Alycidon,
Thanks Derfred, no I don't use a HUD, so, the question is, on a go round, if you are using a HUD, climbing into an overcast at night with your landing lights on, will you not be distracted by the "cloud rush" as you enter the cloud?
I have about a decade on 738 HUDs. I've never experienced that issue. I use the HUD for every takeoff including night into IMC. If you don't like it, you just shift your eyes down to the PFD - which you might do if taking off into the sun, for example, but it has never bothered me at night in cloud.
A HUD is designed to allow you to aquire visual cues while still scanning the display, please indulge me and tell me what visual cues you would be looking for in a go round, and how you would avoid this distraction when climbing into the overcast with your lights on?
Yes, acquiring visual cues during approach to land is a major design feature of the HUD, but as I said that is not it's only use. Obviously you are not looking for visual cues during a go-around (unless avoiding isolated CU's visually). As I said, the aircraft can be manually flown more accurately in all phases of flight using the HUD because of it's symbology, sensitivity and field of view. For this reason, HUD usage in all phases of flight is encouraged in my airline.
Following HUD guidance is like having a PFD maybe 10 times the size right in front of your eyes, complete with F/D guidance, FMA display, altitude, V/S, radio alt, speed, speed error (from bug), acceleration, all without the traditional instrument scan required on a PFD/ND.
We don't know whether the HUD was used for this manually flown G/A, but I am merely stating my opinion that if it was, it would not have been a contributing factor to the accident or any lack of S/A that may have occurred.
The HUD has a very clear horizon line stretching from left to right, making it very clear to a pilot looking at the HUD whether his nose is pointing up or down. Much more so than a PFD.
Furthermore, in a more extreme UA, the entire HUD picture changes to a circle with an arrow telling you which way you need to pitch in order to save the day. (If the AF447 pilot had one of these HUD's, it probably would have saved him). I digress, however, because it is possible that in this accident that by the time the aircraft was in a nose down UA, it was probably too late to save it.
I would think that the impression of a false pitch up caused by somatographic illusion would be increased if you were seeing the cloud rushing past through the HUD as you climbed into the overcast, particularly if you have just been airborne for 6 hrs in the middle of the night.
As I have said, I disagree. That's my opinion.
The HUD not only gives you pitch attitude, it gives you a flight path vector. If that flight path vector is above the horizon, you are going up. If it drops below the horizon, you are going down. I've already said the horizon is very obvious on the HUD, and the FPV is generally where your eyes will be focused, because that is what you "fly". If using F/D guidance, you fly the FPV to the F/D, rather than attitude as you would on a PFD.
Because you are left with no doubt about where your aircraft is going, I actually think somatogravic illusion is less likely with a HUD because you have better visual confirmation of what your aircraft is doing compared to what your vestibular system might be telling you.
Also, the PM does not have a HUD, so does not see the same picture and therefore will be using the PFD when not busy with flap/gear retraction or frequency changing and will not really be able to monitor the PF.
The PM does not have a HUD, but does see the same information! The PM sees the exact same aircraft pitch/speed/performance just on a different set of instruments. The F/D commands, if being followed during the G/A, will be the same on the PFD as they are in the HUD (different representation, but come from the same AFDS computer). If anything, two sets of eyes on two different instrument representations should increase redundancy (safety) not reduce it.
The PM's monitoring role is no different and no more or less important whether the PF is using a HUD or not. In fact the PM usually sits there in amazement (or jealousy) at how accurately the Captain is flying. The Captain is only flying more accurately because he has a more sensitive instrument that is easier to use (less scanning required).
The only time the PM misses out is during a low-viz manual landing (eg CAT III) because that is where having the HUD makes possible what would only otherwise be possible with autoland. Not relevant to this situation.
I will provide the caveat that the HUD requires training and practice for proficiency. I understand this crew was not new to the aircraft, but I know nothing of this airline's HUD training or HUD SOP's.