Ptkay’s point #539 about the terrain at Smolensk is worth noting and especially the Russian description of the “death trap”. ...
Could they have been flying some alternative non-standard procedure (GPS ?) using PAR only for monitoring ?
I still think, this is worth something, because it certainly was an
"alternative non-standard procedure".
The contact with the ATC was broken, if the terrain profile shown in some
animations is correct, then, at the NDB antenna point, where they first hit
of the small birch tree, they were in the shade of the road on the top of the hill
and invisible to the PAR radar.
Maybe this "alternative non-standard procedure" was just scud running
according to GPS and radio altimeter, with wrong terrain data in the GPS,
wrong, or non existing maps and rising terrain: it is a "death trap".
Been there done it before, but with a small single engine prop, and the
approach lights were full Calvert. To follow the "undulating terrain"
and finding the runway was not an issue by that speed.
The opinion of the Russian pilot, was by a fighter pilot, who described
such "alternative non-standard procedure" going well in an agile a/c,
but certainly not in Tu-154.
I was just quoting opinions from some Russian speaking forums.
I take no responsibility for correctness.