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AF447

Peter wrote:

Why would they do that? To protect a “national” company?

Two of them. Airbus and Air France.

johnh wrote:

After that and the Concorde book, not to mention the recent total CRM breakdown incidents, it would be a brave person who would set foot on AF.

Indeed. AF has been on my no-fly list for many years, particularly however after the Concorde crash. And that particular one gets worse every time someone opens up about it.

One thing which struck me yet again in the Concorde book was the fact that in France the justice systems have such a high leverage on the results of TSB inquiries. With the case of Concorde as well as in several others, it was the justice system which would come up with explanations of what caused the crash before the TSB even got to work.

Personally I am extremely skeptical against anything the BEA produces when French interests are involved, in particular where Airbus products of any kind are concerned. This also involves reports concerning airplanes operated by other companies than AF.

To make myself clear: I regard Airbusses as extremely safe and ultra-reliable airplanes and I normally have no qualms flying on them, while I have huge reservations towards other models (737 Max comes to mind, which is no my no-fly list with the rest of the 737 fleet on the “avoid” list). What happened in the case of AF447 was no different than the blunders seen on the Concorde crash as well as the A340 in Toronto and several more.

Last Edited by Mooney_Driver at 30 Jan 06:44
LSZH(work) LSZF (GA base), Switzerland

Mooney_Driver wrote:

AF has been on my no-fly list for many years, particularly however after the Concorde crash. And that particular one gets worse every time someone opens up about it.

I was not aware of any controversy on the Concorde crash – do you have some reading you can recommend?

Fly more.
LSGY, Switzerland

Check the books to read thread

Administrator
Shoreham EGKA, United Kingdom

maxbc wrote:

From my understanding it’s quite the opposite. Alternate law REMOVES some parts of the envelope protection and allows for more movement than normal law. There’s no reason that a pitch down would not have recovered the plane (provided it was aerodynamically recoverable of course, which is not a given in a fully developed stall).

According to the book, Alternate Law gives you something like traditional roll control (albeit with a limited max rate, 30 degrees/second as opposed to the usual 15 degrees/second in Normal Law) but pitch control remains in a ‘g-demand’ state where a centred stick demands 1g and a stalled Airbus will remain nose up (applying back trim to remain there) because while stalled it is experiencing……1g.

I forget the fine detail, but he seemed to be saying that while forward stick would have been a good thing there was every chance that because of the combination of the extreme angle of attack and the position of the trim such an input would never (or at least, not quickly enough) have encouraged the computer to command full nose-down elevator deflection.

The killer aspect of the design in Alternate Law appears to be removing the alpha protections but at the same time keeping pitch control in a g-demand mode where the trim does it’s own thing.

Last Edited by Graham at 30 Jan 11:10
EGLM & EGTN

Reading about the bizzare software behaviour in the AF447 avionics reminds me of this old cartoon

I’ve been doing software for ~ 45 years and work on the principle that if I can’t understand something then nobody will be able to use it, because

  • I can’t document it, and then definitely nobody can use it
  • some % of customers will be even thicker than I am

It is very obvious that the Airbus systems design committee was pretty well divorced from what the customers could possibly understand. Even if it was all documented (may have been internally but certainly not externally) no type rating school could teach it and most airline pilots would not be able to absorb it and remember it for many years later.

Boeing have gone for FBW too recently but they kept stuff so “normal” pilots can understand it.

The AF447 pilots were obviously basically button pushers, which didn’t help.

Administrator
Shoreham EGKA, United Kingdom

Back on Pprune whenever several Bus pilots get into a discussion about the “laws”, there are never two of them who agree. Discussions go like…

Pilot 1: Alternate Law engages when … and then … does …
Pilot 2: No, it won’t engage until … and then … only does … if you do …
Pilot 3: It would already be engaged because … but it doesn’t affect … unless …
…etc etc etc.

That said, even button pushers are supposed to know what the buttons do. The problem, however you dress it up, is that the PF was totally clueless about how planes fly. Sure, the Bus’s idiosyncrasies don’t help, but a stall is a stall. And anyway it didn’t stall until he forced it to, by holding the stick full back and presumably counting on the FBW magic to make everything work.

Boeing isn’t exempt either – for the example the bizarre “feature” of the autothrottle that was partly responsible for the Asiana crash at SFO, though once again if the pilots had actually known how to fly a plane it wouldn’t have happened.

