Re: Derate and V-speeds
I think i got the reason based on Matt's explanation even though i could assume something slightly different :
Assuming you accelerate using Derate from brakes realease point till V1 (the original V1 calculated for max performance take off . Now this portion by it self will require more distance than when using max performance take off. Now if you continue from V1 your take off till reaching V2 ,again this portion by itself will be more than before becouse of the lower rate of acceleration .Your TODR overally increases significantly . If you were to stop following V1 then i would not expect the Deceleration distance it self to be much different than before .Your ASDR has icreased too ,but not as much as the TODR . So by definition since V1 is the speed at which it would take the same distance to either continue take off and reach screen height , or come to a full stop it would only make sence to increase V1 when using derate so as to equate the new distance from V1 to screen height with the decelaration distance from V1 to full stop .
I hope the way i wrote it makes sence ......