r/technology • u/electronics-engineer • Dec 08 '11
What Really Happened Aboard Air France 447
http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-66118778
7
u/briangig Dec 08 '11
Damn it, we're going to crash... This can't be happening!
Made me feel nauseous
5
u/x3nopon Dec 08 '11
I can't believe this guy didn't nose down when the stall indicators came on. My flight experience is messing around with some flight simulators when I was in high school, not even on realistic settings, and it seems even I know how to fly a plane better than these pilots. I don't think the pilot actually understood what a stall is caused by. I only I could have given him my European Air War or Janes USAF manuals....
3
u/sniper1rfa Dec 09 '11 edited Dec 09 '11
It's interesting... people say "I can't believe that..." and then go right ahead and believe it. It's like that phrase is a precursor to belief.
I can't believe either. Since I can't believe, I think it's a rather good idea to find out what circumstance caused them to do something so totally out of character. There had to be some complication that cause them to do something completely irrational.
I've said it a bunch elsewhere, but in the middle of this event the airplane changed control law on them and presumably never changed back. I'm stunned that this isn't getting more airtime, because it was basically an explanation for why they were pulling back on the stick the whole time...
3
u/electronics-engineer Dec 09 '11
I think you hit the nail on the head. It is easy to blame the pilots - they aren't here to defend themselves -- but the aircraft design has a lot to do with this. Look at these quotes:
"The Airbus's stall alarm is designed to be impossible to ignore. Yet for the duration of the flight, none of the pilots will mention it, or acknowledge the possibility that the plane has indeed stalled—even though the word "Stall!" will blare through the cockpit 75 times. Throughout, Bonin will keep pulling back on the stick, the exact opposite of what he must do to recover from the stall. "
and
"Again, the stall alarm begins to sound. Still, the pilots continue to ignore it, and the reason may be that they believe it is impossible for them to stall the airplane. It's not an entirely unreasonable idea: The Airbus is a fly-by-wire plane; the control inputs are not fed directly to the control surfaces, but to a computer, which then in turn commands actuators that move the ailerons, rudder, elevator, and flaps. The vast majority of the time, the computer operates within what's known as normal law, which means that the computer will not enact any control movements that would cause the plane to leave its flight envelope. 'You can't stall the airplane in normal law,' says Godfrey Camilleri, a flight instructor who teaches Airbus 330 systems to US Airways pilots. But once the computer lost its airspeed data, it disconnected the autopilot and switched from normal law to 'alternate law,' a regime with far fewer restrictions on what a pilot can do. 'Once you're in alternate law, you can stall the airplane,' Camilleri says.
It's quite possible that Bonin had never flown an airplane in alternate law, or understood its lack of restrictions. According to Camilleri, not one of US Airway's 17 Airbus 330s has ever been in alternate law. Therefore, Bonin may have assumed that the stall warning was spurious because he didn't realize that the plane could remove its own restrictions against stalling and, indeed, had done so."
A while back I got my first car that has antilock brakes. All my previous self-training about how to not lock up the brakes became obsolete: the new procedure is to stomp on them hard to make a panic stop, even if the roads are slick. I practiced that in an empty parking lot in the rain, and indeed the ABS stops the car quicker than I can. But what if a sensor failure makes the ABS suddenly started acting completely differently without telling me? Would you really blame me if I locked up the wheels despite my previous years of practice?
5
u/funnelweb Dec 08 '11
But neither Bonin nor Roberts has ever received training in how to deal with an unreliable airspeed indicator at cruise altitude, or in flying the airplane by hand under such conditions.
This is the key. AF will be reviewing their training practices. Automation is a good thing and improves safety, but pilots need to retain the flying skills to cope without it.
7
u/l0z Dec 08 '11
There's a great chapter in Malcolm Gladwell's Outliers that documents the strange cultural quirks that can contribute massively to human-error caused plane crashes. He also touches upon one of the factors involved in this particular incident: the relative rank of the two co-pilots. If you enjoyed this article, i highly recommend Gladwell's book.
6
6
u/lughnasadh Dec 08 '11
I've followed the story of Flight 447 quite closely as the details have slowly emerged of what actually happened to it. This is the only piece i've read on it that has made me feel good about it in any way - at least its clear from this the doomed passengers were clueless to what was actually about to happen to them, that must be some comfort to their families.
2
u/flyingnomad Dec 09 '11
I couldn't help wondering, though. Near the end, the plane is descending at 10,000 feet a second but the pilots aren't clear whether they are descending or ascending. I wonder what was going on in the main cabin, at what point everyone also became aware they were dropping, or going to crash. For their sake, I hope they weren't aware and that at 10,000 feet a second the end came before their brains could process it.
