Narrative:

Was working iah final approach for runway 8 and 9. Instructed air carrier X to fly heading 060 degrees. As I was finishing the approach clearance to ILS 9 I noticed air carrier X going across localizer. I asked him to verify and he said he wasn't told to join the localizer. I said he was, and to turn left heading 360 degrees and maintain 3500'. He replied maintain 3500', and there were 3 in the cockpit that said I didn't tell him to join (I didn't). I said ok to end discussion, and planned to resequence him for for another approach. The pilot made a right turn, but was at 3500', so everything was ok. I went to other immediate priorities and continued working final approach. As the pilot passed through approximately 200 degrees he asked what heading to roll out on. I replied, 'fly heading 2-3-zero. The pilot continued a right turn northbound. As I noticed this I said, 'air carrier X, since you're turning northbound, turn right heading 230 and make it a tight turn.' air carrier Y was now on a 10 mi final descending through 3900'. I told X to descend immediately to 2000'. I then went to Y and instructed him to maintain 3500'. (However, I called him by wrong company call sign. Both aircraft were visible to each other. However, both took evasive action. Distances were 1/2 mi and 200'. Controllers need to use standard phraseology at all times and pilots need to read back all turns and altitude changes for clarification. Had pilot flown either a 360 or 230 degree heading, problem would not have occurred. He evidently thought I said a right 360 degree turn and roll out on a 230 degree heading (a total turn of 540 degrees). Callback conversation with reporter revealed the following: reporter gave yrs in ATC. Says facility classified incident as pilot deviation. NTSB conducted extensive review and to reporter's knowledge has not changed incident classification. When air carrier X went through localizer the controller phraseology was, 'turn left to 3-6-zero.' thinks flight crew only heard the '3-6-zero' and started 360 degree turn to the right. Traffic vol at time was heavy. Replay of tapes show that controller did not tell air carrier X to intercept ILS localizer at beginning of incident. Not sure of closest proximity between X and Y, but thinks it was about .5 mi and 300-400' vertical. Supplemental information from acn 105495: we heard ATC and preceding aircraft discussing the fact that the aircraft had gone through the localizer west/O intercepting. We had not been instructed to intercept the localizer and maintained the assigned heading through the localizer. The controller then said, 'air carrier X, cleared for ILS runway 9 approach--oh, it looks like you went through the localizer too.' the first officer replied, 'we were not cleared to intercept.' ATC: 'oh yes you were.' the first officer, acm (co-captain) and I all agreed that no intercept clearance had been given. ATC then instructed us to do a right 360 degree turn and to descend to 3500'. At 3500' and in a right turn we asked ATC for a rollout heading. After our second or third inquiry, ATC said, 'roll out 230 degrees.' by that time, we were passing approximately 300 degrees, so I reversed my turn to go back left to 230 degrees. ATC then said something to the effect, 'make your turn to the right and maintain 3500'.' I then reversed the turn back to the right and shortly after that reversal ATC said, 'air carrier X, descend immediately to 2000'.' we started down and he said again, with a great deal of urgency in his voice, 'air carrier X, descend immediately to 2000'--air carrier Y climb immediately to 3500'.' we then, in a break in the clouds, saw air carrier Y at approximately 12 O'clock position. We pushed over and banked slightly to the left passing 200-300' below and behind air carrier Y. Our altitude at the time we saw him was approximately 3000' MSL. We estimated our total sep to be approximately 1/8 mi. The evasive maneuver was not violent nor did it cause any injuries in the cabin.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION AND VERY CLOSE PROX BETWEEN 2 ACR. PLT DEVIATION OR OPERATIONAL ERROR.

