Narrative:

Large transport X was swbnd at FL350. Large transport Y was sebnd at FL370 and needed to be descend to land. Large transport Y was turned 20 degrees left to avoid large transport X and descend to FL330. Aircraft turned right instead of left, which resulted in loss of sep. No tape of conversation was available to determine where mistake was made. Callback conversation with reporter revealed the following: facility tapes were later available, and it was found that the mistake was made by the reporter. He meant to turn large transport Y left, but said right. At the time of turn, the aircraft were 20 mi apart and if the turn had been given correctly, no loss of sep would have occurred. Reporter was asked why he did not delay in descending large transport Y until he was sure there would be latitude sep, and his reply was that ahead of large transport Y there was traffic at his altitude that made an immediate descent necessary. Again, he knew that everything would work out ok if he gave large transport Y a left turn away from large transport X. His thinking on thing and saying another is what caused this system error.

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Original NASA ASRS Text

Title: ACR-LGT TURNED AND DESCENDED THROUGH THE ALT OF ANOTHER ACR-LGT RESULTING IN LESS THAN STANDARD SEPARATON.

Narrative: LGT X WAS SWBND AT FL350. LGT Y WAS SEBND AT FL370 AND NEEDED TO BE DSND TO LAND. LGT Y WAS TURNED 20 DEGS LEFT TO AVOID LGT X AND DSND TO FL330. ACFT TURNED RIGHT INSTEAD OF LEFT, WHICH RESULTED IN LOSS OF SEP. NO TAPE OF CONVERSATION WAS AVAILABLE TO DETERMINE WHERE MISTAKE WAS MADE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: FAC TAPES WERE LATER AVAILABLE, AND IT WAS FOUND THAT THE MISTAKE WAS MADE BY THE RPTR. HE MEANT TO TURN LGT Y LEFT, BUT SAID RIGHT. AT THE TIME OF TURN, THE ACFT WERE 20 MI APART AND IF THE TURN HAD BEEN GIVEN CORRECTLY, NO LOSS OF SEP WOULD HAVE OCCURRED. RPTR WAS ASKED WHY HE DID NOT DELAY IN DSNDING LGT Y UNTIL HE WAS SURE THERE WOULD BE LAT SEP, AND HIS REPLY WAS THAT AHEAD OF LGT Y THERE WAS TFC AT HIS ALT THAT MADE AN IMMEDIATE DSCNT NECESSARY. AGAIN, HE KNEW THAT EVERYTHING WOULD WORK OUT OK IF HE GAVE LGT Y A LEFT TURN AWAY FROM LGT X. HIS THINKING ON THING AND SAYING ANOTHER IS WHAT CAUSED THIS SYSTEM ERROR.

Data retrieved from NASA's ASRS site as of August 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.