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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

#111

Post by JorgeGT »

programmer_dude wrote: post #15

What I don't understand whenever I read anything related to the MCAS system is why does it not check if the plane is in a dangerous nose dive using other sensors the plane might have? Does the average plane not have a gyroscope? My sub 500 dollar phone has both a gyroscope and an inertial measurement unit (accelerometer).

Pitch (q) is not the same as angle of attack (alpha). You can detect q with a gyro, but not alpha. I use this helpful graphic with my students: https://i.stack.imgur.com/A62jW.pngyQ.jpg

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

#112

Post by VBprogrammer »

dvdkhlng wrote: post #77
cjbprime wrote: post #2

This appears to answer the question of why, given that there is a "memory item" for dealing with runaway trim that would have helped, it wasn't followed by the crew: > “They didn’t seem to know the trim was moving down,” the third source said. “They thought only about airspeed and altitude. That was the only thing they talked about.” If this is true, not only did the pilots not realize the trim was the cause of the d…

I'm just wondering: it looks like the absolute trim angle is not visible anywhere in the cockpit? The trim wheel takes multiple revolutions to adjust trim between min/max limits, so looking at the wheel itself, you can only every see changes, not values. Unless you notice the change while it happens, you won't have any indication as to the unusual trim angle? Thinking about that I wonder whether there was even a meas…

There is a trim position indication. It's to the left and right of the throttles. It's a critical thing to check before starting the takeoff roll.

You can see it on the copilot's side here by the trim wheel.

http://www.b737.org.uk/images/stabtrim_200.jpg

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

#113

Post by foldr »

ceejayoz wrote: post #110
foldr wrote: post #61

Earlier quoted context omitted.

No, the captain would not, because only one pilot has their hands on the controls in any given instance (with the possible exception of rotation at takeoff).

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.

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

#114

Post by bookofjoe »

rusk wrote: post #67
mjburgess wrote: post #65

Earlier quoted context omitted.

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…

Yes, but, its no excuse for relaxing operational rigor. Those who fail to learn from history are doomed to repeat it. And if you repeatedly ignore the lessons of experience then you are to blame .

"Those who cannot remember the past are condemned to repeat it."—George Santayana (The Life of Reason: Reason in Common Sense. Scribner's, 1905: 284)

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

#115

Post by zcid »

michaelt wrote: post #82
matt4077 wrote: post #42

Earlier quoted context omitted.

How would it even be possible for US pilots to sustainably have „much higher levels of experience“? Do non-US pilots fly only two days a week? Do they all die before age 40? This stereotype of dingy third-world airlines with incompetent, untrained pilots borders on racism. At the very least, one should notice that flying the world’s newest airliner in significant numbers is incompatible with one‘s preconceptions.

Hypothetically, aspiring US pilots could be required to spend years flying cargo, or working abroad, or in the military, or paying $$$$ for training, to rack up the required flight hours to be eligible for US passenger jobs. (I have no idea if this is the case or not - I'm merely saying it's possible)

Typically, it takes at least 2 years for a pilot to earn enough hours to get hired on at a regional airline in the US. Add on several more years of jet experience before you can be qualified to work at a major airline or one of the larger cargo companies like UPS or FedEx.

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

#117

Post by cal5k »

mjburgess wrote: post #65
bookofjoe wrote: post #55

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…

This is the issue I have with the media - moreso than any particular bias, media loves to paint a narrative when, in truth, random events are more likely to blame (though in fairness this is a human flaw borne from the heuristic value of narrative). Accidents happen in complex systems - rather than burning the people involved at the stake, we should recognize the inherent complexity of safety hurtling an aluminum tube full of humans through the air at just below the speed of sound, review the accident in a calm and sober fashion, and make the necessary changes to prevent a similar accident in the future

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

#118

Post by dvdkhlng »

VBprogrammer wrote: post #112
dvdkhlng wrote: post #77

Earlier quoted context omitted.

I'm just wondering: it looks like the absolute trim angle is not visible anywhere in the cockpit? The trim wheel takes multiple revolutions to adjust trim between min/max limits, so looking at the wheel itself, you can only every see changes, not values. Unless you notice the change while it happens, you won't have any indication as to the unusual trim angle? Thinking about that I wonder whether there was even a meas…

There is a trim position indication. It's to the left and right of the throttles. It's a critical thing to check before starting the takeoff roll. You can see it on the copilot's side here by the trim wheel. http://www.b737.org.uk/images/stabtrim_200.jpg

Yes, thinking about that, not having any pilot-visible indication would be quite some point of failure at lift-off.

Still wondering whether MCAS and other automatation systems have a representation of that position indication. I can't currently come up with an idea of how to implement that in an easy, yet error-resilient way. Usually you would initially drive into a reference position, then integrate the motor's actions to arive at an absolute value, but integration would potentially add up subsequent errors, and obviously you can't re-do the referencing step while in the air.

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

#119

Post by VBprogrammer »

dvdkhlng wrote: post #118
VBprogrammer wrote: post #112

Earlier quoted context omitted.

There is a trim position indication. It's to the left and right of the throttles. It's a critical thing to check before starting the takeoff roll. You can see it on the copilot's side here by the trim wheel. http://www.b737.org.uk/images/stabtrim_200.jpg

Yes, thinking about that, not having any pilot-visible indication would be quite some point of failure at lift-off. Still wondering whether MCAS and other automatation systems have a representation of that position indication. I can't currently come up with an idea of how to implement that in an easy, yet error-resilient way. Usually you would initially drive into a reference position, then integrate the motor's acti…

A potentiometer (or something fancier) directly attached to the stabilizer would do it. I'm not sure if they do have one or not. They rate of movement on the stab trim is different depending on the source of the trim change so it's possible they have a PWM controller with some feedback.

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

#120

Post by _archon_ »

LoSboccacc wrote: post #99
zw123456 wrote: post #13

The thing I don't understand about that MCAS system is why it would continue to drive the nose of the plane down even when the pilot is reefing on the stick to pull up. The cruise control in my car automatically disengages when I hit the brakes, it doesn't continue to accelerate to keep the car going 60 while I am jamming on the brakes, in an emergency, I don't have time to find the off switch. Similarly, I would thi…

> why it would continue to drive the nose of the plane down even when the pilot is reefing on the stick to pull up well this other crash was caused by a pilot puling up a plane all the way to its ceiling and stalling it, so there's that, so things can go wrong whether if you do and if you don't allow for easy control overrides. https://en.wikipedia.org/wiki/Air_France_Flight_447#Third_in... the trick seems to find th…

The AF 447 crash is one of the reasons MCAS was created. It's the exact scenario MCAS was designed to prevent: High altitude, high-speed, nose-up stall. This was more likely than the NG and dinosaur generations of 737 due to the engine relocation forward and up (causing a pitch-up moment due to thrust).

AF 447 should never have happened. The copilot crashed the plane, and the pilot and pilot on break had no indication or feedback that he was holding the stick back (crashing the plane by causing a stall). There was no feedback, and the controls deferred to his inputs when the pilot was trying the opposite command (which would have saved the flight). On top of this, the stall warning buzzer was turning off when they were so deep into the stall that the airspeed dropped below a certain threshold, and every time the nose was pitched down and airspeed increased, the buzzer came on again.

Airbus has a controls feedback, stall buzzer parameters, and training problem. 447 should never have gone down.

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