On an lda approach, aircraft drifted off course toward parallel traffic.

Attributes
ACN	490100
Time
Date	200010
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : stl.airport
State Reference	MO
Altitude	msl bound lower : 1200 msl bound upper : 2100
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : stl.tower
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	ils other localizer
Flight Phase	descent : approach
Route In Use	approach : instrument non precision
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : stl.tower
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 30r
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	490100
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
ASRS Report	490099
Events
Anomaly	non adherence : clearance non adherence : company policies non adherence : published procedure other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : returned to intended or assigned course
Supplementary
Problem Areas	Flight Crew Human Performance Weather
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATC facility: stl tower. Location: stl lda DME runway 30L. While on localizer runway 30L at stl, we were directed to maintain visual contact with another S80 on ILS final on runway 30R. We reported aircraft in sight and acknowledged this clearance with tower. At some point inside the FAF while monitoring the aircraft on final to runway 30R, we drifted off the lda DME runway 30L final and were directed by tower to turn left to rejoin the runway 30L final. We corrected immediately and continued approach and landing without further comment by stl tower. WX was 4 SM visibility which limited acquiring the runway until near the map.

Original NASA ASRS Text

Title: ON AN LDA APCH, ACFT DRIFTED OFF COURSE TOWARD PARALLEL TFC.

Narrative: ATC FACILITY: STL TWR. LOCATION: STL LDA DME RWY 30L. WHILE ON LOC RWY 30L AT STL, WE WERE DIRECTED TO MAINTAIN VISUAL CONTACT WITH ANOTHER S80 ON ILS FINAL ON RWY 30R. WE RPTED ACFT IN SIGHT AND ACKNOWLEDGED THIS CLRNC WITH TWR. AT SOME POINT INSIDE THE FAF WHILE MONITORING THE ACFT ON FINAL TO RWY 30R, WE DRIFTED OFF THE LDA DME RWY 30L FINAL AND WERE DIRECTED BY TWR TO TURN L TO REJOIN THE RWY 30L FINAL. WE CORRECTED IMMEDIATELY AND CONTINUED APCH AND LNDG WITHOUT FURTHER COMMENT BY STL TWR. WX WAS 4 SM VISIBILITY WHICH LIMITED ACQUIRING THE RWY UNTIL NEAR THE MAP.

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.