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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

#41

Post by wereHamster »

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).

Note that AoA and the angle of the airframe body (relative to the horizon) may not be the same. Even if the airframe is pointing downwards (below the horizon) or really high up doesn't mean the wings have a sufficient AoA to generate lift.

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

#42

Post by matt4077 »

CyberFonic wrote: post #10

One of the factors that has been quickly glossed over is the low level of experience of some of the pilots in both the Indonesian and Ethopian accidents. In the USA, due to much higher levels of experience pilots have been correcting for the MCAS actions effectively and complaining about it to NASA (in order to avoid being branded as whistle-blowers by their airlines).

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.

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

#43

Post by philpem »

neuronic wrote: post #32
piquadrat wrote: post #27

Earlier quoted context omitted.

> Same when two pilots give different instructions. That's only true for Airbus (and probably contributed to the loss of Air France 447, https://en.wikipedia.org/wiki/Air_France_Flight_447 ). In Boeing airplanes, the movement of the two yokes is synchronized.

> 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.

If they're mechanically linked, the captain would at least feel the first officer countering their inputs -- giving a prompt that they need to communicate their intentions more clearly!

I'll defer to a pilot to say whether they are mechanically linked -- it sounds like they are on Boeing aircraft but possibly not on Airbus?

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

#44

Post by ody4242 »

pishpash wrote: post #34
dannyw wrote: post #17

Earlier quoted context omitted.

Because MCAS never assumes the input sensors could be faulty.

Sounds like a shitty and incompetent design. Grounding the plane was the right decision.

Totally agree.

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

#45

Post by rational_indian »

wereHamster wrote: post #41
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).

Note that AoA and the angle of the airframe body (relative to the horizon) may not be the same. Even if the airframe is pointing downwards (below the horizon) or really high up doesn't mean the wings have a sufficient AoA to generate lift.

Can't the IMU sense if you are generating lift (or not)?

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

#46

Post by rational_indian »

Tepix wrote: post #37
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).

Gyroscopes by themselves can not sense the orientation of a body moving through three dimensions.

Why not? I thought this is precisely what gyroscopes did.

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

#48

Post by ekianjo »

TheSpiceIsLife wrote: post #40
ahoka wrote: post #25

Earlier quoted context omitted.

If anyone wonders this is how it looks like: https://youtu.be/-X01uY0bJs0?t=48

And sounds ? The trim wheels moving also makes a sound?

From the videos I have seen in cockpit it does seem to make a sound as it rolls.

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

#49

Post by WalterBright »

TheSpiceIsLife wrote: post #40
ahoka wrote: post #25

Earlier quoted context omitted.

If anyone wonders this is how it looks like: https://youtu.be/-X01uY0bJs0?t=48

And sounds ? The trim wheels moving also makes a sound?

Yes. The ratcheting sound is deliberate, so the pilots don't need to see the wheels spin to know the trim is running. Also note that there's a white stripe on the wheel so it's easy to see it is running.

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

#50

Post by WalterBright »

losvedir wrote: post #33
dukoid wrote: post #30

Earlier quoted context omitted.

To my understanding, the trim wheels are moving frequently for small adjustments -- and it's possible to switch the wheel movement off if this becomes too annoying.

Also not a pilot but I don't think you can switch the wheel off. You can, however, disable the electric motors that spin the wheel, which is what the checklist for runaway trim tells you to do, and what was supposed to have been done here.

The spinning wheels are directly connected to the stab trim via cables. If the trim motors fail, the pilots can turn those wheels by hand (there's a folding crank on them) to manually adjust the trim.
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