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Software Bug Caused Qantas Airbus A330 To Nose-Dive
pdcull writes "According to Stuff.co.nz, the Australian Transport Safety Board found that a software bug was responsible for a Qantas Airbus A330 nose-diving twice while at cruising altitude, injuring 12 people seriously and causing 39 to be taken to the hospital. The event, which happened three years ago, was found to be caused by an airspeed sensor malfunction, linked to a bug in an algorithm which 'translated the sensors' data into actions, where the flight control computer could put the plane into a nosedive using bad data from just one sensor.' A software update was installed in November 2009, and the ATSB concluded that 'as a result of this redesign, passengers, crew and operators can be confident that the same type of accident will not reoccur.' I can't help wondering just how a piece of code, which presumably didn't test its input data for validity before acting on it, could become part of a modern jet's onboard software suite?"
sure, but the number of accidents will likely still be fewer than those caused by human drivers.
Cant be worse then the drivers out there.
"Have you ever thought about just turning off the TV, sitting down with your kids, and hitting them?"
This, from the same company, while building the A380 megajet decided to upgrade half of their facilities to plant software version 5, while the other half decided to stick with version 3/4. And did not make the file formats compatible between the two versions, resulting in multi-month delays of production as a result.
Point being, in huge projects, simple things get overlooked (with catastrophic results). My favorite is when we slammed a $20 million NASA/ESA probe in to the surface of mars at high speed because some engineer forgot to convert mph in to kph (or vice-versa).
moox. for a new generation.
There were people against airbags, too, because they killed some people who otherwise wouldn't have died. You work on fixing those things. But whether the system as a whole is worthwhile is judged on whether it saves more than it kills.
Are you seriously accusing Google of being malicious in developing a driver-less car? Do they have a stake in keeping the population numbers down or something?
While I agree that software will never be bug free, it will quite possibly save many more lives as human drivers are terrible. They are prone to panicking under pressure, misjudging distances, unable to handle a car as efficiently as possible, take too many risks (swerving in and out of traffic, following too close), drive under the influence of drugs and alcohol, get distracted by phones, screaming kids among many other things that well written and tested software could do better.
Do you also want pilots to fly planes manually at all times and remove auto-pilot since software can never be perfect?
I know, those evil monsters and their want to improve the lives of people by inventing things. Since there might possibly be a bug that may cause issues they should just stop and throw in the towel right? I mean humans are perfect drivers as is so why fix something that's not broken.
"I can't help wondering just how could a piece of code, which presumable didn't test its' input data for validity before acting on it, become part of a modern jet's onboard software suit?""
How about reading the darned final report, conveniently linked in your own blurb? There was lots of validity checking. In fact, some of it was relatively recently changed, and that accidentally introduced this failure mode (the 1.2-second data spike holdover). (Also, how about someone spell-checking submissions?)
we're going to see a huge change in programming methods coming pretty soon. Today, A.I. is still math and computer based. The problem is that data, input, and all of the algorithms you're going to write can result in a plane nose-diving -- even though no human being has ever chosen to nose-dive under any scenario in a commercial flight.
Why was an algorithm written that could do something that no one has ever wanted to do?
The shift is going to be when psychology takes over A.I. from the math geeks. It'll be the first time that math becomes entirely useless because the scenarios will be 90% exceptions. It'll also be the first time that psychology becomes truly beneficial -- and it'll be the direct result of centuries of black-box science.
That's when the programming changes to "should we take a nose-dive? has anyone ever solved anything with a nose-dive? are we a fighter jet in a dog fight like they were?" Instead of what is it now: "what are the odds that we should be in a nose-dive? well, nothing else seems better."
Even on the road today this is an issue. Doesn't matter how good of a driver you are. If one other idiot on the road is driving crazy, you could get killed no matter how you drive. Weakest link and all that...
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
Which is actually Airbus relies on sensor input over the "pilot". Boeing believes in the opposite. I'm inclined to believe Airbus in that the majority of accidents are human error over computer error.
The problem with aviation accidents is the relatively small sample size. With cars there will be much better data (i.e. more data points).
If anything computer driven cars will be better - since due to the safety "fears" like the OP, they will be programmed to be cautious. They have to be better at handling conditions than human operators, otherwise it's instant blame. They have to be better to the degree that you can blow the stats out of the water. e.g. When the first computer driven car hits a person, they need to say "well based on hours on the road, if it was human driving this it would have hit 30 kids by now".
I trust Google's engineers not to get me killed more than I trust the vast majority of drivers, especially knowing how little it takes to get a drivers license. So far, the only incident involving one of Google's self-driving cars is when a human was in control (i.e., it was sheer coincidence that it was one of those cars); statistically speaking, they're the safest vehicles currently in existence. At least software can be fixed; try as we might, we haven't yet fixed stupid. I'm trying to look up how many are mechanical failures versus human error but this hotel internet connection sucks, but I'd be willing to bet the vast majority of problems are people's faults (and of mechanical failures, most of those probably would have been preventable with proper maintenance)
That said, I won't be beta testing this one.
How are sites slashdotted when nobody reads TFAs?
It's so interesting to see people's reaction to the whole driver-less car thing. It's incredible to see the kind of ethical thought-experiment that must necessarily go through everyone's mind when they come to this conclusion: How many lives must be saved before I will tolerate someone being brutally slain by a malfunctioning computer?
Every day, children are run down by drivers who are not paying attention, tired, drunk, or just plain don't have time to react. Since a driver-less car is incapable of being drunk, tired, or distracted, then it's a safe bet that they'll be much better at avoiding those accidents that can be avoided. But the reality is that the latter scenario (no time to react) would still lead to the deaths of many children (and others!).
At what point does it become "worth it"? When the driver-less car causes 1/10th as many fatalities? 1/100th? 1/1,000th? How many human deaths must be prevented by letting computers drive cars before we're willing to accept 1 single death by those same computers?
It's a real-life example of the "Trolley Problem"
http://en.wikipedia.org/wiki/Trolley_problem
I can't help wondering just how could a piece of code, which presumable didn't test its' input data for validity before acting on it, become part of a modern jet's onboard software suit?"
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I'm surprised there are people who think that we have the technology to program computers to make decisions about how to control things like airplanes better then a human being.
Computers excel at solving mathematical problems with definitive inputs and outputs, but our attempts to translate the problem of controlling an airplane, or an organism, into a simple circuit...will necessarily be limiting.
