Something seems completely overlooked here..
The best analysis available so far indicates an almost linear descent from 4km to first impact at about 1.1km. Even if giving ATC the privilage to chose any fixed angle as the glideslope, still only one of the points (4km, 3km and 2km) may have been actually "on glideslope", with one high or low, and at least one completely out of tolerance.
However even more interesting I find the time differences here. Looking at the CVR transcript, we can see the following:
39:50.2 00.0 Outer marker (6.1km)
40:13.5 +23.5 ATC: 4..
40:26.6 +13.1 ATC: 3..
40:38.7 +12.1 ATC: 2..
40:56.0 +17.3 Inner marker (1.1km)
Sec/km, from outer to inner marker:
11.75
11.75
13.1
12.1 So far an average of 12.2 sec/km
19.2
7.0 sec/km extra. Or 158%. (From 2km to inner marker 1.1km)
To burn up this amount of time in 900m would simply be impossible. It did not happen. What does this mean? Clearly the
calls of 4km, 3km and 2km were given by ATCO several seconds too early. Or in distance..
about 400-600m too early.
It is hence possible that the crew were evaluating their heights rather correctly, in respect to the distance from runway they were given. When the last "100" was called by navigator (or automatic?) , they would then believe that they were almost out of the ravine.. Hence pretty much on glideslope. The "100" was called at 1750m, but if they were "feeling the time", or in other way using it for navigational plot, from ATC notified "2km", then they would believe they were around 1150-1250m. Hence in perfect position for their height, and at a point where RA should have been off my no more than 15-20m. So they would believe they were at 80-85m, but they were actually at 50m. Or similarly, when at 1600m, they could believe they were at 1000m, past the ravine completely. While they were actually just over the bottom of it.
As for the ATC radar display. Assuming they had no LCD but rather the most simple available, the flight path would look something like this, with the black line drawn by operator as a help line for the minimum acceptable height:
While I'm not a conspiracy theorist, I can't avoid to make the objective realization, that it must be extremely simple, both in technology and practice, to fix this equipment to show an imaginary "on slope" aircraft path/signal at the time of this incident, with the ATCO completely unaware. But that is useless to discuss, as no evidence may ever confirm it. So, assuming the display showed what is indicated, I can't really see how he can call "on glideslope".