kcljj
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Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 5:32 pm

http://www.telegraph.co.uk/technolog...7-Damn-it-were-going-to-crash.html

Having lurked around for many years, I finally decided to register. However, I rather hoped that my first post would be about happier matters.
Recently, the Telegraph published the above article. I thought it made for a fascinating read. Basically, they tried to link Airbus' fly by wire system to the horrible events of AF447.
Without trying to create any A v B nonsense (which the article is filled with), I just wanted to know what you guys think. Normally, news articles on aviation are sensationalised and inaccurate. In this instance, even though it jumps to conclusions which have not been verified yet, I think they have a point.
I did a search and it seems no one has brought this up yet. So it would be nice to get some objective feedback on this? If what they argue is true, I do believe that procedures should be changed in light of this.
 
AirbusA370
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 5:50 pm

There was an almost identical crash of a 727 in the 70's (Harriman State Park). 727s are the most un-computerized and un-flybywired aircrafts you can imagine. So I don't think that Airbus' FBW was among the main or contributing causes of the AF447 accident.

Let's rather talk about bad/non-existing CRM in AF447's cockpit. With a properly working crew this whole thing wouldn't have happened...
 
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garpd
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 5:51 pm

I've stated this a few times before, of the 9 pilots I personally know, 5 of them are Airbus pilots, 3 are Boeing pilots and 1 is a senior instructor at a flying school.

All of them agreed that if the A330 that night had been equiped with the traditional yoke, the other pilots would have been able to see precisely what the PF was doing, namely pulling back on his stick for almost all of the descent, and would have corrected his actions.
The flight instructor says that outside of the simulator it is difficult to appraise an Airbus pilot trainee's handling of the flight controls for this very reason. He has to crane his neck and unbuckle his seatbelt to see what he/she is doing.

Is this the fault of FBW? No.

Further to above, the Airbus pilots also agreed that their should be some sort of mechanism installed that moves both sticks in tandem, giving the PNF or an observer an overview on the movements the PF is making.

I should stress that neither of the pilots mentioned above are suggesting this was the cause of the accident. They are just making observations from the preliminary reports which suggest the PNF and eventually the Captain had no idea the PF was pulling back on his stick for almost the entire descent.
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AirbusA370
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 5:55 pm

Quoting garpd (Reply 2):
All of them agreed that if the A330 that night had been equiped with the traditional yoke, the other pilots would have been able to see precisely what the PF was doing, namely pulling back on his stick for almost all of the descent, and would have corrected his actions.

And how do you explain the 727 accident I mentioned? When both pilots think that the plane is in a dive and close to overspeed, pulling back the yoke/stick seems the right action.
 
trex8
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 5:55 pm

Correct me if I am wrong but my take on what reports have so far been made public on the crash is that the issue wasn't the PNF not being aware of what action the PF was doing but neither realizing the correct action was to put the nose down.
 
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garpd
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 6:11 pm

Quoting AirbusA370 (Reply 3):

And how do you explain the 727 accident I mentioned? When both pilots think that the plane is in a dive and close to overspeed, pulling back the yoke/stick seems the right action.

1) You posted that as I was typing my post.
2) Apart from the plane crashing and the Pitot freezing, there is no similarity. The crew could SEE what each other was doing. Something which does not appear to have been the case on AF447.

Quoting AirbusA370 (Reply 1):
Let's rather talk about bad/non-existing CRM in AF447's cockpit

Agreed. I believe non existant CRM did play a much bigger part in this crash. If Bonin had told Robert he was pulling back on his stick, Robert would probably have barked corrections at him.
The fact that Bonin didn't say anything does constitute a lack of skill and CRM.

In the confusion of the alarms, buffeting and wind noise, both Dubois and Robert did not look over to look at what Bonin was doing, nor did they ask him. Bad CRM? Perhaps.

However, you cannot just ignore fact that Robert or Dubois could not easily see Bonin continuing to pull back on his stick. Had he been pulling on a yoke, his actions would have been very clear to see.

As in all crashes, there are many elements to this one. The inability of the crew to easily see what the PF is doing with his stick does, IMO and those of my pilot friends, constitute a contributory element to this crash.
Again, I'm not saying it was the primary cause of the crash or the only tripping point, merely that it was part of a chain.

[Edited 2012-04-28 11:43:18]
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zeke
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 6:38 pm

Quoting kcljj (Thread starter):
So it would be nice to get some objective feedback on this?

I do not think the article is that bad. They have to make the article somewhat less technical for the public to digest

Quoting garpd (Reply 2):
All of them agreed that if the A330 that night had been equiped with the traditional yoke, the other pilots would have been able to see precisely what the PF was doing, namely pulling back on his stick for almost all of the descent, and would have corrected his actions.

Does not matter what they can see in terms of control inputs, none of them was able to identify the attitude, or identify what instruments had failed. One needs to know what inputs to make first. If they have just let go of the control column, the FBW would have actually recovered the aircraft.

A lot of people sware black and blue if it was them, or of it had conventional yoke, or this, or that, after the event it would not have happened, however they have the hindsight of knowing the nature of the problem in a zero g, zero airspeed environment. You put a person in an unnatural environment like a cockpit on a dark night, in cloud with no visual clues, they are actually significantly disabled, none of their sensors are working for them. The ONLY information that will save them if the flight instruments.

No event is ever the result of one action/feature. The common theme in these type of incidents is the pilots fail to recognise the problem in the first place.

Quoting trex8 (Reply 4):
Correct me if I am wrong but my take on what reports have so far been made public on the crash is that the issue wasn't the PNF not being aware of what action the PF was doing but neither realizing the correct action was to put the nose down.

Yes.