Narrative: WAS WORKING IAH FINAL APCH FOR RWY 8 AND 9. INSTRUCTED ACR X TO FLY HDG 060 DEGS. AS I WAS FINISHING THE APCH CLRNC TO ILS 9 I NOTICED ACR X GOING ACROSS LOC. I ASKED HIM TO VERIFY AND HE SAID HE WASN'T TOLD TO JOIN THE LOC. I SAID HE WAS, AND TO TURN LEFT HDG 360 DEGS AND MAINTAIN 3500'. HE REPLIED MAINTAIN 3500', AND THERE WERE 3 IN THE COCKPIT THAT SAID I DIDN'T TELL HIM TO JOIN (I DIDN'T). I SAID OK TO END DISCUSSION, AND PLANNED TO RESEQUENCE HIM FOR FOR ANOTHER APCH. THE PLT MADE A RIGHT TURN, BUT WAS AT 3500', SO EVERYTHING WAS OK. I WENT TO OTHER IMMEDIATE PRIORITIES AND CONTINUED WORKING FINAL APCH. AS THE PLT PASSED THROUGH APPROX 200 DEGS HE ASKED WHAT HDG TO ROLL OUT ON. I REPLIED, 'FLY HDG 2-3-ZERO. THE PLT CONTINUED A RIGHT TURN NBND. AS I NOTICED THIS I SAID, 'ACR X, SINCE YOU'RE TURNING NBND, TURN RIGHT HDG 230 AND MAKE IT A TIGHT TURN.' ACR Y WAS NOW ON A 10 MI FINAL DSNDING THROUGH 3900'. I TOLD X TO DSND IMMEDIATELY TO 2000'. I THEN WENT TO Y AND INSTRUCTED HIM TO MAINTAIN 3500'. (HOWEVER, I CALLED HIM BY WRONG COMPANY CALL SIGN. BOTH ACFT WERE VISIBLE TO EACH OTHER. HOWEVER, BOTH TOOK EVASIVE ACTION. DISTANCES WERE 1/2 MI AND 200'. CTLRS NEED TO USE STANDARD PHRASEOLOGY AT ALL TIMES AND PLTS NEED TO READ BACK ALL TURNS AND ALT CHANGES FOR CLARIFICATION. HAD PLT FLOWN EITHER A 360 OR 230 DEG HDG, PROB WOULD NOT HAVE OCCURRED. HE EVIDENTLY THOUGHT I SAID A RIGHT 360 DEG TURN AND ROLL OUT ON A 230 DEG HDG (A TOTAL TURN OF 540 DEGS). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR GAVE YRS IN ATC. SAYS FAC CLASSIFIED INCIDENT AS PLTDEV. NTSB CONDUCTED EXTENSIVE REVIEW AND TO RPTR'S KNOWLEDGE HAS NOT CHANGED INCIDENT CLASSIFICATION. WHEN ACR X WENT THROUGH LOC THE CTLR PHRASEOLOGY WAS, 'TURN LEFT TO 3-6-ZERO.' THINKS FLT CREW ONLY HEARD THE '3-6-ZERO' AND STARTED 360 DEG TURN TO THE RIGHT. TFC VOL AT TIME WAS HEAVY. REPLAY OF TAPES SHOW THAT CTLR DID NOT TELL ACR X TO INTERCEPT ILS LOC AT BEGINNING OF INCIDENT. NOT SURE OF CLOSEST PROX BTWN X AND Y, BUT THINKS IT WAS ABOUT .5 MI AND 300-400' VERT. SUPPLEMENTAL INFO FROM ACN 105495: WE HEARD ATC AND PRECEDING ACFT DISCUSSING THE FACT THAT THE ACFT HAD GONE THROUGH THE LOC W/O INTERCEPTING. WE HAD NOT BEEN INSTRUCTED TO INTERCEPT THE LOC AND MAINTAINED THE ASSIGNED HDG THROUGH THE LOC. THE CTLR THEN SAID, 'ACR X, CLRED FOR ILS RWY 9 APCH--OH, IT LOOKS LIKE YOU WENT THROUGH THE LOC TOO.' THE F/O REPLIED, 'WE WERE NOT CLRED TO INTERCEPT.' ATC: 'OH YES YOU WERE.' THE F/O, ACM (CO-CAPT) AND I ALL AGREED THAT NO INTERCEPT CLRNC HAD BEEN GIVEN. ATC THEN INSTRUCTED US TO DO A RIGHT 360 DEG TURN AND TO DSND TO 3500'. AT 3500' AND IN A RIGHT TURN WE ASKED ATC FOR A ROLLOUT HDG. AFTER OUR SECOND OR THIRD INQUIRY, ATC SAID, 'ROLL OUT 230 DEGS.' BY THAT TIME, WE WERE PASSING APPROX 300 DEGS, SO I REVERSED MY TURN TO GO BACK LEFT TO 230 DEGS. ATC THEN SAID SOMETHING TO THE EFFECT, 'MAKE YOUR TURN TO THE RIGHT AND MAINTAIN 3500'.' I THEN REVERSED THE TURN BACK TO THE RIGHT AND SHORTLY AFTER THAT REVERSAL ATC SAID, 'ACR X, DSND IMMEDIATELY TO 2000'.' WE STARTED DOWN AND HE SAID AGAIN, WITH A GREAT DEAL OF URGENCY IN HIS VOICE, 'ACR X, DSND IMMEDIATELY TO 2000'--ACR Y CLB IMMEDIATELY TO 3500'.' WE THEN, IN A BREAK IN THE CLOUDS, SAW ACR Y AT APPROX 12 O'CLOCK POS. WE PUSHED OVER AND BANKED SLIGHTLY TO THE LEFT PASSING 200-300' BELOW AND BEHIND ACR Y. OUR ALT AT THE TIME WE SAW HIM WAS APPROX 3000' MSL. WE ESTIMATED OUR TOTAL SEP TO BE APPROX 1/8 MI. THE EVASIVE MANEUVER WAS NOT VIOLENT NOR DID IT CAUSE ANY INJURIES IN THE CABIN.

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.