They can only test that the computer program will behave as expected, but there is no test to prove that the behavior we attempted to implement is actually a "good" way to behave under all circumstances.
nothing in software is ever free of bugs. just because it's a bug-fix doesn't preclude the possibility of the bug-fix itself (or its side effects) from introducing new bugs, or being an incomplete fix which just happens to pass whatever inadequate test was thrown at it.
Sure, the same way any bug is fixed forever. But software is still loaded with bugs. Even a completely bug-free system will accumulate bugs over time as the code is maintained and/or features are added.
have you SEEN the way meatware AI operates a car? At least a google driverless car would use its turn signal before suddenly jerking into a turn and trying to kill me on a bike with a right hook.
Speaking of faulty sensors, that's pretty much what goes down when meatware AI has a certain alcohol content. Or uses a cellphone. Or eats fast food. Or puts on makeup. Or deals with newer meatware instances in the back seat. Or looks down to adjust the radio. Or falls alseep. Or is distracted in thought. Or....
Your post is full of FUD. A million people die annually because of human drivers. A driverless car killing half that many would still be an improvement.
www.un.org/ar/roadsafety/pdf/roadsafetyreport.pdf
Right, because bug fixes never introduce bugs. Code just keeps getting better and better and better.
What are you? some kind of person that doesn't read the actual articles or documents? Oh wait.. this is slashdot. Here let me copy paste some text for you
So there you go, there actually really was validity checking performed. Multiple times per second in fact, by three separate, redundant systems. Unfortunately all 3 systems had the bug. Here is the concise summary for you:
I don't need to test my programs.. I have an error correcting modem.
Airbus poached engineers from Toyota!
done much driving lately?
even if MS wrote the software, it'd definitely be well in the top 2 percentile as far as driving skills go.
see how input data validation works in your brain when you're tired, drunk or just distracted?
This is such a common fallacy -- we would expect an AI driver to be fucking perfect before we would ever call it "safe". Sure, they will have bugs, and people will die. But they will have nowhere near as many bugs as the meat computer that we have in our heads. Amazing as it is, the human brain is simply not meant for the types of tasks that we often apply it to, and as such, tens of thousands of people die on the road each year. Even if the adoption of driverless cars cut that down to 1% of the current death rate, people would still be screaming about the cars killing us. George Carlin was right; some people are really fuckin' stupid.
To the haters: You can't win. If you mod me down, I shall become more powerful than you could possibly imagine
the idea that a bunch of automatically piloted vehicles is somehow a better solution to city transport than mass-transit, it boggles my mind.
real people do not have money to maintain their cars properly. things are going to break. there are not going to be 'system administrators' to fix all the glitches that come up when cars start breaking down after a few years.
there will be problems. do i know which problems? no, but i know the main problem.
arrogance amongst revolutionaries. it is historically a pattern of the human species. declaring that nothing could go wrong is usually a precursor to a lot of things going wrong. not because the situation was unpredictable, but because human beings in an arrogant mindset tend to make a lot of mistakes, be reckless, and try to cover their asses when things go wrong.
but successful engineering is the anti-thesis of arrogance. nobody worth his salt is going to say 'what could go wrong'? they are going to have a list of 500 things that could go wrong, and all the ways they have tried to counter-act those wrong things happening.
After all, buying planes that someone else made is outsourcing. However I am not sure they'd fair better building their own.
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It's bad idea for a specific reason.
There are two "brains" that can operate the car. Google can make a pretty decent brain, but it is not going to come remotely close (in any way) to the human brain in terms of its ability to perceive the environment (sensors), make sense of it (pattern recognition), and put it all into context (experience, extrapolation).
Google will excel in reaction times and advanced planning. Through Google it will be possible to mitigate traffic by solving a very human problem, which is cooperation towards a common goal. Google could react faster, and with less overcompensation, to a car drifting into its lane.
Where Google will fall far short is recognizing the road rage in the driver next to it (beating his hands on the steering wheel and screaming), the lack of concentration (woman putting her lipstick on), etc. Putting those things in context and assigning risk to drivers next to you is not something Google will be able to do from its sensors. However, even the average driver is getting cues in so many ways about what is really going on around them.
The reason why it is a bad idea, is that while Google is operating, the human brain is off. It's not instant-on either. Driving is a constant level of concentration, even when it seems like you are doing it "subconsciously". From start to finish, the average driver is pretty aware of their surroundings and processing an impressive amount of data. A human brain will beat Google every time on those terms.
When Google fails, or "judges" the environment poorly, how quickly can the human brain come back online, evaluate the current environment, take control, and make the required adjustments?
Until the Google brain is able to fully replace a human brain, it is not a good idea to involve the two in a hybrid system. The lag between the two systems taking control from one another is just too great.
Self-parking is fine, and limited operations involving high efficiency traffic lanes where human control is not permitted will be fine. As long as the transition into those operations is in a time frame a human can deal with.
Example being, the human brain pulls the car along the high efficiency traffic lane, "tags" the Google brain in to insert itself into the traffic. The Google brain then notifies the driver and validates proper control and awareness before exiting the traffic and turning control over to the human driver. Failure means Google pulls the car to the left in the emergency lane and brings the car to a full stop.
Any other kind of operations just seems fundamentally unwise to me because of the hybrid nature and inherent limitations of Google's AI, advanced as it may be for now.
My threshold for letting a computer operate a car no differently than a human, is the computer can meet or exceed the human's ability in every respect. That is not true right now, and will not be true for decades.
You may trust a Google car more than the average driver, but that is only really true if the Google car also has no driver.
This sounds very much like the failure of the Pitot tubes (used to measure airspeed) on the A330 that chrashed in the Atlantic on 1 june 2009.
Actually, this would presumably have saved AF447, as the crash was caused by the pilot holding the nose up in a stall. Probably because the stall warning apparently turned off when he pulled the stick back and turned back on when he pushed it forward, so the correct action to get out of the stall seemed to be causing it.
Which is actually Airbus relies on sensor input over the "pilot". Boeing believes in the opposite. I'm inclined to believe Airbus in that the majority of accidents are human error over computer error.