And this is not just AF447, it has happened a number of times in the past, some with fatal, some with non fatal results. This is from an NTSB report of a 717 that had an unreliable airspeed event in 2005, "Contributing to the incident was the flight crew's improper response to the erroneous airspeed indications, their lack of coordination during the initial recovery of the airplane to controlled flight, and icing conditions.”

Sound familiar ?

Even if you look at the 737 crash on approach in AMS, 3 pilots monitoring the aircraft, none of them were able to detect the problem. Before someone recovers an aircraft, they have to know what the issue is.
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Daysleeper
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 6:38 pm

Quoting kcljj (Thread starter):
Having lurked around for many years, I finally decided to register. However, I rather hoped that my first post would be about happier matters.
Recently, the Telegraph published the above article. I thought it made for a fascinating read. Basically, they tried to link Airbus' fly by wire system to the horrible events of AF447.
Without trying to create any A v B nonsense (which the article is filled with), I just wanted to know what you guys think. Normally, news articles on aviation are sensationalised and inaccurate. In this instance, even though it jumps to conclusions which have not been verified yet, I think they have a point.
I did a search and it seems no one has brought this up yet. So it would be nice to get some objective feedback on this? If what they argue is true, I do believe that procedures should be changed in light of this.

This issue has been covered more than once in the many AF447 threads posted over in tech ops.
Here are the three most recent ones;

AF447

AF447

AF447

But, if you want to save yourself a little time, the general consensus is that AF447 crashed because the crew not only allowed the aircraft to stall, they then performed the wrong recovery method further exacerbating the issue

It’s also worth bearing in mind that the FBW/Side stick system used by airbus has now been in service almost 30 years, any inherent design issue would have come to light a long time ago.

[Edited 2012-04-28 11:56:54]
 
PGNCS
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 6:48 pm

Quoting Daysleeper (Reply 7):

This issue has been covered more than once in the many AF447 threads posted over in tech ops.
Here are the three most recent ones;

No kidding...

Quoting Daysleeper (Reply 7):
But, if you want to save yourself a little time, the general consensus is that AF447 crashed because the crew not only allowed the aircraft to stall, they then performed the wrong recovery method further exacerbating the issue.
Quoting Daysleeper (Reply 7):
It’s also worth bearing in mind that the FBW/Side stick system used by airbus has now been in service almost 30 years, any inherent design issue would have come to light a long time ago.

I've flown both and the general consensus among people who have actually FLOWN Airbus FBW is that it's a nonissue.

Quoting garpd (Reply 5):
The Airbus pilots I mentioned all took a long hard look at their flightdecks and did some soul searching. They all agreed that for all of it's benefits, it does lack something other flightdecks do not: The ability of both pilots to know what the other one is doing by sight alone. For only on Airbus flightdecks are the control sticks positioned in such a way that the a pilot cannot see what inputs his/her opposite number is inputting into their stick. This obviously was not deliberate, but a natural limitaion owing to their positions.
Quoting garpd (Reply 2):
The flight instructor says that outside of the simulator it is difficult to appraise an Airbus pilot trainee's handling of the flight controls for this very reason. He has to crane his neck and unbuckle his seatbelt to see what he/she is doing.

I have flown and instructed a LOT in the Airbus (and lots of Boeing, Douglas, and Lockheed, too,) and it is difficult to see the actual stick position from the jumpseat or from the IOS in the simulator. It is generally not difficult to see the stick displacement when looking across the cockpit. There's no soul searching required here: recognizing the attitude of the aircraft and making appropriate corrections were the problem with Air France 447, not the fact that it had no yokes.

Quoting zeke (Reply 6):
No event is ever the result of one action/feature. The common theme in these type of incidents is the pilots fail to recognise the problem in the first place.

Couldn't be said better. Thank you, zeke.
 
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garpd
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 7:01 pm

Quoting zeke (Reply 6):
Does not matter what they can see in terms of control inputs, none of them was able to identify the attitude, or identify what instruments had failed. One needs to know what inputs to make first. If they have just let go of the control column, the FBW would have actually recovered the aircraft.

Partly agreed. At the onset of the incident, neither Pilot appears to have understood the situation.
However, later on it seems they did identify their high rate of descent as a stall. Yet Bonin kept his stick planted in the nose up position. Neither Robert or Dubois appear to have noticed him doing so until Bonin himself said what he was doing.

Quoting PGNCS (Reply 8):
There's no soul searching required here: recognizing the attitude of the aircraft and making appropriate corrections were the problem with Air France 447, not the fact that it had no yokes.

I am not saying it was. Please, read what I write, don't just skim. I have made it abundantly clear that the lack of control input overview may just be a contributory factor. As the linked article in the OP focuses on that point, so does my reply.

Quoting zeke (Reply 6):
No event is ever the result of one action/feature. The common theme in these type of incidents is the pilots fail to recognise the problem in the first place.

Again, I am not, I repeat, NOT saying the lack of side stick visibility was the single event resulting in the crash.
But I do agree with the second part of that statement.
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strfyr51
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 7:56 pm

as the side stick is not inherently easy to see from the opposite Pilot position there IS a solution To the delimma.
I'm SURE Airbus apologists will disagree but this IS Simple. Install a position indicator on both sides that take voltage or resistance readings from the side stick transducers to generate a position signal to the opposite crewmwmber.. The indication would be: for the SSTK in neutral.. T he light inside the position indicator would show dead center in a round 2" guage. Any displacement from Neutral would move the indication light to the bottom for full Nose UP and to the top for full FWD or Nose Down. to the Left for left wing down and to the right for Right wing down, This would also be backed up by the ECAM flight control page where the opposite pilot might review to what position the flight controls are displaced to minimize expenses this COULD only indicated on the PIC position. the SIC has the ecam screen . But! More effective is installed on Both pilot positions . the flight control page could also have a momentary contact switch on each side of the pedestal that switched the Lower ECAM display to the Flight control Page when pushed for as long as it's pushed.
 