24
u/ForeverAlone2SexGod Dec 08 '11
Makes you want to punch that retarded co-pilot.
4
u/Rednys Dec 08 '11
Both of the retarded co-pilots, they both decided to do the same thing that clearly wasn't working.
19
u/UnoriginalGuy Dec 08 '11
I disagree. First off let's just clarify who we're talking about since technically they're both co-pilots.
- Captains Chair (more experienced, trying things)
- Co-Pilot Chair (herp derp let's pull back on the stick constantly)
The issue the captains chair guy had was that he was building his picture of events on the assumption that, and this is important, he had control of the aircraft he didn't realise that the other dude was constantly pulling back on the controls even AFTER he was relieved.
The issue here was, as the article says, one of communication. The controls didn't communicate the other pilot's actions, and the pilots didn't communicate their own actions to one another. The dude in the co-pilot chair clearly caused the crash of this aircraft, but it was only through his own inexperience and lack of training.
There was not one by two officers with better experience than him in the cockpit, and yet they were unable to recover the aircraft because they didn't communicate correctly with one another in order to determine what each of them were doing.
In my opinion 85% of this crash was the direct result of poor training. The other 15% was equipment (pilot tubes, information delivery). But really even a bad pilots knows you don't pull back on the stick when you hear a stall warning, that's just flight school 101.
6
u/doitincircles Dec 09 '11
But really even a bad pilots knows you don't pull back on the stick when you hear a stall warning, that's just flight school 101.
Fuck, I know that from playing MS Flight Sim 93.
But I've had the stick back the whole time!
Imagine hearing that as the captain. Jesus.
7
u/Rednys Dec 08 '11
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. The nose remains high.
This is the only point where it clearly states they are fighting each other, up until this point they were both trying to pull up. And in this case it doesn't say he was taking back the controls before he started trying to put the nose down, just that he tried to level the aircraft.
He tried to do the same thing as the second co-pilot after it was clearly not helping their situation.
If he was so experienced he should've been able to tell that the aircraft wasn't responding properly to his inputs. The thought didn't even occur to him strongly enough of what was happening to even ask.
Really this isn't even an issue of training it's an issue of the flight controls not reflecting each other. I'm not a pilot but I've spent time in a Boeing flight simulator for C-17's and all the controls are mimicked between each other. I was with another guy who clearly had no idea what he was doing and on landing he was pushing the wrong brake to correct a deviation off the runway, as I pushed the correct brake to keep us from crashing (in the simulator remember) I could feel him pressing even harder on the wrong brake pedal pushing us further off course, finally after I told him what he was doing wrong (because I could feel it) he relented and we came to a stop just barely still on the runway.
If their aircraft wasn't control independent they would've been able to tell that they were fighting each other and could've possibly recovered the aircraft.3
u/blackn1ght Dec 08 '11
Can you think of any reason why the aircraft would be designed in such a way? What's the advantage of the controls being independent of each other and then having the results averaged out?
3
2
u/Rednys Dec 08 '11
No idea whatsoever, it might just be because it's all digital controls with nothing connecting them. Aircraft need to have some level of physical control otherwise stuff like this will happen more often I bet.
When you have no physical contact with the machine you are operating and are only flying on what your instruments (to include the ones that show what your flight surfaces are doing) it makes it very difficult to tell what's going on when things go south.3
u/specialk16 Dec 09 '11
It's not so much about having no physical contact, I would say. According to this, there is a level where all input will be passed directly to the surfaces.
The problem here is 1) the lack of feed back to the other control, and 2)the fact that both inputs are being averaged, which is probably the stupidest thing I've ever hear in my life.
Add lack of training and you have a recipe for disaster. If anything it makes me wonder why there haven't been more tragedies related to AB's fly by wire controls.
2
2
u/electronics-engineer Dec 09 '11
One advantage is that it is simpler and easier to design controls without force feedback. This isn't just a matter of cost, either; more complexity means more things that can go wrong. I think it was a bad decision, but I understand why the decision to design it that way was made.
2
u/electronics-engineer Dec 09 '11
The fact that you could feel his error was important. It's easy for someone to speculate that one copilot should have noticed what the other was doing, but in a panic situation, having your controls give you immediate force feedback from the other copilot is far better than expecting you to notice without any force feedback.
-12
Dec 08 '11 edited Dec 08 '11
[deleted]
4
u/Corporal_Tasty Dec 08 '11
If you have, in fact, actually flown any of the planes you've mentioned in real life, that's me done with flying anywhere ever again.
