Narrative:

On arrival into las via the tyssn 1 arrival, ATC reported the aircraft was approximately 3 mi wsw of the RNAV fix -- idented as suzsi. In addition, ATC advised that it appeared the aircraft was flying at a ground speed of 280 KTS. Crew advised ATC that aircraft's position indicated at suzsi RNAV fix at 10000 ft MSL and KIAS of 210 KTS. Crew noted IRS ground speed of 260 KTS and KIAS speed of 210 KTS. Crew requested ATC provide radar vectors to ensure terrain and location guidance. ATC cleared us to fly a heading to intercept the las ILS runway 25L localizer and track inbound. Crew performed clearance and subsequent visual approach to runway 25L with no further complications. ATC advised us to contact las TRACON upon arrival and advised crew that there was no problem, but just to call. I contacted las TRACON supervisor and discussed the matter. He reviewed the ATC concern and advised there as no report being filed. I conveyed that the aircraft appeared to be in the location that was depicted on the arrival chart. Furthermore, I would have maintenance check out the system on the aircraft. At no time did any previous controller identify any discrepancy concerning routing or speed. No FMS/FMC errors were noted prior to the initial ATC notification. Las maintenance performed avionics checks and no discrepancies noted. On the outbound flight, system was checked en route against known fixes and confirmed with ATC. No discrepancies were noted. In addition, a check was performed at the termination of flight comparing the actual location against the gate coordinates and a .06 mi discrepancy was noted. Crew suspects that the ATC radar had an anomaly which caused a misident of actual location during that phase of flight. Recommendation: have coordinates added to charts to add additional identify capabilities to crew while in-flight.

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Original NASA ASRS Text

Title: B757-200 CREW HAD THE APCH CTLR REQUEST THE CAPT CONTACT THE TRACON SUPVR. THE APCH CTLR TOLD THE CREW THEY WERE 3 MI OFF COURSE AND AT A SPD OF 280 KTS.

Narrative: ON ARR INTO LAS VIA THE TYSSN 1 ARR, ATC RPTED THE ACFT WAS APPROX 3 MI WSW OF THE RNAV FIX -- IDENTED AS SUZSI. IN ADDITION, ATC ADVISED THAT IT APPEARED THE ACFT WAS FLYING AT A GND SPD OF 280 KTS. CREW ADVISED ATC THAT ACFT'S POS INDICATED AT SUZSI RNAV FIX AT 10000 FT MSL AND KIAS OF 210 KTS. CREW NOTED IRS GND SPD OF 260 KTS AND KIAS SPD OF 210 KTS. CREW REQUESTED ATC PROVIDE RADAR VECTORS TO ENSURE TERRAIN AND LOCATION GUIDANCE. ATC CLRED US TO FLY A HEADING TO INTERCEPT THE LAS ILS RWY 25L LOC AND TRACK INBOUND. CREW PERFORMED CLRNC AND SUBSEQUENT VISUAL APCH TO RWY 25L WITH NO FURTHER COMPLICATIONS. ATC ADVISED US TO CONTACT LAS TRACON UPON ARR AND ADVISED CREW THAT THERE WAS NO PROB, BUT JUST TO CALL. I CONTACTED LAS TRACON SUPVR AND DISCUSSED THE MATTER. HE REVIEWED THE ATC CONCERN AND ADVISED THERE AS NO RPT BEING FILED. I CONVEYED THAT THE ACFT APPEARED TO BE IN THE LOCATION THAT WAS DEPICTED ON THE ARR CHART. FURTHERMORE, I WOULD HAVE MAINT CHK OUT THE SYS ON THE ACFT. AT NO TIME DID ANY PREVIOUS CTLR IDENT ANY DISCREPANCY CONCERNING ROUTING OR SPD. NO FMS/FMC ERRORS WERE NOTED PRIOR TO THE INITIAL ATC NOTIFICATION. LAS MAINT PERFORMED AVIONICS CHKS AND NO DISCREPANCIES NOTED. ON THE OUTBOUND FLT, SYS WAS CHKED ENRTE AGAINST KNOWN FIXES AND CONFIRMED WITH ATC. NO DISCREPANCIES WERE NOTED. IN ADDITION, A CHK WAS PERFORMED AT THE TERMINATION OF FLT COMPARING THE ACTUAL LOCATION AGAINST THE GATE COORDINATES AND A .06 MI DISCREPANCY WAS NOTED. CREW SUSPECTS THAT THE ATC RADAR HAD AN ANOMALY WHICH CAUSED A MISIDENT OF ACTUAL LOCATION DURING THAT PHASE OF FLT. RECOMMENDATION: HAVE COORDINATES ADDED TO CHARTS TO ADD ADDITIONAL IDENT CAPABILITIES TO CREW WHILE INFLT.

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.