During IAP ILS approach to runway 9R at atl, an air carrier medium large transport drifted north toward runway 8L while parallel approachs were in progress.

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Attributes
ACN	153953
Time
Date	199008
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 2800 msl bound upper : 2800
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : atp
Experience	flight time last 90 days : 175 flight time total : 4000 flight time type : 1000
ASRS Report	153953
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe non adherence : clearance non adherence : published procedure other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Miss Distance	horizontal : 7000 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On approach in atl on 9R (IFR ILS), localizer captured, G/south was alive, on FMA panel 'localizer cap'/'altitude' was displayed, captain dialed in 180 degrees on heading knob, aircraft tracked in on localizer course of 092 degrees, we noticed the FMA reverted to 'heading select' and the aircraft was drifting to the left (north). As soon as we noticed it, I turned to the south and at the same time the final approach monitor called and said air carrier X, 'your drifting left, turn right immediately' (we were in the turn already). We rogered him and tracked in on the localizer (of 92 degree right). An air carrier Y aircraft was shooting a parallel approach to 08L (to the north). No evasive action was performed by him. We were approximately 1-1 1/2 dots left of course. We made an uneventful landing in atl. Nothing else heard. The autoplt was coupled to the ILS and should have followed the 280 degree course when it went to 'heading' select. Instead the aircraft flew the 092 degree heading and drifted to the north due to winds. The time frame was only 20 seconds or so--enough time to cause the problem. I have no answers to why it went from 'localizer cap' to the 'heading sel' mode; it should not have happened. All company procedures were followed in this ILS approach.

Original NASA ASRS Text

Title: DURING IAP ILS APCH TO RWY 9R AT ATL, AN ACR MLG DRIFTED NORTH TOWARD RWY 8L WHILE PARALLEL APCHS WERE IN PROGRESS.

Narrative: ON APCH IN ATL ON 9R (IFR ILS), LOC CAPTURED, G/S WAS ALIVE, ON FMA PANEL 'LOC CAP'/'ALT' WAS DISPLAYED, CAPT DIALED IN 180 DEGS ON HDG KNOB, ACFT TRACKED IN ON LOC COURSE OF 092 DEGS, WE NOTICED THE FMA REVERTED TO 'HDG SELECT' AND THE ACFT WAS DRIFTING TO THE LEFT (N). AS SOON AS WE NOTICED IT, I TURNED TO THE S AND AT THE SAME TIME THE FINAL APCH MONITOR CALLED AND SAID ACR X, 'YOUR DRIFTING L, TURN R IMMEDIATELY' (WE WERE IN THE TURN ALREADY). WE ROGERED HIM AND TRACKED IN ON THE LOC (OF 92 DEG R). AN ACR Y ACFT WAS SHOOTING A PARALLEL APCH TO 08L (TO THE N). NO EVASIVE ACTION WAS PERFORMED BY HIM. WE WERE APPROX 1-1 1/2 DOTS L OF COURSE. WE MADE AN UNEVENTFUL LNDG IN ATL. NOTHING ELSE HEARD. THE AUTOPLT WAS COUPLED TO THE ILS AND SHOULD HAVE FOLLOWED THE 280 DEG COURSE WHEN IT WENT TO 'HDG' SELECT. INSTEAD THE ACFT FLEW THE 092 DEG HDG AND DRIFTED TO THE N DUE TO WINDS. THE TIME FRAME WAS ONLY 20 SECS OR SO--ENOUGH TIME TO CAUSE THE PROB. I HAVE NO ANSWERS TO WHY IT WENT FROM 'LOC CAP' TO THE 'HDG SEL' MODE; IT SHOULD NOT HAVE HAPPENED. ALL COMPANY PROCS WERE FOLLOWED IN THIS ILS APCH.

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.