Narrative:

Approaching bos from the south for an ILS DME 33L. We were on a 060 degree heading at 5000 ft. Clearance was issued to us to turn left to 350 degree, descend and maintain 4000 ft, slow to 170 KTS. I acknowledged the clearance and read it back to him. He then issued air carrier Z traffic at 2 O'clock 3 mi at 3000 ft. I responded traffic in sight to which there was no response from the controller. He (ATC) then started issuing clrncs to other traffic. We continued on heading as assigned and watched air carrier Z pass below and just to our left. We then passed through the localizer on previously assigned heading (although we did not state it verbally, we both assumed that the controller was having us fly through the localizer for additional spacing on air carrier Z which we also assumed that we were following). Approximately 45 seconds after flying through the localizer of 350 degree heading ATC asked us if we were intercepting the localizer. I replied 'no sir'. He then issued an immediate left turn to some heading to which I replied 'ok left turn say again the heading'. To which he replied 'just turn left immediately -- immediately, it does not matter what heading just turn left and commuter Y turn left immediately to (some heading).' at this point, in a 30 degree left bank, I saw commuter Y also in a tight left turn. Relative to us he was at 12:30 O'clock and same altitude less than 1 mi. Controller then said to us that 'last clearance issued had been to intercept the localizer'. I stated, 'no sir, it was not'. He then issued a '300 degree heading to reintercept the localizer cleared for the approach'. Approach and landing from that point were uneventful. Contributing factors: 1) very high ATC workload. Controller had to break a widebody transport off of the approach behind us because 'there are 9 aircraft on the localizer and in just don't have room for you'. 2) possibly the controller had intended for us to either a) follow air carrier Z on the approach and thought he had issued the clearance for us to intercept or B) issued the clearance to us and it was 'stepped on' by another transmission, or C) intended on a late turn on (or fly-through to reintercept localizer) for spacing on Z traffic and forgot about us.

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Original NASA ASRS Text

Title: LTSS BTWN ACR AND COMMUTER WHILE ON VECTORS TO ILS APCH. OPERROR.

Narrative: APCHING BOS FROM THE S FOR AN ILS DME 33L. WE WERE ON A 060 DEG HDG AT 5000 FT. CLRNC WAS ISSUED TO US TO TURN L TO 350 DEG, DSND AND MAINTAIN 4000 FT, SLOW TO 170 KTS. I ACKNOWLEDGED THE CLRNC AND READ IT BACK TO HIM. HE THEN ISSUED ACR Z TFC AT 2 O'CLOCK 3 MI AT 3000 FT. I RESPONDED TFC IN SIGHT TO WHICH THERE WAS NO RESPONSE FROM THE CTLR. HE (ATC) THEN STARTED ISSUING CLRNCS TO OTHER TFC. WE CONTINUED ON HDG AS ASSIGNED AND WATCHED ACR Z PASS BELOW AND JUST TO OUR L. WE THEN PASSED THROUGH THE LOC ON PREVIOUSLY ASSIGNED HDG (ALTHOUGH WE DID NOT STATE IT VERBALLY, WE BOTH ASSUMED THAT THE CTLR WAS HAVING US FLY THROUGH THE LOC FOR ADDITIONAL SPACING ON ACR Z WHICH WE ALSO ASSUMED THAT WE WERE FOLLOWING). APPROX 45 SECONDS AFTER FLYING THROUGH THE LOC OF 350 DEG HDG ATC ASKED US IF WE WERE INTERCEPTING THE LOC. I REPLIED 'NO SIR'. HE THEN ISSUED AN IMMEDIATE L TURN TO SOME HDG TO WHICH I REPLIED 'OK L TURN SAY AGAIN THE HDG'. TO WHICH HE REPLIED 'JUST TURN L IMMEDIATELY -- IMMEDIATELY, IT DOES NOT MATTER WHAT HDG JUST TURN L AND COMMUTER Y TURN L IMMEDIATELY TO (SOME HDG).' AT THIS POINT, IN A 30 DEG L BANK, I SAW COMMUTER Y ALSO IN A TIGHT L TURN. RELATIVE TO US HE WAS AT 12:30 O'CLOCK AND SAME ALT LESS THAN 1 MI. CTLR THEN SAID TO US THAT 'LAST CLRNC ISSUED HAD BEEN TO INTERCEPT THE LOC'. I STATED, 'NO SIR, IT WAS NOT'. HE THEN ISSUED A '300 DEG HDG TO REINTERCEPT THE LOC CLRED FOR THE APCH'. APCH AND LNDG FROM THAT POINT WERE UNEVENTFUL. CONTRIBUTING FACTORS: 1) VERY HIGH ATC WORKLOAD. CTLR HAD TO BREAK A WDB OFF OF THE APCH BEHIND US BECAUSE 'THERE ARE 9 ACFT ON THE LOC AND IN JUST DON'T HAVE ROOM FOR YOU'. 2) POSSIBLY THE CTLR HAD INTENDED FOR US TO EITHER A) FOLLOW ACR Z ON THE APCH AND THOUGHT HE HAD ISSUED THE CLRNC FOR US TO INTERCEPT OR B) ISSUED THE CLRNC TO US AND IT WAS 'STEPPED ON' BY ANOTHER XMISSION, OR C) INTENDED ON A LATE TURN ON (OR FLY-THROUGH TO REINTERCEPT LOC) FOR SPACING ON Z TFC AND FORGOT ABOUT US.

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