To the bottom of the sea: Bin Laden's last day – CBS Evening News – CBS News

The operation’s helicopters — reportedly a HH-60 “Pave Hawk” and a CH-47 — came under fire from security forces firing from the roof of the compound. The Pave Hawk had mechanical failure and made a hard landing after half the platoon “fast roped” into the compound. At least two other helicopters were part of the initial assault. When the Pave Hawk couldn’t get back in the air, it was destroyed to protect the ship’s sensitive avionics and communication equipment.

(Italics mine.) Right. Because no one was shooting at them or the helicopter at this point. Why is it that alll helicopters crash because of mechanical failure and never because they were shot down? What constitutes mechanical failure? Does a SAM to the engine constitute mechanical failure???