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The crash of Air France flight 447 (2021)

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

#221

Post by turnsout »

logifail wrote: post #170
turnsout wrote: post #165

Earlier quoted context omitted.

In the case of 447, they were warned about a stall, repeatedly.

> In the case of 447, they were warned about a stall, repeatedly It's not that simple. When the aircraft's computer considered the inputs invalid, the stall warning was muted . When they decreased the pitch (would be essential to recover from the stall!) the stall warning sounded . "The angle of attack had then reached 40°, and the aircraft had descended to 35,000 feet (10,668 m) with the engines running at almost 10…

Yes, all of that is true, but the stall warning did sound almost immediately once autopilot disengaged—the crew was just too freaked out to know what to do with the warning.

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

#222

Post by pazimzadeh »

jcalvinowens wrote: post #135
pazimzadeh wrote: post #120

Earlier quoted context omitted.

> During flight 447’s plunge toward the sea, the flight directors disappeared every time the forward airspeed dropped below 60 knots. This was because an airspeed below 60 knots while in flight is so anomalous that the computers are programmed to reject such a reading as false. Furthermore, at an angle of attack threshold which corresponded quite closely to 60 knots, the stall warning would cease for exactly the same…

Yes. That's the only place it's mentioned, IMHO it is central to the whole thing.

I agree that they buried the lede. You might have stopped reading before it. I'm usually completionist, I'd rather skim than miss a big chunk of text.

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

#223

Post by mplanchard »

rich_sasha wrote: post #182

As someone who follows aviation and flew the Flight Simulator quite a bit when young, I don't quite understand how it all happened. The mechanics are clear, but aren't pilots trained _ad nauseam_ precisely against this kind of events? It read like this was two panicking guys shouting at each other. By contrast, listening to the recording of the Hudson River landing, it was stunning just how eerily calm the pilots was…

My understanding is that this incident is one of the reasons why pilots are now trained ad-nauseum for such events, but that training for things like high-altitude stalls was not the norm previously

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

#224

Post by Mawr »

flyinghamster wrote: post #138
whinenot wrote: post #132

Earlier quoted context omitted.

Sully's 'Miracle on the Hudson' is (largely?) attributed to his skill as a glider pilot.[0] [0] https://en.wikipedia.org/wiki/US_Airways_Flight_1549

Also, Air Canada Flight 143, the Gimli Glider. https://en.wikipedia.org/wiki/Gimli_Glider

Also, TACA Flight 110 - https://en.wikipedia.org/wiki/TACA_Flight_110

Gliding skill highlight: https://youtu.be/H5UUr9RXfTY?t=1312

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

#225

Post by Mawr »

ericbarrett wrote: post #164
cccbbbaaa wrote: post #160

Earlier quoted context omitted.

There is an audible “dual input”, which was triggered on this flight.

Interesting, thanks! I’ve read a few accounts of this crash and never picked up on that.

Note that hearing is one of the first things that stop working when a human is under stress [1].

[1]: https://youtu.be/Dl-Fl66Jfao?t=1674

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

#226

Post by thatswrong0 »

dreamcompiler wrote: post #220
thatswrong0 wrote: post #136

Earlier quoted context omitted.

> Air speed could be extrapolated from previous air speed and inferred from ground speed, engine thrust, and known weather. I think this is probably the main sticking point. I don't think you can do this accurately without some direct measurement. If the plane thinks its air speed is fine but it's actually approaching its stall speed because it guessed its airspeed incorrectly, that'd be really bad.

Stall is determined solely by angle-of-attack, which TFA points out. Airspeed doesn't factor in to whether the computer thinks it's about to stall. Here's the relevant sentence: "Crews involved in similar incidents reported that they assumed the brief stall warnings were generated by the erroneous airspeed readings, a not unreasonable interpretation which breaks down only when one learns that the stall warning calcul…

Except that AoA vanes are not perfect and are speed sensitive.

