"but what about if at 10 degrees your engine decide to quit? or you encounter a windshear? I think the aircraft will sink much more than if it was at a steeper attitude.". .. .As for windshear, many manuals tell you to delay rotation and build up "smash". Some companies do this procedurally to improve revenue loads. My company calls this delayed rotation, "Improved Performance Takeoff. As for an engine quitting, you'll have so many more visual refrences available to you at 10 degrees. Look out the window and "step on" the runway centerline. I've flown military heavies where, accelerating in ground effect with an engine loss was standard procedure. In the equation of lift, V squared is the dominant figure, not AOA. At 20 degrees, you'll have a more dynamic situation and you're closer to the ground. . .. .Anyways my 10 degree technique presumes excess runway and no obstecles. I've always felt the plane will fly when it's damn well good and ready to. I'll only force it to fly if I'm running out of runway or have to clear an obstecle.