For any given set of limiting conditions, based on the data used by the airline and applicable regulations based on certification and airworthiness minima- there exist only on factor that can be controlled by the by the performance planners that is weight; so field performance (ASDA v.s ASDR) or obstacle clearance-acceptable performance AEO and OEI from the screen through the net flight path at the applicable airport's RWY's. So, by Regulating the Takeoff
Weight, for applicable limiting factors, to an almost unlimited variety of possible circumstances (from flight test data); the data held by a particular operator for a particular type depends upon 1. the certification, 2, the certification's authority's requirements, specific airline data that the may have at hand due to special operational considerations etc..
Types of limiting conditions/ factors may include the following 1. field length-ASDA, Obstacles, MEL's, Configurations (flap setting for TO), Power settings, Bleeds and Packs, MLW at next field, Rwy conditions, winds, OAT, operation's long haul or short haul, personal minima and so forth. So, for a huge number of limiting possibiliies a maximum takeoff weight is scheduled for that field and(whatever schedules and data exist.
Now your side is to see that your actual take off weight v.s chosen thrust settins (derates, assumed temperature for reduced thrust) and configuration 9flap, weather, winds, OAT, (CoG for stab setting), is within in the limits of the one dependent variable that you are truly responsible for is speed (now my above post I wanted to avoid saying Vee
) So you set these speed based on whatever your data RTOW's are calculated and based upon. your TO analysis, as mutt has said, seems to be a gross error check for the FMC, becuse for the most part you cannot control weight and definitly not RWY conditions. Now, if your data is BF then so be it, if you have an approved choice of V1 speed if there's a big cross wind don't get too close to V1Mcg if you can help it (the ADM part). To find out for sure what data is being used and what assumptions are made and if your V speeds are BF or what ever, well ask the performance specialist how they calculate your RTOW's-I hope i dididn't make anything up
