EMB145 crew had track deviation in stl class B airspace.

Attributes
ACN	500058
Time
Date	200101
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : stl.airport
State Reference	MO
Altitude	msl single value : 3500
Environment
Flight Conditions	Mixed
Weather Elements	other
Aircraft 1
Controlling Facilities	tracon : t75.tracon
Operator	common carrier : air carrier
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer only : 12l other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : t75.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 12r other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 300 flight time total : 3400 flight time type : 300
ASRS Report	500058
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical inflight encounter other non adherence : clearance other anomaly other other spatial deviation
Independent Detector	atc equipment other atc equipment : radar other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert none taken : detected after the fact
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

While joining the runway 12L dca/DME localizer at stl, the autoplt improperly captured the localizer, flying about 1/4 - 1/2 DOT off course. This took us closer to the ILS runway 12R, where an MD80 was on a parallel approach. The first officer took over manually and rejoined the lda, simultaneously with 2 ATC prompts. We had the MD80 in sight visually, there was no conflict. The approach was continued to a normal landing and nothing further was mentioned. Upon landing, I talked with another captain that landed ahead of us, and he said the same thing happened. Taxiing out on the next turn, we heard yet another aircraft experience the same thing. Wind conditions were a strong tailwind on the intercept heading, shearing to a strong crosswind on the approach. I feel this caused some confusion in the autoplt corrections, as well as late turns from ATC. Future prevention would be to take corrective action sooner, perhaps manually.

Original NASA ASRS Text

Title: EMB145 CREW HAD TRACK DEV IN STL CLASS B AIRSPACE.

Narrative: WHILE JOINING THE RWY 12L DCA/DME LOC AT STL, THE AUTOPLT IMPROPERLY CAPTURED THE LOC, FLYING ABOUT 1/4 - 1/2 DOT OFF COURSE. THIS TOOK US CLOSER TO THE ILS RWY 12R, WHERE AN MD80 WAS ON A PARALLEL APCH. THE FO TOOK OVER MANUALLY AND REJOINED THE LDA, SIMULTANEOUSLY WITH 2 ATC PROMPTS. WE HAD THE MD80 IN SIGHT VISUALLY, THERE WAS NO CONFLICT. THE APCH WAS CONTINUED TO A NORMAL LNDG AND NOTHING FURTHER WAS MENTIONED. UPON LNDG, I TALKED WITH ANOTHER CAPT THAT LANDED AHEAD OF US, AND HE SAID THE SAME THING HAPPENED. TAXIING OUT ON THE NEXT TURN, WE HEARD YET ANOTHER ACFT EXPERIENCE THE SAME THING. WIND CONDITIONS WERE A STRONG TAILWIND ON THE INTERCEPT HDG, SHEARING TO A STRONG XWIND ON THE APCH. I FEEL THIS CAUSED SOME CONFUSION IN THE AUTOPLT CORRECTIONS, AS WELL AS LATE TURNS FROM ATC. FUTURE PREVENTION WOULD BE TO TAKE CORRECTIVE ACTION SOONER, PERHAPS MANUALLY.

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.