Confusion between tower and flight crew at dtw about which runway to use for takeoff.

Attributes
ACN	145969
Time
Date	199005
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dtw
State Reference	MI
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : takeoff ground : holding
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 205 flight time total : 5000 flight time type : 1500
ASRS Report	145960
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	incursion : runway other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	none taken : detected after the fact other
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

We were cleared to taxi to runway 21L at dtw with a 20 mi hold on taxiway arc. Subsequently we were cleared to position and hold on runway 27 with a left turn to 260 degrees upon receiving takeoff clearance. Tower cleared us for takeoff on 27. I said no, that we were supposed to be on 21L, not 27. Captain then told tower we were taking off on runway 27. Our takeoff performance was computed for runway 27. Strange field along with confusion about the exact clearance given. Could have been serious trouble, although the takeoff was uneventful. We heard no reply from the tower or departure.

Original NASA ASRS Text

Title: CONFUSION BETWEEN TWR AND FLT CREW AT DTW ABOUT WHICH RWY TO USE FOR TKOF.

Narrative: WE WERE CLRED TO TAXI TO RWY 21L AT DTW WITH A 20 MI HOLD ON TXWY ARC. SUBSEQUENTLY WE WERE CLRED TO POS AND HOLD ON RWY 27 WITH A LEFT TURN TO 260 DEGS UPON RECEIVING TKOF CLRNC. TWR CLRED US FOR TKOF ON 27. I SAID NO, THAT WE WERE SUPPOSED TO BE ON 21L, NOT 27. CAPT THEN TOLD TWR WE WERE TAKING OFF ON RWY 27. OUR TKOF PERFORMANCE WAS COMPUTED FOR RWY 27. STRANGE FIELD ALONG WITH CONFUSION ABOUT THE EXACT CLRNC GIVEN. COULD HAVE BEEN SERIOUS TROUBLE, ALTHOUGH THE TKOF WAS UNEVENTFUL. WE HEARD NO REPLY FROM THE TWR OR DEP.

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.