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A B757 flight turns early onto a false localizer intercept signal, receiving a GPWS alert prior to the PF resolving the issue of heading and altitude 20 mi east of oak, ca.
| Attributes | |
| ACN | 571623 |
| Time | |
| Date | 200301 |
| Day | Fri |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : oak.airport |
| State Reference | CA |
| Altitude | msl single value : 3200 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : nct.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B757 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 29 other |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : instrument pilot : flight engineer pilot : commercial pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 6200 flight time type : 330 |
| ASRS Report | 571623 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : clearance non adherence : published procedure other spatial deviation other spatial deviation |
| Independent Detector | aircraft equipment : gpws |
| Resolutory Action | flight crew : returned to intended or assigned course flight crew : took precautionary avoidance action flight crew : overrode automation |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance Navigational Facility |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
B757 on approach to runway 29 at oak airport. Aircraft at 3200 ft MSL told to 'fly 240 degree heading to intercept localizer, runway 29.' aircraft began an early turn to final approach course (294 degrees). Since on autoplt, it seemed to capture a false localizer signal, thus beginning a turn prior to actual localizer final. Realizing the turn was commenced onto final improperly, PF disconnected the autoplt and began to turn back to heading 240 degrees. At this time, the GPWS began to announce 'terrain, terrain' alert. To cancel alert, PF executed a climb to 3400 ft MSL while maintaining safe visual separation from ground. This aircraft seemingly interpreted an incorrect localizer signal which caused an early (unassigned) turn to localizer final, and consequently created a false 'terrain' alert from the GPWS. Aircraft automation executed a 54 degree course deviation from that assigned, and PF executed a 200 ft climb off assigned altitude as a result of automation inadequacies.
Original NASA ASRS Text
Title: A B757 FLT TURNS EARLY ONTO A FALSE LOC INTERCEPT SIGNAL, RECEIVING A GPWS ALERT PRIOR TO THE PF RESOLVING THE ISSUE OF HDG AND ALT 20 MI E OF OAK, CA.
Narrative: B757 ON APCH TO RWY 29 AT OAK ARPT. ACFT AT 3200 FT MSL TOLD TO 'FLY 240 DEG HDG TO INTERCEPT LOC, RWY 29.' ACFT BEGAN AN EARLY TURN TO FINAL APCH COURSE (294 DEGS). SINCE ON AUTOPLT, IT SEEMED TO CAPTURE A FALSE LOC SIGNAL, THUS BEGINNING A TURN PRIOR TO ACTUAL LOC FINAL. REALIZING THE TURN WAS COMMENCED ONTO FINAL IMPROPERLY, PF DISCONNECTED THE AUTOPLT AND BEGAN TO TURN BACK TO HDG 240 DEGS. AT THIS TIME, THE GPWS BEGAN TO ANNOUNCE 'TERRAIN, TERRAIN' ALERT. TO CANCEL ALERT, PF EXECUTED A CLB TO 3400 FT MSL WHILE MAINTAINING SAFE VISUAL SEPARATION FROM GND. THIS ACFT SEEMINGLY INTERPED AN INCORRECT LOC SIGNAL WHICH CAUSED AN EARLY (UNASSIGNED) TURN TO LOC FINAL, AND CONSEQUENTLY CREATED A FALSE 'TERRAIN' ALERT FROM THE GPWS. ACFT AUTOMATION EXECUTED A 54 DEG COURSE DEV FROM THAT ASSIGNED, AND PF EXECUTED A 200 FT CLB OFF ASSIGNED ALT AS A RESULT OF AUTOMATION INADEQUACIES.
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.