What really happened aboard Air France 447 • Hacker News Board

Re: What really happened aboard Air France 447

#311

Post by crististm » Thu, Dec 08, 2011, 9:10 PM UTC

rguzman wrote: post #37

maeon3 wrote: post #27

Pilot stalls the plane out of panic to get out of the storm, ignoring 75 reminders that you are stalling and losing altitude, does nothing to remedy the stall until it is too late. I expect blunders like that from drunk drivers.

way too easy for you to say without being in the situation. heavy turbulence, no visibility, confusing situation, very likely that he was disoriented, operating a very complex set of computer programs hooked up to a very complex set of physical controls that have a myriad of potential configurations and points of failure while trying to debug it at the same time in a panic and making quick decisions. from his vantage…

Exactly.But how do you do what is right (push forward - which is go down) when all your instincts tell you want up (pull)? This is the same as driving a car in a rally. Drivers there know to drive into the slippage to recover control. But if you're a normal driver you'll do exactly the opposite. My question is - do they train enough to break their instinct?

Re: What really happened aboard Air France 447

#312

Post by crististm » Thu, Dec 08, 2011, 9:24 PM UTC

abstractbill wrote: post #305

krschultz wrote: post #243

Earlier quoted context omitted.

I find the fact that the control sticks do not move together the most troubling design flaw. Bonin's actions were not obvious to the other two pilots, if the other pilot saw his stick pulled all the way back when he knows they need to get the nose down and pick up airspeed, he'd instantly know what was wrong. Instead he is looking at instruments and talking to the other pilot and is completely unaware of how self-inf…

That, and the fact that the computer chooses to average inputs from the two sets of controls even when they're very different. One pilot pulling back, and the other pushing forward and the system just quietly averages them out rather than sounding another alarm?

This clearly looks like an anomaly that the plane should detect and correct. Or at least announce somehow. The computer should average only when controls are consistent with each other.

You never know what's the time when you have two clocks.

Re: What really happened aboard Air France 447

#313

Post by maximusprime » Thu, Dec 08, 2011, 9:26 PM UTC

crististm wrote: post #308

maximusprime wrote: post #182

scary how incompetent they seem

They did not have enough training in such situations. The captain seemed more competent, but he was not on the controls to do the right thing. It's the same situation when untrained people drive cars to their limit. If the car slips then you should slightly steer in the direction of the slippage which is most of the time opposite to where the road turns. If you're not trained to do that you won't do it.

Do you really need training to say "I'm pushing the stick backwards now", "what are you doing over there?" etc

Surely that sort of basic communication about what you're doing should be one of the first things you learn...

Re: What really happened aboard Air France 447

#314

Post by crististm » Thu, Dec 08, 2011, 9:30 PM UTC

runningdogx wrote: post #29

I've followed the discussion of the AF447 investigation on several flight discussion forums. The PF (Bonin) apparently never became aware of his angle of attack (once the airplane fully stalled, AOA was absurdly high). He did not seem to be aware that his constant inputs had caused the Airbus's THS (trimmable horizontal stabilizer, horizontal flaps on the tail) to deflect to maximum in order to try to keep the nose u…

indeed, a computer can continue to estimate for a certain amount of time the readings of the lost sensor. You can think of solutions. But its strange to see so many cases of lost planes because of pitot problems.

Re: What really happened aboard Air France 447

#315

Post by georgemcbay » Thu, Dec 08, 2011, 9:39 PM UTC

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.

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.

Re: What really happened aboard Air France 447

#316

Post by crististm » Thu, Dec 08, 2011, 9:45 PM UTC

bdonlan wrote: post #55

sliverstorm wrote: post #43

Earlier quoted context omitted.

Ah, I was not aware they already could. My next question is why not make themselves de-ice better? This maybe seems trollish or silly, but in all seriousness, if your sensors aren't good enough, first rule out improving the sensors before you try to compensate with the system.

