Hacker News Reader

> Add a display that shows the current positions of both control sticks

Yes! From the article: "As the plane approaches 10,000 feet, Robert tries to take back the controls, and pushes forward on the stick, but the plane is in "dual input" mode, and so the system averages his inputs with those of Bonin, who continues to pull back.

If this is true, it's insane. What does it mean to "average" the inputs of both pilots if one is full forward and the other one full back?? It should say "conflicting command; make up your mind".

The article alludes to the old system where the stick was just the one same stick for both pilots: no possible conflicts there.

The new planes should have a way to emulate that.

I was shocked that new airplanes use joysticks are just simple inputs and don't give (some) feedback on the current state of the current control surfaces or the state of the other joystick.

This seems like a "feature" of analog controls that you'd want to take forward to fly-by-wire systems.

For me the 'averaging' of two controls seem totally bizarre. One pushing forward and one pulling back and the computer thought that was OK?

My fear of flying is reaching new heights.

Maybe this is a good thing if a more experienced pilot needs to 'hold the hand' of the other ofr some fine tuning manouvers, but when the commands are opposite from each other than it realy makes no sense that it decides to average them out and in doing so, basically respondes to none as desired (possibly having the operator use more force to get the desired response).

The analog stick seems much more reliable in this way, only one source of control of the aircraft, period.

- Delineate command better, e.g. Captain, Co-pilot #1, Co-pilot #2 so that who is in charge is clear.

This antiquated idea has killed many more people than it would have saved in this case. Read about CRM:

http://en.wikipedia.org/wiki/Crew_resource_management

I think a classic example is:

http://en.wikipedia.org/wiki/Avianca_Flight_52

The plane crashed because it burned all of its fuel in a holding pattern waiting to land in JFK. When the flight engineer noticed this, he was afraid to tell air traffic control, who he believed was "higher up" than he was (and he therefore had no right to question their decision). The result was 65 dead people.

There are several cases where a lower-ranking person has noticed something that the captain has not. And when they didn't do anything about it, people died.

Your link doesn't say that there isn't a clear chain of command, it says that there should be a culture that allows professional disagreement or calling to attention. Just because the captain is declared top dog doesn't mean that protocol demands subordinates must remain quiet.

Yes, the link doesn't say that, but research further and you'll find that the concept of a hierarchy is what CRM aims to eliminate. It's the First Officer's job to take the flight controls from the captain if the FO thinks the captain is doing something dangerous. Not to ask for permission, but to immediately do. This goes against the concept of a hierarchy, but is why they put two sets of controls up there.

I think you'd still do better to have a manual selection of which input is commanding, with an option of having both sticks linked and moving together.

BTW, who is commanding the plane (by inputs) and who is commanding the crew are entirely separate questions. I think one of the serious issues that MUST be addressed here is the issue of conflicting commands to the plane.

Two options.... 1) Place all controls between the pilots so they can easily see what eachother is doing or 2) Place a selection switch and indicator that allows a pilot to unambiguously take control of the plane and disable the other input, or to keep them in linked mode where they move together and provide tactile feedback as to what the other input is doing.

What happens if they're fighting each other?

At least there's feedback, and you can immediately see what's happening! In the current configuration, Bonin's stick inputs were nearly unknowable to the other officer.

Then they have to fight! You can't delegate responsibility to the "system" to resolve such a fight. A fight is a fight. And if it's happening, you can't automagically get rid of the fight.

An additional case that I know about, the Tenerife airport disaster: http://en.wikipedia.org/wiki/Tenerife_airport_disaster

Quoting:

  Speculation regarding other contributing factors includes:
    The flight engineer's apparent hesitation to challenge Van Zanten
    further, possibly because Captain Van Zanten was not only senior in rank,
    but also one of the most able and experienced pilots working for the airline.

  As a consequence of the accident, sweeping changes were made to
  international airline regulations and to aircraft... Hierarchical
  relations among crew members were played down. More emphasis was
  placed on team decision-making by mutual agreement.

Wouldn't the Air France 447 crash be an instance where a low ranking officer did not notice errors & was given too much control of the plane, resulting in the deaths of many people?

It sounds like both co-pilots were having mental blocks while operating together in the cockpit. With Bonin stalling the plane, while Robert is unable to figure out why the plane was not responding like he thinks it should & the insecurity of these events leads him to defer to the captain, who is not present.