Sometime in a flight like AF447 the computer doesn't know jack either and gives up the ghost. In the AF477 flight(equipment airbus A330), apparently, the pitot sensors gave inconsistent readings and the autopilot disengaged. What insued was apparently what can happen when you have pilots that are error prone and a computer that doesn't know what the hell to do to help them. In these situations, I think it's prudent to still have a system that defaults to the pilot as if they knew what to do when they know the sensors have crapped out and apparently even Airbus agrees with this. Unfortunatly, it appears that the AF447 pilots were not up to the challenge in this circumstance.
A million people die annually because of human drivers. A driverless car killing half that many would still be an improvement.
When a human driver kills another human being, the courts can punish that person and allow for the victim's family to claim compensation.
When a driverless car kills a human being... ?
Maybe we could copy the system we have for vaccines
[Fuck Beta]
o0t!
Clearly the solution is that I, as the only decent driver around, will be the only person allowed to drive myself, while everybody else must be using these Google cars.
You hold the people who made the car responsible? They better analyze the hell out of every single tiny problem that crops up and make details and fixes public. This is why all these driverless softwares must be open source. Any 'benefits' of making it proprietary would come at the cost everyone's safety.
And besides, it doesn't really matter how someone is punished for wrongdoing. You judge whether it's an improvement or not; you don't judge on how best to get retribution. Otherwise, you could hypothetically end up choosing a system that causes a lot of problems as long as it's easy to blame someone for causing them.
I have left slashdot and am now on Soylent News. FUCK YOU DICE.
One of the AF447 pilots killed the others, and the passengers.
Also, I am shocked that the Airbus sidesticks don't move in unison. If the left seat stick had gone all the way back when the right seat pilot pulled on it, then the left seat pilot would have immediately understood and dealt with the situation. Every other airplane works like this - why don't Airbuses?
That's surely a relevant problem, but not one which is insurmountable. We have the same problem with any piece of automated machinery don't we? If an elevator malfunctions and people die, who should be sued? Yet, it doesn't stop us from using one.
It's an issue of overall efficiency and safety for everyone. In the long run, it will save lives, improve quality of life, be more efficient etc. The downside of having to blame a "dumb" machine for a lost life/accident, is possibly more palatable than the alternative of having to blame a human driver, another human being whose life will be ruined by the accident.
Lastly, we already have so many automated things. Self-driving trains, airplanes etc. Is a car really that different?
A good driver, by definition, mitigates the bad driver by taking appropriate actions to reduce the risk. It is not how you drive, its how you manager the drivers around you that makes you a good driver.
And that would make it different than today when i nearly got ran over by a moron playing with his cell....how exactly? when I was a kid we were taught "This is a 2000 pound weapon, you treat it like a weapon and respect it or someone could die, maybe you, maybe someone else" and even then we still liked to drive fast but today? Jesus tap dancing christ I've not seen a bigger bunch of dipshits in my entire life than what I see on the road every damned day! Dipshit men playing with their phones, dipshit women putting on makeup AND playing with their phones, its like moron bumper cars out there pal!
That is why the other day when I saw my oldest a couple of car lengths ahead of me (and I knew he couldn't see me from where i was at) and saw him pull over into a lot and get out i just had to pull in behind him. I just knew why he had pulled in but when I asked him and he said "Somebody called me so i was pulling over so I could return the call" i immediately pulled out a twenty and handed it to him, saying "Having a brain is a damned rare thing in this world, smarts should be rewarded".
Frankly i'm all for Google car because at its worst it can't be as dangerous as the braintrusts on our roads. With my oldest taking 18 hours next semester its not HIS driving I worry about every day, its the dipshits with too many toys and not enough functional brain cells. If the Google car takes the keys away from even 20% of these numbnuts frankly the accidents will plummet, and that can only be of the good.
ACs don't waste your time replying, your posts are never seen by me.
Same goes for Boeing.
With Airbus, there are different levels of control that the pilot has, according to the condition of the plane, flight envelope and flight mode. If there are serious failures, an Airbus pretty much starts to behave like the controls of a Boeing.
In case the plane is cruising and the autopilot disengages, it is no different from the autopilot of a Boeing disengaging. In both planes, the pilots will have been playing Angry Birds while they should have been monitoring the plane:). So that still is human error... The avionics systems are only to assist the pilots. they are not there so that they have time to pull out the playstation.
Also, who gets the blame?
The way it is now, if I cause the accident, then I am responsible for it, because I either caused the accident myself (being drunk/asleep/distracted is no excuse) or my car failed in such a way that it caused the accident (I tried to stop, the brakes failed and I hit the car in front of mine). It was also my responsibility to maintain the car, so I am responsible even if it was the car that failed.
Now, if the driverless car hits another car and there was no mechanical failure that I could have prevented by properly maintaining the car (and no, programming the AI would not be my responsibility), who pays for the damage? I certainly won't, since I should not be responsible for something that was not under my control*.
What if a bug in the software causes the car to drive, even though the red light is on?
* If a normal car goes out of control it is because I failed to maintain it and something broke (maintenance was under my control) or did something that caused it to go out of control (drove too fast for example).
DISCLAIMER: I hate air travel, but do it most weeks.
I have worked in and around the safety critical software industry for over 20 years. The level of testing and certification that the flight control software for a commercial aircraft is subjected to far exceeds any other industry I'm familiar with. (I'm willing to be educated on nuclear power control software however.)
The actual problem on the Qantas jet was a latent defect that was exposed by a software upgrade to another system. So the bug was there for a long time and I'm sure there are still others waiting to be found. But this doesn't stop me getting on a jet at least twice a week.
As a software professional and nervous flyer, do problems with the aircraft software scare me? No not really. What scares me is the airline outsourcing maintenance to the lowest bidder in China, the pilots not getting enough break time, the idiotic military pilot who ignores airspace protocol, and the lack of english language skills in air traffic controllers and cockpit crew across the region where I fly (English is the international standard for Air Traffic Control).
A good friend is a senior training captain on A330's, and in all the stories he tells software is barely mentioned. What get's priority in the war-stories is the human factors and general equipment issues - dead nav aids, dodgy radios, stupid military pilots. One software story was an Airbus A320 losing 2 1/2 out of 3 screens immediately after takeoff from the old Hong Kong airport. The instructions on how to clear the alarm condition and perform a reset were on the "dead" bottom half of one of the screens.
