B737 WITH ZJX AT FL370 EXPERIENCED TCAS RA WITH OPPOSITE DIRECTION TFC AS CTLR ERRED IN DSCNT CLRNC ISSUANCE; RA ACTION(S) SAVED SEPARATION.

Date: 2006-01 · Aircraft: B737-700 · Phase: cruise

Anomalies: conflict-airborne-conflict

Synopsis

B737 WITH ZJX AT FL370 EXPERIENCED TCAS RA WITH OPPOSITE DIRECTION TFC AS CTLR ERRED IN DSCNT CLRNC ISSUANCE; RA ACTION(S) SAVED SEPARATION.

Narrative

WHILE IN CRUISE AT FL370 ENRTE TO BWI; WE RECEIVED A TA FOLLOWED ALMOST IMMEDIATELY BY AN RA COMMANDING A DSCNT IN EXCESS OF 2000 FPM. I IMMEDIATELY DISENGAGED THE AUTOPLT AND FOLLOWED THE HUD RA GUIDANCE; XCHKING THE VSI; WHICH SHOWED THE 2000+ FPM DSCNT REQUIREMENT. MY FO NOTIFIED ZJX THAT WE WERE DSNDING DUE TO AN RA. WE HEARD ANOTHER COMPANY ACFT (FLT NUMBER UNKNOWN) THAT WAS PASSING OVER US OPPOSITE DIRECTION AT FL380 ALSO INDICATE THAT THEY HAD RECEIVED AN RA. AFTER DSNDING ABOUT 1000 FT; THE RA QUIT AND WE CLBED BACK TO FL370. MY FO MONITORED THE TCAS DISPLAY DURING THE EVENT AND SAID THE OTHER ACFT SHOWED +500 FT DIRECTLY OVER THE TOP OF US AT THE CLOSEST POINT. PRIOR TO THE RA; WE HAD BEEN IN LIGHT TO MODERATE CHOP AT FL370. WHILE WE WERE EXPERIENCING FAIRLY LARGE MACH EXCURSIONS (.74 - .81 MACH); I WAS MONITORING OUR ALT AND THE AUTOPLT APPEARED TO BE DOING A GOOD JOB OF MAINTAINING ALT (+/-40 FT). MY INITIAL IMPRESSION DURING THE EVENT WAS THAT THE ACFT FLYING OVER US AT FL380 HAD INADVERTENTLY DEVIATED FROM THEIR ALT DUE TO THE TURBULENT FLT CONDITIONS AND CAUSED THE RA. HOWEVER; WHEN WE QUERIED ZJX AFTER THE EVENT; THE CTLR INDICATED THAT THE OTHER FLT HAD BEEN CLRED TO DSND FROM FL380 TO FL320. I LATER SPOKE WITH A SUPVR AT ZJX TO TRY TO FIND OUT IF THIS WAS AN RVSM ISSUE OR CTLR ERROR. THE SUPVR ADVISED ME THAT SHE HAD ALREADY COMPLETED AN INVESTIGATION OF THE EVENT; AND THE EVENT WAS DUE TO CTLR ERROR (THERE WERE SIGNIFICANT RTE DEVS OCCURRING DUE TO WX IN THE AREA AND THE CTLR HAD APPARENTLY FORGOTTEN ABOUT US WHEN HE CLRED THE OTHER COMPANY ACFT TO DSND THROUGH OUR ALT; HE WAS PULLED FROM DUTY FOLLOWING THE EVENT). SHE INDICATED THAT THE QUICK RESPONSE TO THE RA BY BOTH ACFT HAD PREVENTED AN OPERROR. IF THERE WAS EVER A SITUATION THAT PROVED THE WORTH OF TCAS; THIS WAS IT. WITHOUT TRYING TO BE OVERLY DRAMATIC; BOTH MY FO AND I BELIEVE THAT; BUT FOR THAT RA; 2 COMPANY JETS PROBABLY WOULD HAVE COLLIDED AT FL370 THAT NIGHT.

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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.