDER TORONTO CTR CTL. WE WERE GIVEN CLRNC 'AFTER SSM; CLRED DIRECT UM (CHURCHILL FALLS NDB).' CAPT AND FO BOTH VERIFIED COORDINATES FOR UM: WAYPOINT #6. AFTER PASSING SSM (XB46Z); CAPT SELECTED WAYPOINT CHANGE AND INSERTED WAYPOINTS #2-6. HE THEN SELECTED XTK ERROR/XTK HDG. DUE TO SIZE OF HDG CHANGE (ABOUT 20 DEGS?) CAPT ELECTED TO USE HDG SELECT KNOB ON THE AP NAV MODE SELECTOR AND TURNED TO A HDG TO CORRECT TO THE TRACK SSM-UM. THIS WAS ABOUT 5 DEGS N OF THE DESIRED GND TRACK. AFTER VERIFYING WAYPOINT #6; I SELECTED YVO VOR (OUR NEXT ORIGINALLY FILED WAYPOINT) ON #2 NAV RADIO AND WE APPEARED TO BE TRACKING IN THE PROPER DIRECTION. I SET COURSE TO YVO (070 DEGS) ON MY CDI AND NOTED WE WOULD TRACK SLIGHTLY N OF YVO. MY HSI SWITCH WAS SELECTED TO 'RADIO' AND REMAINED THAT WAY. SINCE WE WERE STILL IN TORONTO RADAR CTL AND OUR POS WAS CURRENTLY OFF OF THE COVERAGE OF THE N ATLANTIC PLOTTING CHART; I DID NOT ATTEMPT TO PLOT OUR NEWLY CLRED TRACK OR POS. ABOUT THIS TIME; SEVERAL DISTRS OCCURRED. THE CAPT MADE HIS PA ANNOUNCEMENT TO THE PAX. NEXT; CTL WAS TRANSFERRED TO MONTREAL CTR WHO VERIFIED WE WERE 'RADAR IDENTED' AND REQUESTED US TO VERIFY OUR ESTIMATE FOR UM. WE WERE TRACKING N OF YVO WHICH SEEMED TO CONFIRM OUR TRACK TO UM. A SHORT TIME LATER; MONTREAL CTR RPTED 'RADAR SVC TERMINATED; CONTACT MONCTON CTR AT 70 DEGS W ON 134.0.' THE NEXT DISTR WAS THAT THE FLT ATTENDANTS DELIVERED OUR CREW MEALS. THE CAPT ATE FIRST AND I WAITED UNTIL MY MEAL WAS READY. I SELECTED PRESENT POS ON INS 3 TO WATCH FOR 70 DEG W. I DON'T RECALL WHAT THE CAPT HAD SELECTED ON INS 1. MY INS 2 WAS STILL ON TIME-DISTANCE. I TRIED TUNING IN UM ON ADF 2 BUT COULD NOT GET A SATISFACTORY SIGNAL. (I BELIEVE THE SELECTOR MIGHT HAVE BEEN IN 'ANT' VERSUS 'ADF' WHICH CAN BE AN EASY MISTAKE AFTER DOING THE PREFLT TEST OF THE ADF.) APCHING 70 DEGS W; I ATTEMPTED TO CONTACT MONCTON CTR WITH NO RESPONSE. AT THAT POINT; I NOTED THAT THE NAV MODE SELECTOR WAS STILL ON 'HDG.' I CHKEDXTK ERROR AND SAW THAT WE WERE WELL OFF COURSE N OF TRACK. I TUNED IN SCHEFFERVILLE VOR; YKL; AND NOTED WE WERE WELL N OF YKL AND SHOULD HAVE BEEN S. THE CAPT SELECTED WAYPOINT CHANGE; #0-6; INSERTED; AND SELECTED INS ON THE MODE SELECTOR. THE ACFT MADE A SHARP R TURN DIRECT TO UM (ABOUT AN 80 DEG HDG CHANGE AS I RECALL). I RAISED