7 ms·

Echoes of AF447 here. I thought that Airbus makes the only airliners with no feedback when there are dual inputs applied, and Boeing takes a decidedly different

by rmk 4y ago

Echoes of AF447 here. I thought that Airbus makes the only airliners with no feedback when there are dual inputs applied, and Boeing takes a decidedly different approach. Can someone experienced with this explain how this could have happened?

8b16380d 4y ago
Does sound like 447, and a result of the airbus’ dual stick system. Boeing’s yoke system is connected between the pilot and copilot, so much easier to detect opposite inputs. Also the yoke is right in front of each pilot, instead of on the opposite sides as is the case with the dual sticks in airbus planes, which could be a source of confusion/opposite input problems.
- venj 4y ago
  the plane involved in a Boeing 777. That's right in the title of the article.
hkwerf 4y ago
I've repeatedly heard stated that after a sufficient amount of force is applied to controls, "the link" between the controls is severed or deactivated, without any details regarding how this is done or what the actual effect is. Here's an article stating exactly that: https://english.alarabiya.net/News/world/2022/04/28/Pilots-pulled-controls-in-opposite-directions-in-Air-France-landing-scare-Report https://english.alarabiya.net/News/world/2022/04/28/Pilots-p... > If opposing forces on the two columns pass a certain limit, the link between them is deactivated or “desynchronized” to prevent accidents in the case of one side getting jammed.
- deleted 4y ago
  [deleted]
- herendin 4y ago
  In the 777 it's a direct mechanical linkage between the controls, with a torque-driven breakout which temporarily severs the link if there's too much difference in the two pilots' inputs That still leaves the question of how to interpret opposing inputs for the physical control surfaces, though
- WalterBright 4y ago
  On the 757, the two control columns are linked with a roller bearing in a detent (notch). With enough torque applied, the bearing will come out of the notch and the columns can move independently.
- Animats 4y ago
  It's a purely mechanical linkage. I've been trying to read the patent (US 5782436A). The USPTO has a new single-page web app. It's awful for finding by patent number, and worse when you want a full screen image of a drawing. It's clear that if one yoke is jammed and the other is moved with enough force, a spring loaded pin is forced out of a notch and the connection between the two yokes releases. What's not clear is how the linkage still connects to the flight controls. The idea seems to be that the one which is moving wins. What is clear is that, if your side becomes disconnected, your yoke doesn't do anything. No wonder one pilot was frantic. It seems that you get reconnected by moving the disconnected yoke to agree with the one in control. Then the pin falls into the notch and the yokes are connected again. Not sure about that. You can see the pin and notch in the patent drawings. This is independent of the fly-by-wire system. That's downstream from these mechanical devices. I wonder if pilot training includes knowledge that yoke disconnection is possible.
  - hkwerf 4y ago
    > I wonder if pilot training includes knowledge that yoke disconnection is possible. Probably, I've heard https://www.youtube.com/c/MentourPilotaviation https://www.youtube.com/c/MentourPilotaviation talk about it as well.
  - epse 4y ago
    They are trained in this. If disconnected, each yoke will control "their" half of the plane. This is mostly intended to maintain some level of controllability if one of the yokes were to get blocked or seized mechanically, this is not intended for human issues
  - mnw21cam 4y ago
    If the linkage breaks, then each pilot gets to control the control surfaces on one side of the aircraft.
willidiots 4y ago
Entirely speculating, but it sounds like the fundamental problem is that they had a confused Captain and First Officer who both thought they were the Pilot Flying. Human factors / psychology issue. Sure, on a Boeing you'll feel the other pilot's input, but if you're tired enough, or panicking because the plane's not doing what you expected, you might not get the hint. Task saturation - followed by loss of situational awareness - is a very real problem in today's airliners, particularly during takeoff and approach/landing. You're trying to do a ton of things in a small amount of time, while dealing with a dynamic situation outside, and in this case after a long, tiring flight over the Atlantic. There are a great series of (dated but still good) videos from American Airlines about automation dependency, human factors and the simple but very real problems that develop as a result - often leading to panic and disaster when things go wrong. Search YT for "children of the magenta".