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EPA001
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 7:59 pm

Quoting zeke (Reply 6):
Even if you look at the 737 crash on approach in AMS, 3 pilots monitoring the aircraft, none of them were able to detect the problem. Before someone recovers an aircraft, they have to know what the issue is.

And that crash happened in much, much better weather conditions and on a fairly low approach speed.

So it is clear these events can still happen in modern airliners. But developments in training (CRM) and better instrumentation will continue to strive for making the chances that such events can happen, smaller and smaller.
 
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EPA001
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:01 pm

Quoting strfyr51 (Reply 10):
as the side stick is not inherently easy to see from the opposite Pilot position there IS a solution To the delimma.

There is no dilemma on that part. Read the previous threads and the ones in the Tech/ops section. Then you will know that the side stick is not the issue. Never was, and never will be.
 
Daysleeper
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:03 pm

Quoting strfyr51 (Reply 10):
as the side stick is not inherently easy to see from the opposite Pilot position there IS a solution


Nothing personal, but given PGNCS's experience I'm inclined to agree with him in that this isn't an issue.

Quoting PGNCS (Reply 8):
It is generally not difficult to see the stick displacement when looking across the cockpit.
 
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ssteve
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:13 pm

The article is fairly good, I think. It just doesn't pull any punches at all.

Quote:
Meanwhile, Bonin’s instinct was again to pull back on the control stick. He left it there despite the stall warning that blared out some 75 times. Instead of moving the stick forward to pick up speed, he continued to climb at almost the maximum rate. If he had simply set the control to neutral or re-engaged the autopilot, all would have been well.

However, is the above true? I've thought he was fighting the planes tendency to roll. Was any relaxation towards neutral making him feel like the plane was rolling strongly? What would letting go really have done to the plane's attitude? I've felt that it sounds like Bonin shut off his mind and tried to keep the wings level while deferring to someone else to tell him what went wrong-- does that make any sense given the previous 8000 posts on this subject? The recent tech ops threads dive much farther into CRM and instrument minutiae.
 
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airmagnac
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:19 pm

Quoting garpd (Reply 2):
and would have corrected his actions.

Your reasoning, and that of the article, seems to be
- PNF did not react to the situation (did not push the SS forward) [observation O1]
- If he had seen the stick being held back by PF he would have understood the problem. That's totally obvious ! [Hypothesis H1]

From O1 and H1, we deduce that PNF did not know what PF was doing [conclusion C1]

- The **only** way a PNF can know what commands a PF is giving is to observe his stick movements [Hypothesis H2]
- On Airbus that is not possible because of non-coupled sticks [Hypothesis H3]

From C1, H2 and H3, you deduce that the Airbus cockpit architecture prevented PNF from reacting : he could not see the other side, so could not possibly know what was going on, and so could not realize what he had to do.
Therefore the Airbus cockpit ergonomy contributed to the crash. QED



However I see all 3 hypotheses as questionable:
# H3 (not being able to observe the other SS) might be true, but see PGNCS’ post in reply 8. It’s not as clear-cut as “you can’t see anything of what the other pilot is doing”.

# H2 (you can **only** observe control inputs by observing the other SS) is the main point of misunderstanding behind all the arguments about the A cockpit. It is crucial here to understand that the control devices of a FBW aircraft are fundamentally different from those in a non FBW airplane.

In a none FBW, the pilot controls directly the surfaces, which are only indirectly linked to attitude etc…through the airplane’s dynamics. More simply, there is no direct transposition between what you see (instruments) and what you command (controls).
On FBW aircraft the computers take care of this "translation" for the pilot, and so the controls are actually directly linked to the aircraft attitude, speed etc…. Which means that the pilot can directly “see” what commands are being input into the system simply by looking at the PFD.

Caveat : once the plane was waaaaay outside its envelope that did quite not hold true anymore, because the plane could physically not obey the commands of the pilot. But it was true for a relatively long time into the accident.


# H1 is the hypothesis I would be most careful with. I just don’t think one can consider as “obvious” that PNF would have seen a yoke movement, immediately shouted Eureka ! and reacted correctly to save the day.
I mean, you could state as “obvious” that any pilot flying at 35 000 ft would b every careful about the possibility of stalling if the plane suddenly climbs 3000ft with no additional thrust.
And yet, it seems it isn’t that obvious...

Actually nothing is very obvious here. Because we simply don’t know what the pilots were thinking and so why they acted as they did.
Just for the PNF :
He waited 30 seconds before reacting to the initial climb and ordering the PF to descend. Why wait so long ?
Why did he concentrate on calling the captain, instead of helping the PF fly the plane (procedures, suggestions) ?
Why did he never ask the PF to explain clearly what he was trying to do ?
Why did he not react at all to the stall warning ?
Why did he wait so long before trying to do something with the controls ?
Why did he not suggest anything, and instead made a short and feeble attempt to take over the controls ?
And so on…

I think the AF447 discussions always come back to the same thing : we need to know what was going on inside the pilots’ minds if we are to make any definitive conclusions. About Airbus ergonomic choices, or about anything else. But for that, you need to gather experts in psychology, ergonomics, flight ops, and aircraft systems …

Oh wait, that rings a bell…   
What did the BEA decide to do ?

Conclusion : the final report should be interesting !
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par13del
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:22 pm

Quoting Daysleeper (Reply 13):
Nothing personal, but given PGNCS's experience I'm inclined to agree with him in that this isn't an issue.

