Air carrier report on confusing ATC instructions during taxiing ground holding traffic.

Attributes
ACN	294402
Time
Date	199501
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mia
State Reference	FL
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	ground : holding ground other : taxi
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
ASRS Report	294402
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Deviation

Narrative:

Flight was cleared to taxi to runway 9L. When flight was in #1 position for runway 9L tower advised clear for takeoff on runway 12. Flight crew advised tower that a short delay would be necessary for new input data to FMC. Tower advised that the delay could be taken in position. Flight was then cleared into position and hold. Flight crew acknowledged and began taxi. Tower then advised clear for takeoff on runway 9L. Aircraft made turn toward runway 9L and approaching the runway hold line captain stopped aircraft as landing traffic crossed threshold for runway 9L. Tower then advised that we had been cleared into position on runway 12. Captain told tower that flight crew had not heard the second clearance to proceed onto runway 12. Captain then told tower that airplane would not proceed onto any runway until we understood the clearance and the FMC data was updated as required. Tower acknowledged and after a very short delay we were cleared into position on runway 12 for departure.

Original NASA ASRS Text

Title: ACR RPT ON CONFUSING ATC INSTRUCTIONS DURING TAXIING GND HOLDING TFC.

Narrative: FLT WAS CLRED TO TAXI TO RWY 9L. WHEN FLT WAS IN #1 POS FOR RWY 9L TWR ADVISED CLR FOR TKOF ON RWY 12. FLC ADVISED TWR THAT A SHORT DELAY WOULD BE NECESSARY FOR NEW INPUT DATA TO FMC. TWR ADVISED THAT THE DELAY COULD BE TAKEN IN POS. FLT WAS THEN CLRED INTO POS AND HOLD. FLC ACKNOWLEDGED AND BEGAN TAXI. TWR THEN ADVISED CLR FOR TKOF ON RWY 9L. ACFT MADE TURN TOWARD RWY 9L AND APCHING THE RWY HOLD LINE CAPT STOPPED ACFT AS LNDG TFC CROSSED THRESHOLD FOR RWY 9L. TWR THEN ADVISED THAT WE HAD BEEN CLRED INTO POS ON RWY 12. CAPT TOLD TWR THAT FLC HAD NOT HEARD THE SECOND CLRNC TO PROCEED ONTO RWY 12. CAPT THEN TOLD TWR THAT AIRPLANE WOULD NOT PROCEED ONTO ANY RWY UNTIL WE UNDERSTOOD THE CLRNC AND THE FMC DATA WAS UPDATED AS REQUIRED. TWR ACKNOWLEDGED AND AFTER A VERY SHORT DELAY WE WERE CLRED INTO POS ON RWY 12 FOR 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.