Since the polish media and some people in the forum are starting once again to consider A/C having stopped descend at 100m, i am diggin out my drawing of the vertical approach path which i
posted last summer and which - amazingly - is still quite valid in the lights of the now available FDR data.
As this drawing was made matching CVR with terrain profile, lets match it with the FDR data this time.
First, we check out the FDR plot of the radar alitude:
Following a steep altitude decrease, the radar altitude levels in at around 100m between 10:40:42 and 10:40:49 with a 5 second jump from 100m to 109m and back.
Secondly, we look at the approach/terrain drawing:
The time between 10:40:42 and 10:40:49 is exactly the time when the aircraft overflew the slope of a 1km wide and ~40m deep dell.
Thus, even though the aircraft was still descending after the first 100m callout, the ground separation aka radar altitude naturally leveled in at ~100m for around 8 seconds until the deepest point of the terrain was reached.
As the terrain descended even steeper than the glidepath of the aircraft, the radar altitude shortly raised from 100m to 109m.
It is all clear!
On the other side, if the aircraft had in fact stopped to descend at 100m QFE, then - because of the descend in terrain - the FDR would have registered a steadily increasing radar altitude curve from 100m to 140m in between the 8 seconds in question.
But this is not the case!
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For those interested: I found a nice vertical terrain profile of the approach path to smolensk airport
here.