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What really happened aboard Air France 447

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Re: What really happened aboard Air France 447

#71

Post by jrockway »

Klinky wrote: post #30

Co-pilot Robert, after finally getting full control back from Co-pilot Bonin: "Damn it, we're going to crash... This can't be happening!" Co-pilot Bonin, who had been pulling back & stalling the plane during the crisis: "But what's happening?" Pretty much sums it up. I am thinking that perhaps Bonin had shellshock & may not have even realized he was holding the stick back. Perhaps the more experienced Robert didn't t…

- Delineate command better, e.g. Captain, Co-pilot #1, Co-pilot #2 so that who is in charge is clear.

This antiquated idea has killed many more people than it would have saved in this case. Read about CRM:

http://en.wikipedia.org/wiki/Crew_resource_management

I think a classic example is:

http://en.wikipedia.org/wiki/Avianca_Flight_52

The plane crashed because it burned all of its fuel in a holding pattern waiting to land in JFK. When the flight engineer noticed this, he was afraid to tell air traffic control, who he believed was "higher up" than he was (and he therefore had no right to question their decision). The result was 65 dead people.

There are several cases where a lower-ranking person has noticed something that the captain has not. And when they didn't do anything about it, people died.

Re: What really happened aboard Air France 447

#72

Post by cellularmitosis »

kmort wrote: post #9
citricsquid wrote: post #6

The lack of reaction to "Stall!" implies one of two things; either it was broken and the sound didn't play or the complete lack of understanding about what the word "Stall" meant with the pilots. Has either of these been proposed and discussed? The author of this piece doesn't seem to touch on why they ignore "Stall!", unless it's been confirmed the sound had been heard (on the recording maybe?) and they did indeed u…

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 computer partially ignore your control will always lead to people railing the controls all the way in the direction they want. That's just human nature.

This is just like having someone who was raised on cars with traction control drive on ice for the first time. They'll notice the car isnt accelerating as fast as it normally would, and their natural reaction will be to push the gas pedal down EVEN FURTHER! Bingo - your control system just extracted the exact opposite of rational human behavior. If they didn't have traction control, they would have heard the engine rev and the tires spinning, and they would have backed off of the gas.

If the pilot weren't under the mistaken impression that the computer would limit his input, he would have NEVER pulled the stick all the way back and held it there - he instead would have been very careful to pull the stick back only just enough to ascend safely.

The airline industry may think normal law is a feature. I consider it an abomination

You either give the human full control, or cut their control entirely. You DO NOT give them partially limited control. That only encourages exaggerated inputs.

Re: What really happened aboard Air France 447

#73

Post by antoinehersen »

sliverstorm wrote: post #43
jarcoal wrote: post #40

Earlier quoted context omitted.

Supposedly they do de-ice themselves, but that obv didn't work properly here.

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

The fact that the heating element was not effective enough was a known fact. Since similar incident of lost of air speed had already happened. Pitot were being replaced with beefier heating elements. It was just not considered a high priority.

Re: What really happened aboard Air France 447

#74

Post by antoinehersen »

sliverstorm wrote: post #43
jarcoal wrote: post #40

Earlier quoted context omitted.

Supposedly they do de-ice themselves, but that obv didn't work properly here.

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

The fact that the heating element was not effective enough was a known fact. Since similar incident of lost of air speed had already happened. Pitot were being replaced with beefier heating elements. It was just not considered a high priority.

Re: What really happened aboard Air France 447

#75

Post by jarek »

jrockway wrote: post #69
sliverstorm wrote: post #43

Earlier quoted context omitted.

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

There is other debris that can clog pitot tubes. Birgenair Flight 301 crashed because some wasps built a nest in a pitot tube during an extended layover: http://en.wikipedia.org/wiki/Birgenair_Flight_301 189 people died. (Also note the failure to react properly to the stall warnings. This comes up again and again.)

I wonder if in a couple of decades we'll look back at pitot tubes and wonder what the hell we were thinking using such a fragile solution.

(Of course, in a couple of decades we'll probably have a much more accurate external method of finding out speed/airspeed.)

