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A B747 responded to a false TCAS warning by first descending then climbing. TCAS circuit breaker was pulled to stop warning with no traffic in the area.
| Attributes | |
| ACN | 805813 |
| Time | |
| Date | 200809 |
| Local Time Of Day | 0001 To 0600 |
| Place | |
| Locale Reference | atc facility : zzzz.artcc |
| State Reference | FO |
| Altitude | msl single value : 330 |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzzz.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B747-C/F |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Route In Use | enroute : pacific |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 180 flight time total : 21000 flight time type : 1200 |
| ASRS Report | 805813 |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude |
| Independent Detector | aircraft equipment : tcas other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem flight crew : returned to assigned altitude |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
Received a descent TCAS warning. Responded immediately with a descent. Target on the TCAS showed our altitude at 12 O'clock position and right on top of the airplane. Target symbol was red. We complied with the TCAS prompt for about 1000 ft when the TCAS ordered a climb. We advised ATC that we were complying with a TCAS warning. It was then we noticed that the conflicting traffic symbol showed our altitude as we ascended staying constantly with us. Visually we did not see any traffic at our 12 O'clock position. We queried ATC if they had any traffic around us and they replied in the negative. We quit following the TCAS advice and returned to our assigned altitude of FL330. After contacting our maintenance and recycling the TCAS circuit breaker we received another false TCAS warning with similar descent and climb commands. We ignored the advice and again contacted our maintenance. We were instructed to pull the TCAS circuit breaker and render the system inoperative. Our dispatch advised ATC that we were preceding to ZZZ with the system deactivated.
Original NASA ASRS Text
Title: A B747 RESPONDED TO A FALSE TCAS WARNING BY FIRST DSNDING THEN CLBING. TCAS CIRCUIT BREAKER WAS PULLED TO STOP WARNING WITH NO TFC IN THE AREA.
Narrative: RECEIVED A DSCNT TCAS WARNING. RESPONDED IMMEDIATELY WITH A DSCNT. TARGET ON THE TCAS SHOWED OUR ALT AT 12 O'CLOCK POS AND RIGHT ON TOP OF THE AIRPLANE. TARGET SYMBOL WAS RED. WE COMPLIED WITH THE TCAS PROMPT FOR ABOUT 1000 FT WHEN THE TCAS ORDERED A CLB. WE ADVISED ATC THAT WE WERE COMPLYING WITH A TCAS WARNING. IT WAS THEN WE NOTICED THAT THE CONFLICTING TFC SYMBOL SHOWED OUR ALT AS WE ASCENDED STAYING CONSTANTLY WITH US. VISUALLY WE DID NOT SEE ANY TFC AT OUR 12 O'CLOCK POS. WE QUERIED ATC IF THEY HAD ANY TFC AROUND US AND THEY REPLIED IN THE NEGATIVE. WE QUIT FOLLOWING THE TCAS ADVICE AND RETURNED TO OUR ASSIGNED ALT OF FL330. AFTER CONTACTING OUR MAINT AND RECYCLING THE TCAS CIRCUIT BREAKER WE RECEIVED ANOTHER FALSE TCAS WARNING WITH SIMILAR DSCNT AND CLB COMMANDS. WE IGNORED THE ADVICE AND AGAIN CONTACTED OUR MAINT. WE WERE INSTRUCTED TO PULL THE TCAS CIRCUIT BREAKER AND RENDER THE SYS INOP. OUR DISPATCH ADVISED ATC THAT WE WERE PRECEDING TO ZZZ WITH THE SYS DEACTIVATED.
Data retrieved from NASA's ASRS site as of May 2009 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.