So having an indicator on the panel which shows the position of the stick is not helpful?
FBW and cockpit displays and positioning of equipment is an evolving issue, no FBW today is perfect, no cockpit layout is either, we learn from accidents, if one had said CRM was an issue at AF before this accident one can imagine the battle royal, go figure.
 
Daysleeper
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:38 pm

Quoting par13del (Reply 16):
So having an indicator on the panel which shows the position of the stick is not helpful?

I didn't say that, I said given what has been posted by PGNCS and other AIrbus pilots for that matter, being able to see the SS isn't an issue for someone sitting in either of the two pilots seats.
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:48 pm

Quoting par13del (Reply 16):
having an indicator on the panel which shows the position of the stick is not helpful?

There are any number of things that you could add to the cockpit as indicators, however, this has to be balanced by whether their potential usefulness is outweighed by their potential to become a distraction.

A number of pilots who actually fly airbus aircraft have said that they don't see any issue with directly sighting the sidestick on the other side of the cockpit. Perhaps some of them might like to express their views on whether such an additional indicator would be a benefit or a potential distraction ?
 
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par13del
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 8:57 pm

Quoting Daysleeper (Reply 17):
I didn't say that,

Never said you did my friend, simply asking a question. Oft times when a post like strfy51 is made it is overlooked or lumped in with the general trend of defense or offense in a A versus B discussion or who / what is at fault in the accident.

I read the majority of the AF accident threads and there was a mass of information including some interesting observations of ways things could be improved. In time when the dust settles we may actually see some variations applied, you never know, we may be able to say the thought originated on a.net  
 
PHX787
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 9:04 pm

From what I read about the CVRs, the aircraft had airspeed readings which weren't accurite, and the pilots were using the fly-by-wire joystick to try to "correct" whatever was happening, isn't that correct?
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tdscanuck
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 9:05 pm

Quoting kcljj (Thread starter):
Basically, they tried to link Airbus' fly by wire system to the horrible events of AF447.

Although I appreciate that they're trying to distill a highly technical issue into one for public consumption, fly-by-wire had NOTHING to do with the crash. The exact same crash would happen in a non fly-by-wire aircraft with the same cockpit design.

When people talk about Airbus "fly-by-wire" they are almost always actually talking about either the sidestick or the envelope protection, neither of which are inherently fly-by-wire (they're just easier to implement if you already have fly-by-wire).

Quoting garpd (Reply 2):
All of them agreed that if the A330 that night had been equiped with the traditional yoke, the other pilots would have been able to see precisely what the PF was doing

Again, this is confusion about different features. There is *nothing* about a yoke that would inherently fix this event; what they're talking about is slaved controls (one control moves the same as the other). You can have slaved controls with or without fly-by-wire, with or without envelope protection, and with or without a yoke.

Quoting SSTeve (Reply 14):
I've thought he was fighting the planes tendency to roll.

There's no evidence for that in the FDR, as far as I'm aware. The plane should have still been in roll rate control (Airbus guys out there?)...if so, the flight controls would have countered any tendency to roll automatically.

Quoting SSTeve (Reply 14):
What would letting go really have done to the plane's attitude?

Airbii, like all other current airliners, are naturally stable. It should have nosed over and recovered from the stall. If not counteracted quickly by the flight crew, however, that would likely have resulted in an overspeed.

Tom.
 
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garpd
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 9:26 pm

Quoting tdscanuck (Reply 21):
There is *nothing* about a yoke that would inherently fix this even

You misunderstand. Perhaps I wasn't clear enough.
When I said yoke, I meant slaved units. I just said "Yokes" as they are traditionaly slaved. The point being made is, a slaved system may have helped in this situation by making the PNF aware of the PF's control inputs.

[Edited 2012-04-28 14:36:46]
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amccann
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 9:59 pm

I am no pilot, and I understand that commanded flight path vector is different than control stick position, but I was always under the impression that Airbus Primary Flight Displays did show the commanded flight path vector. It would at least show where in relation to the artificial horizon the aircraft was commanded to go. Are there any Airbus pilots out there than can provide input?
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ssteve
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RE: Airbus' Fly By Wire To Blame For AF447?

Sat Apr 28, 2012 10:13 pm

Quoting tdscanuck (Reply 21):
Quoting SSTeve (Reply 14):
I've thought he was fighting the planes tendency to roll.

There's no evidence for that in the FDR, as far as I'm aware. The plane should have still been in roll rate control (Airbus guys out there?)...if so, the flight controls would have countered any tendency to roll automatically.

I didn't mean to revisit this, but the BEA report would make it appear that when the captain returned to the cockpit, the plane was banking 32 degrees right, and the F/O roll command position was at the left limit stop. At some point in the years this has been talked about, that amount of dealing with the roll attitude made me wonder if he was as mentally focused on a plane trying to roll as anything else. I can't find what he continued to do with the roll control after that... except that at that moment he had it at the left limit and the plane was rolling farther right. I simply don't think the article's characterization of the sidestick inputs as one-dimensional (pulled back) was totally accurate. He hit the left limit stop before he hit the nose-up stop.

[Edited 2012-04-28 15:16:28]
 
Ruscoe
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 12:37 am

IMO if the control sticks were connected, and if the stall warning below 60 knots was not counter intuitive
the pilots would have recovered,

To just blame the pilots and there training, is only part of the solution, to improving air safety.

Airbus cockpit philosophy also needs a review, not just a defense.

Ruscoe
 
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Starlionblue
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 2:19 am

Quoting Ruscoe (Reply 25):
IMO if the control sticks were connected, and if the stall warning below 60 knots was not counter intuitive
the pilots would have recovered,

To paraphrase Zeke above, hindsight is 20/20. It is easy for us to sit here and say that x should have happened. The pilots seemed so far behind the aircraft I don't know if seeing the sticks move would have helped.

