An air carrier B727 heading track deviation observed by ATC is chalked up to a random event.

Attributes
ACN	346230
Time
Date	199609
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : dfw
State Reference	TX
Environment
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zfw
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	346230
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
ASRS Report	346231
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other controllera
Resolutory Action	aircraft : equipment problem dissipated other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

ATC facility: ZFW. Location: dfw/067/45. Approximately XA30L, tracking 067/dfw, ZFW instructed us to fly 040 degrees to reintercept the airway. Both captain's and first officer's CDI's indicated on course. After informing ATC we were indicating on course but turning. Center informed us we were south of the radial and our track was going to cause a traffic conflict. When the controller called the center of the airway both CDI's indicated approximately 1 to 11/2 needle width off course north indication. Both CDI's had tested normal on ground prior to departure. No other discrepancies reported by ATC for remainder of flight and no cockpit abnormalities noted for duration of flight.

Original NASA ASRS Text

Title: AN ACR B727 HDG TRACK DEV OBSERVED BY ATC IS CHALKED UP TO A RANDOM EVENT.

Narrative: ATC FACILITY: ZFW. LOCATION: DFW/067/45. APPROX XA30L, TRACKING 067/DFW, ZFW INSTRUCTED US TO FLY 040 DEGS TO REINTERCEPT THE AIRWAY. BOTH CAPT'S AND FO'S CDI'S INDICATED ON COURSE. AFTER INFORMING ATC WE WERE INDICATING ON COURSE BUT TURNING. CTR INFORMED US WE WERE S OF THE RADIAL AND OUR TRACK WAS GOING TO CAUSE A TFC CONFLICT. WHEN THE CTLR CALLED THE CTR OF THE AIRWAY BOTH CDI'S INDICATED APPROX 1 TO 11/2 NEEDLE WIDTH OFF COURSE N INDICATION. BOTH CDI'S HAD TESTED NORMAL ON GND PRIOR TO DEP. NO OTHER DISCREPANCIES RPTED BY ATC FOR REMAINDER OF FLT AND NO COCKPIT ABNORMALITIES NOTED FOR DURATION OF FLT.

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.