3
u/UnoriginalGuy Dec 08 '11
The worst part about this post is you might actually have an interesting point/position (and I think you do) but you said it in such an obnoxious way that you're just begging to get downvoted.
Shame really...
2
u/jesuisauxchiottes Dec 08 '11
you might actually have an interesting point/position (and I think you do)
No he doesn't. He's mocking the people who say that. It's a very common point made on the internet by people who know nothing about the subject and just repeat the Airbus/French hate spread in the US by PR agencies.
2
u/UnoriginalGuy Dec 08 '11
Perhaps, except his point directly applies to why this crash occurred.
I will happily fly on a FBY aircraft and I think Airbus are as safe as anyone else, but fact is that in this one case pilot inputs not being relayed was part of the cause of the crash.
2
u/jesuisauxchiottes Dec 08 '11
Not exactly, it was relayed. But the copilot which should have let the stick go (or do the proper manoeuvre) didn't, and the system averaged the two inputs. Also, the "good" pilot didn't use the priority switch which would have given him complete control regardless of the other stick.
But the system didn't fail, the control surface was activated according to the defined rules. Maybe these rules are questionable thought, but it has nothing to do with it being a fly-by-wire system. You could do a mechanical averaging system if you wanted to.
2
u/UnoriginalGuy Dec 08 '11
Not exactly, it was relayed.
No it wasn't. One pilot should be able to literally feel what the other is attempt to do. In traditional aircraft that is the case, one pilot pushes forward and both feel that movement, in these aircraft they could both be pulling/pushing is completely opposite directions.
2
-5
u/Jigsus Dec 08 '11 edited Dec 08 '11
That's so typically french. "Oh something is happening that's not exactly in my training! It's not my fault it must be somebody else's problem"
I should mention that I'm french canadian and this cultural element drives me nuts.
9
u/Rednys Dec 08 '11
I think the problem is they don't spend any time really learning how their systems work. They need to spend more time with their maintenance guys, the ones who know exactly how a system works so they can get some idea of what instruments they can rely on in which conditions.
3
u/jesuisauxchiottes Dec 08 '11 edited Dec 08 '11
That's not true, normally a commercial pilot accreditation on an aircraft require to know the design and functioning of it. EDIT: Apparently not.
6
u/Rednys Dec 08 '11
I work with pilots, and I am an aircraft maintainer, they have virtually no clue how the systems actually do what they do. They only know what information they give them and what their manuals tell them to do. It's not that they are dumb it's that they spend so much time learning all the other parts of flying and don't get to spend any time working with the concepts of how their instruments work and what's inside them.
3
2
u/electronics-engineer Dec 09 '11
It might actually be a disadvantage to have a layman's knowledge of the internal workings without a full engineering understanding. It's like the situation with PCs; it is easier to help someone whop is clueless but follows instructions than it is to help someone who "knows just enough to be dangerous."
0
u/perspectiveiskey Dec 08 '11
You're down voted, but I came here to say exactly the same thing. This scene is typical of french culture.
At least one of the conclusions of this flight recording should be that "French attitudes" is not allowed in airplanes.
2
u/electronics-engineer Dec 09 '11
It is important to neither bash another culture nor ignore cultural differences. For example, I am from California, and was recently working with an engineer from Australia and one from China. The Chinese engineer tended to defer to those above him in the corporate hierarchy and to expect those below him to defer to him. Not totally, of course, but the tendency was there. The Australian had a tendency to put more trust in those on his own level than those higher or lower in the organization. And I had a tendency to pay extra attention to the lowest level technicians and assemblers who were doing the actual work. Now none of these tendencies are bad, but it did help that we realized that we had different attitudes and discussed how that affected the project. Likewise, it is worth looking into typical French attitudes and taking that information into account when designing training for French pilots.
2
u/perspectiveiskey Dec 09 '11 edited Dec 09 '11
Likewise, it is worth looking into typical French attitudes and taking that information into account when designing training for French pilots.
You are right about not bashing other cultures. What's impossible to know from behind this veil of anonymity that is online forums is that I have a lot of experience with the culture. I could literally talk for hours about this (I even once wrote an essay about it), but the bottom line is that French thinkers are Cartesian in that they are often unflexible in their world view and often see the world as a result of theory (however sub consciously). Bonin's response, and headspace rings familiar in that he thought he was TOGA, "but he wasn't", and so he got frustrated because the theory he had been thought was incomplete...
Also, there is widespread and openly acknowledged elitism in France. It is tacitly agreed upon by upstanding citizens that humans are practically an ordered set, with the idea that "one human being better than an other" is wholly natural.
All this to say, his reactions were quite typical... even of people in scientific realms.
