From the accident report, when the HUD reverts to upset mode, the mental reference has to change from FPA to attitude; - this requires significant mental readjustment. Also the FD is removed.
This was noted by
Fursty Ferret in
Flydubai crash at RVI final report out , and that the “
The HUD symbology on both the 737 and 787 is pretty terrible”, but how is this reported to the regulators, considers equipment reassessment or associated SOPs, checks training implications, etc, …
The change of ‘mental model’ - switching from one format to another could be similar to reverting from head down instruments to visual, which has been shown to take 2-4 secs, i.e. a delay in re-establishing sufficient awareness for the task - upset recovery.
Other questions about the HUD; the accident report shows views of the HUD during the approach, it is unclear if these are either a mathematical simulation or from a training simulator.
Assuming that the top-right dial display is AoA, then the adjacent digital values appear not to correspond with the aircraft manoeuvre and speed.
Nose up, fig 65, 1.4. Alternatively in fig 66, -0.6.
Nose down, fig 70, 3.6.
Why should this be ?
And for all those who demand “we must have AoA displayed - upset recovery”; the HUD Upset / de clutter mode removes the AoA display !!!
Anyone able to confirm this via training simulator / real aircraft / HUD.