As for the stall warning, it was on for almost a minute. At any point the pilot not flying could have asked the pilot flying what he was doing, or just simply taken priority and pushed the nose down.

Quoting Ruscoe (Reply 25):
Airbus cockpit philosophy also needs a review, not just a defense.

Ok, but what changes would you suggest? If they had followed the "no airspeeds" procedure or even let go of the controls they would have been fine. Note that those two solutions are not Airbus specific.

Sure, the fact the sticks do not move may have exacerbated pilot disorientation, but they had many other clues such as a stall warning blaring at them.
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kcljj
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 2:26 am

Quoting Daysleeper (Reply 7):
This issue has been covered more than once in the many AF447 threads posted over in tech ops.
Here are the three most recent ones;

AF447

AF447

AF447

But, if you want to save yourself a little time, the general consensus is that AF447 crashed because the crew not only allowed the aircraft to stall, they then performed the wrong recovery method further exacerbating the issue

It’s also worth bearing in mind that the FBW/Side stick system used by airbus has now been in service almost 30 years, any inherent design issue would have come to light a long time ago.

Many thanks for the links. I guess I shall have to brush up on my searching skills.
Having read the discussion, I totally understand that the crash was caused by a number of contributory factors. I guess that my question could be posed more carefully. Was not being able to see the PF's inputs because of the way the side stick worked, a large contributory cause.
In the discussion, from what I can distil, the most likely argument given what we know right now is that not seeing the movement of the side stick was unimportant in light of the deficiencies in CRM and the crew failing to identify and correct the problem.
I guess airmagnac is correct in saying that without knowing what was going in the pilots' minds, we could never know the exact causes. However, given the experience of the crew, I just can't help but think that the way that the side stick works may have exacerbated and added to the problems in the flight deck rather than help it.
Feel free to tear this unfounded believe apart  
 
PPVRA
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 2:31 am

Quoting tdscanuck (Reply 21):
Again, this is confusion about different features. There is *nothing* about a yoke that would inherently fix this event; what they're talking about is slaved controls (one control moves the same as the other). You can have slaved controls with or without fly-by-wire, with or without envelope protection, and with or without a yoke.

There may be one: a giant yoke moving between your legs is more difficult to miss than a side stick across the cockpit that may or may not be easy to see. Especially if your eyes are glued to the instruments trying to make sense of them.

I say side stick, instead of slaved controls, because my understanding is that the non-flying pilot would probably not even be touching the side stick if he wasn't flying. He wouldn't have felt it moving anyways.

But, I am no pilot or engineer. . .
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 3:20 am

Quoting garpd (Reply 2):

I've stated this a few times before, of the 9 pilots I personally know, 5 of them are Airbus pilots, 3 are Boeing pilots and 1 is a senior instructor at a flying school.

All of them agreed that if the A330 that night had been equiped with the traditional yoke, the other pilots would have been able to see precisely what the PF was doing, namely pulling back on his stick for almost all of the descent, and would have corrected his actions.
The flight instructor says that outside of the simulator it is difficult to appraise an Airbus pilot trainee's handling of the flight controls for this very reason. He has to crane his neck and unbuckle his seatbelt to see what he/she is doing.

The problem with this theory is also the crash of West Caribbean Airways flight 708. The co-pilot knew exactly what was wrong, they were stalled much like AF447 was, the captain was pulling the yoke back, he knew that too, yet they did not take appropriate action and crashed as well.
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 3:40 am

Quoting PPVRA (Reply 28):
I say side stick, instead of slaved controls, because my understanding is that the non-flying pilot would probably not even be touching the side stick if he wasn't flying. He wouldn't have felt it moving anyways.

That's the idea. One pilot flying. Regardless of yoke or stick, moving or non, slaved or non, the pilots made the very basic mistake of not being clear on who was controlling the aircraft. The controller should not matter.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
David L
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 8:46 am

Quoting Daysleeper (Reply 7):
This issue has been covered more than once in the many AF447 threads posted over in tech ops.

   And in the Civil forum, too.

Quoting Ruscoe (Reply 25):
IMO if the control sticks were connected, and if the stall warning below 60 knots was not counter intuitive
the pilots would have recovered,

And yet:

a) The PNF and Captain kept telling the PF he was "going up" and needed to "go down".

b) The PNF briefly took control before it was taken back by the PF, in both cases quite uncooperatively.

c) They failed to respond to the stall warning for 54 seconds before it was deactivated.

d) There have been more accidents where an interconnected yoke was held nose-up in a stall.

An incorrect UAS memory item was executed, the UAS checklist was not performed, they didn't follow procedures to identify which instrument(s) had failed therefore they were unable to trust the instruments that would have helped them, e.g. large nose-up attitude and decreasing altitude.

Quoting PGNCS (Reply 8):
the general consensus among people who have actually FLOWN Airbus FBW is that it's a nonissue.

And there's the difference - assumption versus experience.  
 
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garpd
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 9:18 am

Quoting RickNRoll (Reply 29):

The problem with this theory is also the crash of West Caribbean Airways flight 708. The co-pilot knew exactly what was wrong, they were stalled much like AF447 was, the captain was pulling the yoke back, he knew that too, yet they did not take appropriate action and crashed as well.

That has nothing to do with the point being made.

On AF447, both Robert and Dubois DID NOT KNOW Bonin was pulling back on his stick. When he finally told them, Dubois said NO.

The point being made here is that a large yoke in front of the PNF moving back in tandem with the other would have instantly alerted Robert that Bonin was pulling back despite being told to push forward.

