northwing-
I'm in charge of the 3 engine ferry program at my airline, and I've done a number of them "for real".
There is no V1 on a 3 fry takeoff. If anything happens on the ground at any speed, we keep it on the ground. There is also no obstacle clearance guarantees if you lose a 2nd engine. The only 2 engine performance that is required is a gross 1.2% gradient in final segment.
To protect ourselves to some extent, if the runway permits it, we increase the Vr speed to the min 2 engine Vmca and climb at that speed in second segment.
No way anyone's going to try a single engine t/o. (I hope!)
