Narrative:

The FMS was prepared by the first officer this evening who would be the flying pilot. As procedure the FMS flight plan accuracy and position initialization accuracy was verified by us (flying and non-flying pilot) and final flight plan verification would be accomplished; as it was shortly after ATC clearance issuance to assure accuracy for runway/SID initial altitude; etc. Following the brief taxi out and the completion of all checklists a takeoff clearance was issued by ATC stating cleared for takeoff and first fix. This clearance was read back by the first officer and the takeoff commenced. During initial power up the first officer (flying pilot) commanded N1. This should set takeoff thrust through the thrust management system automatically. However initial selection did not engage this system. Now airborne and through 400 ft AGL the first officer commanded LNAV; which was promptly selected by me. I noted on [the] captain's HSI the white LNAV becoming LNAV green at which time I responded; 'LNAV;' engaged and verified on [the] map and FMS that the active waypoint was as assigned. Continuing with post takeoff duties ATC; between 2;300 MSL and 2;500 MSL; cleared us to leave tower frequency to departure. The initial contact with departure control at 2;500 MSL and climbing was greeted by the controller's great sense of urgency to turn right and fly a heading of 200 degrees followed by ATC [asking] if we were having navigational problems. [Upon] verification of our first FMS navigation fix; its position locked in straight ahead as the first active waypoint; I responded; 'no; what do you show?' the reply was in essence that we were not navigating properly to the first assigned waypoint. It was now that a potential navigation error affecting our lateral track possibly occurred and that before we would fly much further we would begin navigation accuracy checks and detailed discussions about possible causes.one thing we know is that at the time of takeoff the surface winds were relatively calm. The international relief officer (international relief officer) did note a very significant wind direction and velocity change (not mentioned in the ATIS) occurred between 1;000 AGL and 3;000 AGL. The airborne winds were recorded by the international relief officer as 226/31. This would mean; for us; that with the flight directors giving basically a straight ahead command to fly direct to the active waypoint on essentially runway heading; that combined with the extreme change in airborne winds and despite of what the FMS and flight director systems were showing; we were going to be drifting east of the desired track. Soon after passing the first active waypoint we all noticed a small jump in the map display on both pilots HSI's. Was this correlation due to the initial lack of N1 engagement? It's quite possible. However; following extensive navigation accuracy checks; the navigation system was determined by us to be valid to safely continue this flight. The flight continued without any further occurrence.current procedures now [have us] check FMS and runway positions prior to takeoff; but if a navigation system is going to fail; takeoff is not the place. Obviously the takeoff phase being most critical; we would have to accept the current system and its flaws or spend the money to provide total redundancy and razor thin accuracy by updating all current systems and providing current technology to all aircraft utilizing GPS and error management systems. This should reduce if not eliminate this type of problem in the future and provide the pilots with a precision tool to properly handle this RNAV SID.

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Original NASA ASRS Text

Title: A B767 Captain was informed upon contacting Departure Control that he was not maintaining the correct RNAV departure path. All aircraft systems appeared normal with the correct RNAV departure entered in the FMS.

Narrative: The FMS was prepared by the First Officer this evening who would be the flying pilot. As procedure the FMS flight plan accuracy and position initialization accuracy was verified by us (flying and non-flying pilot) and final flight plan verification would be accomplished; as it was shortly after ATC clearance issuance to assure accuracy for runway/SID initial altitude; etc. Following the brief taxi out and the completion of all checklists a takeoff clearance was issued by ATC stating cleared for takeoff and first fix. This clearance was read back by the First officer and the takeoff commenced. During initial power up the First Officer (flying pilot) commanded N1. This should set takeoff thrust through the thrust management system automatically. However initial selection did not engage this system. Now airborne and through 400 FT AGL the First Officer commanded LNAV; which was promptly selected by me. I noted on [the] Captain's HSI the white LNAV becoming LNAV green at which time I responded; 'LNAV;' engaged and verified on [the] map and FMS that the active waypoint was as assigned. Continuing with post takeoff duties ATC; between 2;300 MSL and 2;500 MSL; cleared us to leave Tower frequency to Departure. The initial contact with Departure Control at 2;500 MSL and climbing was greeted by the Controller's great sense of urgency to turn right and fly a heading of 200 degrees followed by ATC [asking] if we were having navigational problems. [Upon] verification of our first FMS NAV fix; its position locked in straight ahead as the first active waypoint; I responded; 'no; what do you show?' The reply was in essence that we were not navigating properly to the first assigned waypoint. It was now that a potential NAV error affecting our lateral track possibly occurred and that before we would fly much further we would begin NAV accuracy checks and detailed discussions about possible causes.One thing we know is that at the time of takeoff the surface winds were relatively calm. The IRO (International Relief Officer) did note a very significant wind direction and velocity change (not mentioned in the ATIS) occurred between 1;000 AGL and 3;000 AGL. The airborne winds were recorded by the IRO as 226/31. This would mean; for us; that with the flight directors giving basically a straight ahead command to fly direct to the active waypoint on essentially runway heading; that combined with the extreme change in airborne winds and despite of what the FMS and Flight Director systems were showing; we were going to be drifting east of the desired track. Soon after passing the first active waypoint we all noticed a small jump in the map display on both pilots HSI's. Was this correlation due to the initial lack of N1 engagement? It's quite possible. However; following extensive NAV accuracy checks; the NAV system was determined by us to be valid to safely continue this flight. The flight continued without any further occurrence.Current procedures now [have us] check FMS and runway positions prior to takeoff; but if a NAV system is going to fail; takeoff is not the place. Obviously the takeoff phase being most critical; we would have to accept the current system and its flaws or spend the money to provide total redundancy and razor thin accuracy by updating all current systems and providing current technology to all aircraft utilizing GPS and error management systems. This should reduce if not eliminate this type of problem in the future and provide the pilots with a precision tool to properly handle this RNAV SID.

Data retrieved from NASA's ASRS site as of April 2012 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.