A great example of software doing it's job is the TCAS system - Traffic Collision Avoidance System (http://en.wikipedia.org/wiki/Traffic_collision_avoidance_system). To quote my friend "If it had lips, he'd kiss it". It's saved his life, and the lives of 100's of passengers, at least twice. Both times through basic human error on the part of the pilot of the other aircraft.
One final thought - on average about 1000 people die in commercial aviation incidents each year world wide (source: aviation-safety.net) . In the USA, over 30,000 people die in vehicle accidents every year.
I think you're looking at it all wrong. This has nothing to do with a comparative death ratios. This has everything to do with liability. At the end of the day, people want a legitimate target to point their finger at regardless of the fact injury or death could have been prevented. If people are allowed to take Google to court and render justice, then I'm sure this new automated driving technology would be ok in their minds. OTOH, if Google is given sanctuary from public lawsuits, hell no!
Life is not for the lazy.
Because we can find one thing humans do better than computers, we should stick to human driven vehicles? What about comparing the overall quality of the two systems? Of course we should demand that the computer was better than a human to a certain, defined, degree, but to demand that it is better in all respects? Why choose the inferior solution because the other is not perfect?
As I understand it the problem with "voting" is that it requires the three systems to produce identical (or very close to identical) results under non-fault conditions. That means you have to write an extremely detailed specification and that in turn means you can end up with all the teams implementing the same bug either because the bug was in the specification or because the specification while strictly correct lead all the teams into making the same mistake.
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
Basing A.I. on psychology will be only a stop gap measure, on the way to the true solution to this sort of problems: basing A.I. on evolutionary anthropology. You see, both the crew and the passengers can be modeled as as tribe, trying to adapt their stable trajectory based culture to changing conditions, namely a nose dive. As more and more air tribes experience such disruptions to their familiar environment, you will find that some develop better coping strategies than others. After a number of generations, all air passengers will be descendants of the air tribes with the more successful coping strategies, and you will find that nose dive causing bugs no longer matter. The people on board will have learned to deal with it. They will probably even have developed tools, either to survive the crash, or to patch firmware on board.
Yep, my wife got hit by a semi while sitting stopped at a red light.
"Which is actually Airbus relies on sensor input over the "pilot"
Fly-by-wire flight controls by their nature treat pilot inputs as a "request" which they attempt to implement with their parameters such as G-limiting and stability augmentation.
Lose enough sensors (unlikely) or get the wrong inputs and you can lose control.
"This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
That same could be said for every other part of the plane. The story sounds made up. By you, your lecturer, or the engineers themselves, who knows.
Posting anon because I moderated.
I had a very similar problem once with firmware on a TI DSP. The symptom was that a peltier element for controling laser temperature would sometimes freak out and start burning so hot that the solder melted. After some debugging, it turned out that somewhere between the EEPROM holding the setpoint, and the AD converter, the setpoint value got corrupted.
The cause turned out to be a 32 variable that was un-initialized, but always set to 0 by the stack initialization code.
Only the first 16 bits were filled in because that was the value stored in the EEPROM. The programming bug was that the other 16 bits were left as is. In >99% of the time, this was not a problem. But if a specific interrupt happened at exactly the wrong moment during initialization of the stack variable, that variable was filled with garbage from an interrupt register value. Since the calculations for the setpoint used the entire 32 bits (it was integer math) it came out with a ridiculously high setpoint.
Having had to debug that, I know how hard it can be if your bug depends on what is going on inside the CPU or related to interrupts.
There may only be a window of less a micro second for this bug to happen, so reproduction could be nigh on impossible.
It's not about choosing one or the other, but hybrid systems operating at the same time.
If you are going to compare quality, the human will win every time. We can give anecdotal evidence about how bad drivers are, but statistics show that driving is not so dangerous that we need to consider stopping it altogether. Really think about it for a second. During your average day, how many really bad drivers did you personally interact with that created a dangerous situation resulting in an accident? Pretty low huh? I would expect so, otherwise insurance would cost thousands and thousands per month, instead of per year.
Humans are not the inferior solution overall right now. Not by far.
It is also not because Google is not perfect either. Specifically, it is because of the time required, and the complexity of shifting control from Google to the driver. Once such a system becomes normal to a driver, their attention is not going to be on the road, but on their interaction with other devices. You cannot reasonably expect a person to be in complete awareness, hands at 10-2, ready in a split second to take control. You would get too bored without immediate feedback, your mind would drift. This would be completely normal too.
This is not to say that the system itself might not be useful, but it would have to be under very controlled conditions excluding human drivers altogether. It could work, provided the shifting of control was at a controlled rate in relatively controlled conditions. Give the human being time to adapt and obtain situational awareness.
As cool as this sounds, it is just not ready to fully replace a human, unless it could perform at a human level or better. The dream of a car that can drive itself completely under all conditions is still some ways away.
The idea of changing carpool lanes over to high efficiency lanes where human control is not allowed seems like a more pragmatic approach that decreases the complexity and uncertainty that the Google system has to deal with. It has very high value as well since it can optimize traffic patterns far better than a human simply because it can cooperate with a much larger number of cars over greater distances. A human could never hope to do that with our inherent limitations.
That system could realize some serious fuel savings and increase productivity by essentially mimicking an airplane in auto pilot mode. The human is really just there to get the system to the point where it can safely transition in and out of a computer controlled lane. That will be extremely advantageous to overall traffic.
Some roads near my house have deliberate pinch points which rely on drivers playing chicken with each other. Its called traffic calming. Several bike riders have died in collisions with cars where the car driver absolutely refused to give way to a bike and as a result caused a crash. The game of chicken depends of certain assumed characteristics of the drivers of both vehicles. Heavy trucks will burn through and expect a small car to give way for example.
Now, my wife's car has automatic headlights and this means the headlights are always on. You see the safest approach with headlights is to always have them on and the logic can only be built to take the safe approach. But what happens if human drivers learn that automatic cars will always give way at pinch points (because it is the safest way to behave) and start to assume they will never have to give way in this situation?
Its a three laws of robotics type of question but I think the point is that traffic as we know it is an inherently human invention, and software won't really be able to work with it.
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I feel "eat your own dog food" should apply.
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This type of story isn't new and i'd imagine its pretty common. When you know there are corner case bugs unpatched that were only 1 in 10,000,000 chance of being triggered in a given flight, do you still want to risk relying on your software for your life or death? Nah. What those engineers weren't doing was listening to the Boeing engineer's list of bugs and that they'd be doing the exact same thing whenever a new system's hot off the assembly line.