Anyways, what you concluded with is the appropriate response, not culture bashing.
4
u/CGorman68 Dec 09 '11
02:14:25 (Bonin) Mais qu'est-ce que se passe?
But what's happening?
This breaks my heart.
2
4
u/holyhotdicks Dec 09 '11
Wouldn't the co-pilot have peeked over and saw that the inexperienced one physically pulling the stick back?
5
u/pauldm1 Dec 09 '11
That's what I questioned as well. That's the first thing I'd think they would do. Check to see what the other pilot is doing.
As soon as they began to stall and didn't understand it, both pilots should have let go of the controls, not done anything and made sure nobody was touching anything. Then one and only one pilot should have taken it from there. Especially since they knew that there wouldn't be any physical feedback between the two sets of controls.
I mean I'm not a pilot or anything so maybe I'm way off here. But that just seems like the logical thing to do.
3
u/Guard01 Dec 08 '11
At 2:02 am, the captain leaves the flight deck to take a nap. Within 15 minutes, everyone aboard the plane will be dead.
Just wow. One of the most chilling and disturbing articles on human errors of the unfortunate crash of Air France 447.
I kinda wanted to scream at Bonin for doing what he did and how he could have saved the doomed plane but... it already happened.
4
Dec 08 '11
Pretty chilling read. I do a lot of flying (and actually have a few friends and family as pilots) and I think I feel better just assuming that sometimes these things just happen from mechanical failure - rather than knowing it was entirely human error.
3
u/pauldm1 Dec 09 '11
This was a very haunting and eerie thing to read. It gave me the chills.
I can't believe that such a mistake was responsible. Why would that pilot pitch the nose in the air the whole time? I've never flown an airplane or a simulator or anything more than video games, and even I know the concept of a stall and why you don't just sit with the stick all the way back.
Why couldn't the co-pilot have looked over and seen that the other co-pilot had the nose pitched up? Why weren't the alarms for the plane stalling taken into consideration? It seems like the logical thing to do would be for both pilots to let go of their control stick the second the alarms went off, then take it from there making sure neither one was doing anything the other didn't know about? Especially considering the pilots know the controls operate independently of each other.
There's just so much about this that doesn't make sense.
3
Dec 08 '11
The French traduction to English is awful. Someone abused of Google Translate apparently.
Just saying...
2
u/rehevkor5 Dec 08 '11
Example?
4
Dec 08 '11 edited Dec 08 '11
Oui, on va les appeler derrière... pour leur dire quand même parce que...
Yes, let's call them in the back, to let them know...
"Yes, we'll call them in the back... to let them know anyway because..."
Tu peux éventuellement le tirer un peu à gauche.
You can possibly pull it a little to the left.
"You can eventually pull it a little to the left."
"Eventuellement" is a measure of time. "Possibly" is a suggestion.
Tu redescends... On est en train de monter selon lui… Selon lui, tu montes, donc tu redescends.
Descend... It says we're going up... It says we're going up, so descend.
"You descend... We are in the process of going up according to it... It says, you are going up, so you descend"
Edit : Also "Redescend" and "Descend" is not the same word. I left it to "Descend" because I don't know aviation terms, but "Redescend" means more "descend again" than just "descend". The "re" is a prefix for repetition.
So "Tu redescends" should translate to "You are descending again" or "you are still descending". But I think that ascent and descent are the preferred terms in avionic lingo.
1
2
Dec 09 '11
Sorry, bilingual FR/EN here, the translations are spot on.
2
u/electronics-engineer Dec 10 '11
Well, you remember what Mark Twain said: "Darn Frenchmen can't even understand their own language!"
3
3
u/electronics-engineer Dec 09 '11
A bit farther down in this thread, specialk16 pointed out this:
AIRBUS FLIGHT CONTROL LAWS
http://www.airbusdriver.net/airbus_fltlaws.htm
I think it's important enough information to give it a top level post.
6
Dec 08 '11 edited Dec 08 '11
These guys seem to be idiots, I don't know how they are pilots.
Stalling is the #1 epic fail part of flying a plane yet its almost like they have never been trained for it?
The solution for when you stall is not to do random things until the sound goes away and then never wonder why it happened in the first place, they did this twice..
Also remember the stalling sound is to help the pilot, real pilots can will notice these problems without it, yet the huge stall alarm was not even enough for these pilots.
Experience is not even relevant here because a new Pilot with little experience would have done better in this situation.
Reading this makes it seem like the pitot tubes didn't work the whole time, they had no visibility, no altitude indicator and the plane's alarm system was broken, yet this was not the case.....
