What really happened aboard Air France 447 • Hacker News Board

Re: What really happened aboard Air France 447

#341

Post by assemble » Fri, Dec 09, 2011, 3:27 PM UTC

bjornsteffanson wrote: post #295

Sort of off-topic, but does anyone know anything about the software the Airbus (or any commercial aircraft, really) runs? I'd be really interested to know how abstracted the code is from the hardware.

It's highly version controlled. Changing software versions on a plane usually means changing a lot of hardware too. After removing the boxes from the a/c, they can be returned to the manufacturer and the new software can be installed.

We test it in a ground-based simulator rig with the exact computers that would be on an a/c. If it gets approved, we put it on an airplane and we go fly the plane around a lot to make sure the software works.

A software upgrade almost always means switching out the hardware, because that's one way we ensure conformity.

Re: What really happened aboard Air France 447

#342

Post by ansible » Fri, Dec 09, 2011, 4:53 PM UTC

kelnos wrote: post #320

bambax wrote: post #146

Earlier quoted context omitted.

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 t…

I really don't like the idea in general that 'normal law' mode lets the pilots yank the controls any which way and the computer (supposedly) prevents the plane from leaving the safe flight envelope. I believe that sets up the wrong attitude in the pilot's mind about having to carefully and thoughtfully control the aircraft.

If the flight computer is having to intervene and change the flight controls, then at the very least there should be a force-feedback mechanism in the stick which tells the pilot he's doing something wrong, and that he really shouldn't be yanking back the stick that hard.

The other bad part of the user interface is that the two sets of flight controls are not linked, like they were in the old days. With side sticks, it is not easy to see what the other pilot is doing. And averaging the control inputs of the two pilots is INSANE, in my opinion. Only one pilot should be flying the plane, and it needs to be quite obvious who that is at all times.

The CRM mechanism to take over flight controls should not be saying the words "I have control", it should be flipping a big switch on the center console that visibly indicates who has control.

Re: What really happened aboard Air France 447

#343

Post by ansible » Fri, Dec 09, 2011, 4:57 PM UTC

jarek wrote: post #322

Florin_Andrei wrote: post #249

Earlier quoted context omitted.

> Of course, very little airliner training happens outside a simulator, which can you can stall without damaging anything. Maybe they should apply mild taser shocks to pilots stalling in the simulator. I'm not being snarky. There should be some kind of physical consequence of making bad mistakes, otherwise it's too disconnected from reality.

The result of that would be pilots doing everything in their power to avoid entering stall and thus learning less about behaviour while in stall and exiting stall. I'm not sure that's a desirable outcome. Sometimes you have to fail to learn.

Well, you can turn off the shocks for training days when they are practising stall recovery, but leave on the shocks for regular situations.

Re: What really happened aboard Air France 447

#344

Post by DasIch » Fri, Dec 09, 2011, 6:32 PM UTC

crististm wrote: post #307

acabal wrote: post #48

That was one of the tensest things I've read in a while. My heart was pumping up until the end. The level of stress, confusion, and terror those pilots, not to mention the passengers, must have experienced must have been truly terrible.

My thoughts exactly. While reading this I could not think about the same counter-intuitive reaction that people have when they drive and the car slips. Most people steer in the direction of the road when the single action to regain control is to slightly steer in the direction of the slippage.

That very much depends on the angle, speed, acceleration and traction you have and whether you are slipping in the front or back.

That being said in reality most people don't have the training and experience to regain control anyway, which makes the very counter-intuitive option of crashing your car in a way that doesn't/is unlikely to kill anyone a fairly good option.

Re: What really happened aboard Air France 447

#345

Post by dhughes » Fri, Dec 09, 2011, 6:51 PM UTC

lutorm wrote: post #263

dhughes wrote: post #44

I don't think the average person realizes that for aircraft pilots ice is a constant worry even in tropical areas of the world. The temperature drops 1.98C for every 1,000 feet you go up so you can see quite quickly how fast you can enter an area below the freezing point of water. Icing of the pitot tube and carburetor are a constant worry at least for prop driven aircraft. Right from day one you're taught what to lo…

I never got far enough along to learn about wing icing I ran out of money for lessons Hey, me too! (And 9/11 happened which made it a lot harder for foreigners to fly.) But I did have the opportunity to get a lesson in how to avoid carb icing without carb heat when I pulled the carb heat control straight out of the dash on our 152. ;-)

I'm not surprised most of the 152s are probably from the 1970s and are used constantly for training it's amazing the last even with strict control of inspections and repairs.

I learned on a Cessna 152 too but one day we had to use a 172 it was like a Cadillac compared to the 152.

Re: What really happened aboard Air France 447

#346

Post by acqq » Fri, Dec 09, 2011, 6:57 PM UTC

ansible wrote: post #342

kelnos wrote: post #320

Earlier quoted context omitted.