We have computer controlled trains in my city, and the rumor mill kept chupring away that the engineers would never touch them with a ten foot pole, but to my knowledge there's never been a serious derailment or automation related fatalities (lots of jumpers sadly, but I guess that comes with the territory).
Bye!
It looked like half of one 32-bit word was combined with half of another 32-bit word during queue assembly on at least some occasions. But there are errors not explained by that.
This is why I like fuzzing. Sending random and/or corrupted data to software to evaluate the software's robustness and sensitivity to corrupted inputs. For a project like this I would like to send simulated inputs from regression tests and recorded data from actual flights to the software while fuzzing each playback, repeat. Let a system sit in the corner running such tests 24/7.
In theory some permutation of the data should eventually resemble what you describe.
The Airbus will also change the throttle to the engines without moving the throttle levers whereas the Boeing will move the levers to where the computer set the throttle, When the autopilot takes a crap and you put your hands on the throttle, you must remember that the controls are lying to you and act accordingly.
A brilliant transplant surgeon has five patients, each in need of a different organ, each of whom will die without that organ. Unfortunately, there are no organs available to perform any of these five transplant operations. A healthy young traveler, just passing through the city the doctor works in, comes in for a routine checkup. In the course of doing the checkup, the doctor discovers that his organs are compatible with all five of his dying patients. Suppose further that if the young man were to disappear, no one would suspect the doctor.
An engineer would realise that since these patients are all missing one different organ, then one of them can be cut up to save the other four, saving the moral dilemma since any one of them would have died anyway. Philosophers are always looking for the perfect question, but an engineer knows there is always a better solution. All an engineer needs to know is how his car killed someone the last time and he can fix it.
When Argumentum ad Hominem falls short, try Argumentum ad Matrem
In the AF477 accident, the junior copilot panicked under the sudden workload and kept pulling back on the control stick until the plane was beyond any hope. Neither of the copilots nor the captain (who was absent from the flight deck when the problems started) figured out this until the plane had stalled irrecoverably into a 60 degree angle-of-attack stall.
I'm not sure if you are serious or mocking people that rant about being "defensive drivers".....
Back in my Finnish Air Force days I talked to a captain who had flown the F-18C in his last three active flight years. He told that when you're straight and level in the Hornet and peek over your shoulder you probably see the ailerons swaying back and forth as the computer tries to keep the plane stable.
Interesting here would be some statistics. How many Boeings have come into serious trouble, and how many Airbuses?
Besides the GP's point about Airbus pilots being unable to override the computer being complete and utter bollocks (Airbus' still have a analouge actuator control (Electronic) in them), there have been a few near misses which if it were not possible to take manual control would have resulted in a crash such as the JetBlue landing at LAX in 05.
On the other hand, there have been incidences with Boeing aircraft which are believed would have been solved by automated systems such as AA flight 965 (Colombia 1995) where if the airbrake was automatically retracted the pilot would have been able to climb a way safely.
Here is a good post on the subject. According to the ASTB who conducted the investigation there have only been 3 such incidents in 128 Million hours of A330 operation as of 2008. That is a damn good rate of failure wouldn't you say? Pilot error being the cause of approx 48% of all accidents, Airbus or Boeing. Modern aircraft are getting safer all the time, they see more mechanics and engineers in a week then your car will see in its entire lifetime. Everything is checked and double checked, anything suspicious gets replaced. I never think I'm in danger stepping onto an an Airbus or Boeing aircraft.
The whole Airbus Vs Boeing argument is a dick pulling contest between biased pilots. It's like a Xbox/PS3 fanboy war. Utterly senseless to third party observers (and bronzed fingered PC gamers) Now amongst the 25 worst airlines you have a 1 in 850,000 chance of dying and I dont fly any of those airlines (1 in 9.2 million for the 25 best), hence my practice of congratulating myself at the check in counter as I've survived the most dangerous part of air travel, the drive to the airport. Compared to our road toll, our air toll is minuscule.
Calling someone a "hater" only means you can not rationally rebut their argument.
I consider myself an above average driver, as do most.
I'd even take it further: I'd hand over my driving to an autumatic car in a second if it meant all the other morons would have to do the same.
For those addicted to driving: yes, I'd love to force you to take your self-driving to the circuit, where it belongs (once the driverless cars have proven to have less than half the accident rate of humans).
Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
I don't think anyone's out to force you to use a driverless car.
But if you do aquire one, don't be suprised if one morning you get in and find the interior is all spaced out white with whispy grey lines that lack contrast.
Good point. Look at the summary: " operators can be confident that the same type of accident will not reoccur".
Only someone with no fucking clue of how software works can ever write something that stupid...
I wonder if Google will be found liable when someone dies out of their car. After all, if they make the fallacious promise of "bug free", they should be held responsible for bugs. And without the promise, I fail to see how anyone will give them a license to mass produce this thing.
Write boring code, not shiny code!
On Airbus vehicles, if the avionics computers crash, the airplane crashes. There's exactly ZERO way to pilot the computer manually in such a failure.
Completely untrue. When the avionics 'crash', the flight system progresses through 'alternate' to 'direct' law where the pilot has direct control of the plane.
Moreover, the avionics system can and does overrule pilot input. So if you get sensor malfunctions like this, even if the pilot is trying desperately to save the plane, the computer can still crash you.
Have a look at the statistics (pages maintained by a pro-Boeing pilot, by the way) and you'll see (i) for all your hysterical fear of Airbus aircraft, the fly-by-wire Airbus aircraft (i.e. all except A300 and A310) are just as safe as their Boeing counterparts (ii) there are no examples of an Airbus crash caused by the computer overriding the will of the pilot.
injuring 12 people seriously and causing 39 to be taken to the hospital.
That is why you keep your safty belt shut.
If you don't like the feeling, losen it a bit, but keep it closed.
I really wonder why people keep taking such nonsense risks and open the seat belt directly after launch.
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
What a load of uninformed bullshit - Airbus has several levels of computer control, called laws, one of which is Direct Law which passes all inputs directly to the control surfaces. And if that isn't enough, they have mechanical backup controls for all surfaces on the flight deck, so even with a completely dead computer the aircraft is still flyable.
You sir, are talking complete shit, but that seems to be normal when someone wants to put Boeing on a pedestal over Airbus.
