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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 30th Sep 2014, 12:49
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Cool Guys
In alternate law pitch control, handling remains similar to normal law except that it has no protections. Only in roll it is different where it behaves like other aircrafts with natural stability.
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Old 30th Sep 2014, 13:39
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Originally Posted by PJ2
What is reasonable is personal preferences, even using the same reasons; but a preference isn't an argument.
Personal opinion or preference would not count much.
You can fly millions of hours and don't need to bother what kind of setup is in your cockpit, but then AF447 arrives where 3 crew members are disconnected if and how flight controls inputs are applied or not ... The Airbus setup is not the cause for the crash, but one of the contributory factor and had to be listed as such in the BEA report.
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Old 30th Sep 2014, 14:18
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very much do not think the crew ever knew they had stalled.
I agree. I was reading the vanity fair article (excellent btw) and it was mentioned how the stall alarm cuts out at obscenely high AoA. This created a situation where Bonin would lower the nose and the stall alarm would kick in again, adding further confusion and loss of confidence in the instrumets I'm sure.

It's also an interesting inight into system design. It might work perfectly for all sensible flight regions, but there's always that 1 untested case where a fault in the logic appears.
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Old 30th Sep 2014, 15:22
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vilas
This is very interesting thread which keeps running but the question is did the pilots know that the aeroplane had stalled?
Apparently they don't know ... but ..
Before the stall occur ... Robert ask Bonin to descend (go down) and he answered "Ok I go down" and in the same time he was pulling on the stick
So if Bonin had follow the Robert advise ... no stall
Helas .. Robert don't see that Bonin was pulling instead of pushing ....
The first reactions of Robert were good .. asking to go down and level wings
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Old 30th Sep 2014, 15:41
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Originally Posted by DozyWannabe
In some ways, this ingrained perception that pilots who made mistakes must have been in some way deficient was negated as far back as "Fate Is The Hunter". The only pilot in the book that Gann explicitly refers to as being incompetent and having obtained his position by deception is eventually found out and loses his career, but is not killed as a result of his incompetence.
In that "Capt. Dudley" episode it is also interesting to see what Capt. Gann does when he has to realize that this fellow pilot, one that he fully trusted and even kind of admired, is totally mishandling their aircraft. (Thanks for making me pick up that book again. )
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Old 30th Sep 2014, 15:46
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jcjeant
They were in instrument conditions. Airbus or Boeing what does one look at? Going down or up looking at what? the side stick? Airbus pilot looks at N1 or EPR gauge for thrust not at throttle movement similarly the pitch change is to be noticed on the PFD not on side stick. These guys are talking and doing things but from time they lost auto pilot no one has looked at the PFD till they crashed. It cannot be put down to anything else.
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Old 30th Sep 2014, 15:48
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CONF iture;

Thank you for your response. As you know though the data is thin, we have more examples of control columns in the full-aft position than we do sidesticks when loss-of-control or a full-stall has occurred.

It is true prima facie that when you can't observe something you can't make a judgement of it but there are numerous clues to the condition of the aircraft still present. There are only two examples in which these clues did not help the crew - the Perpignan crew, because the AoA sensors were frozen and the crew would not have been able to diagnose the problem to respond correctly, and this one which had the descent rate indication with the nose-up and full power.

If the stick is "contributory" then the control column logically (for the argument to work), must not be and this is not the case.

Cool Guys, re, "I really think the designers of this system could of been a bit kinder to the pilots."

Well, in what way?

I can only think of one, and it occurred to me the first time I flew the A320. IIRC correctly, during the takeoff roll the "iron cross" symbol was in view and one could see what the other pilot's stick was doing. As a "beginner" on Airbus I thought it was an excellent solution to the relative lack of visibility. But then the symbol disappeared just after rotation and I honestly thought, "whaa...?", because, I thought, it was so useful to see what the other guy's stick was doing. And it never came back during any phase of flight, and I thought it should any time the autopilot was disengaged, particularly on final.

