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

Mon Apr 30, 2012 1:24 am

Being a Boeing fan I find myself surprised that I am defending the Airbus A330 on Air France flight 447. The aircraft did everything that it was supposed to do but the confusion that had taken hold in the cockpit was overwhelming. That being said, one of the prototype F/A 18 hornets crashed during testing when it entered an extreme spin. After testing McD-D found that the aircraft could have been recovered with the proper control inputs. Their solution was to incorporate a "spin recovery switch" in the flight control software that would make all the cockpit displays go blank and display an arrow showing the pilot which way to move the stick to recover from the spin. It seems to me that Airbus could incorporate the same type of device in their software to make it display the proper control movement to recover the aircraft from an unusual attitude. Something like this might have dispelled some of the confusion in that cockpit.

How far off base am I? Would this even be possible?

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

Mon Apr 30, 2012 2:45 am

Quoting tdscanuck (Reply 49):
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.

Fair. But paraphrasing you in the other thread, it is possible these guys were so disoriented that even moving controls would not have helped.

Quoting arluna (Reply 50):
Their solution was to incorporate a "spin recovery switch" in the flight control software that would make all the cockpit displays go blank and display an arrow showing the pilot which way to move the stick to recover from the spin. It seems to me that Airbus could incorporate the same type of device in their software to make it display the proper control movement to recover the aircraft from an unusual attitude. Something like this might have dispelled some of the confusion in that cockpit.

How far off base am I? Would this even be possible?

First off, I guess the problem in this scenario would be that the aircraft might not have had the data for this kind of feature. The pitot data was, after all, invalid for much of the upset.

Secondly, the pilots were not believing the instruments as it was. The didn't believe the stall warning, or at least didn't take corrective action. An arrow or similar visual clue might just have added to the confusion and/or might have been treated as just more instrument errors.

Thirdly, unlike modern fighters airliners are designed to be stable. There is often no need for more than letting go of the controls for the aircraft to regain stability. This was, I believe, also the case here.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 6:00 am

Quoting arluna (Reply 50):
It seems to me that Airbus could incorporate the same type of device in their software to make it display the proper control movement to recover the aircraft from an unusual attitude. Something like this might have dispelled some of the confusion in that cockpit.

How far off base am I? Would this even be possible?

It exists today; whether Airbus has it or not I'm not sure, but Boeing now has modified heads-up-display symbology on the 787 that does exactly what you describe.

Quoting Starlionblue (Reply 51):
Fair. But paraphrasing you in the other thread, it is possible these guys were so disoriented that even moving controls would not have helped.

True; I don't actually believe that slaved controls would have prevented this accident, I was just pointing out that the debate (here) is about pilots' awareness of each others' actions, not about the flight path vector of the aircraft itself.

Quoting Starlionblue (Reply 51):
Secondly, the pilots were not believing the instruments as it was. The didn't believe the stall warning, or at least didn't take corrective action. An arrow or similar visual clue might just have added to the confusion and/or might have been treated as just more instrument errors.

This is my feeling too...so much situational awareness and CRM breakdown had to happen to even get the airplane into a stall that I don't have any faith in any aircraft warning/indication based solution. The crew appears to have decided that they couldn't trust anything the airplane was telling them (even though everything except airspeed was correct, that was only briefly incorrect, and the airplane correctly told them the airspeed was incorrect). It's going to be far more productive to figure out, and correct, whatever in the man/machine interface allowed them to become so distrustful of their aircraft so quickly. Once situational awareness is lost it's extremely difficult to get back and almost no amount of corrective tools on the airplane side are going to do it.

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

Mon Apr 30, 2012 7:23 am

Quoting tdscanuck (Reply 49):
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.

Reading the tape transcript, the PNF seems to have been busy getting the Captain back to the cabin. He was preoccupied with other things.
 
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Starlionblue
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 9:10 am

Quoting RickNRoll (Reply 53):
Reading the tape transcript, the PNF seems to have been busy getting the Captain back to the cabin. He was preoccupied with other things.

That confused me a bit. Why did it take so much of his time? If the pilots were handling a crisis, wouldn't a call to an F/A with "Get the captain in here ASAP?" have been the best thing to do?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
rfields5421
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 3:45 pm

Quoting Starlionblue (Reply 54):
That confused me a bit. Why did it take so much of his time? If the pilots were handling a crisis, wouldn't a call to an F/A with "Get the captain in here ASAP?" have been the best thing to do?

