A RADIO OPERATOR RELAYED A CLRNC FOR ZOA BUT FAILED TO OBTAIN A CORRECT READBACK CAUSING AN OPERROR.

Narrative

ACR #2 AND ACR #1 WERE PROCEEDING TO NARITA; JAPAN; VIA ATS RTE B586. BOTH ACFT WERE AT FL350. XFER ESTIMATES SHOWED THE REQUIRED 10 MINS LONGITUDINAL SEPARATION. THE ACFT POS RPTS FOR WAYPOINT PAYEE INDICATED THAT SEPARATION HAD REDUCED TO 9 MINS. IMMEDIATELY; THE ZOA CTLR ISSUED CLRNCS TO SFOXA FOR DELIVERY TO BOTH OF THE ACFT WHICH WOULD ESTABLISH ADEQUATE LONGITUDINAL SEPARATION AT THE NEXT WAYPOINT; OMLET. THE CLRNC FOR ACR #1 WAS: 'ATCC ACR #1 TO CROSS OMLET AT OR AFTER XA34; MAINTAIN MACH .85 OR LESS; ISSUE TIME CHK.' THE FLT WAS ORIGINALLY ESTIMATING OMLET AT XA32Z. THE RADIO OPERATOR DELIVERED THE CLRNC ACCURATELY; BUT DID NOT OBTAIN A PROPER READBACK. AS A RESULT; THE 2 FLTS PROGRESSED OMLET WITH LESS THAN THE REQUIRED LONGITUDINAL SEPARATION AND WE WERE CHARGED WITH AN OPERROR. THE RADIO OPERATOR APPARENTLY HAD A QUESTION ABOUT THE READBACK BECAUSE HE REPEATED THE AT OR AFTER TIME AND MACH SPD SEVERAL TIMES TO ENSURE THAT THE FLC GOT BOTH OF THESE ELEMENTS OF THE CLRNC RIGHT. THE PROB WAS THAT THE MOST CRITICAL PART OF THE CLRNC; TO PROGRESS OMLET 2 MINS SLOWER THAN ESTIMATED; WAS MISSED BY THE FLC. THE FLT PROGRESSED OMLET AT THE ORIGINALLY ESTIMATED TIME OF XA32Z. IN REVIEWING THE RECORDING OF THE EVENT; ALTHOUGH A LOW TONE CAN BE HEARD AT THE BEGINNING OF THE READBACK; THERE CLRLY WAS NOT ENOUGH TIME FOR THE FLC TO HAVE SAID THE WORDS 'CROSS OMLET AT OR AFTER' AT THE BEGINNING OF THE READBACK. THIS WAS A READBACK/HEARBACK ERROR.