But as I flew the Airbus types, "knowing" became second-nature and the position of the sidestick not being a source of direct information, (primarily because the movements are so tiny that it is not possible to judge position relative to the stick's 'null' position), became irrelevant and the PFD and engine instruments became primary - subconsciously, as we do as pilots. The "sources" of aircraft state changed from what I knew in the Boeings/Lockheeds/Douglas's, and though subtlely different, it worked as well in all the circumstances I encountered. I suspect you'd get roughly the same notions from any Airbus pilot.

Though there are almost two dozen examples of crews stalling their transport aircraft over the past dozen years or so, I doubt if we'll see an accident like this one again. But we'll see others for reasons discussed and well understood.
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Old 30th Sep 2014, 18:52
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vilas
These guys are talking and doing things but from time they lost auto pilot no one has looked at the PFD till they crashed
Robert certainly (on the beginning of the sequence "Bonin climb episode" ) looked at the PFD and this is why he asked Bonin to go down and level wings
Bonin responded OK to the requests but performed one only (by also looking at the PFD)
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Old 30th Sep 2014, 18:59
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Thank you for your response. As you know though the data is thin, we have more examples of control columns in the full-aft position than we do sidesticks when loss-of-control or a full-stall has occurred.
Indeed when the two pilots are on the same frequency (or in the same analysis error) control colums in the full-aft position will occur
In the AF447 case .. it's clear that Bonin and Robert are not on the same frequency .. on the beginning of the event
Bonin want to climb and Robert want to descend
If it was control columns ... who whon ?
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Old 30th Sep 2014, 20:08
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jcjeant;

You know as well as I do that the sidestick takeover buttons are for that very purpose - when you need to either take control momentarily, (to avoid dual sidestick inputs), or completely locking-out the sidestick on the other side due to a more serious problem, (pilot incapacitation, for example).

In the control column case IIRC you can break the elevator control-cable "channels" to separate control columns in a B767, (Egyptair case) and in the L1011. Other than that, (DC8, DC9 case), the "winner" will be he who, for whatever reason in the moment, is the physically stronger.

I'd take the sidestick lockout solution over the other solutions.
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Old 30th Sep 2014, 20:17
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You know as well as I do that the sidestick takeover buttons are for that very purpose - when you need to either take control momentarily, (to avoid dual sidestick inputs), or stop inputs from the other side due to a more serious problem, (pilot incapacitation, for example).
On Airbus .. you don't check the stick position of the pilot at your right or left .. you check simply the PFD and you know all .. I'm right ?
OK ...
Now Robert ask to descend (as good Airbus pilot he check the PFD) and Bonin answer "OK I descend"
Robert continue "as good Airbus pilot" to check the PFD and see the climb continue ...
Or Bonin just answered "I descend" ..
So now "as good Airbus pilot" Robert can think .. maybe that is something wrong with instrument ... the doubt can take root .. the catasrophe sequence can unfold .....
What if Robert had seen the Bonin stick position ?
This is a infinite debate
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Old 30th Sep 2014, 20:37
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If you parse the argument thus, yes, it is atomized and therefore infinite in variations of "reading PFDs, knowing sidesticks or columns, listening to the airplane, etc., etc.

But if you "gestalt" what went on over a period of about two minutes, what teases out of the background noise is the clear potential for assessing what had happened and what was happening.

One indeed can see by referring to the PFDs alone, that that is unquestionably the case. Put another way, one can rescue the airplane by reference to the PFDs.

The infinite quest is not the what or how, it is the why.
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Old 30th Sep 2014, 21:59
  #493 (permalink)  
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It might work perfectly for all sensible flight regions, but there's always that 1 untested case where a fault in the logic appears

Which is why it is so critical that original and modification design having any direct impact on piloting must be assessed rigorously by experienced flight test folks. I am sure that this occurred throughout at Airbus .. just tragic that this outlier caught everyone out ...

But if you "gestalt" what went on over a period of about two minutes, what teases out of the background noise is the clear potential for assessing what had happened and what was happening.

One of the underlying problems - here and in general - is mental overload.

I'm sure we have all experienced the sort of problem.

