@roulis, Machinbird:
You've sent me off on an interesting bit of late-night quickfire research on the subject, so thanks.
Roulis, you're almost certainly correct in terms of theory, but as always the devil is in the details - or in this case, the context. M. Klopfstein's early HUD research was groundbreaking - and indeed a quick check shows the HUDs of European-made fighters to have a basic circular display (one 'needle' plus digits in the centre), the F-16 to have a linear vertical tape display (similar to civil PFDs) and the F/A-18 to have a digital display only. However then - as now - an HUD is intended to be complementary and/or supplementary to the primary flight instruments, and not a single point of reference in itself.
As far as primary flight instruments go, a bit of Google-bashing drew my attention to a seminal 1949 report for the Journal of Applied Psychology by one Walter F. Grether - probably the best retrospective can be found at this link:
http://repository.asu.edu/attachment...010N_11979.pdf
However, further supporting info on the study can be found with a Google search on "Grether 1949 altimeter".
The gist of the findings was that the traditional three-pointer dial design proved to be by far the most susceptible to misreads, and the optimum dial design used a single pointer with a dual-drum digital counter (which I'm guessing evolved into the combination drum/pointer altimeter that later became nearly ubiquitous prior to the advent of the PFD). The study also noted, however, that the vertical "tape" design (at a concept/experimental-only stage at the time of the report) was very close in terms of speed of reading and not far off in terms of reading accuracy.
It's worth reading through the article linked above, as it gives a very useful precis of how the modern civil PFD evolved, and some very interesting background info on the primary design considerations - the short version being that, as ever, it was a compromise.
Circling back around to the original point, I think the only thing we can be largely certain of is that the PNF was referring to the two PFDs and the standby in general rather than a specific area of the PFD. Taking that into account we know that if everything bar the ASI was functioning correctly, the ADI would have showed the aircraft nose-high, the altimeter's digital display would have been increasing with the "tape" and supplementary pointers indicating an increase, and with the V/S pointer ("vario") indicating a climb.
Notably, the V/S indicator is an angled pointer (albeit 'virtual'), and this would tend to indicate that the designers of the Airbus PFD knew that being able to read this at a glance would be important. Later in the sequence, the PF does refer to being unable to read the "vario", but if I recall correctly this was after the aircraft was well established in the stall, descending rapidly and with the consequent airframe vibrations making the display more difficult to read - something which would have still been the case with a "steam-gauge" V/S indicator.
So at the point in the sequence being discussed, the PNF at least was able to ascertain that all three PFDs, when taken as a whole, indicated that the aircraft was climbing.
@M'bird - I think our posts crossed in the ether, so I'll respond here if that's OK.
Originally Posted by
Machinbird
Remember? The crew of AF447 was tasked to suddenly take control and hand fly their aircraft. They failed this elementary task. One of the first things they lost control of was maintaining altitude.
True, however I think that interpretation is lacking in a few pertinent details which are important in this case. Firstly, the crew were handed control of the aircraft as you say - but that does not necessarily mean immediately making control inputs without first properly assessing the situation, which is what the PF did here. Learmount, whatever you think of him, is probably on the money when he says that if the PF had done nothing, the aircraft would probably have remained fairly stable - a bumpy ride, certainly, given the weather conditions, but in actuality plenty of time to observe and assess before reacting. Secondly, the PF's immediate response (pulling up on the sidestick) looks very much to me like a textbook "startle response" (similar to ColganAir and West Caribbean) - this in effect compounded a second abnormal situation on the PNF before the latter had time to process the first (being the AP drop-out and UAS). Thirdly, the PF seems to have developed an erroneous mental model very quickly - but fails to communicate what he thinks is wrong to the PNF. To my mind, this means that there was no effective "crew" as such, just two individuals - one whose SA quickly deteriorated, and the other trying to work out what was happening with a rapidly worsening situation.
Obviously, both systems of altitude display work, but which works better from the human standpoint?
...
The counter pointer type display is more nearly an actual altitude error signal and for small errors, it is easy to pick out the amount of error by the angle of the 1000' needle as stated by roulishollandais. For rapid climbs/descents, the rapidly rotating 1000' needle draws attention to itself and is unmistakable.
Right, but as I stated above, the V/S pointer is angled, to assist determination of climb/descent at a glance in concert with the altimeter tape. It was certainly effective enough for the PNF to state that all three displays indicated "going up" (presumably nose-up and climbing) before he started becoming confused and second-guessing himself.