A WDB ACR CREW TOOK OFF AT A HIGH ALT ARPT ON A HOT DAY. THEY WERE SURPRISED AT THE LOW EPR SETTING GIVEN THEM BY THEIR COMPUTER.

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CONDITION: HIGH ALT ARPT 1400 FT AGL. MAX TKOF GROSS WT LIMIT 323000. HOT 31 DEGS C; PACKS OFF; ANTI-ICE ON; ENG PWR. PWR SET WITH AUTO THROTTLE. SLOW ACCELERATION ATTRIBUTED TO HIGH/HOT/HVY. PWR SEEMED OK -- IN MIDDLE 1.30'S EPR RANGE. WITH LONG RWY; ACFT ACCELERATION LOOKED BARELY ACCEPTABLE BUT ADEQUATE. ROTATED AT V1 HAVING USED MOST OF THE 12000 FT RWY. JUST AFTER ROTATION; PWR; IN AUTOMATIC CORRECTED TO ABOUT 1.49 EPR. COMPANY POLICY DEPENDENT ON AUTOMATED WT AND BAL AND PERFORMANCE DOES NOT REQUIRE PLTS TO DETERMINE PWR SETTING. IN THIS CASE; 3 PLTS (1 RELIEF) ACCEPTED A LOW PWR SETTING FOR TKOF BECAUSE IT WAS 'COMPUTER GENERATED' AND AUTOMATIC. SLOW ACCELERATION PUT PF IN A BOX. PLANE FAST ENOUGH TO TKOF ONLY AT END OF RWY; USING TOO MUCH RWY LENGTH TO ALLOW A REJECTION AT V1. THIS AIRLINE MUST CHANGE SOP. REQUIRE A NUMBER TO BE GENERATED TO XCHK THE AUTOMATIC PWR SETTING. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTING CAPT; A CHK AIRMAN; SAID THAT 31 DEGS C AND ANTI-ICE ON ARE CORRECT. THE ENG MANUFACTURER USES THIS PROC AS AN INTERIM FIX FOR A FAN BLADE TIP SCRUBBING PROBLEM. THE RPTR SAYS THAT THE 1.49 EPR IS CORRECT ALSO; HE CHKED IMMEDIATELY AFTER TKOF. HE SEEMS TO BE MORE AT EASE WITH THIS PROC NOW; AND HAS A 'GOUGE' FOR CHKING THE EPR SETTING THAT COMES FROM THE COMPUTER.