- cryptonector 4y ago
  > my airplane > your airplane [lets go controls] Those are the words to be exchanged to avoid confusion.
  - willidiots 4y ago
    Yeah, simple enough. Also simple enough to go-around when you're obviously slow and going to be short of the runway, but look at Asiana 214. I do wonder if there's some training deficiency or cultural issue that leads to this scenario in Air France flights.
    - cryptonector 4y ago
      This makes me think of Loic Suberville's videos on language...
  - Retric 4y ago
    Sure, just make sure that happens exactly that way 1,000,000 times without any failures… And that’s the root of many issues in aviation. It works 99.99% of the time is not always good enough.
gerdesj 4y ago
AF447 was (I read the WP article on it) at 38,000 feet and ice seems to be implicated and quite a few other things. This incident was at 1670 ft. My reading of the article is a P and CP being twats: "During the go-around on the Air France flight, the captain was making nose-down inputs, while the first officer was pulling back on the controls." I'm just a simple civvy but I was an air cadet and learned enough about flying in a single engine trainer to know that only one person should have control. You literally say "I have control" - "You have control" - "I have control". These muppets didn't seem to do that: "It took until 07:52:06, for the captain to become the only person making control inputs." In the very guarded language of accident review I would say that is a damning indictment of the behaviour of the pilot and co-pilot as being completely reckless and bloody stupid.
- alistairSH 4y ago
  That’s all correct, but AF447 was exacerbated by the pilot and copilot (actually 2 copilots, IIRC, the senior pilot was on break) fighting each others controls as the plane flew towards the ocean. The pitot tube was giving bad readings (frozen over), but from what investigators can tell, one control was trying to pull up and even out and the other was still pitching down to gain speed (per the warnings given by the faulty pitot tube).
  - gerdesj 4y ago
    A car, plane or whatever should only have one driver/pilot. Planes have dual controls by default but this sort of nonsense should not be allowed to happen. This was not AF447 so what on earth happened? I'm guessing inadequacy of some sort and that's on the industry as a whole.
    - phil21 4y ago
      In cases like this it's almost always some variation of normalization of deviance. If company culture doesn't strictly enforce callouts 100% of the time, it's easy to get into a routine of everything being just fine 100's of times until it isn't. Really these sorts of things show there should be a failsafe mechanism that provides tactile/haptic feedback to the pilots if the other inputs are "fighting" theirs. Even an audible alarm isn't enough, as you'll likely get more than a few of those during events where it matters. Proper CRM of course should make this "impossible" - but in high stress moments any more layers of swiss cheese you can add the better.
ncmncm 4y ago
Nowadays planes will yank on the controls on their own initiative, most destructively e.g. in the case of a certain pair of 737MAXs. They probably assumed that is what was going on. That the other pilot was doing something obviously wrong is not a natural assumption, when there is an alternative. It seems like Air France has got some procedural drills to work on. One would have hoped that happened already. Somebody should check, this time.
- tyingq 4y ago
  Technicality, but the 737MAX MCAS was rolling a trim wheel, not moving the yoke.
  - ncmncm 4y ago
    Exerted force on the yoke via the elevator, driven by the trim tab. But they also yank directly on the yoke, for lots of reasons.
exidy 4y ago
> I thought that Airbus makes the only airliners with no feedback when there are dual inputs applied This factoid will not die on HN. Conflicting inputs on an Airbus are handled by averaging and an audible "DUAL INPUT" cockpit warning.[1] In the case of AF447, the co-pilot used his "Priority Takeover" button which meant only his control inputs were in effect. If you wanted to say there is no physical feedback, then you would be correct. [1] https://safetyfirst.airbus.com/app/themes/mh_newsdesk/documents/archives/dual-side-stick-inputs.pdf https://safetyfirst.airbus.com/app/themes/mh_newsdesk/docume...
- rmk 4y ago
  Yes, that is what I meant. And any other type of feedback would be likelier to be ignored. That's why there's a stick shaker in addition to auditory and other warnings when the plane stalls, even in fly-by-wire planes.

