J_T,
The programs that mcdhu is talking about use the first principle method of takeoff calculation, they are extremely precise and can offer an increase in takeoff weight of around 8,000 kgs (B747-400) over the older calculation method (model tables).
The effect of rounding up temperatures depends on how much the temperature spread is, again for the B744 we are looking at 1,500 kgs per degree C. So rounding up 1 degree isnt too bad, but rounding to the nearest 5 wouldnt be wise.
mcdhu You are achieving the regulatory minimums, that much is guaranteed. Whilst it appears that the comfort margins are reduced, you have the benefits of certification changes that are more representative of the actual aircraft operation, for example, Accel/Stop distance accountability for worn brakes and the acceleration of the aircraft with thrust after V1 rather than maintaining a constant speed.
Additionally, your airline performance engineers now have the ability to account for line up distance, stopping margin, multiple slopes and runway surface condition. These were never available through the AFM.
So to answer your question, "is it wise?".... My answer is yes.
Mutt.
Last edited by mutt; 22nd June 2005 at 18:51.