What really happened aboard Air France 447 • Hacker News Board

Re: What really happened aboard Air France 447

#131

Post by jarek » Thu, Dec 08, 2011, 9:01 AM UTC

jpiasetz wrote: post #113

jarek wrote: post #103

Earlier quoted context omitted.

There is a really great write-up of the Hudson river ditching in Vanity Fair: http://vanityfair.com/style/features/2009/06/us_airways20090... . Gripping, intense, interesting, and in the end incredibly inspiring due to the emergency going exactly right .

Interesting in that account the person in charge said "my aircraft". May have helped with Air France to eliminate the two people pulling on the stick.

The Popular Mechanics account of AF447 leaves out some quotes and doesn't explain their content very clearly, unfortunately, but it appears they were doing that, more or less.

"02:11:37 (Robert) Commandes à gauche! Left seat taking control! [...] At any rate, Bonin soon after takes back the controls."

Sometime after 2:12:15: "As the plane approaches 10,000 feet, Robert tries to take back the controls, and pushes forward on the stick, but the plane is in "dual input" mode, and so the system averages his inputs with those of Bonin, who continues to pull back."

"02:13:43 (Robert) [...] À moi les commandes! [...] Give me the controls! [...] At any rate, without warning his colleagues, Bonin once again takes back the controls and pulls his side stick all the way back." Next timestamp is 02:14:23 and crash is 02:14:28.

It's not really clear whether Bonin announced his first retaking of controls. I believe protocol would in fact give him formal control if he did, despite his confusion. Robert appears to have been communicating his control correctly but Bonin appears to have been providing input during this time. We'll never know if he didn't realize he was providing input or if he didn't realize someone else was trying to control the plane.

Re: What really happened aboard Air France 447

#132

Post by rohit89 » Thu, Dec 08, 2011, 9:05 AM UTC

nikcub wrote: post #86

I simply don't undersand (or don't comprehend) how the pilots don't know these things. My knowledge of planes is 4 hours of pilot lessons and watching a few documentaries on the Discovery channel yet I know that pulling the nose up of a plane would stall, that when you get bad readings from instruments you cross-check, and that a frozen pitot tube giving bad airspeed readings is very likely in high-altitude storms. I…

Things can tend to go out the window when you are going through high stress.

>> 02:14:23 (Robert) Putain, on va taper... C'est pas vrai! Damn it, we're going to crash... This can't be happening!

What a frightening moment. I can only imagine what was going through his head at that moment.

Re: What really happened aboard Air France 447

#133

Post by joshAg » Thu, Dec 08, 2011, 9:07 AM UTC

teyc wrote: post #102

The state of UX design has advanced so much, perhaps we need more UX testing so that even pilots who are unfamiliar with a plane could figure out what to do. Amazon probably does more with figuring how to help users checkout their shopping cart than plane designers helping pilots get a plane out of a stall. Alternate law and normal law introduces two modes. This breaks one of the rules of user experience, especially…

pitot tubes just measure longitudinally forward airspeed (ie the direction the plane is going). altimeters measure asl (above sea level) altitude, and gyros measure angle of attack and accelerations.

I believe there is a way to tell stall just from altimeter and gyro readings when combined with state information (flap position, gear up/down, &c.) about the plane.

great points about the ui design, though.

i think the biggest issue, though, was the controls not announcing (either through force feedback or a blaring alarm or an urgently blinking light) conflicting input on the control sticks. does anyone know why this is a feature in the first place?

Re: What really happened aboard Air France 447

#134

Post by bambax » Thu, Dec 08, 2011, 9:08 AM UTC

cellularmitosis wrote: post #72

kmort wrote: post #9

Earlier quoted context omitted.

The author did touch on it: "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."

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

Very interesting insight. But I think you're both right and wrong.

It's certainly true that computer assistance and correction leads to bad habits. I drive a motorcycle and will never drive one with ABS, because I know from many people that once you have a bike with ABS, the moment you ride one without, you fall, usually in less than half a mile: you're used to stepping furiously on the brakes, and that is quite unforgiving when there is no ABS ;-)

But it's also probably true that computer assistance saved many more lives than it took.

It just shouldn't turn off on its own; or, people should have extensive training with assistance off ("alternate law").

Re: What really happened aboard Air France 447

#135

Post by joshAg » Thu, Dec 08, 2011, 9:09 AM UTC

weaksauce wrote: post #33

greiskul wrote: post #14

Earlier quoted context omitted.

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

True. But, how would you want to handle the situation of two equally competent(at least in the eyes of the employer) co-pilots vying for control? should it always go to one? always go to the other? have a switch controlled? controlled by whom? not easy questions if you ask me. edit: I actually can't think of a good way to do that other than have a manual switch on the console that would switch between the two control…

perhaps have the plane decide which input seems more rational, then announce who has control.

