Narrative:

Thermal VOR was the first fix on the route, followed by tnp. The navigation computers on board always lead a turn so as not to overfly the course and then have to correct to regain it. In the turn over thermal VOR, on its way to tnp VOR the aircraft led the turn as always. We were advised by the ZLA controller that we were 4 mi left of trm VOR as we turned over it and that we would have to watch that in the future. I do not know if it was a software problem common to the fleet or inherent in that aircraft only. I have seen this happen on several occasions without any mention from ATC so I assumed it was a normal FMS procedure. I have submitted a report similar to this to the company technicians to see if this aircraft operated outside the normal parameters.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACFT X OVERSHOT THE TURN OVER THE VORTAC, WAS ALERTED BY ATC, RPTR WAS UNCERTAIN IF THIS WAS INHERENT IN THE FMC OR JUST A FLUKE.

Narrative: THERMAL VOR WAS THE FIRST FIX ON THE RTE, FOLLOWED BY TNP. THE NAV COMPUTERS ON BOARD ALWAYS LEAD A TURN SO AS NOT TO OVERFLY THE COURSE AND THEN HAVE TO CORRECT TO REGAIN IT. IN THE TURN OVER THERMAL VOR, ON ITS WAY TO TNP VOR THE ACFT LED THE TURN AS ALWAYS. WE WERE ADVISED BY THE ZLA CTLR THAT WE WERE 4 MI L OF TRM VOR AS WE TURNED OVER IT AND THAT WE WOULD HAVE TO WATCH THAT IN THE FUTURE. I DO NOT KNOW IF IT WAS A SOFTWARE PROB COMMON TO THE FLEET OR INHERENT IN THAT ACFT ONLY. I HAVE SEEN THIS HAPPEN ON SEVERAL OCCASIONS WITHOUT ANY MENTION FROM ATC SO I ASSUMED IT WAS A NORMAL FMS PROC. I HAVE SUBMITTED A RPT SIMILAR TO THIS TO THE COMPANY TECHNICIANS TO SEE IF THIS ACFT OPERATED OUTSIDE THE NORMAL PARAMETERS.

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.