> From the A330/A340 FCTM (Flight Crew Training Manual) section 8.110.4:

> The ADRs provide a number of outputs to many systems and a blockage of the pitot and/or static systems may also lead to the following:

> …

> Alpha floor activation (because AOA outputs from the sensors are corrected by speed inputs)

From what I can tell, these systems are all pretty complicated and have undergone significant real world testing to ensure that the expected protections actually work, assuming the flight computer is receiving accurate data. Which is precisely why they have Alternate Laws - if they can’t guarantee that these protections can work, then they won’t.

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

#227

Post by _cenw »

matheusmoreira wrote: post #179
brazzy wrote: post #93

Earlier quoted context omitted.

>It's tempting to blame the inexperienced first officers, their training, or the CRM failures on this flight, but the blame for this crash has to land squarely on the atrociously bad UX of the Airbus cockpit. Hard disagree. No matter how bad the UX, there just isn't any conceivable situation where Bonin's pulling up the rudder for minutes on end wasn't suicidally dangerous, or made any sense at all.

I have to agree with you. Even non-pilots who play video games have enough common sense not to do that: they notice that when they climb sharply they lose speed and eventually stall and that when they dive back down it gives them their speed back and allows them to recover. His inexperience cannot be denied. Must have been terrifying for the pilot when the plane's safeties and automation suddenly disengaged. Uncertai…

> Even non-pilots who play video games have enough common sense not to do that

But in video games you likely have good visibility and an external view. AF447 did neither. The human ear is actually really terrible from telling a pitch up stall condition from a pitch down overspeed one, lacking visual references.[1]

[1]: https://en.wikipedia.org/wiki/Sensory_illusions_in_aviation (somatogravic)

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

#228

Post by _cenw »

Tronno wrote: post #98

In post-mortems involving pilot error, what strikes me is that airliner cockpit design sounds so convoluted, unintuitive, and just plain bad . The burden of disentangling this bad design is always placed on the pilots - through extensive training and rote memorization - which inevitably fails under stress. In this particular example, consider: - the opposing pilot inputs being signaled only by a pair of little green…

The ECAM is where one needs to look and start debugging. The pilots here didn't really do that. Audible warnings are only really used if they're extremely time sensitive (GPWS, Stalling, Dual Input).

There is no "cacophony of warning lights". The overhead panel is a designed to have all buttons not be illuminated, so if you're checking what's wrong, you can immediately tell by there being a light indicator on it. Here this was limited to two ADIRs indicating FAULT. Nothing more.

I think this might help: https://www.youtube.com/watch?v=0a06A78iXnQ

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

#229

Post by _cenw »

batiste wrote: post #197
Tronno wrote: post #98

In post-mortems involving pilot error, what strikes me is that airliner cockpit design sounds so convoluted, unintuitive, and just plain bad . The burden of disentangling this bad design is always placed on the pilots - through extensive training and rote memorization - which inevitably fails under stress. In this particular example, consider: - the opposing pilot inputs being signaled only by a pair of little green…

There should be a calm AI voice stating what they should be doing based on some heuristics. Based on angle of attack, engine power and the last recorded reliable speed, I feel a simple system should be able to make projection of the current speed and throw some warning when pilot input are becoming real stupid.

It exists, and it'a called the ECAM. Last recorded reliable airspeed is usually never used, because an upset condition can change it very drastically fast. These systems help resolve upsets way more often then they miss and these engineers did their homework.

Hearing is also the first sense to go when people panic; this flight had the stall warning blaring for over a minute straight and it didn't occur to the pilots that they may not be in overspeed, but stall.

(It is of course not perfect, sometimes conditions become dependent on one another and their order is not always great - see this simulated simultaneous engine fire and engine failure right after takeoff, where flying on your burning engine might be better than turning into a 1000ft glider: https://www.youtube.com/watch?v=ZRbLLO385_c)

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

#230

Post by whycome »

braza wrote: post #143
whycome wrote: post #42

Earlier quoted context omitted.

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

Fine it’s a strong word in that context; the likelihood of the Captain and the Flying Pilot 2 make the same inputs as the FP1 it’s way reduced. The Captain also lost the screen disagreement that happened.

I wasn’t questioning your use of the term. It was my first time encountering it and was just trying to gather the context of your use (and understand a new word). I think the usage there was fine
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