Re: What really happened aboard Air France 447

#136

Post by Nick_C » Thu, Dec 08, 2011, 9:10 AM UTC

teyc wrote: post #126

Nick_C wrote: post #120

Earlier quoted context omitted.

> how does a plane know it's stalling if the pitot tubes are frozen Angle of attack sensor. AoA is the actual definition of a stall as it measures the point at which airflow breaks away from the wing, reducing lift. Re your other points on computer warnings, cockpits can get pretty noisy when shit happens with various alarms, buzzers, horns and voices going off. There's actually a tendency to reduce the number of dif…

There's actually a tendency to reduce the number of different alarms and use screen information to indicate the problem Yes, that'd be good UX. There should be only one actionable task presented at any time to correct errors. In any case, user testing is more important than guidelines. I wonder if grouped alarms make any sense. For instance you can group all alarms related to stalling together, and present the one th…

With the Qantas incident, they had something like 146 msgs appear on the screen spread over about 5 or 6 pages. So they were forcibly distracted from solving the problem from a top-down approach to having to investigate and cancel each of the 146 msgs, and that was why the two extra pilots were such a godsend, they were able to help out.

Re: What really happened aboard Air France 447

#137

Post by akronim » Thu, Dec 08, 2011, 9:10 AM UTC

If you want to get into root cause analysis, it sounds like the incorrect radar setting got them in the situation in the first place. Obviously the way the pilots dealt with that situation from then on was suboptimal, but avoiding situations where there is a chance for bad decision making is also important.

Re: What really happened aboard Air France 447

#138

Post by jarek » Thu, Dec 08, 2011, 9:11 AM UTC

teyc wrote: post #102

The state of UX design has advanced so much, perhaps we need more UX testing so that even pilots who are unfamiliar with a plane could figure out what to do. Amazon probably does more with figuring how to help users checkout their shopping cart than plane designers helping pilots get a plane out of a stall. Alternate law and normal law introduces two modes. This breaks one of the rules of user experience, especially…

The autopilot turning off altogether is the biggest equipment problem here (along with averaging/independent sticks). An alarm will surely be necessary but I don't see how killing off autopilot helps since the pilots probably won't have any better of an idea. Perhaps this specific incident caught an ugly edge case.

There is actually a fair amount of ergonomics and interfaces design that goes into these systems - at least equal to Amazon's shopping cart, probably more. Same goes for systems like ATC.

"Stall" does mean "dive now" to every pilot. It is extremely questionable whether including this information explicitly would help at all in the chaotic, confused environment in the cockpit at the time. "Why are you pulling the stick back" is way too long as well, although it does raise a fair point about keeping both pilots aware of each other's control inputs.

Re: What really happened aboard Air France 447

#139

Post by einhverfr » Thu, Dec 08, 2011, 9:14 AM UTC

abk wrote: post #114

nikcub wrote: post #86

I simply don't undersand (or don't comprehend) how the pilots don't know these things. My knowledge of planes is 4 hours of pilot lessons and watching a few documentaries on the Discovery channel yet I know that pulling the nose up of a plane would stall, that when you get bad readings from instruments you cross-check, and that a frozen pitot tube giving bad airspeed readings is very likely in high-altitude storms. I…

Surely there must be more to it. Clearly all of us who've played a flight simulator know that going up too fast will cause you to lose speed and eventually stall and fall until you regain enough speed to stabilize. Sadly in this case it sounds like a mix of overconfidence (not avoiding the storm, trusting the plane more than the stall warnings, not waking up the captain until it was too late) and a lack of training f…

Interestingly I have not played flight simulators since the 1980's, but I know of overspeed stalls (usually mach tucks) in part from being fascinated about historical engineering, and ran into the issue when looking at WWII aircraft (interestingly the first confirmed incidents of overspeed stalls were with the propeller-driven Lightening aircraft in WWII).

Re: What really happened aboard Air France 447

#140

Post by joshAg » Thu, Dec 08, 2011, 9:15 AM UTC

sliverstorm wrote: post #47

crikli wrote: post #45

Earlier quoted context omitted.

Our bodies are horrible when it comes to spatial awareness. Pilots are trained to ignore sensory input like the feel of gravity, the feel of being in a dive/climb/bank and use the instruments to make determinations about what the aircraft is doing. Usually those feelings are dead wrong. It's amazing how flying into a cloud bank, even though you've been flying straight and level, suddenly your body screams at you that…

Ah, that bit about being trained to ignore their body is interesting. I was not aware of that, and it answers my question pretty well.

when instruments were first introduced to planes, most people thought that something caused all instruments to malfunction like crazy as soon as they entered clouds due to the ghost spatial effects the pilots assumed were true ("I can't be turning, I feel like I'm going in a straight line!" or "I can't be going straight, I feel like I'm turning").

If I remember correctly, the average lifetime of a non-instrument trained pilot in instrument only conditions is measured in seconds, because these ghosting effects are so strong.