Quoting David L (Reply 31):

a) The PNF and Captain kept telling the PF he was "going up" and needed to "go down".

Exactly.

Quoting David L (Reply 31):
) The PNF briefly took control before it was taken back by the PF, in both cases quite uncooperatively.

Why can a pilot take control without the other's say so?
I know this is more of an issue with CRM, but should there not be some sort of safeguard in place to stop a pilot taking control without warning? Like the PF has to hit a button?
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 9:41 am

Quoting garpd (Reply 32):

There is "a button". It's the same button as the autopilot disconnect on the top of the sidestick.

Once again we have thread where a few posters are unwilling, or unable, to recognise or accept the views of those with a lot more experience and knowledge. They just sit there with their fingers in their ears.

I have thousands of hours experience flying 737, 747, 777, 320 and 330's. I've tried before to put across an experienced and balanced viewpoint, but I've stopped bothering. Some just aren't interested in being educated.
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 10:14 am

Quoting garpd (Reply 32):
Robert and Dubois DID NOT KNOW Bonin was pulling back on his stick

How can you be so sure ?
Is it explicitly stated in a BEA report, is it easily deducible from the known facts ?

Quoting garpd (Reply 32):
would have instantly alerted Robert

Maybe....And so what ?
How can you be so sure that he would then have pushed the stick forward ?
At 2:13:39 (so very late in the event) he was even telling the PF "remonte ,remonte, remonte " ("Climb, climb, climb")
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 10:29 am

Quoting ThrottleHold (Reply 33):
They just sit there with their fingers in their ears.

Could one try another body part using the exact same letters ?   

Some thirty years after the Airbus FBW architecture was basically frozen, 25 years after the first flight ( Feb 22, 1987 ), some haven't still accepted that it's now here to stay and that very soon, the yoke solution will be in a minority of aircraft.
.. and what tells you that B will forever stick ( !!! ) to their solution ? So far, there are more manufacturers going the A way than the B...

[Edited 2012-04-29 03:44:42]
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Starlionblue
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 11:01 am

Quoting garpd (Reply 32):
On AF447, both Robert and Dubois DID NOT KNOW Bonin was pulling back on his stick. When he finally told them, Dubois said NO.

The point being made here is that a large yoke in front of the PNF moving back in tandem with the other would have instantly alerted Robert that Bonin was pulling back despite being told to push forward.

Basic airline pilot training: only one person flies at a time...

Quoting garpd (Reply 32):
Why can a pilot take control without the other's say so?
I know this is more of an issue with CRM, but should there not be some sort of safeguard in place to stop a pilot taking control without warning? Like the PF has to hit a button?

AFAIK, there's an arrow on the screen in front of the pilot pointing at who has priority. A pilot can take priority by pressing the button, or override completely by holding for, I think, 30 seconds.

The reason a pilot can take control (on Airbus and Boeing) over the wishes of the other is in case of pilot incapacitation.
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 11:30 am

Quoting ThrottleHold (Reply 33):
Once again we have thread where a few posters are unwilling, or unable, to recognise or accept the views of those with a lot more experience and knowledge. They just sit there with their fingers in their ears.

I appreciate your frustration, but conversely there are also many of us which do listen and are certainly willing to be educated.

I don’t have a vast amount of experience or knowledge and very rarely post in tech-ops because of that, but like many others I read through the posts here daily. Please don’t let a few very vocal idiots with their own agenda put you off posting, your contributions and those of other all the experienced posters here are greatly appreciated.
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 11:58 am

Quoting airmagnac (Reply 34):
How can you be so sure ?
Is it explicitly stated in a BEA report, is it easily deducible from the known facts ?

The pilots had agreed they were falling. Only after that did Bonin tell them he's been keeping the nose high.

To quote the transcript:
02:13:42 (Captain) Non, non, non... Ne remonte pas... non, non.
No, no, no... Don't climb... no, no.


Is that the reaction of someone fully aware of what the PF has been doing?
I don't think so.

Quoting airmagnac (Reply 34):
Maybe....And so what ?

Wow, imagine if that attitude being levelled at the rudder PSU on 737s.

Quoting airmagnac (Reply 34):
At 2:13:39 (so very late in the event) he was even telling the PF "remonte ,remonte, remonte " ("Climb, climb, climb")

But moments before, he had taken control and pushed the stick forwards.

Quoting Starlionblue (Reply 36):

Basic airline pilot training: only one person flies at a time...

I know that as much as the next person on this forums. But what does that have to do for or against the slaved control stick theory?
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airmagnac
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 12:30 pm

Quoting garpd (Reply 38):
02:13:42 (Captain) Non, non, non... Ne remonte pas... non, non.
No, no, no... Don't climb... no, no.

And here the captain was talking to...the PNF ! NOT the PF...
It was an answer to the PNF's urge to "climb, climb, climb" I quoted myself.
So it does not prove anything WRT whether the captain or PNF knew what the PF was doing with his stick

Quoting garpd (Reply 38):
Wow, imagine if that attitude being levelled at the rudder PSU on 737s.

See my reply 15.
My main point is that you keep considering as obvious that the PNF would immediatly push his stick forward after realising the PF had been pulling. That is the cornerstone of your argument. But it is just not true. Your blanket assumption does not hold, I explained why I think so in reply 15

The thing is I do not know for sure if they knew what the PF was doing, nor can you know for sure that they did not
We just don't know anything.
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airmagnac
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 12:36 pm

Quoting Pihero (Reply 35):
So far, there are more manufacturers going the A way than the B...

