Narrative:

Tower gave hold short instructions and advised an 8 min delay for release for flow control into destination airport. New captain and jump seat occupant. (Another company captain on same aircraft.) began conversation on cold WX operations and suggestions for new captain on engine ice use for this particular takeoff (blowing snow). Tower gave instructions during this conversation and I repeated them back -- and I'm still not sure what the tower instructions were or what I repeated back (ie, 'cleared for takeoff,' or 'position and hold'). Once on the runway, the captain exchanged the control of the aircraft for my radios. I remarked, 'my aircraft, with brakes released' and commenced takeoff. At 80 KTS of airspeed (approximately 1000 ft down the runway), the tower cleared us for takeoff and to fly runway heading. We continued and were told at 1000 ft AGL to contact departure. After the clearance for takeoff, while we were on the takeoff roll, the rest of the takeoff went normal. How problem arose: 1) talking during hold short period. 2) selective hearing or poor listening skills. 3) no clarification with ATC. 4) poor crew communication. 5) the biggest factor was my assumption that since the captain did not set the parking brake before or after relinquishing aircraft control to me, that we were cleared for takeoff. Company policy is to set parking brake any time you come to a complete stop. With no brake set, I assumed it was a rolling start takeoff. Solutions: no talking on the hold short. Clarify position and hold or cleared for takeoff with the captain and ATC. Better communications and work on listening skills. Finally, do not assume -- inquire -- communicate!

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Original NASA ASRS Text

Title: FO OF A B737-500 STARTS TKOF ROLL BEFORE BEING CLRED FOR TKOF.

Narrative: TWR GAVE HOLD SHORT INSTRUCTIONS AND ADVISED AN 8 MIN DELAY FOR RELEASE FOR FLOW CTL INTO DEST ARPT. NEW CAPT AND JUMP SEAT OCCUPANT. (ANOTHER COMPANY CAPT ON SAME ACFT.) BEGAN CONVERSATION ON COLD WX OPS AND SUGGESTIONS FOR NEW CAPT ON ENG ICE USE FOR THIS PARTICULAR TKOF (BLOWING SNOW). TWR GAVE INSTRUCTIONS DURING THIS CONVERSATION AND I REPEATED THEM BACK -- AND I'M STILL NOT SURE WHAT THE TWR INSTRUCTIONS WERE OR WHAT I REPEATED BACK (IE, 'CLRED FOR TKOF,' OR 'POS AND HOLD'). ONCE ON THE RWY, THE CAPT EXCHANGED THE CTL OF THE ACFT FOR MY RADIOS. I REMARKED, 'MY ACFT, WITH BRAKES RELEASED' AND COMMENCED TKOF. AT 80 KTS OF AIRSPD (APPROX 1000 FT DOWN THE RWY), THE TWR CLRED US FOR TKOF AND TO FLY RWY HDG. WE CONTINUED AND WERE TOLD AT 1000 FT AGL TO CONTACT DEP. AFTER THE CLRNC FOR TKOF, WHILE WE WERE ON THE TKOF ROLL, THE REST OF THE TKOF WENT NORMAL. HOW PROB AROSE: 1) TALKING DURING HOLD SHORT PERIOD. 2) SELECTIVE HEARING OR POOR LISTENING SKILLS. 3) NO CLARIFICATION WITH ATC. 4) POOR CREW COM. 5) THE BIGGEST FACTOR WAS MY ASSUMPTION THAT SINCE THE CAPT DID NOT SET THE PARKING BRAKE BEFORE OR AFTER RELINQUISHING ACFT CTL TO ME, THAT WE WERE CLRED FOR TKOF. COMPANY POLICY IS TO SET PARKING BRAKE ANY TIME YOU COME TO A COMPLETE STOP. WITH NO BRAKE SET, I ASSUMED IT WAS A ROLLING START TKOF. SOLUTIONS: NO TALKING ON THE HOLD SHORT. CLARIFY POS AND HOLD OR CLRED FOR TKOF WITH THE CAPT AND ATC. BETTER COMS AND WORK ON LISTENING SKILLS. FINALLY, DO NOT ASSUME -- INQUIRE -- COMMUNICATE!

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.