IAS
Great thread but I have to throw a spanner in the works, All Perf data based on IAS (V1,Vr,V2) which can spike up and down and does not represent the aircraft's true kinetic energy v runway length to stop in/obstacles then to be cleared if you go. Should we not really have data based on G/S and weight v runway details and brake capabilities? Think about it, its much more logical than saying your life depends on pitot pressure at the moment the engine fails.