I was looking at that. As far as I can tell, among the latest commercial FBW aircraft designs (excluding A & B) :

BOMBARDIER

- Bombardier CSeries : sidesticks
http://www.flycseries.com/deck.asp

- Bombardier Global 7000/8000 : yokes,
chosen more for commonality with Global 5000/6000 rather than ergonomics (sidesticks were considered, as used on the CSeries)
http://www.flightglobal.com/news/art...-new-bombardier-global-duo-354669/
http://www.flightglobal.com/news/art...biggest-bombardier-globals-363207/


EMBRAER

- Embraer E-Jets : yokes

-Embraer Legacy : sidesticks
http://www.flightglobal.com/news/art...fly-by-wire-executive-jets-348254/


DASSAULT

- Dassault Falcon 7X : sidesticks
http://www.dassaultfalcon.com/aircraft/7x/avionics.jsp


SUKHOI

- Sukhoi Superjet 100 : sidesticks
http://sukhoi.org/eng/planes/projects/ssj100/
http://www.airliners.net/photo/Sukho...d=247f1dd28849e0097f709af896940bb3


MITSUBISHI

- Mitsubishi MRJ : yokes
http://www.flightglobal.com/news/art...mrj-cockpit-and-structures-225636/


GULFSTREAM

- Gulfstream 650 : yokes
http://www.flightglobal.com/news/art...es/g650-as-good-as-it-gets-316577/
"so that pilots would be aware of control inputs being made by the autopilot."
Yet the wiki article suggests that the yokes are preserved for commonality with the G550


COMAC

- COMAC 919 : sidesticks (actually the cockpit should be shared with the CSeries)
http://www.flightglobal.com/news/art...-cseries-c919-co-operation-369766/

(Please complete my list if I've forgotten any project !
I left the Antonov 148 out, even though it is FBW + yokes, because the design process took 20 years following the end of the USSR so I am not sure the design choices are really representative.)


So only 2 companies (Gulfstream and Mitsubishi) chose to go with a column instead of sticks. Embraer and Bombardier use yokes, but they are moving towards side-sticks on their newer designs.

If sticks were really inherently flawed, it makes you wonder if the all these other companies are crazy. Or maybe sidesticks can actually be a satisfactory choice after all ?
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David L
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 2:09 pm

Quoting garpd (Reply 32):

Why can a pilot take control without the other's say so?
I know this is more of an issue with CRM, but should there not be some sort of safeguard in place to stop a pilot taking control without warning?

How would such a safeguard decide whether or not a take-over is justified? How would it decide which pilot should be flying? There's a procedure for transferring control in normal circumstances and there's another for cases where one control is obstructed or jammed. There's also an aural and visual "Dual input" warning.

Quoting garpd (Reply 32):
Quoting David L (Reply 31):

a) The PNF and Captain kept telling the PF he was "going up" and needed to "go down".

Exactly.

I'm not sure I see how that makes your point.

Quoting garpd (Reply 38):
To quote the transcript:
02:13:42 (Captain) Non, non, non... Ne remonte pas... non, non.
No, no, no... Don't climb... no, no.

Is that the reaction of someone fully aware of what the PF has been doing?
I don't think so.

   Why would they keep telling him to stop doing something they didn't know he was doing and to do the opposite?

After umpteen times of asking, I'm still waiting to hear why interlinked yokes would have helped AF447 yet didn't in more than one accident where a yoke was held back in reaction to a stall.
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 2:33 pm

AeroPeru 603 crashed in similar circumstances with conflicting flight instrument indications due to blocked static ports. The aircraft descended with stall warning activated for long periods while the PF believed the aircraft was overspeeding and didn't recover from the stall. In that case the connected yokes of the Boeing 757 concerned did nothing to improve situational awareness.
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tdscanuck
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 3:50 pm

Quoting garpd (Reply 22):
You misunderstand. Perhaps I wasn't clear enough.
When I said yoke, I meant slaved units. I just said "Yokes" as they are traditionaly slaved. The point being made is, a slaved system may have helped in this situation by making the PNF aware of the PF's control inputs.

That's a good point but it confuses yokes/sidesticks with slaved/not-slaved. They're not the same thing. It causes people to incorrectly criticize sidesticks when sidesticks aren't actually the problem.

Quoting amccann (Reply 23):
I was always under the impression that Airbus Primary Flight Displays did show the commanded flight path vector.

They can. So can Boeing's.

Quoting PPVRA (Reply 28):
I say side stick, instead of slaved controls, because my understanding is that the non-flying pilot would probably not even be touching the side stick if he wasn't flying. He wouldn't have felt it moving anyways.

A non-flying pilot should never have their hands on the controls, whether it's a yoke or sidestick, fly-by-wire or not. The PNF should never *feel* the controls moving. The only cue should be visual.

Tom.
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 6:37 pm

Quoting tdscanuck (Reply 43):
A non-flying pilot should never have their hands on the controls, whether it's a yoke or sidestick, fly-by-wire or not. The PNF should never *feel* the controls moving. The only cue should be visual.

But the visual cue would be quite obvious in a yoke versus a sidestick.

Quoting airmagnac (Reply 40):
If sticks were really inherently flawed, it makes you wonder if the all these other companies are crazy. Or maybe sidesticks can actually be a satisfactory choice after all ?

The way I see it, it's not that sticks are inherently flawed, but that their low profile has disadvantages when it comes to one pilot keeping up with what the other one is doing. Even if a yoke is not slaved, you can pretty easily see/tell what the pilot next to you is doing.
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 6:48 pm

Quoting PPVRA (Reply 44):
Quoting tdscanuck (Reply 43):
A non-flying pilot should never have their hands on the controls, whether it's a yoke or sidestick, fly-by-wire or not. The PNF should never *feel* the controls moving. The only cue should be visual.