As discussed on other threads - there was a not optimal crew dynamic going on in the cockpit.

The very experienced PNF was in the left hand seat. He is specifically trained to only fly from the right hand seat. He is also aware of AF policy that he is to never to fly from the left hand seat. He is also aware that the Captain has placed the least experienced PF 'in charge'.

The PF was relatively new to the aircraft and route. Not unqualified for his duties by any means. But certainly less experienced.

If the PNF relieves the PF and takes over flying - he has to be able to prove (1) the aircraft was in danger - safety of flight was impacted, and (2) the PF was not taking the correct actions.

It likely means grounding for both the PF and PNF for an investigation. It will likely cost one of the two their job. If any second guessing bureaucrat back at AF HQ disagrees with the PNF - he's likely out.

Getting the Captain back to the cockpit puts the responsibility to relieve the PF or take command of the flight to resolve the emergency on the Captain, not the PF.

Unfortunately, the Captain was - to quote someone who knew them "in awe" of the PNF experience and tended to defer to him.

Rather than run the UAS checklist and troubleshoot the problem, the PNF let critical time slip away focused on non-critical tasks.

I don't believe the PNF focused on the problem sufficiently enough to realize the plane was entering a stall, that the aircraft was falling, that they were in mortal danger until about the time the Captain entered the cockpit.

At which point it was too late to save them.

Just my opinion - but again a critical breakdown of CRM.
 
Mir
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 7:59 pm

Quoting zeke (Reply 6):
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.

And if the pilots don't have faith in the instruments (which would be completely understandable given the failures that had just occurred, even that becomes debatable.

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.

  

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

There are a lot of things that could potentially be helpful. But they could also clutter the cockpit or the displays, and there's an expense involved in getting them developed, certified and installed as well. There has to be a cost/benefit analysis in those sorts of things (and by "cost", I'm including the monetary cost and the human factors drawbacks).

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

They can if they're in a certain mode, but they don't normally. I don't think any Boeing PFDs show the commanded FPV either, only the actual FPV.

Quoting airmagnac (Reply 40):
Yet the wiki article suggests that the yokes are preserved for commonality with the G550


I'd tend to believe this is the actual reason. It would be very difficult to keep a common type rating with the G550 the way Gulfstream wants to if the G650 had sidesticks instead of yokes.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
Pihero
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 9:28 pm

Quoting arluna (Reply 50):
Their solution was to incorporate a "spin recovery switch" in the flight control software that would make all the cockpit displays go blank and display an arrow showing the pilot which way to move the stick to recover from the spin.

On the 330, there is a similar philosophy on the PFD.
If the pitch goes over 25° nose up - or 13° nose down - all data except the primary are blanked out. ..At a pitch angle over 30°, red arrows show indicating the direction of the corrections... AF 447 never entered these extremes... so no indication of correct inputs.
As you can see, the conditions they found themselves in haven't been foreseen by the designers ( or anybody else for that matter )
Contrail designer
 
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ssteve
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 9:29 pm

Quoting rfields5421 (Reply 55):
As discussed on other threads - there was a not optimal crew dynamic going on in the cockpit.

The very experienced PNF was in the left hand seat. He is specifically trained to only fly from the right hand seat. He is also aware of AF policy that he is to never to fly from the left hand seat. He is also aware that the Captain has placed the least experienced PF 'in charge'.

I also tend to think the PF shut off his brain and waited for the others to tell him what to do-- wasn't necessarily inexperience, it also could have been deference. I read the PF's comments as a lot of "tell me what to do," which is worrisome. Hell, if the PNF had simply told him they should start the unreliable speeds checklist, it may have ended the basic brain paralysis and perhaps the PF would've started helping to remedy the problem. I think in the crew's defense, they're going to argue that they were in the part of their sleep cycle where they were basically mentally impaired. Maybe they ought to get guys up at 3am and have them jump in the simulator.
 
Pihero
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 10:19 pm

Quoting SSTeve (Reply 58):
Maybe they ought to get guys up at 3am and have them jump in the simulator.

That happens a lot of times as sims rarely sleep !
Contrail designer
 
tdscanuck
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon Apr 30, 2012 10:29 pm

Quoting Mir (Reply 56):
I don't think any Boeing PFDs show the commanded FPV either, only the actual FPV.