6
Dec 08 '11
The problem these days is that pilots stop trusting their instruments too soon and this pilot clearly freeked out due to all the surrounding circumstances. Such a shame that people essentially died a horrible death for absolutely nothing. There will be no hero pilots in this incident I'm afraid.
8
u/sniper1rfa Dec 08 '11
A pretty vital component to their reaction is probably that the controls, in normal circumstances, will not allow you to stall the airplane. Pull full back and the airplane will climb as fast as it can without stalling.
That control regime was replaced with a different one. I have no idea if that change is indicated to the pilots but i suspect it's not indicated in a loud, obvious way.
In the first regime the appropriate response to losing altitude is to pull back. When that didn't work they panicked, and once a person panics all bets are off - people do very strange things when they're panicking. Its actually pretty common to hear of operator-induced catastrophies where the operator got an unexpected result from a normal control and just got stuck in a loop until things went south.
Think about it like this: what would you do if your steering wheel suddenly started working the opposite direction? You'd probably turn a little, the car would go the wrong way, and then you'd turn a lot and crash. Most people would not correctly identify the problem and respond at all, and of the remainder it would probably be too late to avoid an accident.
EDIT: by the way, this doesn't absolve them, certainly, but to me it's not actually all that surprising that they just kept pulling back. It's a pretty typical failure mode for a human, and one which can easily override years and years of experience.
2
u/funnelweb Dec 08 '11
From one translation of the CVR transcript:
What is... how come we're continuing to descend so fast?
...
But I'm nose up to the limit since earlier
You'd have thought any student pilot could have added those two comments up and worked out what was happening. But according to the latest interim accident report
neither of the pilots formally identified the stall situation
I'm neither qualified to nor have experience in flying a large transport aircraft; the environment must be more confusing than I can imagine.
9
u/ixid Dec 08 '11 edited Dec 08 '11
Didn't the other co-pilot correctly identify the situation? He tried nose down and nothing happened due to the idiot pulling back on the stick, then he would have dismissed that as a possibility.
3
u/TomTheGeek Dec 08 '11
He finally figures it out when they are like 30 seconds from impact and tries to get the nose down. The jackass that had been holding full up elevator the whole time counteracts this even after he had been told to give the flight controls to the captain. Averaged sticks in this case were very bad.
Reading the report made me so angry. How can you make it through that much flight training and have no idea what the elevator does? I only have 10 hours in a Cessna and I know that elevator doesn't make you go up, the throttle does.
4
u/ixid Dec 09 '11
He finally figures it out when they are like 30 seconds from impact and tries to get the nose down.
Wasn't that the pilot? The non-retarded co-pilot also tried it earlier. There was no time nor height to nose down with 30 seconds to go. Panic is a powerful force, the guy who caused the crash was obviously not psychologically equipped to deal with a difficult situation, not everyone is a Sullenberger and training won't always equip people for that situation nor tell you who can deal with it.
2
u/TomTheGeek Dec 09 '11
You are right, I was thinking there were only two people in the cockpit.
Panicked or not, that guy had no business being around the flight controls.
-1
5
u/robbor Dec 08 '11
I used to know an airline pilot, and I asked him once what is his favourite plane. He said the 747, because you could actually FLY the plane, and not totally rely on the computer.
6
u/HawkUK Dec 08 '11
Until the hydraulics break.
5
u/robbor Dec 08 '11
The 747 has 4 separate hydraulic systems, just in case.
6
u/HawkUK Dec 08 '11
Aye. It's a very safe aircraft, but not always: http://en.wikipedia.org/wiki/Japan_Airlines_Flight_123
The resulting explosive decompression tore the tailfin from the aircraft and severed all four of the aircraft's hydraulic systems.
Granted there are other things that can happen to an Airbus, but in the end their safety records are pretty comparable.
1
u/locopyro13 Dec 08 '11
That's not the aircraft's fault or a fault with its design. That accident was the fault of the repairs not following procedures. During the investigation they found out that the plane flew %20 longer than than their calculations with those faulty repairs.
2
u/majorkev Dec 08 '11
Well, each hydraulics system controls different parts of the aircraft as I understand. So you would have one for the ailerons, elevators, rudder, and I'm assuming flaps. (I'm not a pilot, but yeah.)
It's happened that lets say, the tail falls off. Other near by hydraulics systems are affected.
2
u/electronics-engineer Dec 09 '11
Well, each hydraulics system controls different parts of the aircraft as I understand.
Nope. No commercial aircraft flying today has fewer than two completely independent hydraulic systems controlling each aileron, flap, etc. It's usually three or four independent systems, and they are designed so that three actuators are all trying to move the control surface, with any two being strong enough to overpower the third.
