[ez]

The vector that the ice/foam hit the wing was glancing.

In support of the ice/foam theory, the object which struck the wing DID appear to shatter after contact.

[fooman]

Of course if the leading edge was damaged, the the zipper effect would be much more likely than if the hit was at the back of the wing.

[LiveFreeOrDie2001]

I think the angle that the foam hit the tiles CAUSES MORE DAMAGE (Shearing) than if it hit at 90 Degrees.

I am an engineer and I find it hard to believe their much better Engineers that I could dismiss the impact angle....