Final, 3 Greens
"...but what about the kinetic energy already in the airframe"
Yikes, haven't thought about stuff like this for
far too long
Whilst I concede that (kinetic energy) would be
additional if our intrepid pilot decided to leave full power on whilst aborting
, if we assume he/she doesn't
the loss of thrust should at least compensate for the inertia/kinetic energy of movement.
Without, hopefully, confusing things here's an example of accelerate-stop distances - albeit for a twin where such things
are in the P.O.H.
Turbo Cessna 310R, 5500lbs (MTOW), pressure alt. 2000', temp +10C, nil wind, Vr = 92KIAS.
Accelerate distance (ground roll) = 1790'
Accelerate-stop distance = 3460'
So stopping, under these conditions, requires 120' less than accelerating. No tricks
- at this speed (92KIAS) the wings are producing sufficient lift to fly. (Stall speed, this config, is 80KIAS)
So does this illustrate that you need less space to brake than accelerate? (Okay, in this aircraft, under these conditions)
So if by 50% TORA you abort there should be sufficient space remaining ahead to brake and stop, within the TORA. (In the context of this discussion, which was that if you are not at 75% Vr by 50% distance)
If you now add-in the other variables - ice, wet grass, - which we agree (I think
) don't affect thrust but do affect braking, we end up where Bookworm started:
The "50% rule" isn't conservative enough.
slim_slag said the same thing too:
"Actually I am far more cautious than that, because I don't want to use all available runway"