Performance figures are usually based on a demonstration of skills by both the manufacturers test-pilots and the regulatory authorities pilots. They then build in fudge factors such as the time allowed to react to a V1 cut. The resulting values should be achievable by any well trained airman.
As for the perfectly new aircraft, performance data is factored for inservice aircraft with specific fuel and drag biases. They have also made some changes in the regulations concerning takeoff calculations, such as changing the certification testing to be based on worn brakes, rather than new brakes.
Now if you really want to make this topic interesting, just ask about how they calculate the effect of crosswinds or contaminated runways during takeoff......................
(It might wake J_T up......)
Mutt.
