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B737-500 crew had track deviation while flying the lynsy 2 RNAV approach into las.
| Attributes | |
| ACN | 584093 |
| Time | |
| Date | 200306 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| State Reference | AZ |
| Altitude | msl single value : 12000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : l30.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-500 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Route In Use | arrival : on vectors arrival star : linsy |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 6000 flight time type : 120 |
| ASRS Report | 584093 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 220 flight time total : 6000 flight time type : 220 |
| ASRS Report | 583924 |
| Events | |
| Anomaly | non adherence : clearance non adherence : far non adherence : published procedure other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued advisory controller : issued new clearance |
| Consequence | other |
| Supplementary | |
| Problem Areas | Company FAA |
| Primary Problem | Company |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Lynsy 2 arrival to las at 12000 ft MSL, 250 KIAS. Just past lynsy, aircraft turned to mirok. Las approach said you are cleared direct utare. This will put you back on the arrival. Lnave showed on course. We preceeded direct to utare. I asked the controller if he showed us on course. He said we were about 3 mi west of track. At this time, I told the controller we were having a navigation problem and would need vectors. He gave us a heading to final, and we landed uneventfully. At no time did we get a 'unable navigation rwp,' and the system checked good. End of runway fix seemed to be right on, and current position and gate coordinates were within 1 mi. System was updated correctly in our departing city, and the switches were in the correct position on the arrival. I really have no idea why the error occurred. The flight flew operations normal on return trip. Traffic was light into las, and there were no problems with approach control. I wish I could give you more, but I really don't know why it happened. Supplemental information from acn 583924: the captain and I discussed what may have caused this problem. We are sure, due to long delays, that the FMC was programmed with the correct runway and updated properly. LNAV was engaged on the arrival, because the aircraft was turning at what we believed were the correct fixes. The LNAV did not show a large position error on the ground in las.
Original NASA ASRS Text
Title: B737-500 CREW HAD TRACK DEV WHILE FLYING THE LYNSY 2 RNAV APCH INTO LAS.
Narrative: LYNSY 2 ARR TO LAS AT 12000 FT MSL, 250 KIAS. JUST PAST LYNSY, ACFT TURNED TO MIROK. LAS APCH SAID YOU ARE CLRED DIRECT UTARE. THIS WILL PUT YOU BACK ON THE ARR. LNAVE SHOWED ON COURSE. WE PRECEEDED DIRECT TO UTARE. I ASKED THE CTLR IF HE SHOWED US ON COURSE. HE SAID WE WERE ABOUT 3 MI W OF TRACK. AT THIS TIME, I TOLD THE CTLR WE WERE HAVING A NAV PROB AND WOULD NEED VECTORS. HE GAVE US A HDG TO FINAL, AND WE LANDED UNEVENTFULLY. AT NO TIME DID WE GET A 'UNABLE NAV RWP,' AND THE SYS CHKED GOOD. END OF RWY FIX SEEMED TO BE RIGHT ON, AND CURRENT POS AND GATE COORDINATES WERE WITHIN 1 MI. SYS WAS UPDATED CORRECTLY IN OUR DEPARTING CITY, AND THE SWITCHES WERE IN THE CORRECT POS ON THE ARR. I REALLY HAVE NO IDEA WHY THE ERROR OCCURRED. THE FLT FLEW OPS NORMAL ON RETURN TRIP. TFC WAS LIGHT INTO LAS, AND THERE WERE NO PROBS WITH APCH CTL. I WISH I COULD GIVE YOU MORE, BUT I REALLY DON'T KNOW WHY IT HAPPENED. SUPPLEMENTAL INFO FROM ACN 583924: THE CAPT AND I DISCUSSED WHAT MAY HAVE CAUSED THIS PROB. WE ARE SURE, DUE TO LONG DELAYS, THAT THE FMC WAS PROGRAMMED WITH THE CORRECT RWY AND UPDATED PROPERLY. LNAV WAS ENGAGED ON THE ARR, BECAUSE THE ACFT WAS TURNING AT WHAT WE BELIEVED WERE THE CORRECT FIXES. THE LNAV DID NOT SHOW A LARGE POS ERROR ON THE GND IN LAS.
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.