B757-200 FLT CREW REPORTS TCAS RA AT FL370 WITH FALCON JET DESCENDING OUT OF FL380. B757 FLT CREW COMPLIES WITH RA AND DESCENDS AS FALCON JET CONTINUES ITS DESCENT.

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WE WERE IN CRUISE FLT AT FL370 ABOUT 85 MI NW OF CVG. I NOTICED A TARGET AT FL380 CONVERGING AT ABOUT OUR 2 O'CLOCK POS. I SAW THAT THE ACFT'S ALT WAS AT FL379 AND THEN FL378; MOST LIKELY IN A DSCNT; CONVERGING ON US. AT THE SAME MOMENT; WE THEN HEARD THE CTLR ASK THAT ACFT; 'WHAT ARE YOU DOING?' AND THEN WE GOT A TA. I DISCONNECTED THE AUTOPLT AND A/T AND THEN WE GOT A 'DSND' RA; WHICH I FOLLOWED. I HEARD THE CTLR TELL THE OTHER ACFT TO LEVEL OFF IMMEDIATELY. THE CTLR THEN TOLD US TO 'TURN L' AND THEN HIS XMISSION WAS STEPPED ON FOR WHATEVER HE SAID AFTER THAT TURN INSTRUCTION. BUT I COMPLIED AND STARTED A L TURN. AFTER A WHILE RA SAID 'REDUCE DSCNT' AND I COMPLIED. A FEW MOMENTS LATER; WE THEN GOT A CONTINUED RA AND THE TCAS TOLD US TO 'INCREASE DSCNT.' THE OTHER ACFT WAS STILL COMING DOWN; SEEMINGLY OBLIVIOUS WE WERE BELOW HIM. AS WE REACHED FL360 THE RA REDUCED OUR DSCNT AND THEN TERMINATED THE RA (CLR OF CONFLICT). WE REMAINED AT FL360 AND INFORMED THE CTLR OF OUR ALT AND HDG WHICH HE TOLD US TO MAINTAIN BOTH. TECHNICAL FACTORS: THE OTHER ACFT DID NOT SEEM TO KNOW THAT THEY WERE DSNDING DOWN UPON US. THIS LED ME TO BELIEVE THAT IT DID NOT HAVE A TCAS AND OUR POS AND ALT WAS UNKNOWN TO THEM. ALLOWING ACFT WITHOUT TCAS EQUIP IN THE HIGH ALT STRUCTURE AND RVSM ENVIRONMENT IS AN ERROR IN AIRSPACE ALLOCATION. THIS SHORTCOMING NEEDS TO BE CORRECTED AS THIS CONFLICT HAS SHOWN US. THE 1000 FT SEPARATION IS FINE BUT YOU MUST BE REQUIRED TO ALSO HAVE TCAS. THE CLOSURE RATES ARE TOO HIGH. WITHOUT TCAS ON OUR ACFT THIS NIGHT; THE OUTCOME WOULD HAVE BEEN A LOT DIFFERENT. HUMAN FACTORS: THIS TCAS CAME OUT OF NOWHERE ON A NICE QUIET EVENING AT CRUISE. IT WAS ABRUPT AND BECAME VERY SERIOUS IN A SHORT PERIOD OF TIME. THE TCAS SHOWED WE MAY HAVE COME AS CLOSE AS 400-600 FT BTWN ACFT IN THE MIDDLE OF A BIG SKY AT CRUISE. FROM MY POS AS CAPT AND PF; I COULD NEVER HAVE SEEN THIS ACFT VISUALLY FROM ITS APCH FROM 2 O'CLOCK POS HIGH AND I DON'T BELIEVE MY FO COULD HAVE SEEN IT EITHER. THIS WHOLE CONCEPT OF VISUAL 'SEE AND AVOID' IN THIS KIND OF ENVIRONMENT IS ARCANE AND OUTDATED. IT IS TIME WE REALIZED THE LIMITATIONS OF THE HUMAN SENSES AND TAKE CORRECTIVE ACTION. SUPPLEMENTAL INFO FROM ACN 761999: CRUISING FL370 85 NW CVG; A FALCON BEGAN DSCNT FROM FL380 JUST SE OF OUR POS; RESULTING IN RA CONFLICT WHICH WAS IMMEDIATELY; PROCEDURALLY EXECUTED BY THE CAPT; PF. ZID QUERIED THE FALCON; 'WHAT ARE YOU DOING?' AND THE FALCON REPLIED THAT HE WAS DSNDING TO CROSS SOME FIX AT FL310 PER ATC INSTRUCTIONS (DEST GRR). TCAS THEN COMMANDED 'REDUCE DSCNT;' WHICH WE DID; WHICH WITHIN SECONDS CHANGED TO 'INCREASE DSCNT' AS THE FALCON CONTINUED TO DSND JUST ABOVE US. ATC THEN INSTRUCTED A L TURN; WHICH WAS ACCOMPLISHED FOLLOWED BY 'CLR OF CONFLICT.' MY CONCERN IS THAT THE FALCON NEVER KNEW WE WERE BELOW HIM; AND CONTINUED THE DSCNT APPARENTLY WITHOUT TCAS GUIDANCE. THE CTLR DELAYED INFORMING HIM OF THE CONFLICT FOR WHATEVER REASON; AND THEN THERE WAS RADIO CONFUSION. I QUESTION THE PRACTICE OF ALLOWING NON-TCAS EQUIPPED ACFT TO CRUISE WITHIN 1000 FT PROX OF OTHER ACFT; DAY OR NIGHT!