B737 departed from mdw begins takeoff roll without clearance. ATC aborts takeoff.

Attributes
ACN	601134
Time
Date	200311
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	ground : takeoff roll
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Experience	flight time last 90 days : 250 flight time total : 5200 flight time type : 2500
ASRS Report	601134
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 8000 flight time type : 6000
ASRS Report	600699
Events
Anomaly	incursion : runway non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance flight crew : rejected takeoff
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

It was the first leg of the pairing in the morning. After pushback from B18, we were given clearance to taxi to runway 31C. As we approached runway 31R, I switched to tower. The captain asked if we were cleared to cross runway 31R, so I queried tower. He said ground control had cleared us, and then we thought he gave us clearance to take off on runway 31C. We taxied across runway 31R to runway 31C, lined up and started the takeoff roll. A few seconds later, I thought tower may have said, 'company flight number, stop.' but it was a little hard to hear over the engine noise, and he didn't sound alarmed. I queried him and he replied, 'company flight number, abort the takeoff and hold short of runway 22L.' we complied with that. He then told us we could turn right, left, or do a 180 degree turn. We said we'd turn right and he cleared us back onto hold runway 31C. We asked if he had given us takeoff clearance and he said he did not. We both thought he did. After arrival into san, we called mdw tower. They said that there was no conflict or incursion and didn't seem too upset. The controller said that he did review the tapes and confirmed he did not give us takeoff clearance. Although, he said he did give us some of the takeoff information on the 'on to hold' clearance and he could see how we made the mistake. It was an abnormally quiet day at mdw with no traffic landing or taking off on runway 31C before us that we would have to wait on. When he cleared us on to hold, he gave us some of the information that they usually give with takeoff clearance. After we did the rest of the checklist, it just felt like we had takeoff clearance. I usually make a point of repeating the clearance after the checklist is complete, but I guess that habit pattern failed me on the first leg of the pairing. Supplemental information from acn 600699: I think that the unusual nature of the 'position and hold' call, combined with the very high level of comfort with home base mdw led to an initial lack of complete focus on the job at hand.

Original NASA ASRS Text

Title: B737 DEPARTED FROM MDW BEGINS TKOF ROLL WITHOUT CLRNC. ATC ABORTS TKOF.

Narrative: IT WAS THE FIRST LEG OF THE PAIRING IN THE MORNING. AFTER PUSHBACK FROM B18, WE WERE GIVEN CLRNC TO TAXI TO RWY 31C. AS WE APCHED RWY 31R, I SWITCHED TO TWR. THE CAPT ASKED IF WE WERE CLRED TO CROSS RWY 31R, SO I QUERIED TWR. HE SAID GND CTL HAD CLRED US, AND THEN WE THOUGHT HE GAVE US CLRNC TO TAKE OFF ON RWY 31C. WE TAXIED ACROSS RWY 31R TO RWY 31C, LINED UP AND STARTED THE TKOF ROLL. A FEW SECONDS LATER, I THOUGHT TWR MAY HAVE SAID, 'COMPANY FLT NUMBER, STOP.' BUT IT WAS A LITTLE HARD TO HEAR OVER THE ENG NOISE, AND HE DIDN'T SOUND ALARMED. I QUERIED HIM AND HE REPLIED, 'COMPANY FLT NUMBER, ABORT THE TKOF AND HOLD SHORT OF RWY 22L.' WE COMPLIED WITH THAT. HE THEN TOLD US WE COULD TURN R, L, OR DO A 180 DEG TURN. WE SAID WE'D TURN R AND HE CLRED US BACK ONTO HOLD RWY 31C. WE ASKED IF HE HAD GIVEN US TKOF CLRNC AND HE SAID HE DID NOT. WE BOTH THOUGHT HE DID. AFTER ARR INTO SAN, WE CALLED MDW TWR. THEY SAID THAT THERE WAS NO CONFLICT OR INCURSION AND DIDN'T SEEM TOO UPSET. THE CTLR SAID THAT HE DID REVIEW THE TAPES AND CONFIRMED HE DID NOT GIVE US TKOF CLRNC. ALTHOUGH, HE SAID HE DID GIVE US SOME OF THE TKOF INFO ON THE 'ON TO HOLD' CLRNC AND HE COULD SEE HOW WE MADE THE MISTAKE. IT WAS AN ABNORMALLY QUIET DAY AT MDW WITH NO TFC LNDG OR TAKING OFF ON RWY 31C BEFORE US THAT WE WOULD HAVE TO WAIT ON. WHEN HE CLRED US ON TO HOLD, HE GAVE US SOME OF THE INFO THAT THEY USUALLY GIVE WITH TKOF CLRNC. AFTER WE DID THE REST OF THE CHKLIST, IT JUST FELT LIKE WE HAD TKOF CLRNC. I USUALLY MAKE A POINT OF REPEATING THE CLRNC AFTER THE CHKLIST IS COMPLETE, BUT I GUESS THAT HABIT PATTERN FAILED ME ON THE FIRST LEG OF THE PAIRING. SUPPLEMENTAL INFO FROM ACN 600699: I THINK THAT THE UNUSUAL NATURE OF THE 'POS AND HOLD' CALL, COMBINED WITH THE VERY HIGH LEVEL OF COMFORT WITH HOME BASE MDW LED TO AN INITIAL LACK OF COMPLETE FOCUS ON THE JOB AT HAND.

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.