An A300 on a nat track lost #1 compass system and deviated 30 NM from course before discovering the error; notifying control; and returning to track.

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Attributes
ACN	676124
Time
Date	200510
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bikf.airport
State Reference	FO
Altitude	msl single value : 33000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : bird.artcc
Operator	common carrier : air carrier
Make Model Name	A300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6500 flight time type : 1500
ASRS Report	676124
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 1000
ASRS Report	676416
Events
Anomaly	aircraft equipment problem : critical non adherence : far non adherence : clearance other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to original clearance flight crew : returned to intended or assigned course flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

En route to keflavik; iceland; we experienced a gross navigation error. We were approximately 8 mins from our next reporting point of 63N; 040W. When the first officer went to make the position report; he noticed that the time and distance had changed and that our position was not where we should have been. Comparing all of the information that we had available (magnetic compass; heading indicator; GPS; and attitude information); we figured the aircraft had flown north of course approximately 30 mi. We immediately turned the aircraft to a southerly heading and reported our deviation and position to ATC. During our re-intercept of the course; we realized that we had lost our #1 compass information. This problem allowed the aircraft to drift/deviate off course even though we were using the autoplt slaved to the GPS for navigation. All of these system are connected; and the loss of #1 system affects the others. The turn or bank that caused the deviation was so small; none of us noticed. More attention and diligence may have prevented this deviation.

Original NASA ASRS Text

Title: AN A300 ON A NAT TRACK LOST #1 COMPASS SYS AND DEVIATED 30 NM FROM COURSE BEFORE DISCOVERING THE ERROR; NOTIFYING CTL; AND RETURNING TO TRACK.

Narrative: ENRTE TO KEFLAVIK; ICELAND; WE EXPERIENCED A GROSS NAV ERROR. WE WERE APPROX 8 MINS FROM OUR NEXT RPTING POINT OF 63N; 040W. WHEN THE FO WENT TO MAKE THE POS RPT; HE NOTICED THAT THE TIME AND DISTANCE HAD CHANGED AND THAT OUR POS WAS NOT WHERE WE SHOULD HAVE BEEN. COMPARING ALL OF THE INFO THAT WE HAD AVAILABLE (MAGNETIC COMPASS; HDG INDICATOR; GPS; AND ATTITUDE INFO); WE FIGURED THE ACFT HAD FLOWN N OF COURSE APPROX 30 MI. WE IMMEDIATELY TURNED THE ACFT TO A SOUTHERLY HDG AND RPTED OUR DEV AND POS TO ATC. DURING OUR RE-INTERCEPT OF THE COURSE; WE REALIZED THAT WE HAD LOST OUR #1 COMPASS INFO. THIS PROB ALLOWED THE ACFT TO DRIFT/DEVIATE OFF COURSE EVEN THOUGH WE WERE USING THE AUTOPLT SLAVED TO THE GPS FOR NAV. ALL OF THESE SYS ARE CONNECTED; AND THE LOSS OF #1 SYS AFFECTS THE OTHERS. THE TURN OR BANK THAT CAUSED THE DEV WAS SO SMALL; NONE OF US NOTICED. MORE ATTN AND DILIGENCE MAY HAVE PREVENTED THIS DEV.

Data retrieved from NASA's ASRS site as of January 2009 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.