The crash of Air France flight 447 (2021) • Hacker News Board

Re: The crash of Air France flight 447 (2021)

#41

Post by _cenw » Fri, Aug 11, 2023, 4:17 PM UTC

markus_zhang wrote: post #24

Does anyone think lack of sleep is the major contributor of this event, or the invalidation of all three speed sensors? I think we do test pilots for alcohol and drug before a flight, but can we also test them for reaction and a couple of hazard scenarios? Do you think it is too much? About the sensors, is there any inexpensive way to increase the heat or anything to prevent it from happening again?

The main takeaway is that somehow the pilot who kept holding the stick back was under the assumption that the correct response to a stall in cruise was to apply full TOGA thrust, not to recover from aerodynamic stall. This is likely because in thicker air, close to the ground, this actually works. It also does not help that a mid-cruise stall is extremely unlikely to happen in normal operation, since normal law[1] prevents keeping the angle of attack this high. They also hit an edge case so unforseen, you could consider it a design fault. Their speed was too low for the stall warning to sound, so every time they moved to recover the plane the stall warning returned, and every time they pulled it back into the stall it disappeared (with the airplane assuming the inputs must be wrong).

I really recommend watching a breakdown of the instruments during the incident.[2] Things happen fast.

[1]: https://docs.flybywiresim.com/pilots-corner/advanced-guides/...

[2]: https://www.youtube.com/watch?v=0a06A78iXnQ

Re: The crash of Air France flight 447 (2021)

#42

Post by whycome » Fri, Aug 11, 2023, 4:17 PM UTC

braza wrote: post #38

Since I started to study airline accidents, so far this one of the most fascinating in terms of human aspects and Crew Resource Management. The fact that the whole situation deteriorated less than 10 minutes after the Captain went to rest, it’s one of the biggest contrafactuals about this case.

> contrafactuals

As in “if the captain didn’t go to sleep, they’d have been fine”?

Re: The crash of Air France flight 447 (2021)

#43

Post by oatmeal1 » Fri, Aug 11, 2023, 4:18 PM UTC

HN seriously just needs to watch Air Disasters. Goes into the details of the investigation, financial consequences, and changes in regulations after disasters.

Re: The crash of Air France flight 447 (2021)

#44

Post by markus_zhang » Fri, Aug 11, 2023, 4:19 PM UTC

_cenw wrote: post #41

markus_zhang wrote: post #24

Does anyone think lack of sleep is the major contributor of this event, or the invalidation of all three speed sensors? I think we do test pilots for alcohol and drug before a flight, but can we also test them for reaction and a couple of hazard scenarios? Do you think it is too much? About the sensors, is there any inexpensive way to increase the heat or anything to prevent it from happening again?

The main takeaway is that somehow the pilot who kept holding the stick back was under the assumption that the correct response to a stall in cruise was to apply full TOGA thrust, not to recover from aerodynamic stall. This is likely because in thicker air, close to the ground, this actually works. It also does not help that a mid-cruise stall is extremely unlikely to happen in normal operation, since normal law[1] pr…

Thanks. Looks like a string of unfortunate events thrown altogether in a short period of time.

I hope I'm never in that position...

Re: The crash of Air France flight 447 (2021)

#45

Post by markus_zhang » Fri, Aug 11, 2023, 4:20 PM UTC

Tronno wrote: post #26

markus_zhang wrote: post #24

Does anyone think lack of sleep is the major contributor of this event, or the invalidation of all three speed sensors? I think we do test pilots for alcohol and drug before a flight, but can we also test them for reaction and a couple of hazard scenarios? Do you think it is too much? About the sensors, is there any inexpensive way to increase the heat or anything to prevent it from happening again?

Re your last question, the article states Air France was in the middle of upgrading the pitot tubes across its fleet when the accident happened.

Thanks, that's good to know.

Re: The crash of Air France flight 447 (2021)

#46

Post by psunavy03 » Fri, Aug 11, 2023, 4:20 PM UTC

I fly a desk herding cats, I mean devs, for a living now. But as a Navy-trained aviator, this and the Colgan Air mishap in Buffalo always make me cringe. I can't entirely judge the crew, because the human mind is a strange thing that has ways of rationalizing truly abnormal situations and behavior. That said, an obvious Crew Resource Management failure compounded the issues here.