This is true. My prior post was in reference to actual FPV (I didn't read carefully enough). There isn't really such a thing as commanded flight path vector in a Boeing because the fly-by-wire laws don't to trajectory control. You just have actual flight path vector and commanded pitch (a hybrid of pitch rate, normal acceleration, and speed stability) and roll rate. In the case of yaw you either have commanded rudder deflection or commanded sideslip, not commanded FPV.

Airbus is pretty similar, minus the speed stability. Although Airbii are often described as "trajectory control" that's really only even partly accurate in pitch and, even then, it's really a commanded trajectory change, not a commanded FPV.

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

Tue May 01, 2012 2:59 pm

I cant help but wonder if having a yoke would have really prevented anything here, as it wouldn't have been moving - the PF apparently had his control stick full back for a long time, and a similar input on a yoke would have kept it in a similar position.

Would the PNF or the Captain have noticed the position of the yoke, or would their perceptions be dependent on movement of the yoke? My experience with other things suggests perception of movement is a greater consideration than the position you are presented with - the yoke could have been full back, but because the PF wasn't making wild movements, perhaps the PNF would never have noticed the position of it, especially as he may have been distracted by summoning the Captain and other tasks while it was being moved in the first place.
 
tdscanuck
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RE: Airbus' Fly By Wire To Blame For AF447?

Tue May 01, 2012 9:23 pm

Quoting moo (Reply 61):
Would the PNF or the Captain have noticed the position of the yoke, or would their perceptions be dependent on movement of the yoke?

It depends on the yoke design, but the general answer is "yes". Full aft on a yoke typically puts it right in your lap; it's very obtrusive and interferes with other motions. It would be very difficult to not notice it.

Tom.
 
mandala499
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RE: Airbus' Fly By Wire To Blame For AF447?

Tue May 01, 2012 9:27 pm

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.

You need to talk to more Airbus pilots, and read the AF447 FDR plots.
Stick was not being pulled back for almost all of the descent.
And I know a heck of a lot more than 5 Airbus pilots who have experience in yoke controlled aircraft. No, they do not have a problem in knowing what the other pilot is doing to the stick. You don't monitor the other guy by seeing what the yoke/stick is doing... you do that by looking at your primary instruments... even when the other guy is a total sidestick newbie. (Numerous cases of takeovers by the Captain on landings when there's a newbie on the right about to screw up, done without even seeing where the other guy's sidestick is.)

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.

Bingo! We keep coming back to that, and add the BEA Trident crash too! But no, anti sidestick people keep ignoring that!

Quoting garpd (Reply 9):
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.

No one ever mentioned stall in that accident.
And no, the stick was not planted in the nose up position! I wish people would bother to look at the FDR plots and see that!

Quoting airmagnac (Reply 15):
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%u2026

Sleepy? Didn't trust the PF? But let's see...
He never did ask the PF what the PF was doing.
The PF reacted to the stall warning, but the wrong reaction. PNF didn't correct/realize.
Feeble attempt? Feeble is rather harsh, but not very far from my opinion!

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.

You really should put the FDR plots, CVR transcript, and narrative together. Not one without the other two. It'll paint a different picture.

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.

2:13:42 is waaaaay too late in the process. They were already below 10,000ft!
BUT, you have to see it within the context of:
2:13:38 CPT Easy with the rudder
2:13:39 PM Climb climb climb climb (literally, "remonte" is "climb back up")
2:13:40 PF But I've been pulling to the back stop for a good while
UNKN CPT No no no don't climb back up
UNKN PM Go down, then
2:13:45 PM So give the me controls. I have control
2:13:47 PF Go on, you have control. We're still in TOGA, right ?

Now, when you look at it that way, it changes the context on why the captain said don't climb back up. The PNF

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?

They can both simultaneously make stick inputs, the FBW will get annoyed and start blurting out "DUAL INPUT".
To take over and isolate the other guy's stick, press the sidestick priority button (same as A/P disconnect button).
Press it long enough, it'll latch on to your stick until you let it go by pressing the button again... the catch is (and safety measure), priority goes to the guy who last pressed the button.

The PF took back control, and I dare say, not uncooperatively. PNF pressed the button while saying "controls to the left", instead of "my controls". If the PNF did not like the PF taking control back, he is to release his button, and then press it again. That never happened. In fact, his inputs ceased as PF took priority.
Conclusion: He pressed it in a momentary concern as the right wing dropped... other than that, no, he didn't object.

Quoting moo (Reply 61):
the PF apparently had his control stick full back for a long time, and a similar input on a yoke would have kept it in a similar position.