Let's go over some of your "mistakes"...
The 787 isn't Boeings first FBW aircraft, they have had one flying since the mid 1990s with the 777. The 787s system is an evolution of the 777s.
AF447 didn't crash because of a computer problem, it crashed because of poor crew relationships in the cockpit - three pilots in that cockpit and not one was interested in what the others were doing. They didn't run basic check lists, they ignored other information, and the pilot flying did completely the wrong thing - the situation was completely survivable if they had carried out the correct procedures, except they didn't. The crash wasn't caused by the computer, it was caused by the pilot taking a stable aircraft and stalling it badly when nothing about the computer error forced him to do that.
Okay, a few facts, the A330 is fly by wire, this means between pilot and control surfaces everything must go through the avionics, if the avionics totally fails then that plane is by definition little more than a glorified missile.
That said, it seems the backups and pilot responded exactly as they should have in this case. The plane pitched, enough to throw the passengers around and cause injuries, pilot disengaged autopilot and corrected, declared an emergency and safely landed at the nearest big enough airport.
Please tell me how he did anything wrong? Please tell me how the rest of the computer systems failed to cause and actual crash Nope neither, the plane was left in one piece on the ground.
The only thing I say is, why did it take Airbus 2 years to find and fix that major bug?
Except that the designers of the software didn't take all possible situations into account. For example, any Fly By Wire Airbus will automatically pitch up if speed increases too far above the maximum airspeed, even when flown manually. This may be a good idea when the airplane is diving (the most likely cause for overspeed), but not when it's straight and level with other traffic immediately above! This has already made several Airbus planes in heavy turbulence suddenly start to climb violently due to a sudden change in airspeed or temperature and overriding the pilot's MANUAL inputs while he's trying to avoid flying into other traffic! That's insane, and it's only one of many reasons why I can't wait to get off the Airbus fleet onto a more sensibly designed plane. (I'm currently an A320 pilot).
WEll as you dont know anything at all about flying let alone commercial pilots, let me inform you.
none of what you dream up is happening up there except for the bad pilots. i know several commercial pilots, they are busy up there with checklists, comms, and do not have time to chat up the stewardesses. There was a little thing that happened in September of 2001, they keep the door locked for the flight.
But you go ahead with your fantasy, it's just like all the fantasy reported on fox news.
Do not look at laser with remaining good eye.
If there are serious failures, an Airbus pretty much starts to behave like the controls of a Boeing.
That's reassuring - "if the shit hits the fan, this aircraft will act like a Boeing" - so why not fly an actual Boeing in the first place? What actually makes an Airbus a better option outside of extreme conditions?
They sentenced me to twenty years of boredom
Another viewpoint on AF447 seems to blame it almost completely on the pilots. http://airsoc.com/articles/view/id/4ef03480c6f8fa6041000005/what-really-happened-aboard-air-france-447
This! I live in a bicycle friendly city and generally use my bike to commute. But even here you see people on their phones in cars on a regular basis (which is actually now illegal here), plus trying all kinds of crazy driving when impatient or not thinking straight. When you're cycling it's much more easy for one of those incidents to turn into a serious injury, since you have no protection at all from other people's vehicles.
But people don't have the mindset that they're operating a dangerous machine that they need to take responsibility for, so they just carry on doing it because they don't believe they're doing anything dangerous. I wish people would be taught more explicitly just how dangerous their car is.
With cyclists the situation is complicated because there's an eternal tension between what the two kinds of vehicles think they should be allowed to do on the road. But it's the same if you're driving, no matter what you do, some other folks either think their car is a toy or that nothing could possibly happen to them.
But the point of the story was that all software has bugs
I seem to remember that at the time of the launch of the 777, Boeing claimed that their processes made it impossible for there to be any bugs in its software -- a position it has moved away from.
Quidnam Latine loqui modo coepi?
Except that the designers of the software didn't take all possible situations into account. For example, any Fly By Wire Airbus will automatically pitch up if speed increases too far above the maximum airspeed, even when flown manually. This may be a good idea when the airplane is diving (the most likely cause for overspeed), but not when it's straight and level with other traffic immediately above!
Except if that other traffic is also an Airbus.
*blinks* You're not well versed in the effect of turbulence on localized airspeed or altitude are you? The sensors will report airspeeds that are only possible in a dive, combined with the loss of altitude even though the angle of attack is level or steady could easily cause software to attempt to pull out of the "dive". That assumes that the plane is allowed to override human input, which is a seriously fucking asinine design if true.
I fail to see how anyone will give them a license to mass produce this thing.
That's because you're not very smart (+1 Ad hominem). We already have a well established market mechanism to handle this problem (+1 Anarcho-capitalist dogma). Insurance actuaries, unlike plebs, don't give a fuck about the emotional attachment to maintaining your own control over the vehicle--because accident rates WILL be lower with driverless cars, regardless of bugs, they will see $$$$ in covering it.
It's not as if automotive liability is a unanswered legal question. Every state has their liability rules, and requires drivers to carry insurance to meet that liability. Why would this change just because the vehicle operator is no longer driving? Car owners will remain required to carry insurance, the insurance companies cover the liability (quite happily since accident rates will be so much lower that by not lowering premiums quite proportionally they will make $$$$).
And without the promise, I fail to see how anyone will give them a license to mass produce this thing.
Uh, the same way hundreds of other life threatening devices are licensed? Medical equipment, nuclear plants, planes, TSA scanners, etc; all depend on software to function properly. And as far as I know there's no promise of being bug free.
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Even on the road today this is an issue. Doesn't matter how good of a driver you are. If one other idiot on the road is driving crazy, you could get killed no matter how you drive. Weakest link and all that...
Everyone who drives faster than me is a maniac. Everyone who drives slower is an idiot.
It is dangerous to be right when the government is wrong.
Exactly, I'm always baffled when I'm flying as a passenger and as soon as the Fasten Seatbelts sign goes off, I hear "click click click click" everywhere around me from people who have no intention of getting up. What the hell is so bad about having a seatbelt fastened on your lap while you're seated that you absolutely have to get rid of it as soon as you possibly can? While sitting in a tube suspended by wings in an airflow that might become turbulent unexpectedly at any time?
As an airbus pilot, I couldn't agree more. In fact, I have yet to meet a pilot who thinks it's a good idea. But hey, it saved quite a few bucks! Same thing for the throttles, by the way. The autopilot may reduce the engines to idle without anyone noticing, because the levers don't move. Airbuses have some pretty amazing and glaring design errors in them.
