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An undetected autoflt malfunction on the skebr RNAV 1 arrival to las, nv. Results in a track deviation.
| Attributes | |
| ACN | 561316 |
| Time | |
| Date | 200209 |
| Day | Thu |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | intersection : skebr |
| State Reference | NV |
| Altitude | msl single value : 13000 |
| Environment | |
| Flight Conditions | VMC |
| Weather Elements | Turbulence |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : l30.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : skebr one |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 150 flight time total : 9800 flight time type : 900 |
| ASRS Report | 561316 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 30000 flight time type : 7000 |
| ASRS Report | 561130 |
| Events | |
| Anomaly | aircraft equipment problem : less severe inflight encounter : wake turbulence non adherence : clearance non adherence : published procedure other anomaly other other spatial deviation |
| Independent Detector | other flight crewa other flight crewb |
| Resolutory Action | controller : issued advisory flight crew : returned to intended or assigned course other |
| Consequence | faa : reviewed incident with flight crew other |
| Supplementary | |
| Problem Areas | Aircraft Environmental Factor Flight Crew Human Performance |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
On the skebr 1 arrival, ATC requested 250 KTS for spacing into las. While on the descent profile, we encountered wake turbulence from the preceding aircraft. When we passed clarr intersection, the aircraft was tracking the arrival. When we crossed over the skebr intersection the aircraft did not follow the turn and continued on the 031 degree heading. We notified ATC and took the corrective action to reintercept the arrival. Upon arrival at the gate, the captain and I discussed the problem with maintenance and came to the same conclusion that the LNAV had malfunctioned. In retrospect, fatigue from the 7 legs and 10+ hour duty day and the uncommanded roll from the wake turbulence may have disengaged the LNAV without either the captain or I realizing it. In the future, I will incorporate a xchk with AFDS to ensure the autoplt is still functioning properly after any type of turbulence that is encountered. Supplemental information from acn 561130: contributing factors: wake turbulence/subsequent discovery the aircraft was having FMS and autoplt problems subsequent write-ups and same problem next day write-up.
Original NASA ASRS Text
Title: AN UNDETECTED AUTOFLT MALFUNCTION ON THE SKEBR RNAV 1 ARR TO LAS, NV. RESULTS IN A TRACK DEV.
Narrative: ON THE SKEBR 1 ARR, ATC REQUESTED 250 KTS FOR SPACING INTO LAS. WHILE ON THE DSCNT PROFILE, WE ENCOUNTERED WAKE TURB FROM THE PRECEDING ACFT. WHEN WE PASSED CLARR INTXN, THE ACFT WAS TRACKING THE ARR. WHEN WE CROSSED OVER THE SKEBR INTXN THE ACFT DID NOT FOLLOW THE TURN AND CONTINUED ON THE 031 DEG HDG. WE NOTIFIED ATC AND TOOK THE CORRECTIVE ACTION TO REINTERCEPT THE ARR. UPON ARR AT THE GATE, THE CAPT AND I DISCUSSED THE PROB WITH MAINT AND CAME TO THE SAME CONCLUSION THAT THE LNAV HAD MALFUNCTIONED. IN RETROSPECT, FATIGUE FROM THE 7 LEGS AND 10+ HR DUTY DAY AND THE UNCOMMANDED ROLL FROM THE WAKE TURB MAY HAVE DISENGAGED THE LNAV WITHOUT EITHER THE CAPT OR I REALIZING IT. IN THE FUTURE, I WILL INCORPORATE A XCHK WITH AFDS TO ENSURE THE AUTOPLT IS STILL FUNCTIONING PROPERLY AFTER ANY TYPE OF TURB THAT IS ENCOUNTERED. SUPPLEMENTAL INFO FROM ACN 561130: CONTRIBUTING FACTORS: WAKE TURB/SUBSEQUENT DISCOVERY THE ACFT WAS HAVING FMS AND AUTOPLT PROBS SUBSEQUENT WRITE-UPS AND SAME PROB NEXT DAY WRITE-UP.
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.