de facto:
add the SPEED INCREMENT above VREF, you are using all flaps up the it should be about vref40+50kts
Last time I looked, Flaps Up speed was F40+70...
Jwscud:
Are the corrections for landing distance linear?
No they are not, as it is roughly:
Energy = Mass * Vg*Vg (squared Vground) thus the speed has a squared effect on the energy contained within the object, thus the energy required to be absorbed to facilitate a stop.
using the QRH Normal landing distance figures to extrapolate to Vref40+70 would not give you an accurate answer
I would agree with this, reference above.
Although the distance from the
Normal Landing Distance tables should never be used, it does give you a good starting point. But only for instance by comparing the additive (difference) for Normal and Non-Normal Max Manual Braking as published in BOTH Normal and Non-Normal tables. This must then
not be used as factual but can be used as a guidance on an indicative increment requirement.
It could indeed be professionally sound to adjust Max Manual Braking with a lesser Autobrake requirement if runway length allows, most airfields we fly into do not have 3400m available to them, if you do operate into those lengths, then use a lower setting but with caution as no guidance exists on them.
Finally, it may be a good idea to have in your mind the deceleration rates for auto brake settings, allowing thus for a rough distance calculation to be made based on any touchdown speed. This rate is what is achieved by auto brakes and is modulated to be achieved, by adding/removing brake pressure due to other stopping factors such as reverse (primary), drag and friction.