Thanks for the feedback,
Eckhard,
We only use MAC 25% when we are looking for a small increase in take off performance after all other means have been tried, as my standpoint is addmitedly that of an operations officer not a pilot I was curious to know exactly what parameter I was playing with, from what I understand 25% is not an optimum setting in terms of aircraft stability and handling for this particular aircraft (737-800) where the normal setting used is between 15 and 20% mac.
These calculations are being carried out in the ops room on a dedicated take off performance tool where we know the airfield to be marginal on the daý.
I just re calculated the figures to confirm the effect on v speeds when changing the mac settings, the only change in all three v speeds was a 1 knot reduction on v2 safety speed from 154knts to 153 knts,(a lower stalling speed) and allowable TOW increased from 77925kgs to 78700 kgs which can make the difference between a tech stop (in this case operating to the Canaries from Scandinavia) or not.
rgds FH
Last edited by Frosty Hoar; 18th December 2002 at 13:12.