How long is long?
PF held the stick full aft "for a long time" occured at 2:11:47 to 2:12:15... at which the pitch was reducing from 15deg nose up to 0. He didn't realize he was stalling (unarrestable nose down pitch movement is one sign of it)... and it happed at the time when the aircraft was also rolling (wing drop, another sign of stall). Basically, he fought the stall he didn't realize. Since the PNF saw the wing drop, he pressed the stick priority button and did not seem to realize also that they were stalling, and when the PF took priority back... he didn't comment, raise concern, or whatever.

When they do not realize they're stalling, stick or yoke, makes no difference. The NW 727 and BEA Trident cases, were samples of not realizing a stall and keeping the nose up by pulling the yoke back... AF447, the NWA 727 and the BEA Trident had one thing in common... Nose up, altimeter falling... all tried to keep the nose up.

Quoting SSTeve (Reply 58):
I also tend to think the PF shut off his brain and waited for the others to tell him what to do-- wasn't necessarily inexperience, it also could have been deference.

Not just the PF, but the PNF too! PF reacted to the stall warning, PNF failed to realize it (12.5deg nose up and TOGA), was not the right action for the situation, instead asking where the captain was.
But yes, what time was it?
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
Acheron
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RE: Airbus' Fly By Wire To Blame For AF447?

Wed May 02, 2012 12:01 am

Quoting moo (Reply 61):
Would the PNF or the Captain have noticed the position of the yoke, or would their perceptions be dependent on movement of the yoke?

As has been said many times before, they ignored a pretty annoying stall warning for a great deal of time. What exactly makes you think having a yoke or slaved sticks would have made a difference other than your perceived notion that a yoke is inherently better than a stick?.

If you and whomever its with you in a cockpit, decide to blast through all the alarms being thrown at you, a yoke won't save you anyway.
 
bueb0g
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RE: Airbus' Fly By Wire To Blame For AF447?

Fri May 04, 2012 8:55 am

Quoting mandala499 (Reply 63):
And no, the stick was not planted in the nose up position! I wish people would bother to look at the FDR plots and see that!

The stick was indeed held at the full aft stop for a large portion of the descent; it was relaxed a few times but brought back to full nose-up afterwards, and was relaxed again before impact.
Roger roger, what's our vector, victor?
 
David L
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RE: Airbus' Fly By Wire To Blame For AF447?

Fri May 04, 2012 12:47 pm

Quoting bueb0g (Reply 65):
The stick was indeed held at the full aft stop for a large portion of the descent

Since that conflicts with the FDR plots issued by the BEA, can I ask where you're getting that data?
 
babybus
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RE: Airbus' Fly By Wire To Blame For AF447?

Fri May 11, 2012 8:00 am

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.

We are all professors of doing the right thing after the event. A pilot with any experience would be trying to do the best he could under the circumstances at the time.

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.

Exactly.
and with that..cabin crew, seats for landing please.
 
LTC8K6
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon May 14, 2012 3:20 am

Was the PNF aware of the initial pull up by the PF while it was occurring?
 
David L
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon May 14, 2012 2:02 pm

Quoting LTC8K6 (Reply 68):
Was the PNF aware of the initial pull up by the PF while it was occurring?

Since neither of them mentioned it, I guess we'll never know. However, looking at Mandala499's spreadsheet, in the few seconds before the PF's first input it looks as if they had dropped slightly below their assigned Flight Level so the PNF probably wouldn't have been concerned by the initial pull-up. They would probably also both have been distracted by the sudden change in circumstances.
 
rfields5421
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RE: Airbus' Fly By Wire To Blame For AF447?

Mon May 14, 2012 2:43 pm

A pitch up is the correct memory item manuever for UAS event.

So pulling back on the stick was the RIGHT thing to do. However, as Mandala499 pointed out the PF was chasing the wrong pitch setting with his stick back, stick forward movements.
 
LTC8K6
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RE: Airbus' Fly By Wire To Blame For AF447?

Tue May 15, 2012 12:36 am

Quoting rfields5421 (Reply 70):
A pitch up is the correct memory item manuever for UAS event.

So pulling back on the stick was the RIGHT thing to do. However, as Mandala499 pointed out the PF was chasing the wrong pitch setting with his stick back, stick forward movements.

I was remembering the initial pull-up as being too much, causing trouble.

I need to go over the reports again.

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