Narrative:

Prior to G/south intercept, RVR runway 21R reported 4400' T/D, 2800' midpoint, 1800' rollout. After G/south was intercepted, RVR runway 21R reported 2800' T/D, 1800' midpoint, 800' rollout. The approach was flown with the autoplt coupled, monitored by the captain. At 200' above the ground, the runway was observed to the right of the nose of the aircraft. Approximately location was 100-150' left of runway 21R centerline, with localizer and G/south indications normal in the cockpit. Aircraft's position was west of the parallel taxiway, as I remember seeing aircraft on the taxiway through the left portion of my windshield. Missed approach was executed. Tower reported RVR had been going up and down with departures from runway 21R. After we missed, dtw was closed to arrs. Diverted to alternate. After landing at ind, a company pilot who was riding in the back of my aircraft told me that he had heard of similar situations at dtw when aircraft had been stacked for departure, and it would be good to submit a NASA report. Callback conversation with reporter revealed the following: after incident reporter made report to company safety committee and also had some contact with ATC facility management at dtw tower. ATC did not seem very concerned and seemed to believe that aircraft lined up on parallel taxiway at northeast end would not interfere with ILS localizer. ATC asked reporter if there were any aircraft on parallel near southwest end of runway, but he could not answer that question as he had not had any visibility contact with that end of the runway, and was back up into clouds before that point. Reporter says that there were a lot of aircraft lined up for takeoff and several were widebody transport and heavy type aircraft. Reporter has talked with other company pilots who have experienced or heard about similar problem on runway 21R ILS approach at dtw.

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Original NASA ASRS Text

Title: ACR ON ILS RWY 21R APCH AT DTW STATES POSSIBLE ILS LOCALIZER COURSE DISPLACEMENT. MADE MISSED APCH.

Narrative: PRIOR TO G/S INTERCEPT, RVR RWY 21R RPTED 4400' T/D, 2800' MIDPOINT, 1800' ROLLOUT. AFTER G/S WAS INTERCEPTED, RVR RWY 21R RPTED 2800' T/D, 1800' MIDPOINT, 800' ROLLOUT. THE APCH WAS FLOWN WITH THE AUTOPLT COUPLED, MONITORED BY THE CAPT. AT 200' ABOVE THE GND, THE RWY WAS OBSERVED TO THE RIGHT OF THE NOSE OF THE ACFT. APPROX LOCATION WAS 100-150' LEFT OF RWY 21R CENTERLINE, WITH LOC AND G/S INDICATIONS NORMAL IN THE COCKPIT. ACFT'S POS WAS W OF THE PARALLEL TXWY, AS I REMEMBER SEEING ACFT ON THE TXWY THROUGH THE LEFT PORTION OF MY WINDSHIELD. MISSED APCH WAS EXECUTED. TWR RPTED RVR HAD BEEN GOING UP AND DOWN WITH DEPS FROM RWY 21R. AFTER WE MISSED, DTW WAS CLOSED TO ARRS. DIVERTED TO ALTERNATE. AFTER LNDG AT IND, A COMPANY PLT WHO WAS RIDING IN THE BACK OF MY ACFT TOLD ME THAT HE HAD HEARD OF SIMILAR SITUATIONS AT DTW WHEN ACFT HAD BEEN STACKED FOR DEP, AND IT WOULD BE GOOD TO SUBMIT A NASA RPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: AFTER INCIDENT RPTR MADE RPT TO COMPANY SAFETY COMMITTEE AND ALSO HAD SOME CONTACT WITH ATC FAC MGMNT AT DTW TWR. ATC DID NOT SEEM VERY CONCERNED AND SEEMED TO BELIEVE THAT ACFT LINED UP ON PARALLEL TXWY AT NE END WOULD NOT INTERFERE WITH ILS LOC. ATC ASKED RPTR IF THERE WERE ANY ACFT ON PARALLEL NEAR SW END OF RWY, BUT HE COULD NOT ANSWER THAT QUESTION AS HE HAD NOT HAD ANY VIS CONTACT WITH THAT END OF THE RWY, AND WAS BACK UP INTO CLOUDS BEFORE THAT POINT. RPTR SAYS THAT THERE WERE A LOT OF ACFT LINED UP FOR TKOF AND SEVERAL WERE WDB AND HVY TYPE ACFT. RPTR HAS TALKED WITH OTHER COMPANY PLTS WHO HAVE EXPERIENCED OR HEARD ABOUT SIMILAR PROB ON RWY 21R ILS APCH AT DTW.

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.