being limited by accelerate-stop distance ONLY explains those rare (one in a thousand or so) takeoffs where your allowable takeoff gross weight actually is limited by accelerate-stop distance. Most of the time it is not. What about those hundreds of twelve thousand foot runways out there? What about all those low-gross weight takeoffs? On a typical takeoff you might have a V1
of 120 knots but realistically you could accelerate to tire speed limit (about 195 knots) and still stop in the remaining runway.
I don't have an up-to-date copy of FAR
Part 1 handy at the moment but V1
is established for weight AND
configuration by the manufacturer with reference to VEF
which is the speed at which an engine is assumed
to have failed. VEF
itself is established with respect to V2
which, in turn, refers to VS
which are both directly affected by gross weight and configuration.
The published V1
is pretty much a function of those other speeds - BUT
it still must permit accelerate-stop on the available runway.
A fairly recent revision also states that V1
is the point when the pilot must have begun the process of rejecting the takeoff. After that point the takeoff must be continued even if the engine is 4th-of-July
on fire! This does not necessarily mean that there is not enough runway left to stop the airplane! It just means for sure that it is safer to continue, get the plane ready and make a more normal landing and deceleration.
Happiness is not seeing another trite Ste. Maarten photo all week long.