Narrative:

It was a ferry flight in an light transport from sbn to ord. We had an altimeter error which was out of our operations manual tolerances. With no passenger on board and our F/a sitting behind us we taxied out to runway 27 completing our checklist with a less than normal amount of professionalism. During the taxi and listening to tower frequency, the tower repeatedly (3-4 times) asked us if we were ready to go. However, we were not finished with the checklist. Holding short of the runway the tower asked us a third time if we were ready since we had to make the 3 min departure window of our edc time. We noticed an small aircraft depart runway 27, and soon thereafter reported our readiness for departure. We were cleared into position and hold runway 27. Laughing about something at the time, we began our before takeoff checklist and normally leaving 'lights on, propellers forward and fuel to flight' portion of the checklist until cleared to go. I just completely did not listen to what the tower had said, because when we came to that part of the checklist, I just called for lights, propellers and fuel. The first officer did as he was asked and I brought up the power and we departed. At the point the wheels came off the ground I realized we had not been cleared to go. The tower also acknowledged my suspicions and asked if we had the small aircraft in sight. We did and there was no evasive action required. We climbed straight out and the small aircraft was making right closed traffic and was on his crosswind leg. We continued with our normal procedures as best we could and tower handed us over to departure. The rest of the flight we were wide awake and when we landed at ord I called sbn tower to profusely apologize for our actions and explained that we felt rushed because he repeatedly asked us if we were ready. The minute I heard the word 'cleared,' I just had blocked out the rest of the clearance and was assuming he wanted us out as quickly as possible. The controller said he understood the situation he created and said no further action would be taken. I now completely listen to the clrncs and continue abiding by a sterile, professional atmosphere during all flight operations, not just revenue trips.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR LTT TOOK OFF WITHOUT TWR CLRNC.

Narrative: IT WAS A FERRY FLT IN AN LTT FROM SBN TO ORD. WE HAD AN ALTIMETER ERROR WHICH WAS OUT OF OUR OPS MANUAL TOLERANCES. WITH NO PAX ON BOARD AND OUR F/A SITTING BEHIND US WE TAXIED OUT TO RWY 27 COMPLETING OUR CHKLIST WITH A LESS THAN NORMAL AMOUNT OF PROFESSIONALISM. DURING THE TAXI AND LISTENING TO TWR FREQ, THE TWR REPEATEDLY (3-4 TIMES) ASKED US IF WE WERE READY TO GO. HOWEVER, WE WERE NOT FINISHED WITH THE CHKLIST. HOLDING SHORT OF THE RWY THE TWR ASKED US A THIRD TIME IF WE WERE READY SINCE WE HAD TO MAKE THE 3 MIN DEP WINDOW OF OUR EDC TIME. WE NOTICED AN SMA DEPART RWY 27, AND SOON THEREAFTER RPTED OUR READINESS FOR DEP. WE WERE CLRED INTO POS AND HOLD RWY 27. LAUGHING ABOUT SOMETHING AT THE TIME, WE BEGAN OUR BEFORE TKOF CHKLIST AND NORMALLY LEAVING 'LIGHTS ON, PROPS FORWARD AND FUEL TO FLT' PORTION OF THE CHKLIST UNTIL CLRED TO GO. I JUST COMPLETELY DID NOT LISTEN TO WHAT THE TWR HAD SAID, BECAUSE WHEN WE CAME TO THAT PART OF THE CHKLIST, I JUST CALLED FOR LIGHTS, PROPS AND FUEL. THE F/O DID AS HE WAS ASKED AND I BROUGHT UP THE PWR AND WE DEPARTED. AT THE POINT THE WHEELS CAME OFF THE GND I REALIZED WE HAD NOT BEEN CLRED TO GO. THE TWR ALSO ACKNOWLEDGED MY SUSPICIONS AND ASKED IF WE HAD THE SMA IN SIGHT. WE DID AND THERE WAS NO EVASIVE ACTION REQUIRED. WE CLBED STRAIGHT OUT AND THE SMA WAS MAKING RIGHT CLOSED TFC AND WAS ON HIS XWIND LEG. WE CONTINUED WITH OUR NORMAL PROCS AS BEST WE COULD AND TWR HANDED US OVER TO DEP. THE REST OF THE FLT WE WERE WIDE AWAKE AND WHEN WE LANDED AT ORD I CALLED SBN TWR TO PROFUSELY APOLOGIZE FOR OUR ACTIONS AND EXPLAINED THAT WE FELT RUSHED BECAUSE HE REPEATEDLY ASKED US IF WE WERE READY. THE MINUTE I HEARD THE WORD 'CLRED,' I JUST HAD BLOCKED OUT THE REST OF THE CLRNC AND WAS ASSUMING HE WANTED US OUT AS QUICKLY AS POSSIBLE. THE CTLR SAID HE UNDERSTOOD THE SITUATION HE CREATED AND SAID NO FURTHER ACTION WOULD BE TAKEN. I NOW COMPLETELY LISTEN TO THE CLRNCS AND CONTINUE ABIDING BY A STERILE, PROFESSIONAL ATMOSPHERE DURING ALL FLT OPS, NOT JUST REVENUE TRIPS.

Data retrieved from NASA's ASRS site as of August 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.