The side sticks do have a button to take complete control (control being given to whoever pushed the button last, so it could go back and forth multiple times if both pilots want control) but very often pilots will forget to push the button when taking over in a critical situation (for example an instructor taking over from a student during a bad landing), resulting in double inputs and very erratic recovery of the airplane.
Why do I need insurance if I'm not actually driving the car? I don't need insurance as a passenger on an airplane or ride the subway. In fact I don't even need insurance to be a passenger in a car, which is exactly what I'd be in a driverless car.
perhaps it's autopilot is better at handling turbulence? or can fly more efficient routes when the plane needs to fly across a jetstream instead of along it? maybe the "better operation in extreme conditions" really is useful.
just my $0.02, and i really know nothing of those systems.
All of the above was encrypted with a Quad ROT-13 method. Unauthorized decryption is in violation of the DMCA.
So how will you reduce the risk of someone next to you suddenly deciding to switch the lanes without checking that you're there? How do you reduce the risk of someone deciding he just has to pass the car in front of him even when there's incoming traffick? How do reduce the risk of someone deciding to test his engine and losing control?
It doesn't matter how good a driver you are; if someone else screws up bad enough, you're dead.
Forget magic. Any technology distinguishable from divine power is insufficiently advanced.
Clearly she should have run the light...
I completely agree, and I think what Google is doing with the driverless car research is great. We all know humans aren't the best drivers, and in Google's preliminary tests their cars seem to have performed very well.
Sadly, it will probably only take one fatality caused by a driverless car for the reactionaries to come out of the woodwork and put some major weight against the technology and its adoption.
So how will you reduce the risk of someone next to you suddenly deciding to switch the lanes without checking that you're there? How do you reduce the risk of someone deciding he just has to pass the car in front of him even when there's incoming traffick?
Um...by not riding beside somebody, especially in their blind spot?
I mean, is this a serious question? Have you never learned defensive driving?
If I had written VMO or MMO instead of "maximum airspeed", you wouldn't have understood what I wrote. Airplanes do have a maximum airspeed (airspeed being the speed relative to the air, as opposed to ground speed). Go too far above VMO, and the plane starts buffeting (a kind of vibration). Go a bit further, and you may lose control completely due to high speed stall, mach tuck, control reversal, etc...
Airbuses do indeed have autothrottles, but engines react rather slowly so, while indeed reducing thrust, the flight control systems pull the nose up as well. They have in one recent incident in my current company, and this had already happened before in several other companies. In one case, there was another plane 1000 feet above and the pilots managed to stop the climb after 700 feet.
There are many possible reasons for a sudden increase in airspeed. Most of the time, it's due to a change in wind. If a 100 knot tailwind suddenly drops to 70 knots, you've just gained 30 knots of airspeed. But the true airspeed doesn't even have to change: in a recent incident in my company, the outside temperature changed by more than 10 degrees in a very short time which increased the mach number above MMO (because the speed of sound changes with temperature). The autopilot immediately disconnected and the flight control computers started a rather violent climb which the pilots could only recover from after climbing more than 500 feet.
So, you say you're a rocket surgeon? What kind of operations have you performed on them?
If I could, I'd mod you +5 funny. I first wanted to reply something serious (the other plane would not get the same change in airspeed), then got the mental image of a stack of airbuses all going up in unison and couldn't help laughing :-)
So how will you reduce the risk of someone next to you suddenly deciding to switch the lanes without checking that you're there? ...
You reduce that risk by not staying next to another driver any longer than you have to.
You watch the drivers around you and anticipate what stupid things they might do that would endanger you. Then you decide what actions you need to take to minimize that risk. Then you take those actions. That's what defensive driving is all about.
It's not easy and can't really be done while jabbering on the phone. And it's not very satisfying to the ego to drop behind another driver who is a little more aggressive than you, but it can pay out in reduction of accidents caused bu others.
Yes, I'm sure one can point out situations where there is little to no opportunity to avoid the actions of others, but in far more situations there is plenty of opportunity to minimize the risks due to other driver's stupidity.
But you'll still own the vehicle right? You insure the cars you own (driverless or not), airlines insure airplanes, and you can bet there's insurance on those subway trains too.
"When information is power, privacy is freedom" - Jah-Wren Ryel
Boeings situation is potentially worse, as their auto throttles move both levers equally, not based on the actual throttle levels of each of the engines. This directly led to crew shutting down then wrong engine on a 737, resulting in a crash in 1989 in the UK.
This happens frequently to motorcyclists). Yes, you can still avoid the other car. Typically, by braking, hard enough to allow them to pull in just in front of you, but not so hard that you get rear-ended by the person behind you. Less frequently, you can accelerate to get in front of them, but you'd best be on a motorcycle and not in a car to pull this maneuver off (much higher rate of acceleration) and you still may not want to (more speed means more energy to crunch things up if it goes badly).
If nothing else, honking the horn will usually get the attention of a driver changing into your lane, but you'd best back that up with maneuvering of your own in case it doesn't cause them to abort their lane change.
"Flame away, I wear asbestos underwear"
I ride a motorcycle almost daily and use the theory that EVERYONE in a vehicle is out to kill me.
This forces you to focus your attention not just the cars but the person driving it.
Plus being able to out brake, out accelerate, and fit through fairly small openings has kept me alive for 30+ years on a bike. Of course, I could get killed on it going home from work tonight.
A bullet may have your name on it, but artillery is addressed to " Whom It May concern"
If you saw the procedures required to get airworthiness certification from the FAA for a critical piece of software, you would shake your head in disbelief. It is almost all about ensuring that every line of code is traceable to (and tested against) a formal requirement somewhere. In spite of greatly increasing software development costs (due to the additional documentation and audit trails required), the procedures do amazingly little to ensure that the requirements or code are actually any good, or that sound software engineering principles are employed. It does not surprise me that GIGO situations occasionally arise -- it is perfectly plausible that a system could meet the certification criteria but shit's still busted because the formal requirements didn't completely capture what needed to happen.
The cost of compliance can also warp the process. A co-worker once told me a story about an incident that happened years ago at a former employer of his. A software system with several significant bugs was allowed to continue flying because the broken version had already received its FAA airworthiness certification. A new version which corrected the bugs had been developed, but getting the new version through the airworthiness certification process again would've been too costly; so the broken version was allowed to continue flying.