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 t…

I really don't like the idea in general that 'normal law' mode lets the pilots yank the controls any which way and the computer (supposedly) prevents the plane from leaving the safe flight envelope. I believe that sets up the wrong attitude in the pilot's mind about having to carefully and thoughtfully control the aircraft. If the flight computer is having to intervene and change the flight controls, then at the very…

I like the idea of linked control, like on the small planes. That's "the principle of least surprise" and also gives the copilot the right information of what another guy is doing -- that was obviously missing here!

However if you add force feedback of the plane computer "correcting you" you'd never know if it's plane or an another guy. Therefore, force feedback from the computer doesn't sound to me as a good idea. Some kind of feedback would be a good thing, but in panic, it wouldn't be noticed. I guess I'd put something like something "protruding up" on the stick when in another mode -- you'd feel and see it.

Finally, switch flipping is unnecessary if you have a force feedback. It think that's really the major feature missing!

Re: What really happened aboard Air France 447

#347

Post by Florin_Andrei » Fri, Dec 09, 2011, 7:29 PM UTC

jarek wrote: post #322

Florin_Andrei wrote: post #249

Earlier quoted context omitted.

> Of course, very little airliner training happens outside a simulator, which can you can stall without damaging anything. Maybe they should apply mild taser shocks to pilots stalling in the simulator. I'm not being snarky. There should be some kind of physical consequence of making bad mistakes, otherwise it's too disconnected from reality.

The result of that would be pilots doing everything in their power to avoid entering stall and thus learning less about behaviour while in stall and exiting stall. I'm not sure that's a desirable outcome. Sometimes you have to fail to learn.

No, what I mean is - tase them when they "crash" in the simulator, not when they stall.

A simulator "crash" is not nearly significant enough to their reptilian brain. Their neocortex may register it as a failure, but for the reptilian brain is just a big nothing.

Adding some physical jolt may drive the lesson deeper in their psyche, that a crash really is a bad thing.

Re: What really happened aboard Air France 447

#348

Post by DasIch » Fri, Dec 09, 2011, 7:38 PM UTC

brc wrote: post #82

cellularmitosis wrote: post #72

Earlier quoted context omitted.

So, here's the problem with this whole normal law / alternate law situation: If a pilot believes he is in normal law, and wants to ascend above the storm, he'll probably just pull all the way back on the stick, thinking "this will cause the computer to ascend as quickly as it can without stalling". AAAARGGHH!!!! This maddening concept of normal law is turning the above insanity into the EXPECTED OUTCOME! Having a com…

This is an important point as cars nowadays have more and more electronic overrides - everything from traction control to stability control to anti-lock brakes to lane departure warnings (and recovery) to emergency braking and speed control. Most of the later ones (emergency braking, speed control, lane departure) are only on expensvie cars, but within 10 years will be standard equipment on all cars. If not by legisl…

Getting a drivers licence in Germany costs roughly 2000€ (2673$), assuming you pass theoretical and practical exams on first try. You need to take 14 theoretical lessons at 90 minutes, 2 of them on technical stuff, you need at least 12 practical lessons, 5 outside of a town, 4 on the autobahn, 3 at night and you will need a couple regular lessons just to get started so most people end up with 20 practical lessons or so.

After all that you will have neither training nor experience with emergency situations, in fact you will barely be able to brake a car so that it stops as fast as possible, which the majority of drivers are simply incapable of.

As nice as it would be to have that training, your assumption that you have to add it is fundamentally flawed in that already nobody can manage his car in such a situation with or without assistance. Apart from that most Americans probably consider what Germans have to do to get a driver's license insane, I doubt they would even seriously consider implementing something similar.

Re: What really happened aboard Air France 447

#349

Post by georgemcbay » Fri, Dec 09, 2011, 8:04 PM UTC

brazzy wrote: post #336

georgemcbay wrote: post #315

Earlier quoted context omitted.

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…

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.

Re: What really happened aboard Air France 447

#350

Post by gnaffle » Fri, Dec 09, 2011, 9:08 PM UTC

Florin_Andrei wrote: post #347

jarek wrote: post #322

Earlier quoted context omitted.

The result of that would be pilots doing everything in their power to avoid entering stall and thus learning less about behaviour while in stall and exiting stall. I'm not sure that's a desirable outcome. Sometimes you have to fail to learn.

No, what I mean is - tase them when they "crash" in the simulator, not when they stall. A simulator "crash" is not nearly significant enough to their reptilian brain. Their neocortex may register it as a failure, but for the reptilian brain is just a big nothing. Adding some physical jolt may drive the lesson deeper in their psyche, that a crash really is a bad thing.

I don't think accidents happen because pilots don't realize crashing is a bad thing, they happen because pilots do the wrong thing. You probably want pilots that have trained on dealing with lots of different failures and can do the right thing as correctly and quickly as possible, not pilots who get stressed and upset recalling the electric shocks they got during training.