|Quoting FlyASAGuy2005 (Reply 4):|
I see that a lot with the CR7s and CR9s. V1 and VR is many times withing 1 or 2 knots of each other, if not the same. I don't know why that is though.
If you work it backward, start with V2
... your safe climb out speed on one engine, under the conditions you are presently flying. Now, think about at what speed do you need to rotate so your initial climb speed is V2
... that will be Vr. Clear enough so far. Vr and V2
are related to altitude/obstacle/ climb performance.
As you know though, V1 is a ground performance speed. Maximum speed at which a rejected take-off is possible, and (likely) stay within the confines of the runway.
But ... what is the airplane is very light, or the runway is very long? It is very possible that V1, could be higher than V2
, and thus Vr. But that can never be, obviously, so V1 is set to the same as Vr. But as pilots we know that when V1 and Vr are the same, the aircraft could conceivably stop on the runway from a speed higher than V1.
Now, we would never do that. Mostly because we don't know how far above V1/Vr the aircraft could be stopped. But it gives one an "impression" the aircraft ground performance capability exceeds current conditions. Conversely, think about a contaminated short runway, in a heavy aircraft, and V1 is far lower than Vr. You then know that aircraft ground performance only equals current conditions.
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!