Originally Posted by GarageYears
another aspect not so obvious is the sand/rock nature of the contact
Mentioned back a couple of hundred posts ago, but probably lost in the clutter:
I'm intimately familiar with various desert surfaces of the eastern Sahara. The desert surface along the northern coastal regions of both Libya and Egypt are gravely plains with clay consolidated sand mixed with gravel extending to a depth of several metres (several tens of metres in places) before bedrock is reached. While I have not actually been to the accident area, from the photos I'm reasonably certain the ground here is no different.
Such a surface is quite firm against vertical compression (will support a car with hardly any noticeable sinking of wheels, and in some places would probably support even an aircraft - at several airports of the region you may see derelict aircraft simply pulled off to the sand), however it is actually quite loose, a hole can easily be dug even with bare hands. In a relatively flat impact scenario, this surface would act more as a shock absorber, having properties somewhat similar to engineered arresting materials. It would dissipate a lot of energy quite fast, and being soft would not directly cause much structural damage. An aircraft landing on it at a shallow angle would probably remain structurally intact (minus landing gear, which would likely shear off, but greatly cushioning impact at the same time), comparable to what one would expect when making a hard landing on a runway. Correct me if I'm wrong, but
AFAIK certification standards involve demonstrating no loss of structural integrity if the aircraft is flown into the runway at normal approach descent rate/speed with no flare whatsoever.
I still believe that for the kind of disintegration we are seeing here, the aircraft must have impacted at an unusual attitude.