According to the article's timeline, dual pitot failure occurred at about 02:10:06. Recovery of one pitot occurred at 02:10:36, and the other at around 02:11:03. That's about 30 seconds to recover one pitot, and 57 seconds to the recovery of the second. When you consider that this all boils down to melting off ice, that's not so bad, really. And if they hadn't royally screwed up their manual handling, it wouldn't hav…

The simulated test is always in a more relaxed environment. But anyway, if your instincts are good they you are OK. The problem is when your instincts tell you to do the opposite of what needs to be done. Probably the pilots need more training to break their instincts?

Re: What really happened aboard Air France 447

#317

Post by dkokelley » Thu, Dec 08, 2011, 9:46 PM UTC

If it hasn't already been discussed, could someone explain the rationale for not making the control sticks mirror each other? I know it's an artifact of old, mechanical linkages, but when two people need to be aware of the control inputs at any given time, why not relay that information by manipulating the controls to match the inputs?

Re: What really happened aboard Air France 447

#318

Post by teyc » Thu, Dec 08, 2011, 10:22 PM UTC

assemble wrote: post #300

jrockway wrote: post #232

Earlier quoted context omitted.

This already happens. I have not been trained to fly an airliner, but I believe that the priority is something like stall, gpws (flying into the ground), tcas (flying into other traffic), master warning, and master caution. These all have their own lights and sounds in the cockpit, and if I know them, so does the flight crew. Presumably the 150 messages that needed to be looked at were all "caution" messages. Too man…

Yeah, I don't know about the a/c in question; however, the Colgan crash was a result of the pilot fighting the stick pusher and winning. The stick pusher is not easy to override. It seems counter intuitive to nose down when you're falling out of the sky, but it's how you recover.

Exactly.

If one were to apply principles of Tao, it would be to yield. Give the stick pusher nothing to push.

Re: What really happened aboard Air France 447

#319

Post by crististm » Thu, Dec 08, 2011, 10:50 PM UTC

maximusprime wrote: post #313

crististm wrote: post #308

Earlier quoted context omitted.

They did not have enough training in such situations. The captain seemed more competent, but he was not on the controls to do the right thing. It's the same situation when untrained people drive cars to their limit. If the car slips then you should slightly steer in the direction of the slippage which is most of the time opposite to where the road turns. If you're not trained to do that you won't do it.

Do you really need training to say "I'm pushing the stick backwards now", "what are you doing over there?" etc Surely that sort of basic communication about what you're doing should be one of the first things you learn...

That too. I just saw a BBC video about this incident and a pilot was saying exactly that - that the pilots should know who is in control and he should pilot the plane to the safety.

But I was thinking about training more in another sense. If your instinct tells you to do something that is opposite of the right thing than you should receive more training to brake your instinct. In this case the right thing to do was probably to push the nose down to gain speed. But if your instinct tells you that going down is not the right thing you won't do it. You should make a concious decision and you are not in the position to do that without prior exposure to the situation.

Re: What really happened aboard Air France 447

#320

Post by kelnos » Thu, Dec 08, 2011, 11:47 PM UTC

bambax wrote: post #146

einhverfr wrote: post #128

Earlier quoted context omitted.

IANA Pilot. I do make aerodynamically correct fixed-wing and lifting-body type paper airplanes, however, and I have had a LOT of fun playing with aerodynamics in this hobby. One thing to keep in mind regaring stall is that it's 100% dependent on angle of attack, not speed (something Popular Mechanics gets entirely wrong). What happens basically is that at a high angle of attack the air layer doesn't track the wing su…

A commenter below (cellularmitosis) makes a very interesting point: Bonin may not have realized he was in "alternate law" (let's call it "mode" instead of "law"). In "normal mode" the computer will not let pilots stall the plane, whatever they do; it will accept the commands up to what it considers dangerous. There's an "envelope" of acceptable plane movements; pilots can move inside this envelope but not outside of…

When in normal law, if you pull the nose up all the way, and are at the edge of the envelope, will the computer even give you a stall warning? I would guess (hope!) not, since the plane is never actually in danger of stalling. Assuming that's the case, a stall warning from the computer should always be heeded.

If that's not the case, and the stall warning sounds even when there's no real danger of stalling (because the controls are operating in normal law), I feel like that's a terrible user interface.