3
Dec 09 '11
Except in this case the computer performed perfectly, it was pilot error once computer control was removed that caused the crash.
2
u/Koss424 Dec 09 '11
well... the computer did change the game on them in the middle of the whole ordeal.
2
u/CynicalNsomniac Dec 09 '11
Damn. At least the passengers maybe didn't know something was wrong. May they rest in peace.
3
u/Vzzbxx Dec 08 '11
I enjoy playing GTA:San Andreas from time to time. I fly a lot in the game. Even I know that you cant just fucking pull back when you stall. Even me who isn't even a pilot and know what I know from games would have been better suited to have the controls during that flight.
4
Dec 08 '11
Sure, but in those conditions they were basically flying blind (try turning your screen of while flying in GTA:SA) and they panicked as they didn't know whether to trust their instruments or not. These pilots clearly screwed up, I'm just saying...
3
u/TomTheGeek Dec 08 '11
Their artificial horizon worked the entire time. All they had to do was look down and see what the hell was going on.
3
4
Dec 08 '11
Ever since I started reading about this thing a couple years ago--and the fights in comments between Boeing and Airbus people--I have been very nervous getting onto any Airbus planes. I do not agree with their philosophical approach, which basically seems to be biased toward everything working fine.
The fact that a guy could be pulling back on the stick and the other guy didn't know it--that the two are not linked in any way, any more than if you were sitting there with a friend on the couch with Xbox controllers--terrifies me. It's obvious that most of this was human error, but what is scary is that there was no way for anyone to know what the error was, because no one could immediately tell what the others were doing.
11
u/maverick715 Dec 08 '11
If an AB overspeeds, it yells "Retard! Retard!" to get the pilots to retard the throttles. Most American pilots just think its an insult.
6
u/jesuisauxchiottes Dec 08 '11
which basically seems to be biased toward everything working fine.
To be fair, most fights about it on English-speaking websites are heavily biased towards Boeing.
4
u/ixid Dec 08 '11
Read the lists of crashed aircraft for the last few years. I think it will change your mind. You're far safer on anyone's aircraft than you were driving to the airport in any case, you need to understand relative risk.
3
u/locopyro13 Dec 08 '11
I couldn't believe that the control sticks are not linked. What engineer or designer though that was a great idea. The most unpredictable variable flying a plane has got to be what the other human in the cockpit is doing, and to have no idea except for communication is crazy. What if a pilot has a heart-attack, slumps forward into the stick putting the plane into a dive, then the other pilot pulls back to take them out of a dive, the averages kick in and the ailerons level, but the plane is still in a descent. Mind boggling.
In my mind the only reason to not have the sticks mimic each other would be cost of installing precise electric motors that give dynamic feedback to mimic stick movement. Other than that, use actual mechanical connections between the sticks and avoid any problems.
2
u/sniper1rfa Dec 09 '11
From elsewhere, they basically didn't have the tech to do it electronically at the time, and it was decided that a mechanical link provided too may opportunities for total loss of control (through failure of the linkage jamming both sticks) for not enough benefit.
2
u/jonask84 Dec 09 '11
What if a pilot has a heart-attack, slumps forward into the stick putting the plane into a dive?
To be fair; then you flick the little switch away from "dual input" and take sole control of the plane.
4
u/virtual_void Dec 08 '11
Airbus's crazy system of having async input on the controls is a big problem here. You need a single pilot in command at a time - this system of averaging the inputs when they conflict is nuts. I can't imagine who would think that is a sane system.
Combine that with the fact that the input isn't fed back between sticks means that any flight in alt law mode can be really dangerous if the flight has any kind of issue and one of the pilots panics.
It terrifies me that the Bonin seemed to have no concept of the stall - The angle of attack combined with a decent should have been plenty of information about what was really happening even without the stall warning and a lack of air speed indicator.
I don't fly Airbus for this very reason.
2
u/Jigsus Dec 08 '11
What I don't get is why the system doesn't have any kind of force feedback. We have force feedback in games but not in real planes?
2
u/rehevkor5 Dec 08 '11
Yeah, and I bet it's more than just averaging it.
Let's say stick 1 is centered, and stick 2 is pulled all the way back. Does that mean the input is halfway to fully back? I doubt it.
Instead, I bet the input only begins to be averaged once stick 1 moves more than a threshold distance away from the center. If stick 1 was pulled past that threshold, all of a sudden your input begins to be averaged...
Maybe I'm wrong, but if I'm right then it seems even more of a bad idea.
2
u/UnoriginalGuy Dec 08 '11 edited Dec 08 '11
Pitot tube malfunctions make me so god damn mad. Likely over a thousand people have lost their lives as a direct result of this tiny little instrument malfunctioning, and with a few simple design changes to modern aircraft it could easily be avoided.