That said, I believe aerobatics and out-of-control flight training need to be a lot more common in the civilian sector for professional pilots than they are. Awareness of your angle of attack, and knowledge of how an aircraft behaves at high AOA close to (and if possible beyond) stall don't seem to be taught well in the civilian sector, or at least outside the tactical jet community. The idea that a professional pilot can't understand that a deeply stalled aircraft can be nose-up and still have a heinous sink rate is profoundly bothering to me, just like the Colgan Air pilots who couldn't recognize severe wing rock as a sign of a deeply-departed state. Both of these required (if even possible at that point) aggressive nose-down pitch inputs to break the AOA. And even then, the aircraft is going to lose a ridiculous amount of altitude before it gains enough airspeed back to give you enough pitch authority to scoop out of the ensuing dive. Horrible.

It also boggles my mind that Airbus didn't think at first to design an aircraft which avoided the split control problem they had. One person and one person only needs to be in control of the aircraft at all times.

Re: The crash of Air France flight 447 (2021)

#47

Post by sokoloff » Fri, Aug 11, 2023, 4:20 PM UTC

TillE wrote: post #31

jmyeet wrote: post #2

It's kind of amazing how many of these accidents can come down to the pilots forgetting the most basic things. In this case, ultimately, the pilot and the co-pilot were exerting opposite controls. One to pull up, one to push the nose down. In a stall you push the nose down to gain aerodynamic lift. That's like Flying 101. But I guess when you panic, the natural instinct of wanting to pull up kicks in when you're rapi…

Yeah the "insane pilot error" crashes always get me. American 587 is another example where, in response to normal wake turbulence, the pilot mashed the rudder back and forth so hard it broke the stabilizer.

There was a widespread misinterpretation/incorrect belief of the certification rules at the time of that crash.

There is an airspeed, called maneuvering speed (Va), at or below which it should not be possible to use the flight controls to remove parts of the aircraft. (The aircraft should run out of control authority or stall prior to exceeding any load limits [which is well before the removal of parts].) Every student pilot is taught this prior to passing their first knowledge test and checkride.

The problem with that is the certification rules for Va are for a single input, not for a cyclically reversing sequence of inputs (which is what the first officer of AA 587 did).

As the details became clear, this was a big topic of learning for many pilots, including myself. AA 587 was caused by the flight crew, but I don't put it into the "insane pilot error" category.

Re: The crash of Air France flight 447 (2021)

#48

Post by mardifoufs » Fri, Aug 11, 2023, 4:23 PM UTC

nocoiner wrote: post #21

moralestapia wrote: post #15

What an amazing article. I know comments here are meant to be more substantial, but this is truly one of the best written content I've ever come across. My most sincere admiration and thank you notes to the author for putting all of this together in such a great way!

She writes one of these a week, and they’re all very high quality. I highly recommending subscribing. Seeing the new post is always one of the week’s highlights, just like how getting the “Money Stuff” edition is a highlight of every weekday morning (er, early afternoon).

Yeah, and even the older articles hold up very well now that tons of them have been updated. It has been part of my weekly routine for 5 years now to read them, and I've got to say that the medium articles are a huge upgrade over the earlier Imgur galleries.

Re: The crash of Air France flight 447 (2021)

#49

Post by markus_zhang » Fri, Aug 11, 2023, 4:23 PM UTC

mcbutterbunz wrote: post #40

t0mas88 wrote: post #27

Earlier quoted context omitted.

Every six months we go in the simulator and practice all kinds of failures and disasters. But lack of sleep is a real issue. Even more on the US side since rest rules are worse than European. Somehow it doesn't get the attention it deserves.

> But lack of sleep is a real issue. Even more on the US side since rest rules are worse than European. Somehow it doesn't get the attention it deserves. IMO this is almost a cultural issue. We don't prioritize sleep as much as we should and even hold lack of sleep as something to be idolized (i.e. sleep = laziness). How many times do we hear about those CEOs or Founders that wake up super early after only 5 hours of…

A side topic, I'm aghasted to know that preschool and primary schools start at 7:40.

God it's going to be tough for my son who refuses to sleep before 10pm.

Re: The crash of Air France flight 447 (2021)

#50

Post by JackFr » Fri, Aug 11, 2023, 4:24 PM UTC

I got this:

  while (true) {
     try {
        airspeed = getAirspeed();
     } catch (Exception e) {
       log.warn(“”,e);
     }
  }