MONCTON CTR ON 128.7 WHO THEN CLRED US DIRECT TO LOACH; WAYPOINT #8. CTR REQUESTED AN IDENT AND OUR LOACH ESTIMATE. MONCTON RPTED RADAR IDENTIFIED AND STATED WE WERE WELL N OF THE CLRED TRACK FROM SSM TO UM. CAPT RPTED THAT WE HAD MADE A NAV ERROR BUT WERE CONFIRMING OUR POS AND PROCEEDING AS CLRED TO LOACH. AT THIS POINT; I PERFORMED AN INS CHK AND FIXED OUR POS AT YVP 160 DEGS/167 NM. ALL 3 INS UNITS AGREED WITH THE FIX. MONCTON THEN RPTED THAT FLT WAS BEING RPTED FOR A 'GROSS NAV DEV.' THE NAV ERROR TOOK PLACE AT ABOUT XB50 CDT (BODY CLOCK) TIME. WE DIDN'T DISCOVER THE ERROR UNTIL ABOUT XD30 CDT. I BELIEVE FATIGUE CONTRIBUTED TO MY FAILURE TO DISCOVER THE ORIGINAL NAV ERROR WHEN IT OCCURRED AND TO BECOME COMPLACENT ABOUT FOLLOWING OUR GND TRACK PROGRESS. I NORMALLY TRY TO GET A NAP DURING THE AFTERNOON BEFORE AN ALL NIGHT FLT. ON THE DAY OF THIS FLT; I WAS UNABLE TO GET MUCH REST DUE TO AN UNUSUAL COMBINATION OF PERSONAL PROBS AT HOME. THESE SAME PROBS MAY ALSO HAVE CAUSED ME TO BE SOMEWHAT DISTRACTED FROM THE BUSINESS OF FLYING AND NAV. THE CANADIAN ATC CTRS RESPONSIBLE FOR OUR FLT HAD RPTED WE WERE STILL IN RADAR CONTACT LONG AFTER THE INITIAL NAV ERROR HAD TIME TO BECOME SIGNIFICANT. AT NO TIME WERE WE ADVISED BY TORONTO OR MONTREAL THAT WE WERE OFF OF THE CLRED TRACK. COM RADIO 2 WAS ON 121.5 THE ENTIRE FLT SO WE COULD HAVE BEEN RAISED BY THAT METHOD IF NECESSARY. I BELIEVE I ONLY HEARD ONE OTHER ACFT TALKING ON THE SAME FREQS WITH TORONTO AND MONTREAL DURING OUR TIME IN THEIR AIRSPACE. WHILE I DON'T BELIEVE THERE IS A PROHIBITION AGAINST USING THE 'HDG' CTL KNOB DURING AN INS DIRECT LEG; MOST CAPTS DON'T. THEY (AND I) NORMALLY USEWAYPOINT CHANGE 0-X WAYPOINTS AND THEN REPEATEDLY REINSERT IN ORDER TO DAMPEN THE CORRECTIONS TO THE SELECTED GND TRACK. EVER SINCE IOE; I WAS TAUGHT TO NEVER SELECT HDG UNTIL THE DSCNT/LNDG PHASE OF THE FLT WHEN CTL IS DIRECTING YOU BY VECTORS AND HDGS. THE LEG WE WERE CLRED FOR (SSM-UM) WAS EXTRAORDINARILY LONG: OVER 800 NM. NORMALLY; CLRNCS LIKE THIS OCCUR OVER THE OCEAN (ON THE PLOTTING CHART) OR IN THE JET AIRWAY NETWORK WHERE IT IS EASY TO MONITOR YOUR PROGRESS. TORONTO CLRED US FOR THIS LEG IN RADAR CONTACT WHICH I BELIEVE GAVE US A FALSE SENSE OF SECURITY AND MAY HAVE MADE US LESS VIGILANT IN MONITORING GND TRACK PROGRESS.