Can anyone help with this one Page 41 of the manual which gives a step by step guide to the v speed calculations , step 4 says determine the desired thrust settings (full or derated)and flap settings for takeoff, my question is how do you determine or decide what flap and derate settings you need i cant find any info about this please can an expert explain this whole process cos i seem to be missing somthingthanks in advanceKav

Oh and also where do you get the assumed temporature to put in the fmcas this figure may be considerably higher to fool the computer in to giving a derated T/O N1 EG 40deg C assumed on a day that is actually 15 deg CthanksKav