Thanks for expanding the points, alf,
It may be clearer just to state that in a tailwind, because the aircraft is going faster, the nose has to be lower in order to maintain the ILS GS, this gives a higher rate of descent. Although this is stating the obvious, these aspects have to be deduced from HUD symbols – not identical to conventional instruments. Thus there may be a higher workload when using HUD.
Not really much pilot "deduction" involved with respect to pitch attitude -- the pilot's primary focus is far more likely to be on the Flight Path Vector which shows where the airplane is going irrespective of configuration or attitude. For that reason, the HUD "boresight" cue (the direct attitude reference) is likely to almost "disappear" due to natural tunnel-vision tendencies under higher workloads.
Reports have indicated that the runway was in view from 700-1000 AGL -- so more than 2 miles from the threshold if on GS.
With an offset LOC the lateral guidance cue has to be ignored whilst flaring in pitch.
That would assume that the FD cue remained in view; we don't know that yet. But the use or non-use of the FD may lead to questions about the need to de-clutter the HUD in the last mile or two to the runway when the LOC is offset. Unlike a conventional ILS where the FD cue can remain in view until touchdown, (and as you've indicated) the LOC and therefore any lateral FD guidance would become a distraction close to the runway.
I would argue that crews have to think out these issues in advance, particularly when using HUD in uncommon situations, and focus their risk assessment on adverse combinations of landing factors so that an alternative landing option can be selected.
My personal HUD experience is limited to the RockwellCollins HGS.
I've been drilling around the internet for some videos or descriptions of how the Marconi HUD works. Does it have automatic de-clutter modes -- e.g., are the airspeed and altitude tapes dropped once the GS is captured or once in final the landing configuration?
Is it fairly easy to cancel the Marconi HUD FD guidance on an ILS and continue with a visual approach mode? Or for example, is it also necessary to de-select the ILS frequency?
The HUD's Flight Path Vector, GS reference line and airspeed deviation cues can remain valuable tools even when the FD is deselected. It's not necessary or even preferable to stow the HUD for an offset LOC; but as you say, the offset LOC and the plans to deal with it have to be part of the briefing.
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