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What really happened aboard Air France 447

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Re: What really happened aboard Air France 447

#211

Post by tcarnell »

akira2501 wrote: post #98
anrope wrote: post #79

Earlier quoted context omitted.

Up to this point, the situation was playing out in a sadly too common case of pilot error, pilot inexperience, which makes up a huge portion of aviation accidents. When I read about the dual input averaging, I literally exclaimed "what?!". I can't believe that, for all the strict standards that flight control software must meet, nobody called this out as a dangerous idea?

Precisely.. I'd also like to know under what circumstances this would actually be used, and be a useful safety feature to have implemented. At the very least, there should be a significant warning in the cockpit when "dual input" mode is active. That is an incredibly dangerous "feature."

completely agree about this 'dual input' mode - crazy.

But also these modern planes seem to jump in and out of 'modes' without any warning or confirmation.

I believe the 2008 plane crash at Madrid (largely pilot error again) also suffered from some confusion about the plane 'mode'. It was set to 'normal flight mode' whilst attempting to take off (or something).

Again, both crashes largely due to 'usability' issues and cockpit design.

Re: What really happened aboard Air France 447

#212

Post by tcarnell »

nchaimov wrote: post #56
flyingkiwi wrote: post #31

Earlier quoted context omitted.

I am a pilot (a small one but instrument rated) - there's no time EVER that you want that, and I am shocked the Airbus does not have a warning that says DUAL INPUT BEING RECEIVED. At the very least, it should give priority to the left seat controls. Was really shocked to read the article.

It does: there's an audible warning that says the words "DUAL INPUT" The English translation of the BEA's third interim report on the flight is available here: http://www.bea.aero/docspa/2009/f-cp090601e3.en/pdf/f-cp0906... It includes the full CVR transcript at the end, which shows that the dual input alarm activated five times.

... so if there was a noise (intercom, radio, talking etc) and you didn't hear the announcement, that's it ,game over.

Re: What really happened aboard Air France 447

#213

Post by nufta »

jarek wrote: post #75
jrockway wrote: post #69

Earlier quoted context omitted.

There is other debris that can clog pitot tubes. Birgenair Flight 301 crashed because some wasps built a nest in a pitot tube during an extended layover: http://en.wikipedia.org/wiki/Birgenair_Flight_301 189 people died. (Also note the failure to react properly to the stall warnings. This comes up again and again.)

I wonder if in a couple of decades we'll look back at pitot tubes and wonder what the hell we were thinking using such a fragile solution. (Of course, in a couple of decades we'll probably have a much more accurate external method of finding out speed/airspeed.)

Being restricted to rich people with "fuck the planet" attitude, hopefully the jet airliner market will be small enough to stall technologically.

Re: What really happened aboard Air France 447

#214

Post by tcarnell »

Too wrote: post #153
greiskul wrote: post #14

Earlier quoted context omitted.

Which raises a very good question, when would you ever want that joystick behaviour?

I guess it could be a cheap workaround to always get smooth transitions when changing pilot. Imagine if one pilot holds full left and the other full right and you press a "switch now!"-button. You would need some kind of transition-period of maybe a second to avoid jerk which could be confusing for the pilot to not know when he has full control and when he is in transition.

good point - but I think a 'dual input' mode is the wrong solution to that problem.

Re: What really happened aboard Air France 447

#215

Post by Tloewald »

brazzy wrote: post #168
LaGrange wrote: post #148

Earlier quoted context omitted.

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.

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.

Re: What really happened aboard Air France 447

#216

Post by Tloewald »

tcarnell wrote: post #209

Presumably the stall warnings were ignored because in "normal law" even if you try to stall the plane, a). the plane will not allow itself to stall and b). the stall warning will still sound. Hence the stall warning SHOULD NEVER SOUND in "normal law" mode. Therefore, the only time a pilot should hear the stall warning is when they actually have to intervene. Ultimately, if the plane was funcioning perfectly well and…

I Like your last line.

The way I think about it is this. A "bug" crashes or causes bad data when running on a computer. A "usability issue" crashes or causes bad data when running on a person.

Re: What really happened aboard Air France 447

#217

Post by gldalmaso »

bambax wrote: post #118
Klinky wrote: post #30

Co-pilot Robert, after finally getting full control back from Co-pilot Bonin: "Damn it, we're going to crash... This can't be happening!" Co-pilot Bonin, who had been pulling back & stalling the plane during the crisis: "But what's happening?" Pretty much sums it up. I am thinking that perhaps Bonin had shellshock & may not have even realized he was holding the stick back. Perhaps the more experienced Robert didn't t…

> 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…

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.

Re: What really happened aboard Air France 447

#218

Post by mtts »

nikcub wrote: post #188
mtts wrote: post #181

Earlier quoted context omitted.

At night, over an ocean, in a storm, with no visibility, in possibly significant turbulance and responsible for the lives of 300 people. I doubt knowledge acquired from an episode of "Air Crash Investigation" is very useful in such a case. Watching documentaries or looking up stuff on the internet does not make anyone an expert. That Bonin guy, as inexperienced as he was, knows far, far more about piloting airplanes…

ye no shit, and I am thinking through how the situation gets to a point where he can forget all that and keep pulling the stick back up

He panicked. What's there not to understand?

Re: What really happened aboard Air France 447

#219

Post by Tloewald »

mikecane wrote: post #194

I'm no pilot, and I haven't read the long discussion here, but I can't see how the pilots can be blamed. That Airbus has nonsensical design. Asynchronous sticks, so the other one in the seat couldn't see the other stick being pulled back? Then averaging of the async controls, allowing one stick to work against the other? As for "alternate law," why was there no alarm like the Stall warning to repeatedly tell those in…

Consider the positive impact of having a weight on a string flailing around in a cockpit when the shit hit the fan. The articificial horizon works on this same principle, but pilots are known to ignore it anyway. The whole point of instrument flying is to se aside your senses and common sense and look at your instruments.

One of the problems was that the plane was unexpectedly stable during the stall so the pilots might have dismissed the stall warnings as disconnected from reality.

Re: What really happened aboard Air France 447

#220

Post by jwr »

mikecane wrote: post #194

I'm no pilot, and I haven't read the long discussion here, but I can't see how the pilots can be blamed. That Airbus has nonsensical design. Asynchronous sticks, so the other one in the seat couldn't see the other stick being pulled back? Then averaging of the async controls, allowing one stick to work against the other? As for "alternate law," why was there no alarm like the Stall warning to repeatedly tell those in…

It's been done before. From the excellent article "The Turn":

> Pilots, too, have relied on pendulums. It is said that an airliner inbound to New York in the 1950s lost all its gyroscopes in heavy weather over Block Island. The captain was a wise old man who had risen with the airlines from the earliest airmail days and was approaching retirement. A lesser pilot might have fallen for the trap of intuition. But the captain simply took out his pocket watch, dangled it from its chain, and began to swing it toward the instrument panel. Flying by the pendulum and the compass, he proceeded the length of Long Island in the clouds. After breaking into the clear near the airport, he landed and wished his passengers a good day.

(the entire article is really worth reading: http://www.theatlantic.com/past/docs/unbound/langew/turn.htm)

But in this case the pilots didn't even need to do that. Their gyros were working correctly, so they had an artificial horizon right in front of them. The attitude of the plane was known. They even recovered their airspeed indicator after 30s (the second one after a minute)! All that was needed was for the pilot to stop pulling on the stick…

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