Wire cutters work ok provided you are in level flight at cruise speed as DPW indicated. They really are only a hopeful last defense to wires possibly being in the area between the rotor and fuse, as you don't want it hitting the main mast.
They are almost to the plane of the rotor, but not higher, or the blades would meet cutter in normal flight. If you are climbing or descending, you likely wouldn't be at the angle for the wires to go into the cutter, they would hit fuse or rotor first, with predictable consequences. If hit at an angle, don't know if it would cut, I would guess that you would as it took tension effect a roll moment to the heli and then the main rotor or tail would intersect the wires, with predictable results.
As it hits the cutter it is guided to the blade which at cruise is more than enough to snap thru it, and as the heli has "Stretched" the wire at that point foreward (if at cruise flight, level attitude, the two ends are pulled away from the 'copter as it continues to move forward, there is at that point of cut, the tension causes those ends to spring away from the heli.
Which the amount of tension at that point it can move the ends get away fairly fast. Likely fast enough that any arc between wouldn't bond them to the cutter. (One should see the results of an arresting cable break, not something I want to repeat twice in my lifetime I assure you.
Realistically it is best to avoid wires altogether. If you see some, FIND the tower and fly over it. Never, if you can avoid it go between towers, as you may not see the wires until the last possible moment.
Had 1 UH-1N suffer a multiple wire strike, the cutter clipped both, there was enough room between them. The cutter had markings consistant with an arc, but I think that when you first hit a wire, you have an arc that now makes the heli equal to the energy level of the wire (power co. Heli's bond themselves tot eh wire before the worker goes to work on them), But if it is at the moment of cutting, I believe the ends move away too fast to be welded to the cutter at that point. If it happened however, I would think it would be a weak point on that wire now being tensioned by the forward speed of the heli and the cutter would still part it (if it were the second? Don't know, ours did a second, but three? Boy I think one could see three wires coming.)
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Marc