Narrative:

We were on the jasen arrival into iad, inside of doccs intersection told to descend to 8000 ft. I saw TCASII traffic in front of us at 7000 ft. In the descent (near ldn, I think), told to turn right to a heading (I think it was 010 degrees) for descent. Then told to descend to 5000 ft and look for VFR traffic at 4500 ft. On TCASII, saw traffic at 4500 ft. As we passed traffic, told to continue descent to 4000 ft. Passing 5500 ft, 2 different aircraft tried to check in with potomac. Controller did not answer them, but told us to switch to a new frequency, then like he was talking to someone else said, 'join localizer.' we were heading about 110 dregs off from localizer course, so the captain asked the controller if he wanted us to join the runway 12 localizer. The controller came back and said, 'yes, turn to heading 090 degrees and join the runway 12 localizer, switch to XXXX.' by then, we were passing through the localizer and I went to 25 degree angle of bank to the right. We then got a TCASII 'traffic, traffic.' there was TCASII traffic north of the runway 12 localizer at about 4000 ft. I do not remember the captain checking in with the new controller because of everything happening at once. But the new controller said 'air carrier X, maintain 5000 ft. You were only cleared to 6000 ft, turn right to a heading of 150 degrees.' we were at 4700 ft and already in a sharp turn to the right. The captain told controller we were cleared to 4000 ft, but controller came back and said no, it was 6000 ft. The captain told controller 2 or 3 times, 'no, it was 4000 ft,' I think that if the first controller had given us an earlier turn to join the localizer, we never would have gotten close enough to the other aircraft to get the TCASII warning. Did the first controller give us a new heading to fly and maybe even a new altitude to stop descent at, but we did not hear it because of other aircraft checking in?

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Original NASA ASRS Text

Title: B767-4300 FLT CREW ASSIGNED HDG, ALT AND FREQ CHANGES ON APCH TO IAD, ONLY TO BE INFORMED AS BEING AT THE WRONG ALT BY PCT CTLR.

Narrative: WE WERE ON THE JASEN ARR INTO IAD, INSIDE OF DOCCS INTXN TOLD TO DSND TO 8000 FT. I SAW TCASII TFC IN FRONT OF US AT 7000 FT. IN THE DSCNT (NEAR LDN, I THINK), TOLD TO TURN R TO A HDG (I THINK IT WAS 010 DEGS) FOR DSCNT. THEN TOLD TO DSND TO 5000 FT AND LOOK FOR VFR TFC AT 4500 FT. ON TCASII, SAW TFC AT 4500 FT. AS WE PASSED TFC, TOLD TO CONTINUE DSCNT TO 4000 FT. PASSING 5500 FT, 2 DIFFERENT ACFT TRIED TO CHK IN WITH POTOMAC. CTLR DID NOT ANSWER THEM, BUT TOLD US TO SWITCH TO A NEW FREQ, THEN LIKE HE WAS TALKING TO SOMEONE ELSE SAID, 'JOIN LOC.' WE WERE HDG ABOUT 110 DREGS OFF FROM LOC COURSE, SO THE CAPT ASKED THE CTLR IF HE WANTED US TO JOIN THE RWY 12 LOC. THE CTLR CAME BACK AND SAID, 'YES, TURN TO HDG 090 DEGS AND JOIN THE RWY 12 LOC, SWITCH TO XXXX.' BY THEN, WE WERE PASSING THROUGH THE LOC AND I WENT TO 25 DEG ANGLE OF BANK TO THE R. WE THEN GOT A TCASII 'TFC, TFC.' THERE WAS TCASII TFC N OF THE RWY 12 LOC AT ABOUT 4000 FT. I DO NOT REMEMBER THE CAPT CHKING IN WITH THE NEW CTLR BECAUSE OF EVERYTHING HAPPENING AT ONCE. BUT THE NEW CTLR SAID 'ACR X, MAINTAIN 5000 FT. YOU WERE ONLY CLRED TO 6000 FT, TURN R TO A HDG OF 150 DEGS.' WE WERE AT 4700 FT AND ALREADY IN A SHARP TURN TO THE R. THE CAPT TOLD CTLR WE WERE CLRED TO 4000 FT, BUT CTLR CAME BACK AND SAID NO, IT WAS 6000 FT. THE CAPT TOLD CTLR 2 OR 3 TIMES, 'NO, IT WAS 4000 FT,' I THINK THAT IF THE FIRST CTLR HAD GIVEN US AN EARLIER TURN TO JOIN THE LOC, WE NEVER WOULD HAVE GOTTEN CLOSE ENOUGH TO THE OTHER ACFT TO GET THE TCASII WARNING. DID THE FIRST CTLR GIVE US A NEW HDG TO FLY AND MAYBE EVEN A NEW ALT TO STOP DSCNT AT, BUT WE DID NOT HEAR IT BECAUSE OF OTHER ACFT CHKING IN?

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.