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Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

reuters.com

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Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#151
post #113

Earlier quoted context omitted.

Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. Mistakes happen. Part of aviation safety is preventing that from becoming fatal.

>Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. That's not what the accident report concludes. There's a clearly audible "dual input" alarm to prevent dual inputs. Dual control inputs only occurred for brief moments during the AF flight.

It's quite clear that wasn't sufficient. "Brief moments" during critical points in an emergency can matter enormously. From the recorder transcript:

> 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. The nose remains high.

02:13:40 (Robert) Remonte... remonte... remonte... remonte...

Climb... climb... climb... climb...

02:13:40 (Bonin) Mais je suis à fond à cabrer depuis tout à l'heure!

But I've had the stick back the whole time!

02:13:42 (Captain) Non, non, non... Ne remonte pas... non, non.

No, no, no... Don't climb... no, no.

02:13:43 (Robert) Alors descends... Alors, donne-moi les commandes... À moi les commandes!

Descend, then... Give me the controls... Give me the controls!

> Bonin yields the controls, and Robert finally puts the nose down. The plane begins to regain speed. But it is still descending at a precipitous angle. As they near 2000 feet, the aircraft's sensors detect the fast-approaching surface and trigger a new alarm. There is no time left to build up speed by pushing the plane's nose forward into a dive. At any rate, without warning his colleagues, Bonin once again takes back the controls and pulls his side stick all the way back.

The crash occurred less than a minute later.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#152

Earlier quoted context omitted.

The commenter appears to have a vested interest in making Airbus look bad, otherwise the comment cannot be logically understood. Is there a case where the averaging of inputs has been proved catastrophic?

Air France 447

Not according to the official accident report. This is a meme spread by an article in Popular Mechanics that came out long before the official report.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#153
post #113

Earlier quoted context omitted.

>Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. That's not what the accident report concludes. There's a clearly audible "dual input" alarm to prevent dual inputs. Dual control inputs only occurred for brief moments during the AF flight.

It's quite clear that wasn't sufficient. "Brief moments" during critical points in an emergency can matter enormously. From the recorder transcript: > 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. The nose remains high. 02:13:40 (…

Check the official accident report and the associated transcript. You appear to be copy/pasting from an old Popular Mechanics article.

https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp09060...

https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.01...

See in particular 2 h 13 min 39,7 and 2 h 13 min 40,6. Both of the pilots at the controls thought that they needed to climb. The captain realizes the mistake, but he's not at the controls, so linked sticks would have made zero difference to his perception of the situation. The accident report concludes that the stall was probably unrecoverable by this point anyway.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#154
post #153

Earlier quoted context omitted.

It's quite clear that wasn't sufficient. "Brief moments" during critical points in an emergency can matter enormously. From the recorder transcript: > 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. The nose remains high. 02:13:40 (…

Check the official accident report and the associated transcript. You appear to be copy/pasting from an old Popular Mechanics article. https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp09060... https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.01... See in particular 2 h 13 min 39,7 and 2 h 13 min 40,6. Both of the pilots at the controls thought that they needed to climb. The captain realizes the mistake…

The section I'm citing is right there on page 31 of your second link. See 2 h 13 min 39,7. More dual input at 2 h 14 min 03,2. Crash at 2 h 14 min 28,4.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#155
post #150

The previous flight had exactly the same issue. This is what that pilot wrote in the logs; After parking, the PIC informed the engineer about the aircraft problem and entered IAS (Indicated Air Speed) and ALT (altitude) Disagree and FEEL DIFF PRESS (Feel Differential Pressure) light problem on the Aircraft Flight Maintenance Log (AFML). The PIC also reported the flight condition through the electronic reporting syste…

I haven't checked but I'd bet STS is speed trim system (Aka Mach trim). Interesting that he came up with a reasonable mental model of what was wrong even though Boeing hadn't given them any details.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#156

Best book I've ever read on the root cause ("tight coupling") of accidents: https://en.wikipedia.org/wiki/Normal_Accidents From its Wikipedia entry: >"Normal Accidents: Living with High-Risk Technologies" is a 1984 book by Yale sociologist Charles Perrow, which provides a detailed analysis of complex systems from a sociological perspective. It was the first to "propose a framework for characterizing complex technolog…

I think this perspective on accidents needs far more emphasis. Many accidents are unavoidable and not the result of some person failing to do some thing. The world isn't a story, people don't have much agency, and events do not happen because people want them to. These "narrative explanations" are mythological just-so stories that attribute the complex interaction of systems to individuals, organizations, etc. in nai…

Do you feel this way about repeat occurrences? Is this an appeal to the reader's sense of fate/destiny?

I work in telecom. When a aReallyBadThing happens, a post-mortem has to be compiled, and steps are taken to ensure that aReallyBadThing doesn't happen again. There are unavoidable perils in telecom, like backhoe operators, weather, train derailments, and malicious actors. However, there are events which do not repeat because people figure out that a software/firmware package is coded to do something wrong, a component fails under certain conditions, an operator does something that they shouldn't, or maintenance isn't done correctly or on time.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#157
post #153

Earlier quoted context omitted.

Check the official accident report and the associated transcript. You appear to be copy/pasting from an old Popular Mechanics article. https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp09060... https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.01... See in particular 2 h 13 min 39,7 and 2 h 13 min 40,6. Both of the pilots at the controls thought that they needed to climb. The captain realizes the mistake…

The section I'm citing is right there on page 31 of your second link. See 2 h 13 min 39,7. More dual input at 2 h 14 min 03,2. Crash at 2 h 14 min 28,4.

That is the point where both pilots at the controls still think that they need to climb. The captain, who realizes the mistake, is not at the controls, so whether or not the side sticks were linked would have made no difference to his perception of the situation.

The official report does not identify the side sticks as a factor in the accident.

If you think you can do a better job of identifying the cause of the accident than the professionals who investigated it, you should explain clearly why.

With regard to dual input, it's clear from the transcript that the pilots noticed the dual input alarms.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#159
post #36

Earlier quoted context omitted.

> In Boeing airplanes, the movement of the two yokes is synchronized. So in case of two equally strong and equally determined pilots you still get averaging of opposing control inputs.

No, the failure mode is not two pilots consciously fighting against each other. The failure mode is two pilots who are UNAWARE they are commanding contradicting inputs. Airbus negligently averages these inputs. This is legacy tech debt because the physical design didn’t leave room to link the two controls. Now they are stuck because they feel they can’t change and have some planes that (dangerously) average the input…

> Airbus negligently averages these inputs.

On an Airbus, in case of dual input the pilots get a voice alarm and a warning lights up right in front of them.

Also the stick has a switch to take priority, in case the other pilot continues to give dual input.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#160

Best book I've ever read on the root cause ("tight coupling") of accidents: https://en.wikipedia.org/wiki/Normal_Accidents From its Wikipedia entry: >"Normal Accidents: Living with High-Risk Technologies" is a 1984 book by Yale sociologist Charles Perrow, which provides a detailed analysis of complex systems from a sociological perspective. It was the first to "propose a framework for characterizing complex technolog…

See also, The Field Guide to Understanding Human Error by Sidney Dekker.
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