I am not sure specifying a hierarchy would have helped so much in this case, but the example crashes given in this thread don't explicitly show that the hierarchical structure was the sole cause of the crashes, there were many contributing factors which lead up to both.

Deliberate selection of inputs would be best. Maybe a switch in the middle that both selects and displays which input is active?

What I don't get is why THE HELL are the two sticks averaged? What's the reasoning behind this? "Hey, one pilot thinks we should descend, the other we should climb, better maintain altitude without telling either one about it". Why?

I found that really bizarre as well. It's also troubling to me that the sticks don't move in concert. That seems like an excellent mode of communicating what the other pilot is doing.

Exactly. I fail to see any benefit to removing feedback on how the plane is actually contolled at any given moment.

I was also really surprised about this after reading the article. I look around to know a bit more about the Airbus design and arrived at this [article](http://msquair.wordpress.com/2011/09/16/pilots-in-the-loop-a...). The problem is not that they are averaged, but it seems to be that they are not coupled.

It seems that it has been known since 1987 that pilots prefer coupled sticks:

    In a 1987 evaluation of side stick controllers Summers et al (1987) found that under simulated ‘surprise’ hand overs pilots Cooper Harper rating of the schemes were (in descending order):

    Coupled sides sticks with algebraically summed inputs (1.4),
    Uncoupled side sticks with algebraically summed inputs and disconnect switch (final A320 implementation) (1.8),
    Uncoupled with algebraically summed inputs and priority logic (original A320 implementation) (3.3), and
    Uncoupled side sticks with with algebraically summed inputs (3.4).

So, Airbus chose to implement the "second best" option (using a disconnect switch). The same article speculates that even though several sound alerts might have been triggered - including a sound alerting of "Dual Input" -, the stress situation makes them insufficient:

    [...] in the circumstances identified as triggering instinctive responses the value of such alerts is degraded due to the inevitable attentional tunnelling that operators experience in high stress situations.

Fascinating and crushingly disheartening. It is obvious that a coupled force feedback mechanism is the simplest human interface solution to showing what is happening between both sticks, and pilots prefer it. I would really LOVE to hear the thinking behind the fool that chose to produce an interface that allows for me to press "up" and you to press "down" and we each get fed the bogus result "up" or "down" while actually it has decided to process it as "asdfasdf".

> - Add a display that shows the current positions of both control sticks. Add an alarm when the two sticks are not within a certain margin of the each other, if both are engaged. Such as if one is full forward & the other is full back.

Even better: when you have two mechanical inputs to a single output channel, mechanically _link_ the two. If Pilot #1 moves the stick, pilot #2's stick should move. So that if there is a disagreement, they can physically observe it in their hands. Any fight over where to put the stick shouldn't be "averaged". It should be physically felt by both pilots so that they realize that there is a conflict and resolve it face to face.

It's similar to why SVN commit conflicts are so damn annoying. But they're designed to be: the only way to resolve a commit conflict is to walk over and meet your conflicter face to face and resolve. Can you imagine if SVN decided to "average the inputs"? What the fuck does that even mean? This entire plane sounds like a UI disaster (modal inputs, etc.)

- Add a display that shows the current positions of both control sticks. Add an alarm when the two sticks are not within a certain margin of the each other, if both are engaged. Such as if one is full forward & the other is full back.

This was my first thought as well. Confusion in one pilot was allowed to cause confusion in the second pilot, because he didn't realize that his partner was doing something unexpected and incorrect. If you make sure a pilot can always detect inconsistent reaction in a co-pilot, you can keep them in sync and prevent spreading confusion. An alarm when the two pilots are out of sync seems like a pretty straightforward benefit.

Yes. Or some kind of haptic connection

Like one stick moving the other...

You can display so much information before you add to confusion in a high stress situation. Haptic feed back could be useful.

I think the simplest solution to the mismatched stick issue is to use servo motors to replicate the old situation--the movement of each stick mirrors the movements of the other.

A pilot wouldn't have to look for some stick position display, or indicator light, if they can easily feel the deflection of the stick.

My understanding--I am not an aviator--is that the current Boeing controls behave this way and have for a long time. Apparently there is a lot of disagreement between the Boeing/US and Airbus/EU schools of thought, with a preference for greater mechanical (rather than electrical) interaction with flight controls on the Boeing side.

