Flight crew of medium large transport incorrectly calculates takeoff performance factors.

Attributes
ACN	114654
Time
Date	198906
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : den
State Reference	CO
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : takeoff ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 6000 flight time type : 250
ASRS Report	114654
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5000 flight time type : 600
ASRS Report	114655
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During the takeoff roll at approximately V1 minus 20 KTS, it became apparent that if an abort was required, we would not have been able to stop on the remaining runway. Prior to takeoff I had recomputed our maximum takeoff weight due to a 6 KT tailwind. After takeoff I rechecked my figures and discovered that I had used the tailwind factor from the 17 degree flaps column instead of the 4 degree flap column. This error resulted in our being 1000 pounds over the maximum gross takeoff weight. In retrospect, I should have taken more time in computing the takeoff weight and also had the first officer figure the weights so as to have a comparison. A contributing factor is approximately 95 percent of our takeoffs are accomplished at 17 degree flap and I might have looked at this column out of a (bad) habit.

Original NASA ASRS Text

Title: FLT CREW OF MLG INCORRECTLY CALCULATES TKOF PERFORMANCE FACTORS.

Narrative: DURING THE TKOF ROLL AT APPROX V1 MINUS 20 KTS, IT BECAME APPARENT THAT IF AN ABORT WAS REQUIRED, WE WOULD NOT HAVE BEEN ABLE TO STOP ON THE REMAINING RWY. PRIOR TO TKOF I HAD RECOMPUTED OUR MAX TKOF WEIGHT DUE TO A 6 KT TAILWIND. AFTER TKOF I RECHECKED MY FIGURES AND DISCOVERED THAT I HAD USED THE TAILWIND FACTOR FROM THE 17 DEG FLAPS COLUMN INSTEAD OF THE 4 DEG FLAP COLUMN. THIS ERROR RESULTED IN OUR BEING 1000 LBS OVER THE MAX GROSS TKOF WEIGHT. IN RETROSPECT, I SHOULD HAVE TAKEN MORE TIME IN COMPUTING THE TKOF WEIGHT AND ALSO HAD THE F/O FIGURE THE WEIGHTS SO AS TO HAVE A COMPARISON. A CONTRIBUTING FACTOR IS APPROX 95 PERCENT OF OUR TKOFS ARE ACCOMPLISHED AT 17 DEG FLAP AND I MIGHT HAVE LOOKED AT THIS COLUMN OUT OF A (BAD) HABIT.

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.