Originally Posted by
His dudeness
The BFU asked for the tapes of the last 6 approaches and 6 out of 6 times the aircraft overshot the centre line. All intercepts were made at 220-240kts GND.
To me it looks as if they just banked the little bugger hard in order to correct onto the LOC and either did not pull, thus the descent rate developed or the aircraft was full of clear ice and had an "high speed stall" when they banked it.
Firstly, a modern Jet, professional flown, a lower weight, approaching the homebase as they done before, KIAS 240, about 1000ft/min idle descent in AP-mode, maybe delayed to select flaps/gear before speed reduced before the OM, to get configured and stabilised at OM.
Just a little frictions, a field of clouds, which had in it centre severe icing, is approaching. Due to idle pwr boots might not operate at max capaility, but still in operational limits.
Just a normal approach, in limits, the overshoot is not avoidable, if ILS is armed to the FD at KIAS above 180. Only area nav like GPS will align perfectly to the LOC. But then the nav-source has to switched to ILS, manually or some system doing it automatically.
But, and now comes my different conclusion.. But, if Apor NAV was selected, Heading has to change BEFORE the aircraft reach LOC (Anfluggrundlinie). According to the picture on page 26, my ipression is that heading was changing just after passing the LOC. That is typically if the approach was not armed. The aircraft levelled monumentally of at 17:14:17:97 -96 ft/min, than reached a bank of nearly 60 degree, speed increased and descent rate reached more than 2000 ft/min. For me it looks like after overshoot the crew tried to solve the situation. Still 3 cases possible: tail stall due to icing of elevator, high speed stall, due to G-load increased stall speed + ice. And 3. loss of control, turns in clouds under non-continuous conditions are prone for illusion, while height was to low to recover.