The linked article said that Boeing indeed to behave this way, and frankly I am not boarding ANY Airbus flights in the future.

Motors can fail.

Use mechanical feedback. Not necessarily rigid connection, but at least some kind of elastic coupling or something. Or, heck, connect them rigidly.

> "This can't be happening!"

I want a device that gives me an electric shock every time I think or say this. If one can restructure one's cognitive habits in a way that replaces thoughts like this with thoughts like "What would explain this? Is this reasonable? What are the alternaives? How can I check this?", many errors will be avoided.

His statement was made out of exasperation 4 seconds before he died. There is very little he could have done to change his fate at that point.

Still an indication of bad mental habits. And it doesn't strike me as out of line with his actions (complete disregard of the empirical information he had) the minutes before.

This one feature may have prevented the crash.

A indicator light, saying the plan is in "alternate law" mode, and SHIT can go wrong, very quickly.

Also an alarm in the pilot resting area that would relay when warnings are detected like stall or switching to alternate law.

Okay. This is how the cockpit apparently looks: http://www.pbase.com/image/47231836

Where are you going to stick the indicator light so that it's impossible to ignore it or mistake it for something else.

http://i.imgur.com/FHz1B.png

Make it a loud, repeated aural indication. Oh wait, the stall warning was just that and got completely ignored...

I think we've discovered the most difficult UX design task on earth.

You know that Don Norman's insights come, in large part, from investigating nuclear reactor controls (Three Mile Island) and air crash investigations.

I am no aviation expert, but according to other posts here the stall warning may have been ignored because Bonin didn't register that they were in alternate law. If they weren't in alternate law, the plane would have automatically limited the amount to which he could pull back.

The most obvious solution to me, if all of that information is accurate, is that there should be a distinct audio stall warning for alternate law.

Instead of the plane saying "Stall... Stall... Stall... " when in alternate law it should probably say "Stall... alternate law... Stall.. alternate law...". Doesn't guarantee you the pilot will listen, but it seems like it is pertinent enough information to push it front and center along with the stall warning.

It seems like that when analyzing this accident. If you analyze another, there may be 2 or 3 other things that would seem "pertinent enough information to push it front and center". And yet more for a 3rd accident.

The problem is that making something more noticeable automatically makes everything else less noticeable...

I agree with you in general that it is a balancing act, but if you're going to have a modal interface (normal law, alternate law) and the plane's flight controls are going to perform differently depending upon that mode, an indicator of which mode you're in is immensely important in any situation.

The two things that seem to big huge contributors to the crash are that the pilots may not have realized they were in alternate law soon enough & one or both pilots did not realize that one of them was holing the stick back stalling the plane.Both of these seem like glaring UX & training issues.

It does not appear that it's very clear when the plane goes into alternate law & it does not appear they receive much training on how to fly in alternate law. Even if they do receive training, you probably do not want your most novice pilot handling the controls in alternate law. Additionally the averaging of the inputs seems to be the most obtuse way for pilots to realize mismatched inputs.

Typically there are two lights, master caution and master warning, that indicate a problem. From there, the details can be read on another screen. Additionally, there are voice alarms for critical events, like "Traffic! Climb now!" or "Fire! right engine!".

I don't know how an Airbus notifies the crew of the switch to alternate law, but I'm willing to bet that the master caution light comes on.

Some ideas:

Illuminate the pilot's footwells with a bright red light. There is normally no illumination there at all, plus it takes up a fairly large percentage of their viewable area when looking at their screens.

Or, change the background colors of all the screens from black to red. That might harm usability too much though. Maybe change all the other switch backlighting over to red. Or change the cabin overhead lighting over to red.

To the greatest extent possible, the entire environment and interface needs to communicate the modal shift. And pilots would need to train on this shift constantly so that recognition, and the appropriate shift in thinking, would happen habitually.

> Illuminate the pilot's footwells with a bright red light

Might interfere with normal/night vision.

At least one of them realized it, but not the one flying. From http://www.bea.aero/en/enquetes/flight.af.447/transcript29ju... :

"At 2h10.16 seconds, the pilot in the left seat, the pilot not flying, says “we have lost the speeds” then “alternate law”"

yes, and I'm not sure under what situation a 'democratic' dual-input mode is a good idea!

Maybe everyone on the plane could have one!