I recall one such very clearly. An experienced 727 crew, but quite a few years' worth of being rusty on the Type, requalifying on the bird over at DFW. First sim session, engine failure, F/E missed this and that, with the result that I ended up with hydraulics out as well. Hadn't had any flying at all for the previous couple of years and was working well and truly above my comfort zone level. I quite clearly can remember seeing the bank continue to increase and fixating on control input to correct. The other driver, being relatively relaxed in the other seat .. put two and two together quickly and pulled back the other pod thottle, giving us time to sort out the rear panel oversight. Very sobering experience and resulted in some soul searching that night over a beer or ten.

Regardless of what we may think of AF447 overall, one really needs to maintain a degree of empathy for what must have been an extremely confusing and confronting situation for the two guys in the hot seats. Just a pity one of them wasn't sitting back relaxed and able to think a little about what might have been going on at the time .. rather than both getting too involved.

Philosophically, from a command management and SOP point of view, not all that different, for example, to the Eastern trimotor Everglades mishap of many years ago ? Trivial problem, breakdown in cockpit discipline, and the bird is lost ..

It's very easy for us greybeards to opine that we wouldn't have been caught out on the day ... but, change the circumstances a little, here and there, and the situation might have been an eye-opener for us in a similar manner .. ?
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Old 30th Sep 2014, 22:19
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Hi John;

Yes, mental overload is certainly an issue - the sim sessions usually reserved a few of those moments for everyone and the Airbus was good at it...!

In fact I was thinking of the examination of the overall, known picture to emphasize that situational awareness can be derived from the PFD even as one may attempt to make the argument about not "seeing the other stick" prevented comprehension, etc. But I agree here, that mental overload quickly became an issue and focus narrowed, (I doubt if anyone heard the stall warning.)

Regarding empathy with these guys, thank you for the reminder - it is indeed easy to type words on a keyboard...
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Old 30th Sep 2014, 22:46
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Originally Posted by PJ2
Regarding empathy with these guys, thank you for the reminder - it is indeed easy to type words on a keyboard...
I should point out that when I make statements along the lines of "should have done this" or "maybe this would have helped", I'm not saying the buck stopped with the crew - far from it. There was supposed to be a whole system that included the builders, the regulators and the airline who should have had their backs - and in this case the approach to the situation could at best be described as "disjointed".

I repeat the point I made a few posts ago - namely that the concept of "blame" is not a useful one when it comes to discussing airline safety.

[PS. PJ2 - I think I'm going to save/bookmark your posts #592 and #595 whenever that subject comes up again - it says everything I've ever said in a much more concise and clear way, and I can only hope that because it comes from a respected pro, folk will be more inclined to listen to you than to me! ]

Last edited by DozyWannabe; 30th Sep 2014 at 23:42.
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Old 30th Sep 2014, 22:58
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Don, I had no doubt that you would be on side with my comments.

However, and I am not immune to the personal deficit either, some of our PPRuNe colleagues at times in discussions of this mishap .. do appear to forget the human fragility aspects.

That more rigorous training, exposure and experience may have changed the outcome is a quite separate topic ..

For those who haven't read much on the general aspects this training paper, while targeting maintenance folk, is a useful plain language telling of the story and may be a useful read.

As Dozy observes, we are all around the fireplace with each having a role to play in minimising the chances that any might get burned ..
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Old 30th Sep 2014, 23:46
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Hi John;

The career always reminded me that I wasn't immune either. We're all smart until we're not. There were a number of times when after reflecting I thought it could have gone 'the other way' and I know I'm not alone.
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Old 30th Sep 2014, 23:53
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John,
All the examples in the training paper had a common factor, the maintenance was interrupted, carried out in a hurry or stages were skipped in order to get the plane out on time. The root of nearly all commercial aviation accidents is money. Commercial pressures to keep aircraft available, pilots abbreviating pre flight checks to get in the air on time, overloading or incorrect weight and balance checks before a hurried departure. Training programmes have been cut back or compressed and maintenance directives deferred for as long as possible in order to maximise profits for the airline and its' shareholders.

Airbus arrived at their cockit design through wanting to save as much weight as possible. Less weight in the aircraft fixtures and fittings means more passenger and cargo revenue and lower fuel costs. Side stick controls meant the cockpit could be made smaller allowing a bit more room for the passenger cabin and an extra row of seats. Not a bad thing in itself, but it can have a negative effect on ergonomics, as has been theorised in this thread.