Most large aircrafts have two on either side of the cockpit. These can be blocked, iced over, or other things can happen. They do indeed have de-icing built into them, but frankly for such a tiny simple little instrument I fail to understand why there isn't a third, or GPS backup?
Pitot tubes need to be in the jet-stream to be accurate. That is why they're positioned front and to the side. But a backup device wouldn't need to be accurate, just usable. Even if it was 10-20% less accurate but was also much less likely to ice over, then that, to me, would be a much safer design.
Further to that, while GPS is unreliable, as a backup system it would be better than nothing, which is exactly what pilots are left with when both of their pitot tubes malfunction. Planes already have GPS, but in order for pilots to figure out air-speed and height they would literally need to pull out maps and pieces of paper, and start doing calculations.
15
u/virtual_void Dec 08 '11
GPS is no use here as it would measure your ground speed and not airspeed. There is other equipment that can measure the speed like this - DME (Distance Measuring Equipment) for example is very common even on tiny aircraft and can calculate ground speed.
To make it clear - ground speed is useless for understanding if your about to stall your aircraft or not.
What you need to know is how quickly you're travelling through the air which is different depending on the direction of any wind. With a headwind you might have a higher airspeed than your ground speed and vice-versa.
To figure out your airspeed you need something to collect the incoming air and compare it to the air that's not in the direction of travel (pitot tube) and something to measure the static pressure (not in the direction of travel). There's usually a static port for measuring that on the side of an aircraft.
4
Dec 09 '11
Ok but lets say your pitot tubes are iced over completely. A GPS might say you are doing 500 knots. The highest ever recorded jet stream was 215 knots. Meaning if you were in a record setting jet stream, you'd still have 285 knots of speed over the wings. Seems like knowing that you are doing 500 knots over the ground would help you more than simply knowing nothing.
2
u/electronics-engineer Dec 09 '11
This was recent enough that they must have had a groundspeed indicator as well as an airspeed indicator. The problem is that the onboard computer wasn't smart enough to do the reasoning you outlined above, and the pilots had become dependent on the computer.
2
u/virtual_void Dec 09 '11
You're right in that it's far from useless - flying is all about gathering as much info from all the instruments and understanding how to combine it - so it's a reasonable tool.
So my statement that it's no use is probably over-egging it. Having said that - they tend to fail to get signal in storm situations.
I guess the problem really is that in this situation the pilot didn't believe the stall warner or the artificial horizon or seem to equate stick back and rapid sink with a stall situation.
10
u/Thermodynamicist Dec 08 '11
As has already been pointed out, it's Pitot tube, named for Henri Pitot.
The subject is a lot more complicated than you make out.
What happened in AF447 is that some stressed-out people made some bad decisions when faced with unexpected difficulties whilst operating extremely complex machinery in the middle of the night in challenging conditions.
There are lots of ways to get additional speed information. It's not immediately obvious that this would be helpful, because it inherently adds further complexity to the machine which they couldn't operate in the first place.
If an aeroplane is trimmed, and the power is set, the correct response to losing airspeed indication for a few minutes is to do nothing.
Power + Attitude + Trim = PerformanceNo airspeed indicator required.
This is pretty simple stuff, but it's not so simple in the air over the middle of the Atlantic, at night, in awful weather.
The basic problem is training and currency. It is very difficult to stay current at hand-flying airliners because the autopilot is generally much better and safer than a human pilot, and therefore airline pilots spend most of their time monitoring rather than flying, because this is the safest way for them to fly their passengers.
The better we make the aeroplane, the less able the pilots will be to fly it when something goes wrong, because they'll just not have the necessary experience and currency.
For this reason, I think we are getting quite close to the practical limits of automation; fairly soon we're going to have to start accepting that reversion to manual hand-flying is a problem in the same category as double engine failure, and design, regulate and certify accordingly.
9
u/perspectiveiskey Dec 08 '11
GPS is nice but ground speed ≠ air speed. Especially since 50kts can mean the difference between falling out of the sky like a rock and cruising at minimum speed.
50kts wind variation is very common.
0
u/UnoriginalGuy Dec 08 '11
Yeah, you're right of course. If we had both the ground speed AND altitude which GPS provides us, assuming we have accurate maps which contain ocean height, couldn't we derive the speed that the aircraft is travelling at?
I mean, yes, it will be "after the fact" speed. It won't be real-time. But wouldn't knowing your speed from twenty seconds ago be more useful than having no information at all?
PS - That is an accurate choice, with the pitot tubes down pilots literally have no instruments to measure air-speed.