Look up "DO-178B" sometime if you're curious...
Aha, yet more uninformed bullshit.
Maybe if you actually read what I wrote, you could come up with some real objections, rather than your own uninformed bullshit.
The 777 has a mechanical backup system, exactly as I stated. Look it up, bozo. All Boeings to date have.
I did not state that Boeings were not "fly by wire", I said they had MECHANICAL BACKUPS. I meant as opposed to entirely (or nearly entirely) fly-by-wire only. It's right there in my comment, in plain English. Further, despite what I stated earlier, even the 787 has electrical/mechanical manual backup in case of computer failure. Of course, if you suffer a complete loss of electrical power (including even the turbine generator), you are SOL either way.
I'm afraid you are spouting pure shite - no aircraft would be certified by either the FAA or the EASA if your stance was correct...
There is a reason that there are so many independent power generation systems onboard a modern (1970s onwards) aircraft, and there is a reason that those systems are checked and certified - there has been zero incidents where an aircraft has completely and utterly lost power during any stage of flight.
And if you dispute that Airbus has been prone to crash due to computer failure, I invite you to look that up, too.
If you look up the Airbus laws yourself, you will see that the only manual control for pitch, for example, is the trim wheel. This is going to do you very little good unless your plane is already in stable horizontal flight... seldom the case when catastrophic failure occurs.
I am *very* familiar with the Airbus control systems, and your assertion that the trim wheel is useless unless in stable horizontal flight just screams that you know fuck all about what you are talking about. You can use the trim wheel to fully control the airframe in all circumstances where you would have to do so with the elevators, because the forces you have to exert during direct mechanical linkages to the elevators would break your arms on a large civil airplane and involve leverage forces that you could not exert from the tiny control columns on modern aircraft.
I'd love you to show us any cases of an Airbus crash that was attributed to computer failure - you won't find one. And I dare you to trot out the Habsheim A320 crash...
On the other hand, we have perfect examples such as the Air Transat flight 236, which lost both engines due to a fuel leak which exhausted the entire fuel supply (and once again missed by the pilots - they completely ignored all the warning signs), and had to glide for 65 miles without engines and only running on the Ram Air Turbine electrical generator. That aircraft landed perfectly safely.
But the main thing -- one I didn't see the point of going into until you decided to butt in -- is that in order to go into "Direct Law" in an Airbus, which is what you might consider your main "manual backup", you have to jump through a lot of hoops, which (as it turns out) pilots just do not have time to do in an emergency.
To put an Airbus aircraft into Direct Law takes precisely two button presses, both within reach of either pilot - but if you aren't in Direct Law, there's really no reason for you to manually put yourself into it, but its there if you want to.
It still amounts to the pilots not being able to control their aircraft when the computer fails.
Again, the same utter shite from yourself.
There's a lot of bullshit touted on the internet about Airbus aircraft - I suggest you actually educate yourself. And I suggest staying away from Wikipedia - there is so much wrong information on there, and so many trolls willing to spend their lives pushing their own warped view through articles such as the ones linked to this, that I no longer consider Wikipedia worth time or effort at all.
Sure - the flight in question was British Midland Flight 92.
The situation I mentioned came about because the pilots shut down the right engine due to vibration and presence of smoke in the cabin - up to the 737NG line cabin air was only taken from the right engine, so thus engine vibration and smoke in the cabin meant the right engine was at issue. However, in this case it was the left engine which had actually failed.
While the left engine was failing, the autothrottle automatically adjusted the fuel flow into it in order to maintain the thrust levels from it - this had the effect of causing an asymmetric thrust selection between the left and right engines - however, the throttle lever actuator only selected a physical position for the right hand engine at its lower thrust level, meaning the autothrottle was actually selecting a higher value which was not indicated in the positions of the throttles (the two throttle levers are linked by one actuator when under autothrottle control, thus they can actually only show the thrust level of one of the engines - in this case, the right engine).
When the pilots turned off the autothrottle to power down the right engine, the left engines selected thrust returned to that of the physical position of its thrust lever - which had the effect of reducing the vibration to the point where the flight crew thought they had indeed turned off the correct engine when they shut down the right engine.
When they were on approach to Midlands Airport, they increased thrust on the left engine, which caused it to fail completely and thus the aircraft crashed short on approach.
This system was highlighted in the crash report, along with a number of other issues with the 737NG design - Boeing did infact have to ground a large number of aircraft before the solution was deployed to the delivered fleet. It was not the sole cause of the crash, but it was something that was heavily highlighted in the chain of events.
I think it's fair to say that some accidents could be avoided by one party taking swift action, but there are also times when the circumstances are such that one driver's carelessness will cause an accident and there isn't much anyone could do about it. While driving, it's not possible to predict anything more than a few seconds into the future, as far as trying to guess what other drivers will do. In a heavy traffic situation, your awareness will be divided between multiple vehicles. Unless both parties are paying attention, it may not be possible for the one attentive party to avoid.
When stopped at a light, you can't even predict whether someone coming up from behind will stop. A lot of people like to slam their brakes at the last second. How do you tell the difference between that person and the one who isn't going to stop at all? And if there is a car in front of you, then what? Quickly back up and change lanes before the other vehicle arrives?
If people think "defensive driving" means "all accidents are avoidable," they're wrong. It can prevent some, but not all. If you want to be totally pedantic about it, all accidents are "avoidable" given adequate foresight--like knowing you should stay home that day because a semi is going to plow through your car at 12:09PM. Until we can peek into the future, though, we have to deal with what we've got.
Check out my world simulator thingy.
The flight control computers implement all control laws, so you're not disabling any computers at all. Let's talk about, say A330. There is a set of three primary control computers (PRIM) that produce data for the control surface actuators, and a set of two secondary computers (SEC). SEC only implements the direct law, PRIM implements all control laws (normal, alternate 1/2, direct, with mode modifications for flare and ground).
The control law downgrading can only be handled automatically. You pretty much have to pull circuit breakers to change it manually. If there's a "catastrophic computer error", say all PRIM computers down due to overheating (has happened at least once due to air conditioning failure) the downgrading or selection of SEC computers will happen automatically, the pilot isn't expected to have to handle that.
A successful API design takes a mixture of software design and pedagogy.