The text below is copied from an HF web forum. There are some important lessons involving certification, and for operators resulting from unforeseen situations perhaps not considered in the SOP: to use HUD at all times. A Windshear GA becoming an upset, the dynamics of equipment and situations vs static evaluation, and erroneous choice of training as a solution.
In normal flight, P1 and P2 use different mental models. When the HUD upset mode appears automatically and unexpected, the Captain is forced to change the mental view and instrument references.
Although a dual HUD installation might alleviate some of the problems, the unconventional format and surprising change during a Windshear GA adds to the surprise and confusion during the GA manoeuvre - controlling pitch and trim.
The overall deficiencies in the HUD format, cf EFIS # 69, and increased workload, suggests that the better, safer option is not to use the HUD all the time.
“The HUD format (certification) and mandated use (operator SOP) would influence awareness.
Normal HUD use is flight director based; a vector display - winged aircraft symbol and circular target, which depicts where the aircraft is going. The ‘command’ task is to match the symbols (video game - skill based) reducing mental workload.
An automatic change to the ‘upset recovery’ format depends on manoeuvre.
This format is attitude based, without the FD, only depicting where the aircraft is pointing. The mental task is ‘interpretive’ - different symbology and format (knowledge based). Mentally demanding, sudden unexpected change, further limits mental resource.
Thus “The F/.O appeared to have a much better grasp of the issue, but was unable to change the outcome,”
… influenced by a better mental model / task, (head down EFIS with FD), but unable to recover due to limiting control - stick forces, trim, conflicting pilot inputs.
HUD approval via STC by-passed formal HF certification and design evaluation, only assessing operations, procedures, and training (OEB).
An opportunity to mask system deficiencies by requiring ‘more training’ (cf 737 Max).
Change the system, not the pilot.”