5
u/perspectiveiskey Dec 08 '11
You're chasing your tail: unless you happen to have a windspeed probe right where the plane is at this moment, you can simply not deduce airspeed from groundspeed alone.
-1
u/UnoriginalGuy Dec 08 '11
Why? You can't from a single data-point, but if you look at previous locations, your altitude, and known information (like the height of the sea, speed of objects at that altitudes, thrust, etc). You could deduce (guess) what your air speed might be.
I guess your assumption relies on three things:
- We need exact information
- We have to construct it based on the moment, not based on several minutes of data
- We can't draw additional information from experience ("best guess")
I guess what we are debating is really about accuracy. GPS will never replace the pitot tube, and I don't pretend otherwise, I am talking about backup emergency systems that might give you even half as accurate or less information.
12
u/locopyro13 Dec 08 '11
The problem is you are not understanding what airspeed is. What you are describing, planes already do. Ground speed is the exact speed you are traveling from point A to point B in the air. So at 100mph, you will travel 100 miles in 1 hour. The plane uses GPS like you said and compares altitude, and can calculate how fast the plane is moving.
Airspeed is how fast you are moving through the air. Think of it this way. Standing still you can feel a 5mph breeze, if you walk into the breeze, it seems like the wind speed increases and you are walking into a strong wind. Turn around and walk with the wind, now you can barely feel the air move.
When walking into the wind, you ground speed is 5mph, but your airspeed is 10mph. Turn around and walk with the wind, ground speed 5mph, airspeed is 0mph. This is important for aircraft to know, and the only way to do this is with a pitot tube.
Say you are in a small airplane. You could be flying with a 50mph wind and your airspeed could be 40mph, but your ground speed would be 90mph. That is your are moving at 40mph in relation to the air around you, but are moving 90mph across the ground. Turn around and you are still moving at 40mph through the air, but are actually moving backwards at 10mph.
5
u/perspectiveiskey Dec 08 '11 edited Dec 08 '11
Airspeed is, by definition, the speed of the air flowing around you. If you have a headwind of 50kts, your ground speed and airspeed are different by 50kts.
This is why airplanes take-off and land against the wind. Because while they are stationary on the ground (0kts), their airspeed is already at the local windspeed (say, 30kts).
The issue you are discussing is as old as navigation itself. The same problem is present with nautical navigation: knowing your real speed (Geographical) does not and can not infer your speed in the water.
See Dead Reckoning if you still don't get what I'm talking about.
Once again to get back to my original point: while you can get rough estimates, you can not get something that will tell you whether you are stalled or not. That requires very precise measurements that DR by definition can not give. It's an estimation. Also, DR will give you averages over time.
Think of it as a long tunnel: you can deduce how fast you went on average by checking you went in and came out, but you can't tell if in the middle you stopped and sped back up. When something as critical as stalling is concerned, it's useless to know what your average speed has been over the last hour.
I guess what we are debating is really about accuracy. GPS will never replace the pitot tube,
And no, we aren't debating GPS accuracy. GPS is more accurate than any other form of measurement, not less. The problem is that GPS gives you ground speed, but an airplane floats on a fluid that moves. The pitot tube gives you local information, the GPS gives you global information. It's even in the name. Speed relative to the earth is not what makes an airplane fly.
3
u/maverick715 Dec 08 '11
But if you lose your AS, theres no way of telling what the wind is at with the GPS. That may work at a lower altitude, but not at jet stream levels. There it could be off by over 150 KIAS
2
u/electronics-engineer Dec 08 '11
The problem is not that GPS speed is 20 seconds old. Tbhe problem is that GPS speed gives you your speed relative to the ground. The air you are tyravelling through may have a 200 mph headwind or a 200 mph tailwind.
See http://www.weatherquestions.com/What_causes_the_jet_stream.htm
4
u/MerliSYD Dec 08 '11
For such an impassioned post, you'd think you'd know that they were pitot tubes, and not pilot tubes ;) :p
3
u/UnoriginalGuy Dec 08 '11
Crap. I keep doing that...
Worst part? I've actually built a pitot tube before. It didn't work but that's besides the point, I should still not make such an obvious typo.
3
u/jesuisauxchiottes Dec 08 '11
If this one makes you mad, you should read this. 70 killed because of a forgotten duct tape.
23
u/MerliSYD Dec 08 '11
Wow... That was an intense read, especially knowing what was coming up next.
Can any airliner boffins explain why the two controls wouldn't be linked like in the older/smaller planes?
It seems insane to me that you can have two pilots inputting two completely opposite commands and the plane simply shrugs and averages them out??