Narrative:

Aircraft aborted initial takeoff roll due to APU still running. On taxi out to runway 32R at ord the #3 engine was shut down to conserve fuel due to departure delays. Approaching the hold short the #3 engine was restarted. The APU was left running to allow for a 2 min cool down. The slide bar for the APU on the mechanical checklist was not slid to the takeoff side as per normal operating procedures. The aircraft was cleared into position and hold and then cleared for takeoff. As power was advanced while still completing the last few items on the mechanic checklist, the takeoff warning horn sounded. The captain returned the throttles to idle. The aircraft rolled forward only a few ft and the captain elected to taxi the aircraft up to the first taxiway entrance and exited the runway. The aircraft was cleared for a second takeoff which was uneventful. The aborted takeoff was caused because the APU was still running. The checklist was not yet complete but the power was being advanced. If the advance of power had been delayed until the checklist was called complete, the APU would have been secured and there would have been no reason to abort the takeoff. The APU should have been secured prior to taking the runway, but was overlooked while attention was focused on landing traffic to runway 27R and heavy radio communications occurring at the time. Fortunately the mechanical checklist works. I have since modified my technique to run my finger down the checklist prior to taking the runway to insure only runway items are left to complete. I run my finger down the checklist again after all items are completed as is normal procedure. Capts can also assist their crews by allowing them sufficient time to complete their checklists and call them complete prior to advancing power.

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Original NASA ASRS Text

Title: ACR LGT TKOF ABORT DUE WARNING HORN. APU HAD NOT BEEN SECURED NOR HAD THE CHECKLIST BEEN COMPLETED.

Narrative: ACFT ABORTED INITIAL TKOF ROLL DUE TO APU STILL RUNNING. ON TAXI OUT TO RWY 32R AT ORD THE #3 ENG WAS SHUT DOWN TO CONSERVE FUEL DUE TO DEP DELAYS. APCHING THE HOLD SHORT THE #3 ENG WAS RESTARTED. THE APU WAS LEFT RUNNING TO ALLOW FOR A 2 MIN COOL DOWN. THE SLIDE BAR FOR THE APU ON THE MECHANICAL CHKLIST WAS NOT SLID TO THE TKOF SIDE AS PER NORMAL OPERATING PROCS. THE ACFT WAS CLRED INTO POS AND HOLD AND THEN CLRED FOR TKOF. AS PWR WAS ADVANCED WHILE STILL COMPLETING THE LAST FEW ITEMS ON THE MECH CHKLIST, THE TKOF WARNING HORN SOUNDED. THE CAPT RETURNED THE THROTTLES TO IDLE. THE ACFT ROLLED FORWARD ONLY A FEW FT AND THE CAPT ELECTED TO TAXI THE ACFT UP TO THE FIRST TXWY ENTRANCE AND EXITED THE RWY. THE ACFT WAS CLRED FOR A SECOND TKOF WHICH WAS UNEVENTFUL. THE ABORTED TKOF WAS CAUSED BECAUSE THE APU WAS STILL RUNNING. THE CHKLIST WAS NOT YET COMPLETE BUT THE PWR WAS BEING ADVANCED. IF THE ADVANCE OF PWR HAD BEEN DELAYED UNTIL THE CHKLIST WAS CALLED COMPLETE, THE APU WOULD HAVE BEEN SECURED AND THERE WOULD HAVE BEEN NO REASON TO ABORT THE TKOF. THE APU SHOULD HAVE BEEN SECURED PRIOR TO TAKING THE RWY, BUT WAS OVERLOOKED WHILE ATTN WAS FOCUSED ON LNDG TFC TO RWY 27R AND HEAVY RADIO COMS OCCURRING AT THE TIME. FORTUNATELY THE MECHANICAL CHKLIST WORKS. I HAVE SINCE MODIFIED MY TECHNIQUE TO RUN MY FINGER DOWN THE CHKLIST PRIOR TO TAKING THE RWY TO INSURE ONLY RWY ITEMS ARE LEFT TO COMPLETE. I RUN MY FINGER DOWN THE CHKLIST AGAIN AFTER ALL ITEMS ARE COMPLETED AS IS NORMAL PROC. CAPTS CAN ALSO ASSIST THEIR CREWS BY ALLOWING THEM SUFFICIENT TIME TO COMPLETE THEIR CHKLISTS AND CALL THEM COMPLETE PRIOR TO ADVANCING PWR.

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.