Flight crew drifts from assigned ILS toward parallel runway ILS.

Attributes
ACN	304630
Time
Date	199505
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : den
State Reference	CO
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : den
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 175 flight time total : 14000 flight time type : 5000
ASRS Report	304630
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 35 flight time total : 14307 flight time type : 9374
ASRS Report	304648
Events
Anomaly	conflict : airborne less severe inflight encounter : weather non adherence : clearance other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
ATC Facility	other physical facility procedure or policy : unspecified
Airport	other physical facility

Narrative:

After intercepting the runway 35L localizer and receiving clearance for the ILS approach, we deviated 1 1/2 dots east of centerline due to strong westerly winds (surface winds were reported to be 0506). We were approximately 18 NM south of the airport. We were correcting back to centerline when ATC inquired if we had intercepted the localizer. We responded that we were correcting course and that we had the traffic ahead on the runway 35R localizer in sight. That traffic was 2 mi ahead and 2000 plus ft below us. ATC cleared us to maintain 10000 ft. When we were back on centerline ATC again cleared us for the runway 35L ILS approach. While we never advised of the other traffic, we did have it in sight visually and on TCASII. Other pilots seem to be having this same problem. Since the prevailing winds aloft at den are frequently out of the west, perhaps ATC should stagger their traffic more than 2 mi.

Original NASA ASRS Text

Title: FLC DRIFTS FROM ASSIGNED ILS TOWARD PARALLEL RWY ILS.

Narrative: AFTER INTERCEPTING THE RWY 35L LOC AND RECEIVING CLRNC FOR THE ILS APCH, WE DEVIATED 1 1/2 DOTS E OF CTRLINE DUE TO STRONG WESTERLY WINDS (SURFACE WINDS WERE RPTED TO BE 0506). WE WERE APPROX 18 NM S OF THE ARPT. WE WERE CORRECTING BACK TO CTRLINE WHEN ATC INQUIRED IF WE HAD INTERCEPTED THE LOC. WE RESPONDED THAT WE WERE CORRECTING COURSE AND THAT WE HAD THE TFC AHEAD ON THE RWY 35R LOC IN SIGHT. THAT TFC WAS 2 MI AHEAD AND 2000 PLUS FT BELOW US. ATC CLRED US TO MAINTAIN 10000 FT. WHEN WE WERE BACK ON CTRLINE ATC AGAIN CLRED US FOR THE RWY 35L ILS APCH. WHILE WE NEVER ADVISED OF THE OTHER TFC, WE DID HAVE IT IN SIGHT VISUALLY AND ON TCASII. OTHER PLTS SEEM TO BE HAVING THIS SAME PROB. SINCE THE PREVAILING WINDS ALOFT AT DEN ARE FREQUENTLY OUT OF THE W, PERHAPS ATC SHOULD STAGGER THEIR TFC MORE THAN 2 MI.

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.