by rmk 4y ago

8b16380d 4y ago

Does sound like 447, and a result of the airbus’ dual stick system. Boeing’s yoke system is connected between the pilot and copilot, so much easier to detect opposite inputs. Also the yoke is right in front of each pilot, instead of on the opposite sides as is the case with the dual sticks in airbus planes, which could be a source of confusion/opposite input problems.

venj 4y ago
the plane involved in a Boeing 777. That's right in the title of the article.

hkwerf 4y ago

I've repeatedly heard stated that after a sufficient amount of force is applied to controls, "the link" between the controls is severed or deactivated, without any details regarding how this is done or what the actual effect is. Here's an article stating exactly that: https://english.alarabiya.net/News/world/2022/04/28/Pilots-pulled-controls-in-opposite-directions-in-Air-France-landing-scare-Report https://english.alarabiya.net/News/world/2022/04/28/Pilots-p... > If opposing forces on the two columns pass a certain limit, the link between them is deactivated or “desynchronized” to prevent accidents in the case of one side getting jammed.

deleted 4y ago
[deleted]
herendin 4y ago
In the 777 it's a direct mechanical linkage between the controls, with a torque-driven breakout which temporarily severs the link if there's too much difference in the two pilots' inputs That still leaves the question of how to interpret opposing inputs for the physical control surfaces, though
WalterBright 4y ago
On the 757, the two control columns are linked with a roller bearing in a detent (notch). With enough torque applied, the bearing will come out of the notch and the columns can move independently.
Animats 4y ago
It's a purely mechanical linkage. I've been trying to read the patent (US 5782436A). The USPTO has a new single-page web app. It's awful for finding by patent number, and worse when you want a full screen image of a drawing. It's clear that if one yoke is jammed and the other is moved with enough force, a spring loaded pin is forced out of a notch and the connection between the two yokes releases. What's not clear is how the linkage still connects to the flight controls. The idea seems to be that the one which is moving wins. What is clear is that, if your side becomes disconnected, your yoke doesn't do anything. No wonder one pilot was frantic. It seems that you get reconnected by moving the disconnected yoke to agree with the one in control. Then the pin falls into the notch and the yokes are connected again. Not sure about that. You can see the pin and notch in the patent drawings. This is independent of the fly-by-wire system. That's downstream from these mechanical devices. I wonder if pilot training includes knowledge that yoke disconnection is possible.
- hkwerf 4y ago
  > I wonder if pilot training includes knowledge that yoke disconnection is possible. Probably, I've heard https://www.youtube.com/c/MentourPilotaviation https://www.youtube.com/c/MentourPilotaviation talk about it as well.
- epse 4y ago
  They are trained in this. If disconnected, each yoke will control "their" half of the plane. This is mostly intended to maintain some level of controllability if one of the yokes were to get blocked or seized mechanically, this is not intended for human issues
- mnw21cam 4y ago
  If the linkage breaks, then each pilot gets to control the control surfaces on one side of the aircraft.

willidiots 4y ago

Entirely speculating, but it sounds like the fundamental problem is that they had a confused Captain and First Officer who both thought they were the Pilot Flying. Human factors / psychology issue. Sure, on a Boeing you'll feel the other pilot's input, but if you're tired enough, or panicking because the plane's not doing what you expected, you might not get the hint. Task saturation - followed by loss of situational awareness - is a very real problem in today's airliners, particularly during takeoff and approach/landing. You're trying to do a ton of things in a small amount of time, while dealing with a dynamic situation outside, and in this case after a long, tiring flight over the Atlantic. There are a great series of (dated but still good) videos from American Airlines about automation dependency, human factors and the simple but very real problems that develop as a result - often leading to panic and disaster when things go wrong. Search YT for "children of the magenta".

