Narrative:

Aircraft had art system (automatic reserve thrust system) inoperative. Maintenance deferred. With system inoperative, only alternate or maximum power takeoff allowed. Takeoff weight was approximately 146000 pounds (maximum aircraft takeoff weight 149500 pounds) for flight from cvg with full passenger load. Takeoff weight for assigned runway 18L was too heavy for any of the alternate takeoff settings, so a maximum power takeoff was necessary. When takeoff clearance was received, engines were brought up and autothrottle engaged as the engines accelerated to target EPR of 2.05. Shortly after engines stabilized, engine #1 N1 crept up to between 102% and 103%. As airspeed was already above 100 KTS, the #1 engine was slightly reduced to bring the #1 N1 to approximately 99% and takeoff continued. After takeoff when our workload permitted, we ran the 'N1, and/or N2 overspd' checklist which told us to make logbook entry of amount and duration of overspd and continue engine operation. We understood the checklist to allow an N1 overspd of 103% without an engine shutdown. Maintenance was notified and told us to keep aircraft engines running without changing aircraft power for them to take engine parameter readings. We also made a logbook entry of #1 engine N1 overspd to 103% (rounded up to be conservative) for approximately 3 seconds. On arrival at the gate, maintenance boarded the aircraft and read the engine parameters showing a #1 engine N1 overspd of 102.5% for 8 seconds. Maintenance advised me that the overspd required an engine change. It did not make sense to me that we were allowed, by the checklist, to continue a flight with an engine that required a change out after landing, so I referenced the 'N1 and/or N2 overspd' checklist only to notice that the 103% overspd applied to N2 and that the limit for N1 overspd was 102%. In other words, the engine should have been shut down. I can't explain how or why I misread the checklist but do believe that if the checklist was divided into 2 separate checklists 'N1 only' on one and 'N2 only' on the other, that this mistake would probably have been avoided.

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Original NASA ASRS Text

Title: AN MD88 CAPT RPTED THAT HE MISREAD AN ENG CHKLIST AND KEPT THE ENG RUNNING, WHEN IT SHOULD HAVE BEEN SHUT DOWN.

Narrative: ACFT HAD ART SYS (AUTOMATIC RESERVE THRUST SYS) INOP. MAINT DEFERRED. WITH SYS INOP, ONLY ALTERNATE OR MAX PWR TKOF ALLOWED. TKOF WT WAS APPROX 146000 LBS (MAX ACFT TKOF WT 149500 LBS) FOR FLT FROM CVG WITH FULL PAX LOAD. TKOF WT FOR ASSIGNED RWY 18L WAS TOO HVY FOR ANY OF THE ALTERNATE TKOF SETTINGS, SO A MAX PWR TKOF WAS NECESSARY. WHEN TKOF CLRNC WAS RECEIVED, ENGS WERE BROUGHT UP AND AUTOTHROTTLE ENGAGED AS THE ENGS ACCELERATED TO TARGET EPR OF 2.05. SHORTLY AFTER ENGS STABILIZED, ENG #1 N1 CREPT UP TO BTWN 102% AND 103%. AS AIRSPD WAS ALREADY ABOVE 100 KTS, THE #1 ENG WAS SLIGHTLY REDUCED TO BRING THE #1 N1 TO APPROX 99% AND TKOF CONTINUED. AFTER TKOF WHEN OUR WORKLOAD PERMITTED, WE RAN THE 'N1, AND/OR N2 OVERSPD' CHKLIST WHICH TOLD US TO MAKE LOGBOOK ENTRY OF AMOUNT AND DURATION OF OVERSPD AND CONTINUE ENG OP. WE UNDERSTOOD THE CHKLIST TO ALLOW AN N1 OVERSPD OF 103% WITHOUT AN ENG SHUTDOWN. MAINT WAS NOTIFIED AND TOLD US TO KEEP ACFT ENGS RUNNING WITHOUT CHANGING ACFT PWR FOR THEM TO TAKE ENG PARAMETER READINGS. WE ALSO MADE A LOGBOOK ENTRY OF #1 ENG N1 OVERSPD TO 103% (ROUNDED UP TO BE CONSERVATIVE) FOR APPROX 3 SECONDS. ON ARR AT THE GATE, MAINT BOARDED THE ACFT AND READ THE ENG PARAMETERS SHOWING A #1 ENG N1 OVERSPD OF 102.5% FOR 8 SECONDS. MAINT ADVISED ME THAT THE OVERSPD REQUIRED AN ENG CHANGE. IT DID NOT MAKE SENSE TO ME THAT WE WERE ALLOWED, BY THE CHKLIST, TO CONTINUE A FLT WITH AN ENG THAT REQUIRED A CHANGE OUT AFTER LNDG, SO I REFED THE 'N1 AND/OR N2 OVERSPD' CHKLIST ONLY TO NOTICE THAT THE 103% OVERSPD APPLIED TO N2 AND THAT THE LIMIT FOR N1 OVERSPD WAS 102%. IN OTHER WORDS, THE ENG SHOULD HAVE BEEN SHUT DOWN. I CAN'T EXPLAIN HOW OR WHY I MISREAD THE CHKLIST BUT DO BELIEVE THAT IF THE CHKLIST WAS DIVIDED INTO 2 SEPARATE CHKLISTS 'N1 ONLY' ON ONE AND 'N2 ONLY' ON THE OTHER, THAT THIS MISTAKE WOULD PROBABLY HAVE BEEN AVOIDED.

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.