LFMD, France

The problem with airliner forums is that people generally generalise (few people are willing to type a lot of text – even if they know it) but actually every Airbus works slightly differently.

Those forums (I was on proon also; got kicked off when EuroGA started in 2012 ) also have an awful lot of pretenders. There is a million simmers out there who hang out on airline forums pretending to be pilots. Some write such amazingly good stuff that only an admin will know who is probably a joker, and on any forum which carries adverts you want maximum participation regardless of content…

Nobody is quite exempt from cockups which is prob100 why Airbus have not been gloating over the 737MAX business They will have had loads of lucky scrapes, most of which have been quietly fixed. It just so happened that the MAX got sold to some exceptionally bad 3rd World operators and they did some “out of envelope flight testing”. Airbus also benefits from what one might call a “friendly ecosystem” (others might call it a “high level of govt/industry/airline/AIB integration” but of course I never said that) whereas Boeing is the Great Satan himself, fighting wars everywhere and being generally despised by the 3rd World, and by champagne socialists in the 1st World

But of course this will never be on the BBC

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

It is very obvious that the Airbus systems design committee was pretty well divorced from what the customers could possibly understand.

I’m trying to imagine the meeting:

“So in Normal Law, which is 99.9% of the time, it is like a video game. The control stick commands performance and the computer works out what to do with the control surfaces to make it happen. If you let go of the stick, it carries on pointing exactly where you left it – the computer fiddles with the control surfaces to make it so – and it also smooths out bumps and gusts as they happen. We also have these envelope protections, so you cannot roll too fast, cannot exceed a certain angle or bank, nor can you get the AoA high enough to stall.”

“This is great. Very safe and also makes accurate hand-flying incredibly easy. What happens when the computer doesn’t have the data it needs to do that?”

“Then in Alternate Law, when the system loses some data, we scrap all the protections and in some ways the controls become more like a traditional aircraft, but not completely – the pilot doesn’t get the ability to directly move the control surfaces, at least not the elevator, and we keep in some computer control of the trim so that it doesn’t follow the natural tendencies that out-of-shape aircraft tend to follow.

“Are you actually insane? If you revert to manual, you revert to manual. You have to make it give direct control of the surfaces back to the pilot and allow the well-understood laws of aerodynamics to act on the aircraft in a way that the pilots will find predictable based on how we all know an aircraft behaves.”

“You are thinking about it incorrectly. You are not properly applying our design philosophy.”

EGLM & EGTN

Peter wrote:

Nobody is quite exempt from cockups which is prob100 why Airbus have not been gloating over the 737MAX business

They have not much reason as the A330 had a similar problem a while ago. QF72 and a 2nd incident were pretty scary. Thankfully it happened at high altitude and was recovered, not without people being injured, but it was not much better than the Max disaster. What people woke up to and (rightly) gloated or were horrified about was the general knowledge, that a 737 can’t be trimmed by hand under certain conditions without some rather hairy “load relief” procedures.



johnh wrote:

The problem, however you dress it up, is that the PF was totally clueless about how planes fly.

That was the basis for it and not only him, but all 3 of them. Of course the fact that AF and Airbus never bothered to think about what happens to the system if they have unreliable airspeed at high altitude was a massive contributing factor. The procedure called for pitch and power values which are find low level but cause massive upsets up high.

The other bit of course is that with all sorts of FDM (flight data monitoring) in place, nobody dares to fly the planes by hand ever. Even less so would they do some seat of the pants flying in Alternate Law during training, not even in the sim, where any alternate law is regarded as abnormal operation. In short, Alternate law will remove protections and as a consequence, the plane needs to be flown like, well, a plane. Stuff like pulling the stick all the way into Alpha Floor does not work under this regime. And of that they were not aware either. AF really has a lot to answer for. And Airbus finally realized that pilots need to fly the darn thing in order to prevent such stuff from happening.

Of course stuff like that does not only happen on Airbusses. The Asiana 777 and the Turkish 737 who both thought their AT systems were holding their airspeed and flying their perfectly servicable airplanes into the ground show that you can muck up Boeings as well. Even if it does not have a killer-Autotrim system working against you.

LSZH(work) LSZF (GA base), Switzerland
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