Narrative:

Flight from bdl (windsor locks, ct) to dtw metropolitan. First officer was flying. Upon initial contact with detroit approach control we were advised to expect ILS to runway 21R. After several vectors we were given a heading of 230 degrees, maintain 5000 ft and intercept the localizer for 21R. We acknowledged this information for 21R. Prior to this time several aircraft approaching dtw from our direction were switched to runway 21L. Approach control then told us to maintain 4000 ft until crossing robbi, cleared for approach to 21R. Contact tower on 118.4. I acknowledged, cleared for approach to runway 21R. At this time I realized that both the crossing fix and the tower frequency were for 21L. Approach frequency was very busy so I immediately went to the tower frequency and checked in for 21R. He then cleared us to land on 21L. We were still IMC at 5000 ft on an intercept heading. I told tower that approach had cleared us for 21R. Tower said negative, cleared 21L, parallel traffic on 21R. We made an immediate left turn to 200 degrees and told tower the same. He informed us that we were still east of the 21L loca. By this time we had switched frequencys to 21L and verified the same. We continued on the 230 degree heading, and conducted the approach and landing without further incident. I do not know exactly what happened at approach control, but all 3 cockpit crewmembers understood 21R on all transmissions. I acknowledged 21R on all replies. It is possible that they gave us a runway change and that it was blocked by another aircraft. Approach was quite busy at this time. If this was the case, we never acknowledged a change, and they never pursued it. We were also never challenged when I readback 21R. We were fortunate to have straightened this out prior to reaching the localizer. It seems that we are back to conditions prior to the 1982 controller strike. Too many aircraft per controller, leading to too much trying to be said to too many aircraft in too short a period of time. Also, when the airwaves get this busy, pilots tend to shortcut replies, and it would seem that this is expected by the controllers. It also leads to an unacceptable level of blocked transmissions, which further frustrates the system. As for myself in this situation, I could have been a little more prepared for this kind of foulup when I heard other aircraft being switched to the left runway, although I really was half expecting it.

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Original NASA ASRS Text

Title: APCH CTLR CLRED LGT FLT APCH 21R AT DTW BUT GAVE FREQ FOR 21L. UPON SWITCHING TO TWR, TWR CTLR CONFIRMED 21L FOR APCH AND LNDG.

Narrative: FLT FROM BDL (WINDSOR LOCKS, CT) TO DTW METROPOLITAN. FO WAS FLYING. UPON INITIAL CONTACT WITH DETROIT APCH CTL WE WERE ADVISED TO EXPECT ILS TO RWY 21R. AFTER SEVERAL VECTORS WE WERE GIVEN A HDG OF 230 DEGS, MAINTAIN 5000 FT AND INTERCEPT THE LOC FOR 21R. WE ACKNOWLEDGED THIS INFO FOR 21R. PRIOR TO THIS TIME SEVERAL ACFT APCHING DTW FROM OUR DIRECTION WERE SWITCHED TO RWY 21L. APCH CTL THEN TOLD US TO MAINTAIN 4000 FT UNTIL XING ROBBI, CLRED FOR APCH TO 21R. CONTACT TWR ON 118.4. I ACKNOWLEDGED, CLRED FOR APCH TO RWY 21R. AT THIS TIME I REALIZED THAT BOTH THE XING FIX AND THE TWR FREQ WERE FOR 21L. APCH FREQ WAS VERY BUSY SO I IMMEDIATELY WENT TO THE TWR FREQ AND CHKED IN FOR 21R. HE THEN CLRED US TO LAND ON 21L. WE WERE STILL IMC AT 5000 FT ON AN INTERCEPT HDG. I TOLD TWR THAT APCH HAD CLRED US FOR 21R. TWR SAID NEGATIVE, CLRED 21L, PARALLEL TFC ON 21R. WE MADE AN IMMEDIATE L TURN TO 200 DEGS AND TOLD TWR THE SAME. HE INFORMED US THAT WE WERE STILL E OF THE 21L LOCA. BY THIS TIME WE HAD SWITCHED FREQS TO 21L AND VERIFIED THE SAME. WE CONTINUED ON THE 230 DEG HDG, AND CONDUCTED THE APCH AND LNDG WITHOUT FURTHER INCIDENT. I DO NOT KNOW EXACTLY WHAT HAPPENED AT APCH CTL, BUT ALL 3 COCKPIT CREWMEMBERS UNDERSTOOD 21R ON ALL TRANSMISSIONS. I ACKNOWLEDGED 21R ON ALL REPLIES. IT IS POSSIBLE THAT THEY GAVE US A RWY CHANGE AND THAT IT WAS BLOCKED BY ANOTHER ACFT. APCH WAS QUITE BUSY AT THIS TIME. IF THIS WAS THE CASE, WE NEVER ACKNOWLEDGED A CHANGE, AND THEY NEVER PURSUED IT. WE WERE ALSO NEVER CHALLENGED WHEN I READBACK 21R. WE WERE FORTUNATE TO HAVE STRAIGHTENED THIS OUT PRIOR TO REACHING THE LOC. IT SEEMS THAT WE ARE BACK TO CONDITIONS PRIOR TO THE 1982 CTLR STRIKE. TOO MANY ACFT PER CTLR, LEADING TO TOO MUCH TRYING TO BE SAID TO TOO MANY ACFT IN TOO SHORT A PERIOD OF TIME. ALSO, WHEN THE AIRWAVES GET THIS BUSY, PLTS TEND TO SHORTCUT REPLIES, AND IT WOULD SEEM THAT THIS IS EXPECTED BY THE CTLRS. IT ALSO LEADS TO AN UNACCEPTABLE LEVEL OF BLOCKED TRANSMISSIONS, WHICH FURTHER FRUSTRATES THE SYS. AS FOR MYSELF IN THIS SITUATION, I COULD HAVE BEEN A LITTLE MORE PREPARED FOR THIS KIND OF FOULUP WHEN I HEARD OTHER ACFT BEING SWITCHED TO THE L RWY, ALTHOUGH I REALLY WAS HALF EXPECTING IT.

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.