cryptonector 4y ago
> my airplane > your airplane [lets go controls] Those are the words to be exchanged to avoid confusion.
- willidiots 4y ago
  Yeah, simple enough. Also simple enough to go-around when you're obviously slow and going to be short of the runway, but look at Asiana 214. I do wonder if there's some training deficiency or cultural issue that leads to this scenario in Air France flights.
  - cryptonector 4y ago
    This makes me think of Loic Suberville's videos on language...
- Retric 4y ago
  Sure, just make sure that happens exactly that way 1,000,000 times without any failures… And that’s the root of many issues in aviation. It works 99.99% of the time is not always good enough.

gerdesj 4y ago

AF447 was (I read the WP article on it) at 38,000 feet and ice seems to be implicated and quite a few other things. This incident was at 1670 ft. My reading of the article is a P and CP being twats: "During the go-around on the Air France flight, the captain was making nose-down inputs, while the first officer was pulling back on the controls." I'm just a simple civvy but I was an air cadet and learned enough about flying in a single engine trainer to know that only one person should have control. You literally say "I have control" - "You have control" - "I have control". These muppets didn't seem to do that: "It took until 07:52:06, for the captain to become the only person making control inputs." In the very guarded language of accident review I would say that is a damning indictment of the behaviour of the pilot and co-pilot as being completely reckless and bloody stupid.

alistairSH 4y ago
That’s all correct, but AF447 was exacerbated by the pilot and copilot (actually 2 copilots, IIRC, the senior pilot was on break) fighting each others controls as the plane flew towards the ocean. The pitot tube was giving bad readings (frozen over), but from what investigators can tell, one control was trying to pull up and even out and the other was still pitching down to gain speed (per the warnings given by the faulty pitot tube).
- gerdesj 4y ago
  A car, plane or whatever should only have one driver/pilot. Planes have dual controls by default but this sort of nonsense should not be allowed to happen. This was not AF447 so what on earth happened? I'm guessing inadequacy of some sort and that's on the industry as a whole.
  - phil21 4y ago
    In cases like this it's almost always some variation of normalization of deviance. If company culture doesn't strictly enforce callouts 100% of the time, it's easy to get into a routine of everything being just fine 100's of times until it isn't. Really these sorts of things show there should be a failsafe mechanism that provides tactile/haptic feedback to the pilots if the other inputs are "fighting" theirs. Even an audible alarm isn't enough, as you'll likely get more than a few of those during events where it matters. Proper CRM of course should make this "impossible" - but in high stress moments any more layers of swiss cheese you can add the better.

ncmncm 4y ago

Nowadays planes will yank on the controls on their own initiative, most destructively e.g. in the case of a certain pair of 737MAXs. They probably assumed that is what was going on. That the other pilot was doing something obviously wrong is not a natural assumption, when there is an alternative. It seems like Air France has got some procedural drills to work on. One would have hoped that happened already. Somebody should check, this time.

tyingq 4y ago
Technicality, but the 737MAX MCAS was rolling a trim wheel, not moving the yoke.
- ncmncm 4y ago
  Exerted force on the yoke via the elevator, driven by the trim tab. But they also yank directly on the yoke, for lots of reasons.

exidy 4y ago

> I thought that Airbus makes the only airliners with no feedback when there are dual inputs applied This factoid will not die on HN. Conflicting inputs on an Airbus are handled by averaging and an audible "DUAL INPUT" cockpit warning.[1] In the case of AF447, the co-pilot used his "Priority Takeover" button which meant only his control inputs were in effect. If you wanted to say there is no physical feedback, then you would be correct. [1] https://safetyfirst.airbus.com/app/themes/mh_newsdesk/documents/archives/dual-side-stick-inputs.pdf https://safetyfirst.airbus.com/app/themes/mh_newsdesk/docume...

rmk 4y ago
Yes, that is what I meant. And any other type of feedback would be likelier to be ignored. That's why there's a stick shaker in addition to auditory and other warnings when the plane stalls, even in fly-by-wire planes.