Narrative:

[We were] cleared the RNAV departure. First officer was the pilot flying captain was the pilot not flying. [We had a] rolling takeoff on a wet runway; change of control from captain to first officer normal. During throttle stand-up and stabilization the left engine spool up lagged requiring rudder inputs to stay on runway centerline. Once engines spooled up pilot flying gave the command 'N1' to engage takeoff mode and set the auto throttles. N1 did not engage and thrust had to be manually set by the pilot flying and adjusted by the pilot not flying. Once takeoff thrust set pilot not flying again tried to engage N1 and was successful. Rotation and gear retraction normal. At 400 ft I called for 'LNAV' and it was engaged. I was using the map mode on the HSI with 10 mile selected. I saw the first fix off to our left and the flight director commanding a left turn. That was not correct. The fix should have been straight ahead. I ignored the flight director and maintained a runway heading. At 1;000 ft RA I started to accelerate and raise the flaps. At approximately 2;500 ft MSL the map display on my HSI shifted to the right. We were now beyond and left of first RNAV waypoint. I started a turn toward the second waypoint to the right to get back on track. At the same time the pilot not flying had contacted departure control and they gave us a 'turn immediately to heading 210' and asked if we had lost our RNAV. The next headings were 230 then 180 then direct. We proceeded to the assigned fix and once we were on center we were given direct a down line NAVAID. We asked center if it looked like we were on course and they said yes. I assume that the FMC did not update the position on takeoff. Because of the wet runway and the lagging left engine my attention was outside looking down the runway. I didn't notice if the position updated to the runway. Once airborne the position updated. Because of strong winds out of the southwest maintaining runway heading caused us to drift to the left toward 18 and the call from ATC to turn right. All subsequent navigation accuracy checks were within tolerances and the systems were fine the rest of the flight. Both the pilot flying and the pilot not flying must make sure the FMC updates position to the runway on a RNAV departure. If not then the takeoff should be stopped since the update should occur when the throttles are first advanced. The abort would be very low speed and the aircraft could exit the runway and a cause determined for the no update. And if required a different departure could be requested.

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Original NASA ASRS Text

Title: A B767-200 without a GPS had a track deviation after a takeoff on an RNAV procedure because the FMC's did not update properly prior to takeoff.

Narrative: [We were] cleared the RNAV departure. First Officer was the pilot flying Captain was the pilot not flying. [We had a] rolling takeoff on a wet runway; change of control from Captain to First Officer normal. During throttle stand-up and stabilization the left engine spool up lagged requiring rudder inputs to stay on runway centerline. Once engines spooled up pilot flying gave the command 'N1' to engage takeoff mode and set the auto throttles. N1 did not engage and thrust had to be manually set by the pilot flying and adjusted by the pilot not flying. Once takeoff thrust set pilot not flying again tried to engage N1 and was successful. Rotation and gear retraction normal. At 400 FT I called for 'LNAV' and it was engaged. I was using the map mode on the HSI with 10 mile selected. I saw the first fix off to our left and the Flight Director commanding a left turn. That was not correct. The fix should have been straight ahead. I ignored the Flight Director and maintained a runway heading. At 1;000 FT RA I started to accelerate and raise the flaps. At approximately 2;500 FT MSL the map display on my HSI shifted to the right. We were now beyond and left of first RNAV waypoint. I started a turn toward the second waypoint to the right to get back on track. At the same time the pilot not flying had contacted Departure Control and they gave us a 'turn immediately to heading 210' and asked if we had lost our RNAV. The next headings were 230 then 180 then direct. We proceeded to the assigned fix and once we were on Center we were given direct a down line NAVAID. We asked Center if it looked like we were on course and they said yes. I assume that the FMC did not update the position on takeoff. Because of the wet runway and the lagging left engine my attention was outside looking down the runway. I didn't notice if the position updated to the runway. Once airborne the position updated. Because of strong winds out of the southwest maintaining runway heading caused us to drift to the left toward 18 and the call from ATC to turn right. All subsequent navigation accuracy checks were within tolerances and the systems were fine the rest of the flight. Both the pilot flying and the pilot not flying must make sure the FMC updates position to the runway on a RNAV departure. If not then the takeoff should be stopped since the update should occur when the throttles are first advanced. The abort would be very low speed and the aircraft could exit the runway and a cause determined for the no update. And if required a different departure could be requested.

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.