Originally Posted by
sonicbum
If You rotate at Your RTOW Vr rather than at Your actual GW Vr You will simply delay the point in space at which You get airborne but You will do so with some extra speed that will potentially be useful if, in the first few hundred feet You encounter WS such that You are likely to lose 15/20 kt, let's imagine a strong tailwind component kicking in at 300-400 ft as a result of local wind phenomena (katabatic winds or so). Anyway as You well know any WS that is likely to be induced by TS activity around the field should be avoided in first place by sitting on the ground till conditions improve.
I agree with your specific example but
that’s not the scenario I described
In other words, what if that useful extra
speed is gone ?
If you are still on the runway AT this RTOW
VR when you encounter a significant airspeed loss due to windshear, you could well lose all that energy you have gained
by staying on the ground longer
So you’re past the point you can reject and still on the ground with no choice but to lift off into a windshear
At this point you have no advantage, no additional airspeed and of course no altitude