But the visual cue would be quite obvious in a yoke versus a sidestick.

I'm not sure I agree with that.

*Again my disclaimer, I am not a commercial pilot.*

Because both Airbus and Boeing Primary Flight Displays (PFDs) show the commanded flight path vector (FPV) the PNF should notice where the PF is commanding the aircraft to fly, in relation to the artificial horizon. Because I am not a commercial pilot and do not know airline standard operating procedures I can not say this with any authority, but I am also under the impression that a primary duty of the PNF is to monitor the cockpit instrumentation, including ECAM/EICAS, FMS/MCP/MCDU, ND, and PFD. If monitoring the PFD the PNF should definitely notice a commanded FPV above the artificial horizon.
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David L
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 7:20 pm

Quoting PPVRA (Reply 44):

The way I see it, it's not that sticks are inherently flawed, but that their low profile has disadvantages when it comes to one pilot keeping up with what the other one is doing. Even if a yoke is not slaved, you can pretty easily see/tell what the pilot next to you is doing.

And yet there's been one accident where nose-up input (or insufficient nose-down input) was applied to an Airbus sidestick during an unrecognised stall (even though two other crew members told the PF to stop doing it) and more than one in yoke-equipped aircraft.

I'm beginning to wonder if I'm seeing information from the CVR and DFDR that isn't there, since you'd have to ignore half of the data I see in order to reach the conclusion that the PNF and Captain didn't know what the PF was doing or that any of them knew exactly what to do or that they were dealing with the issue in a disciplined manner but were only thwarted by not knowing what the PF was doing. On the other hand, I must be missing the evidence that they knew they were stalled and mistakenly thought the PF was taking appropriate action. I must also be missing the evidence that they recognised that the IAS was the only unreliable reading so they could trust all the others. What happened to the UAS procedures, checklists, etc?
 
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 8:34 pm

Quoting Starlionblue (Reply 36):
A pilot can take priority by pressing the button, or override completely by holding for, I think, 30 seconds.

Actually, it's 40 seconds

Quoting airmagnac (Reply 40):
As far as I can tell, among the latest commercial FBW aircraft designs

.....
Thanks for that, as I was to do the same later.

Quoting David L (Reply 41):
I'm still waiting to hear why interlinked yokes would have helped AF447 yet didn't in more than one accident where a yoke was held back in reaction to a stall.

Jetlagged gave an exaple amongst dozens, but it's about useless to try and change the mind of someone so deep into his argument.
Just ask any TRI or checker how many times he/she'd look at the position of the yoke to determine what the student / other pilot is doing. Sometime the info is downright misleading : the 747 for instance - and the worst was the -300 series - had a definite lateral instability at bank angles over 15° and one could well find a turn to the right with a yoke positioned some 70° to the left. So what do we do ? watch the flight path. If it's not correct, try and find what's done wrong... observation one can do,even on a 'Bus.
I daresay that taking over from the A/P on an instrument approach for a manual landing could be quite interesting as one certainly hasn't grasped the way George was achieving its trajectory, leading to some funny loss of the glidepath on the centerline on xwind if one hasn't the patience - and the humility - to wait a few seconds to integgrate in one's mind the actual geometry of the approach..On the 'Bus, it's straight forward : everything is centered... Yet another quality that makes me prefer the SS setup.

Quoting amccann (Reply 23):
I was always under the impression that Airbus Primary Flight Displays did show the commanded flight path vector.

For that, one has to select Track and FPA (flight path angle ) to be displayed instead of the more usual Heading / vertical speed. The uses of TRK/FPA are few : visual flight, circling approaches or GNSS letdowns.

Quoting amccann (Reply 45):
If monitoring the PFD the PNF should definitely notice a commanded FPV above the artificial horizon.

If one takes the final two minutes of AF447, the FPV would have shown a descent at an angle of some 20° or greater. never above the horizon ( showing a climb...)
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Starlionblue
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RE: Airbus' Fly By Wire To Blame For AF447?

Sun Apr 29, 2012 11:07 pm

Quoting garpd (Reply 38):
Quoting Starlionblue (Reply 36):

Basic airline pilot training: only one person flies at a time...

I know that as much as the next person on this forums. But what does that have to do for or against the slaved control stick theory?

It's not an argument against per se. My point is that there is no real argument FOR slaved/interlinked control stick movements being of help in this kind of accident.

See:

Quoting Jetlagged (Reply 42):

AeroPeru 603 crashed in similar circumstances with conflicting flight instrument indications due to blocked static ports. The aircraft descended with stall warning activated for long periods while the PF believed the aircraft was overspeeding and didn't recover from the stall. In that case the connected yokes of the Boeing 757 concerned did nothing to improve situational awareness.

and:

Quoting Pihero (Reply 47):
Just ask any TRI or checker how many times he/she'd look at the position of the yoke to determine what the student / other pilot is doing. Sometime the info is downright misleading : the 747 for instance - and the worst was the -300 series - had a definite lateral instability at bank angles over 15° and one could well find a turn to the right with a yoke positioned some 70° to the left. So what do we do ? watch the flight path. If it's not correct, try and find what's done wrong... observation one can do,even on a 'Bus.

As I understand it then, the pilots should be aware of the flight path in other ways than looking at the yoke/stick movement.
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tdscanuck
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 12:01 am

Quoting Starlionblue (Reply 48):
As I understand it then, the pilots should be aware of the flight path in other ways than looking at the yoke/stick movement.

Slaved controls don't do anything to tell you about flight path; they do a lot to tell the PNF what the PF or autopilot is doing. That's the argument; that the PNF would have realized (more) that the PF was holding the nose high rather than nosing over to recover from the stall.

Tom.

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