Well, after reading all those posts of "experts" ... my input would be that it's quite difficult to say : HUD will do that, will induce those problems .... and PFD by the contrary ...
simply because it all depends of the MODEL of HUD you have, and the associated symbols displayed in it.
I've been flying HUD since 1984, a very advanced one which was changing a difficult aircraft into an easy one - simply because it was, and is still the best on the market. I flew after maybe 15 or 20 different ones, some of them really poor (horizon ? energy brackets ? FPV looking as a FPV when it simply was not...) Also the fact that the industry and the manufacturer can put anything they want in a HUD - well, in fact anything the test pilots want, and even the line pilots want. I have seen such ridiculous solutions "in order to prevent pilot disorientation" ....
Suffice to say that with a good HUD, you can make a barrel roll at low altitude in poor weather and horizon conditions, where you would have been killing yourself with the same aircraft without the HUD (yes, some had, and some hadn't)
Same for a HUD as for a head-down cockpit instrument : a nice one (russian, french often) will be a tremendous advantage, which will make you the pilot say "waoww.." when a poor design - such as some AOA indicators from anglo-saxon world - will make you move away from the stuff, with the assorted wrong conclusions. Did you know by example that you can find on the market HDI combined with HSI ?
When I became an airline pilot, I was so disappointed by how those aircraft were backwards. Then came, eventually and slowly, HUD for transport aircraft - and once again, some great, and some utterly complicated. Anyway, in cruise for hours they have nothing else to do than looking at it, and the approaches are always linear and simple, so I guess after some time they become familiar with the design, no matter how cluttered it might be..
So Derfred, sorry, your comment was about ONE type of HUD, not all the HUDs in general.
Last edited by recceguy; 9th May 2016 at 06:26.