Hi interfrequentflyer... When I was opening the link I found immediately the stat discussion "Averages and outliers" that I liked very much (math acuracy), despite what the author was saying was not new -Mandelbrot told that many decades ago as a part of his works on systems dynamic in finance (his work) and after that fractals- but always forgotten in actual works, airspace or finance included. and despite I did not understand why Winnerhofer gave that link in AF447.12
"We" have leaved and lost the traditional skils of aviation, but "we" did not accept the strict logic and math rules of the new IT world emerging in airspace. The result is dummy pilots who no more understand their planes and are unable to understand them. It is why I'm plaiding for a higher level in math, IT, physic in airspace, pilots included, and that has a price, the price of the modern IT world that we are not able to stop.
And I did not read "The C* continuum"... reading the comments on PPRuNe about C* I'm seeing that common acurate définitions are still missing. It is strange and paradoxal, because we see many planes are flying. In fact aswell militaries like gums or civilian like PJ2 with a great and safe experience of FBW both are flying with the very FIRST FEEDBACK used by human : Sight with eyes, on the natural or artificial horizon or Hud. Effectively the Side stick works with Nz as the term "1/s" in the equation lets no doubt (A33Zab) , but both gums and PJ2 do not matter : the first adds the sight feedback to that équations (don't forget that the stick is always creating a transient and not a steady situation, ie starting a simple turn with bank), the second learns to do only little quiet movements giving time to the system to follow his understanding of action on the stick (still short around tenths of second).But many ordinary pilots have not that ability to counteract in fact these sytems done to correct low turbulence, and not able to correct heavy windshear (to be discussed) and are in big trouble when incidents happen.
Last edited by roulishollandais; 9th Feb 2015 at 18:06.
Reason: excessive interligne
Exactly - and that is why it has precisely nothing to do with a supposed design issue with C* in stall - they were not in C* in stall.
Would you like to check your facts sir? The first stall occurred in Normal law and caused a drop to Direct law. The stall at the top of the steep climb occurred in abnormal attitude law, which is also a degraded form of C* Law.
If XL (and G-THOF) illustrate any design flaw it is with underslung engines, not C* - but in my opinion every design decision has compromises, no design is perfect in every scenario, and what it really illustrates is the perils of trying to recover a pitch upset by adding thrust when your thrust line is below COG.
Granted the underslung thrust line does not help the pitch up situation, but I think you are giving it too much credit. The little A-4 Skyhawk I used to fly had a THS also and it would do a dandy tailstand if the trim ran away nose up and that aircraft had the thrust line through the cg (or close enough). It is the THS being out of position that is the hazard, the underslung engines are just an additive problem. You expect the engine effects. You do not expect the unresponsive THS which may also be trimmed well away from normal airspeed range.
From what I can see, C* works a treat when it is working right. It is just that when it doesn't have correct inputs that is can be a handful to corral, particularly for the weak stick jockeys. For oldtimers such as myself, C*U is probably more intuitive, but FBW in general is extremely dependent on its data inputs for proper operation. How such degradation is detected and presented to the crew is an area that can still stand further examination and improvement.
Ian W, excellent points (#1195); you address the underlying problems. Some further thoughts on these, but from a slightly different view.
The key point is what we assume ‘it’ be – “what’s it doing now” is generally automation focussed. An alternative is to questioning what is the aircraft is doing, what do ‘we’ want the aircraft to do (to achieve the objective), and what would the best means of achieving that; manual or auto. And if auto which modes, and are they suitable for the objective. The process is one of questioning the overall situation as opposed to accepting automation without question.
“What is it doing” implies the crew don’t understand, hold an inappropriate awareness, or are unable to relate current activity with a situation. Crews need to consider what aspects are required to understand the situation before choosing a course of action. Think before acting. This approach would be radically different to the current mantra of ‘read the mode annunciators’. It is impossible to gain a full understanding of what the aircraft is doing from a small set of two or three lights.
The industry has to turnaround the focal point of awareness; not autos, aircraft first, … Plane, Path, People; Aviate, Navigate, Communicate (with the autos), Manage (automation). Older pilots may only have had one focus, the aircraft; extensive automation has turned this around, thus it’s time to rethink training and the mental approach to operations to accommodate these ‘automation’ changes.
“…automation surprise and cognitive overload” automation generated situations can be surprising, individuals will be surprise, but cognitive workload is manageable. As above don’t attempt to determine the situation from lamps. Look at the instruments, the aircraft, the flight path, then consider automation - knowing what to look at and when – having knowledge of what is important in a particular situation.
Note: I am not a pilot, nor a mechanical engineer. But I do write software and it seemed like a system of this kind could be implemented, tested, certified and put to good use by all Airbus aircraft in the future. I might have misunderstood how the fly-by-wire system works or made irrational assumptions, I am all ears to be told otherwise!
Interesting that this software blogger is saying he doesn't understand how the AIRBUS FBW works
Can anyone answer my question about the PF in AF447....Pierre-Cedric Bonin. It is often mentioned that he was a glider pilot. So am I. And glider pilots are commonly intensively trained to recognise and recover from unusual attitudes. Did Bonin hold any FAI certificates at all? where did he do his gliding? and how many hours and qualifications did he have in unpowered flight? I am not clever enough to discover the answers....perhaps someone who understands the French systems can help?
I wish I could still find the page I dug up back in 2010 with the details. As best I can remember, it mentioned Bonin undergoing some kind of basic, intermediate and advanced gliding qualifications over a year or so - certainly more effort than a single week would provide.