Maximising the return on investment is all that matters to airlines these days, aircraft and crew are just resources to be used to the fullest extent possible without actually losing an aircraft through fatigue, crew or mechanical. You can be sure that the company analysts at all of the big airlines have factored in the acceptability of losing an aircraft or two against profits and insurance costs.

I recall reading about the existance of a confidential memo many years ago which indicated that paying for the loss of three aircraft during their operational life would be cheaper than delaying further production for modifications and doing a recall to fix a design fault that had been discovered. This mentality is by no means confined to the aircraft industry. Every day products are released to market with known deficiencies. The manufacturers find it more profitable to just replace faulty goods rather than redesign the product.

Even when human lives are at stake, it often takes an extraordinary amount of campaigning to to get the fault fixed. How many vehicle manufacturers have maintained that their products were perfectly safe before issuing a recall notice to all owners? It all comes down to money.
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Old 1st Oct 2014, 00:18
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Old 1st Oct 2014, 00:41
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Originally Posted by G0ULI
Airbus arrived at their cockit design through wanting to save as much weight as possible. Less weight in the aircraft fixtures and fittings means more passenger and cargo revenue and lower fuel costs. Side stick controls meant the cockpit could be made smaller allowing a bit more room for the passenger cabin and an extra row of seats.
With respect, I beg to differ.

Sure, weight and complexity savings were a factor and it would be daft to deny it. But such things were in fact very much secondary factors. I've touched on this before so I'll try to keep it brief, but the Airbus FBW flight deck is designed as it is for a primary specific purpose, and that is to have an unprecedented level of flight deck commonality across the fleet, regardless of whether the type is a short-haul narrowbody or a long-haul widebody.

In the early '80s, Airbus was still something of a newcomer and they used the fact that FBW technology was tried-and-tested by the military and space programmes of the '70s to offer something no other manufacturer could. In effect, they turned their status as a newcomer with only two proven legacy types into an advantage. The fact that the British and French aero research industry had collaborated on the Concorde "minimanche" project (from which the Airbus sidesticks were developed) also influenced the decision.

Another factor leading to the "clean slate" thinking regarding the flight deck was that the traditional linked yoke design was an outgrowth of the days when the flight surfaces were directly linked to the light surfaces by cables. That one crew member could see/feel what the other was doing was actually a side-effect. The *real* reason they were linked was because in a situation where one person's muscle force was insufficient to work against the aerodynamic pressure against the flight surface, it was possible to combine the muscle force of two to do so. In real terms, there was no significant need for "follow through" outside of a trainer.

With the advent of large widebody types came all-hydraulic control systems (i.e. there was no manual reversion) - simply because the flight surfaces (and the forces acting against them) were so large that muscle power alone would be insufficient to move them. The last western narrowbody jetliners to have manual reversion were the B737 and the DC-9, and I've read plenty of posts on here from airline veterans which made clear that even airliners of that size were very tough to handle in the manual reversion scenario. So much so that Boeing's intended replacement for the B727 (i.e. the B757), despite being smaller than the widebodies, had no manual reversion at all (i.e. it was all-hydraulic).

Once you remove the "extra muscle power" requirement that goes with direct cable connection, then you effectively remove a significant reason (arguably the most significant - as this is an airliner, not a trainer) for the controls to be connected.

Obviously, back in 1988 there was a degree of consternation from the piloting community as to how this evolution would pan out - after all on paper it looked like a significant change from what had gone before. But I'd say that a safety record that holds its own now we're at 26 years and counting of this technology being on the line suggests that the design has proven itself. Undoubtedly there are pros and cons in an ergonomical sense, but that comes with the territory.

As PJ2 has kindly pointed out, the fact is that there are currently more accidents involving aircraft with traditional controls where the PNF has not picked up on what the PF was doing than there have been with the passive sidesticks.

The scuttlebutt that has Airbus working in league with the beancounters to make pilots' lives harder is as pernicious as it is false.
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