Narrative:

WX was impacting the moorefield sector, aircraft were deviating south of J8 into the marlinton sector en route to hvq. An air carrier was followed by air carrier X 45 mi in trail. 20 mi west of air carrier X there was another air carrier, all were at FL310. Cga Y was at FL330, proceeding from fty-mol-hgr-har-zer (pottsville, PA). Cga Y route was slightly east of the opposite direction track of the other aircraft. Anticipating turning air carrier X wbound (behind the parallel air carrier) for in-trail spacing for ZID center, cga Y was descent to FL280 after passing the first air carrier. Air carrier X was then turned right heading 270 degree. The pilot refused the turn, saying that it would put him into an overhang. (The presence of an overhang was unknown to me, as the parallel air carrier was in the area.) I asked air carrier X to turn right as much as feasible and he said that he could make a slow right turn of about 10 degree. Cga Y was turned right 30 degree for traffic, pilot said transmission was garbled. I transmitted again, repeating the 30 degree turn to the right and told him no delay through FL290. Cga Y acknowledged this time. Air carrier X and cga Y passed with less than required separation (3.7 NM/1200'). If air carrier X could have taken the turn to 270 degree the 2 aircraft would have passed with 12-15 mi lateral separation. Also, if cga Y had received the first transmission, they would have passed with more than 5 mi lateral separation. (It was later computed that cga Y was only descending at 1000 FPM.) while not an excuse for the incident, I feel that tmu (formerly flow control) should have instituted WX routing rather than letting aircraft deviate on their own around this WX system. The area supervisor was told at the XA00 am briefing that the WX would dissipate in an hour or so. At XB30 local the tops were in excess of FL400. The incident occurred at XB55 local.

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Original NASA ASRS Text

Title: CGA DESCENDED THROUGH ALT OF AN ACR RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: WX WAS IMPACTING THE MOOREFIELD SECTOR, ACFT WERE DEVIATING S OF J8 INTO THE MARLINTON SECTOR ENRTE TO HVQ. AN ACR WAS FOLLOWED BY ACR X 45 MI IN TRAIL. 20 MI W OF ACR X THERE WAS ANOTHER ACR, ALL WERE AT FL310. CGA Y WAS AT FL330, PROCEEDING FROM FTY-MOL-HGR-HAR-ZER (POTTSVILLE, PA). CGA Y ROUTE WAS SLIGHTLY E OF THE OPPOSITE DIRECTION TRACK OF THE OTHER ACFT. ANTICIPATING TURNING ACR X WBOUND (BEHIND THE PARALLEL ACR) FOR IN-TRAIL SPACING FOR ZID CENTER, CGA Y WAS DSCNT TO FL280 AFTER PASSING THE FIRST ACR. ACR X WAS THEN TURNED RIGHT HDG 270 DEG. THE PLT REFUSED THE TURN, SAYING THAT IT WOULD PUT HIM INTO AN OVERHANG. (THE PRESENCE OF AN OVERHANG WAS UNKNOWN TO ME, AS THE PARALLEL ACR WAS IN THE AREA.) I ASKED ACR X TO TURN RIGHT AS MUCH AS FEASIBLE AND HE SAID THAT HE COULD MAKE A SLOW RIGHT TURN OF ABOUT 10 DEG. CGA Y WAS TURNED RIGHT 30 DEG FOR TFC, PLT SAID XMISSION WAS GARBLED. I TRANSMITTED AGAIN, REPEATING THE 30 DEG TURN TO THE RIGHT AND TOLD HIM NO DELAY THROUGH FL290. CGA Y ACKNOWLEDGED THIS TIME. ACR X AND CGA Y PASSED WITH LESS THAN REQUIRED SEPARATION (3.7 NM/1200'). IF ACR X COULD HAVE TAKEN THE TURN TO 270 DEG THE 2 ACFT WOULD HAVE PASSED WITH 12-15 MI LATERAL SEPARATION. ALSO, IF CGA Y HAD RECEIVED THE FIRST XMISSION, THEY WOULD HAVE PASSED WITH MORE THAN 5 MI LATERAL SEPARATION. (IT WAS LATER COMPUTED THAT CGA Y WAS ONLY DESCENDING AT 1000 FPM.) WHILE NOT AN EXCUSE FOR THE INCIDENT, I FEEL THAT TMU (FORMERLY FLOW CONTROL) SHOULD HAVE INSTITUTED WX ROUTING RATHER THAN LETTING ACFT DEVIATE ON THEIR OWN AROUND THIS WX SYSTEM. THE AREA SUPVR WAS TOLD AT THE XA00 AM BRIEFING THAT THE WX WOULD DISSIPATE IN AN HOUR OR SO. AT XB30 LOCAL THE TOPS WERE IN EXCESS OF FL400. THE INCIDENT OCCURRED AT XB55 LOCAL.

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.