B777 flight crew has a track heading deviation during cqy arrival to dfw.

Attributes
ACN	699430
Time
Date	200606
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	msl single value : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : d10.tracon tower : fai.tower
Operator	common carrier : air carrier
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude descent : approach
Route In Use	arrival star : dietz
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	699430
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	699431
Events
Anomaly	non adherence : published procedure other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued advisory flight crew : returned to intended or assigned course flight crew : returned to original clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

After passing dietz; on the CQY6 arrival the aircraft began a turn to the right. I had my head down and had just changed and executed the approach to runway 17C. The captain said 'what's going on?' followed by 'dietz dropped out.' I inserted dietz and executed it. The aircraft rolled from a right bank back to a left bank toward dietz. As the aircraft was in the turn back to dietz; ATC asked 'where are you going?' captain responded 'direct dietz.' ATC replied 'maintain 250 KTS and descend to 8000 ft.' there was no other mention of our minor deviation. We had both checked the arrival and waypoints and have no explanation as to when and why dietz dropped out. With dietz missing the aircraft started a turn toward hornz after passing tacke. The deviation was brief and resolved quickly. Supplemental information from acn 699431: on STAR into dfw when we received landing runway first officer entered information and executed which gave duplicate waypoints. When he cleaned up FMC somehow dietz intersection got deleted and aircraft started turn to next waypoint.

Original NASA ASRS Text

Title: B777 FLT CREW HAS A TRACK HDG DEV DURING CQY ARR TO DFW.

Narrative: AFTER PASSING DIETZ; ON THE CQY6 ARR THE ACFT BEGAN A TURN TO THE R. I HAD MY HEAD DOWN AND HAD JUST CHANGED AND EXECUTED THE APCH TO RWY 17C. THE CAPT SAID 'WHAT'S GOING ON?' FOLLOWED BY 'DIETZ DROPPED OUT.' I INSERTED DIETZ AND EXECUTED IT. THE ACFT ROLLED FROM A R BANK BACK TO A L BANK TOWARD DIETZ. AS THE ACFT WAS IN THE TURN BACK TO DIETZ; ATC ASKED 'WHERE ARE YOU GOING?' CAPT RESPONDED 'DIRECT DIETZ.' ATC REPLIED 'MAINTAIN 250 KTS AND DSND TO 8000 FT.' THERE WAS NO OTHER MENTION OF OUR MINOR DEV. WE HAD BOTH CHKED THE ARR AND WAYPOINTS AND HAVE NO EXPLANATION AS TO WHEN AND WHY DIETZ DROPPED OUT. WITH DIETZ MISSING THE ACFT STARTED A TURN TOWARD HORNZ AFTER PASSING TACKE. THE DEV WAS BRIEF AND RESOLVED QUICKLY. SUPPLEMENTAL INFO FROM ACN 699431: ON STAR INTO DFW WHEN WE RECEIVED LNDG RWY FO ENTERED INFO AND EXECUTED WHICH GAVE DUPLICATE WAYPOINTS. WHEN HE CLEANED UP FMC SOMEHOW DIETZ INTXN GOT DELETED AND ACFT STARTED TURN TO NEXT WAYPOINT.

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.