Narrative:

We were established on the cetus 2 arrival into dtw. Tracking the 147 degree radial inbound to dxo VOR, approach control instructed us to turn to a heading of 030 degrees. Upon reaching gloze intersection (dxo 8 DME), the first officer was the PF. As I was heads down reviewing the ILS runway 21L approach plate, the first officer started a right turn to a heading of 030 degrees as assigned by ATC. As he turned, he stated 'passing gloze.' since he was on the assigned heading, I dialed in the localizer frequency for runway 21L. About the same time approach called and said, 'hey, you missed the turn for gloze, turn back to a heading of 300 degrees.' we acknowledged him and turned back immediately, and also apologized for the early turn. Contributing factors included the GPS and the crew. The first officer misinterped the GPS. He saw the GPS reading 8 mi from gloze, and thought it was reading 8 mi from dxo VOR. Thinking we were at gloze, he turned to the 030 degree assigned heading. Actually he turned 16 mi from dxo instead of 8 mi. I didn't notice because I was reviewing the approach plate and had my head down when he turned. Before I picked up on what happened, approach called and gave us the heading back to gloze. In my opinion, this occurred because the GPS actually lowered our level of situational awareness. Relying too much on the GPS during the arrival, we failed to confirm our position with the VOR. Had we done this, I wouldn't be writing this report.

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Original NASA ASRS Text

Title: A DC9-40 FLC TURNS TOO EARLY FOR VECTORING TO DTW. FO HAD USED THEIR GPS FOR THE POS WITHOUT REF TO THE VOR DME.

Narrative: WE WERE ESTABLISHED ON THE CETUS 2 ARR INTO DTW. TRACKING THE 147 DEG RADIAL INBOUND TO DXO VOR, APCH CTL INSTRUCTED US TO TURN TO A HDG OF 030 DEGS. UPON REACHING GLOZE INTXN (DXO 8 DME), THE FO WAS THE PF. AS I WAS HEADS DOWN REVIEWING THE ILS RWY 21L APCH PLATE, THE FO STARTED A R TURN TO A HDG OF 030 DEGS AS ASSIGNED BY ATC. AS HE TURNED, HE STATED 'PASSING GLOZE.' SINCE HE WAS ON THE ASSIGNED HDG, I DIALED IN THE LOC FREQ FOR RWY 21L. ABOUT THE SAME TIME APCH CALLED AND SAID, 'HEY, YOU MISSED THE TURN FOR GLOZE, TURN BACK TO A HDG OF 300 DEGS.' WE ACKNOWLEDGED HIM AND TURNED BACK IMMEDIATELY, AND ALSO APOLOGIZED FOR THE EARLY TURN. CONTRIBUTING FACTORS INCLUDED THE GPS AND THE CREW. THE FO MISINTERPED THE GPS. HE SAW THE GPS READING 8 MI FROM GLOZE, AND THOUGHT IT WAS READING 8 MI FROM DXO VOR. THINKING WE WERE AT GLOZE, HE TURNED TO THE 030 DEG ASSIGNED HDG. ACTUALLY HE TURNED 16 MI FROM DXO INSTEAD OF 8 MI. I DIDN'T NOTICE BECAUSE I WAS REVIEWING THE APCH PLATE AND HAD MY HEAD DOWN WHEN HE TURNED. BEFORE I PICKED UP ON WHAT HAPPENED, APCH CALLED AND GAVE US THE HDG BACK TO GLOZE. IN MY OPINION, THIS OCCURRED BECAUSE THE GPS ACTUALLY LOWERED OUR LEVEL OF SITUATIONAL AWARENESS. RELYING TOO MUCH ON THE GPS DURING THE ARR, WE FAILED TO CONFIRM OUR POS WITH THE VOR. HAD WE DONE THIS, I WOULDN'T BE WRITING THIS RPT.

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.