Originally Posted by
phllax
Jim,
One last question, in instances of high sustained winds right on the nose on take off, can Vr ever be before V1 on a non-STOL aircraft, and on a runway with enoug length, like Denver's 12,000 and 16,000 foot runways?
I've never seen that, but V1 can have a calculated reduction when there is extra runway available while Vr is not reduced so there would generally be a bigger difference, not a reversal of the two speeds.
One only needs to remember what the two speeds mean:
V1 = in theory the speed at which it takes the same amount of runway to stop as to get airborne. Generally it assumes an engine failure at V1 - the worst case for continuing the takeoff. Winds don't enter into the calculation as best as I remember.
Vr - the speed at which the nose is raised to the initial take-off attitude. Keeping the nose gear on the runway helps acceleration - having the nose up adds aerodynamic drag so reduces acceleration. So the plane shouldn't be airbourne at a speed less than Vr plus a few kts for the time it takes to raise the nose.
You mentioned DEN I believe and in the summer that's a good airport to watch planes taking off. Because planes fly on true airspeed and the indication in the cockpit is indicated air speed, you'll see almost all transport sized planes lift the nose at indicated Vr then roll along on the main wheels until reaching the true airspeed Vr. On the old 727 the difference was about 1000-1500' of runway.
Jim