Re: What really happened aboard Air France 447

#76

Post by nkurz »

ookblah wrote: post #61

Such a tragedy... Forgive my ignorance, maybe some pilots can shed some light on this. In the article it mentions that even though the plane was flying in "alternate" mode, my understanding is that it still has limits to what inputs can be given. That said, even if autopilot is off, why wouldn't the computer have emergency functions to negate strange situations like this? When would pulling completely back on the sti…

why wouldn't the computer have emergency functions to negate strange situations like this?

I think there are two main reasons. First, one is dealing with a situation where the autopilot has disengaged because it is receiving contradictory input from its sensors. How is the computer to know that a second sensor has not failed, and that its notion of what is normal is not? Failures may tend to cluster. The current technological presumption is that in the event of something unexpected, trust the human over the computer. At the current level of technology, this is still often a good bet.

Second, I think the legal situation encourages having a human be the final point of control. Presume that computer overrode the human, and that due to some low-probability unexpected combination of failures this caused the plane to crash despite the pilot doing "the right thing" as proven by the flight recorder. Then picture the size of the lawsuit against the everyone involved in the building and licensing of the plane. Contrast this with the same situation, but with the pilot responsible and dead in the crash. One may find that there isn't much desire from the manufacturer to change the system to take that final responsibility.

Re: What really happened aboard Air France 447

#77

Post by themonk »

jonnycowboy wrote: post #12
huntero wrote: post #5

It's interesting that First Officer Bonin is able to doom the plane by continuing to hold back on his joystick, even when that action isn't having positive results. Had the other first officer pushed his joystick forward, would the plane begin to dive? I assume that one joystick has precedence over the other... It seems dangerous to have two joysticks, both capable of controlling the plane, that have no physical or s…

Airbus' have priority override button which will allow the pilot not flying (PNF) to take command of the aircraft. In hydraulic or "direct" flight controls, both sticks move at the same rate, you need to be stronger than the other pilot. Normally the autopilot and flight control system would have the authority to override the pilot actions (common on A320 etc.) but not all planes have that feature. In addtion, if the…

Should not one pilot say "I Got Her" and tell other pilot that you do nothing, I will take care of it.

Re: What really happened aboard Air France 447

#78

Post by brc »

citricsquid wrote: post #13
yew wrote: post #8

Earlier quoted context omitted.

The articles says it's audible on the recording. Stall alarms are usually very loud. I can't speak for Air France, but in general aviation the word "stall" (in English) is of global significance. I imagine they thought it was malfunctioning, or simply didn't think about it in the heat of the moment.

They don't explicitly state that it is something you can hear in the recording, I made the assumption that the "blackbox" contain not just an audio recording but a log of the computer system -- what actions it took, which is how they know the co-pilot was pulling back the entire time -- and they're basing it off of that. Although the way they phrase it (reading back through the relevant paragraphs now) with the assum…

There are two recordings - the 'black box' which records all the control inputs, readings, etc. Then there is the cockpit voice recorder, which is a separate recording of the pilots voices (and radio traffic, IIRC).

I don't know if the two separate items are in the same 'box' or if they are physically separate, but there are definitely two different things being recorded.

Re: What really happened aboard Air France 447

#79

Post by anrope »

donaldc wrote: post #20

Having multiple joysticks that can be in different positions at the same time and yet all simultaneously affect the flight of the Airbus is a serious design flaw.

Up to this point, the situation was playing out in a sadly too common case of pilot error, pilot inexperience, which makes up a huge portion of aviation accidents.

When I read about the dual input averaging, I literally exclaimed "what?!". I can't believe that, for all the strict standards that flight control software must meet, nobody called this out as a dangerous idea?

Re: What really happened aboard Air France 447

#80

Post by jrockway »

jarek wrote: post #75
jrockway wrote: post #69

Earlier quoted context omitted.

There is other debris that can clog pitot tubes. Birgenair Flight 301 crashed because some wasps built a nest in a pitot tube during an extended layover: http://en.wikipedia.org/wiki/Birgenair_Flight_301 189 people died. (Also note the failure to react properly to the stall warnings. This comes up again and again.)

I wonder if in a couple of decades we'll look back at pitot tubes and wonder what the hell we were thinking using such a fragile solution. (Of course, in a couple of decades we'll probably have a much more accurate external method of finding out speed/airspeed.)

It's hard to measure how fast you're going through the air without being able to sample the air. Pitot tubes are just the tubes that bring the air to the inside of the plane to be sampled; nothing more.
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