Thanks for that, Dozy. So it wasn't just a quick ride to tick the boxes. All the same I think a gliding background, especially the intensive practice in launch failure that should be covered before solo on a winch launch, must be a good background for understanding "what is it doing now!?" The stick is moved steadily back during the launch, but if the cable breaks, and you neglect to move the stick forward for the recovery, a stall and spin is likely.
In the French system such informations can't be published unless the BEA report decides it is a safety clue useful to publish, or if the person himself does these information's public. Years ago they were abuses in displaying these informations, DGAC agents had been fired.
I know this is a bit off topic, but thought I'd ask anyway. Does anyone happen to know what the F/O meant when he asked in reference to ozone "What’s that is it specific to FIT?” at time 2 h 09 min 01? What is "FIT"? I have never come across this acronym before, or maybe it is something so obvious that I am not seeing it?
After listening to the "stall stall" part of CONF iture's sound track several times over, I've come to the conclusion that Airbus has done an excellent job of providing a warning sound that just naturally becomes part of the background commotion with repetition.
Maybe they really should tell you something that you really might need to know like "Alternate Law" or as in the case of the Perpignan A320, "Direct Law." One time, clearly enunciated, should be enough.
Machinbird...regarding warnings blending with others and so on, in fact this accident is such an outlier in so many ways that the fixes applied by way of different messaging, auditory and visual alerting and so on, may rarely if ever be seen again, the risk being that, while this accident "uncovered" some aspects of the design that in these specific circumstances, crew included, we are not assured that there aren't other, different circumstances which, when they do occur and we have once again the benefit of years of analysis, new calls for design changes once again arise.
I'm not disagreeing with you so much as observing (as you have considered, I know) that the designers and the engineers must have done 99.9% of it right given the millions of unremarkable hours flown by Airbus crews, and the thirty-one A330 crews who, in the same circumstances, continued a safe flight to their destination.
The real question is, how far do we go in safe-guarding systems against inappropriate responses? What do we eliminate?...extremely rare conditions aside which potentially cannot be expected or even reasonably assumed?, more automation?, better-trained pilots? And if so, what justifies (and certifies) each response and who pays?, (because the airline passenger won't). How much can we expect (and pay for) from the designers, engineers and test pilots before we can all say, "enough has been done"?
Having watched and participated in this extended discussion on AF447 and related matters for five-and-a-half years now, I think it is important to be mindful of the very great amount of data "on the other side of the question" regarding automation, the Airbus, pilot competency and risk. I suspect it exceeds the usual 10-9 standard for engineering probabilities.
Is it "good enough"? Never, where loved ones' lives are concerned which is why accepting that 99.9% isn't good enough when statistics no longer apply...but, given how this industry does its work, will we know "not good enough" when we see it? The history of "not good enough" and the industry's response is deep in this industry which is why it has a safety record that is enviable by all other industries who must manage risk-to-life.
But it is not just not realistic to have it both ways - it is not possible to have it both ways and so the decisions on what may be reasonable to anticipate and what may be left up to resiliency, robustness, competency and probabilities remain silent until circumstances such as AF447 re-focus the discourse.
I think the one thing that I would like to have seen done different on the design side is the installation of AoA guages.
The rest is on the training side, to include how to use the AoA guages. This crew never knew they stalled. There have been plenty of examples of other crews stalling without knowing it, and those included highly experienced pilots with aerobatic and military backgrounds. The factors that led to them not knowing are several and I know they are known to you.
Pilots are also not trained to know the automation well enough to make predictions on what it will do next, or should do next. The training in the hq in the high altitude regime is scant, and simulators do a poor job of replicating it all. Similarly, training in the hq in degraded modes, particularly at various q-factors is missing.
seagull967, re, "This crew never knew they stalled.", and I think wouldn't have considered pushing the stick fully-forward and holding it there while going down.
I am beginning to appreciate more, primarily from the postings of the military guys who knew these areas and who knew full-stick deflection is always in the tool-kit, the view that even as we have four very clear metrics as to when the airplane is fully-stalled, such information is essentially unhelpful because it is benignly-given, benignly-referenced as a by-the-way in the manual, without any guidance whatsover (at the time) that fully-forward on the stick is what is required when stalled at cruise altitudes. One is not going to do this when terrified and going down - that is why stall training is necessary, but that point has been thoroughly made.
For this reason I think an AoA guage may not have helped, because "fully-forward on the stick for a full minute" would seem suicidal and certainly not natural or intuitive. From the sim experiments, (the replication was quite good even as it is extrapolation), it took 45" and 15,000ft to unload, (to use Machinbird's original term) the wing.
As an aside, you could watch the AoA on the FMC using the ACMS parameters page...but it wouldn't be helpful in these circumstances!
I somewhat agree with you, but I think that if you saw an AoA guage with a CLEARLY defined "red zone" and you are in it, with proper training, a pilot might just do the right thing. Proper training is the key, they have to SEE it in the simulator, not just talk about it. The combination would be quite powerful, and if that does not work, there is nothing except some of the concepts of automatic stall recovery with extending vanes or something similar (not great ideas IMO).
seagull967 and PJ2 AF447 pilots at that point of time did not have the training and technique to deal with the situation. They put the aircraft beyond extremes of flight envelope. You cannot have training solutions to recover from that. Like the captain who barrel rolled the 747 and recovered miraculously do you need training for this how to do it? The main point of training must be that in Airbus alternate law never grab the stick and apply pitch inputs. It maintains the flight path so just look after the bank. Why does any one apply pitch input any way, to change the pitch isn't it? How can that be done without looking at the pitch? This knee jerk reaction initiated and sustained till it didn't matter anymore caused the problem. It was one off irrational act for want of procedural knowledge. You cannot keep trying it out to perfection. Just don't do it is enough.