Unauthorized takeoff attempted after air carrier first officer makes reply to wrong callsign.

Attributes
ACN	242123
Time
Date	199305
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : ord
State Reference	IL
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	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 160 flight time total : 8500 flight time type : 6000
ASRS Report	242123
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 300 flight time total : 6000 flight time type : 450
ASRS Report	242124
Events
Anomaly	incursion : runway non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : became reoriented other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

Flight was departing ord to phl. We were cleared onto runway 32L to position and hold. As we completed our checklist, we received clearance for takeoff. The copilot rogered our takeoff clearance, and he advanced the throttles. About 1000 ft down the runway, tower told us that we had not been cleared for takeoff. I was preparing for a low speed abort when tower came back and cleared us for takeoff, maintain runway heading. After liftoff we discovered that tower was also controling an aircraft on runway 32R. They believed that we had misunderstood the takeoff clearance issued to the other aircraft to be our own. They also informed us that there was no traffic conflict at that time. This incident could have been avoided if we had not misunderstood our clearance (hearback error). The tower had heard and corrected us on our readback. If simultaneous departures from parallel runways were always handled on discrete frequencys. Supplemental information from acn 242124: simply put, we expected a takeoff clearance, to the best of our knowledge we received one, and we were not challenged in our readback. Dual discrete frequencys during tandem parallel runway operations with 1 controller is a recipe for confusion.

Original NASA ASRS Text

Title: UNAUTH TKOF ATTEMPTED AFTER ACR FO MAKES REPLY TO WRONG CALLSIGN.

Narrative: FLT WAS DEPARTING ORD TO PHL. WE WERE CLRED ONTO RWY 32L TO POS AND HOLD. AS WE COMPLETED OUR CHKLIST, WE RECEIVED CLRNC FOR TKOF. THE COPLT ROGERED OUR TKOF CLRNC, AND HE ADVANCED THE THROTTLES. ABOUT 1000 FT DOWN THE RWY, TWR TOLD US THAT WE HAD NOT BEEN CLRED FOR TKOF. I WAS PREPARING FOR A LOW SPD ABORT WHEN TWR CAME BACK AND CLRED US FOR TKOF, MAINTAIN RWY HDG. AFTER LIFTOFF WE DISCOVERED THAT TWR WAS ALSO CTLING AN ACFT ON RWY 32R. THEY BELIEVED THAT WE HAD MISUNDERSTOOD THE TKOF CLRNC ISSUED TO THE OTHER ACFT TO BE OUR OWN. THEY ALSO INFORMED US THAT THERE WAS NO TFC CONFLICT AT THAT TIME. THIS INCIDENT COULD HAVE BEEN AVOIDED IF WE HAD NOT MISUNDERSTOOD OUR CLRNC (HEARBACK ERROR). THE TWR HAD HEARD AND CORRECTED US ON OUR READBACK. IF SIMULTANEOUS DEPS FROM PARALLEL RWYS WERE ALWAYS HANDLED ON DISCRETE FREQS. SUPPLEMENTAL INFO FROM ACN 242124: SIMPLY PUT, WE EXPECTED A TKOF CLRNC, TO THE BEST OF OUR KNOWLEDGE WE RECEIVED ONE, AND WE WERE NOT CHALLENGED IN OUR READBACK. DUAL DISCRETE FREQS DURING TANDEM PARALLEL RWY OPS WITH 1 CTLR IS A RECIPE FOR CONFUSION.

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.