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Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

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Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#41

Post by CaptainZapp »

ams6110 wrote: post #40
CaptainZapp wrote: post #36

Earlier quoted context omitted.

What I think they're absolutely and criminally guilty of is to not ground the plane after the first crash. Instead they wasted time and resources to smear the airline and the pilots. And that's inexcusable.

So any time there's a crash now, we're going to ground the worldwide fleet of that model of aircraft until we have a final report on the cause?

If it happens to a brand new plane? I'd say: Yes; that's reasonable.

At least until the cause is known.

Edit : Some clarification

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#42

Post by 2sk21 »

yg6ht5 wrote: post #39
mhandley wrote: post #10

Earlier quoted context omitted.

Because if you did that, you'd have to alert the pilots when the AoA sensors disagree and MCAS has been disabled. And you can't do that without training them on what that means, notably how the plane will now fly differently with what you might call "relaxed stability" at high angles of attack. And Boeing really really wanted to avoid retraining of pilots because apparently they had a contract with SouthWest that wou…

$1M sounds like pocket change after all that has happened.

Really! This looks like a case of local optimization.

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#43

Post by bredren »

yg6ht5 wrote: post #39
mhandley wrote: post #10

Earlier quoted context omitted.

Because if you did that, you'd have to alert the pilots when the AoA sensors disagree and MCAS has been disabled. And you can't do that without training them on what that means, notably how the plane will now fly differently with what you might call "relaxed stability" at high angles of attack. And Boeing really really wanted to avoid retraining of pilots because apparently they had a contract with SouthWest that wou…

$1M sounds like pocket change after all that has happened.

Market cap loss since crash of flight 303 is $27 billion. https://ycharts.com/companies/BA/market_cap

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#44

Post by [deleted] »

ams6110 wrote: post #40
CaptainZapp wrote: post #36

Earlier quoted context omitted.

What I think they're absolutely and criminally guilty of is to not ground the plane after the first crash. Instead they wasted time and resources to smear the airline and the pilots. And that's inexcusable.

So any time there's a crash now, we're going to ground the worldwide fleet of that model of aircraft until we have a final report on the cause?

[deleted]

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#45

Post by 7952 »

zaxomi wrote: post #22
sergiosgc wrote: post #14

Earlier quoted context omitted.

Worse. Why don't they do it with three sensors and a voting system? By using two sensors, when they disagree, MCAS will have to be disabled. It seems the plane is unstable without MCAS, due to the forward positioning of the engines, requiring specific training and abilities from pilots.

No, it is not unstable without MCAS. MCAS is only designed to change the trim if the airplane is hand flown in flaps-retracted, low-speed, nose-up flight. This is something almost everyone is missing: A normal flight should not encounter this.

I agree that normal flight should not encounter these conditions. Although, does it actually check for air speed before activating MCAS?

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#46

Post by chopin »

dba7dba wrote: post #23
sokoloff wrote: post #20

Earlier quoted context omitted.

40 seconds is an eternity to accomplish the memory items on runaway stab trim non-normal checklist. It’s literally “control column - hold firmly” (already a given, since MCAS only affects manual flight and the increased back pressure required is the cue that something is amiss), “autopilot and autothrottle - disengage” (click-click, click-click), (if runaway continues) “stab trim cutout switches - cutout (both)”, (if…

Main stream media made it sound like 40 seconds is way too short of a time to troubleshoot the issue. But now that you state it that way, I gotta agree with you it's not Only Boeings fault. Sure they are big significant part of the issue. But not the only part.

40s is only enough if you know what to do right away from the start of the situation. A failing sensor may confront the pilots with many (unrelated to a trim runaway) warnings (like unreliable airspeed, stick shaker, alt disagree). That has been the case for Lion Air at least.

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#47

Post by marijnz »

yg6ht5 wrote: post #39
mhandley wrote: post #10

Earlier quoted context omitted.

Because if you did that, you'd have to alert the pilots when the AoA sensors disagree and MCAS has been disabled. And you can't do that without training them on what that means, notably how the plane will now fly differently with what you might call "relaxed stability" at high angles of attack. And Boeing really really wanted to avoid retraining of pilots because apparently they had a contract with SouthWest that wou…

$1M sounds like pocket change after all that has happened.

Exactly, -after-.

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#48

Post by sheeshkebab »

As an airplane passenger that’s mostly amazed at butt’s ability to fly 10km up in the air while I’m enjoying peanuts and listening to music, I’m going say it’s a good thing that an extra MCASH, or whatever it is, is a good thing.

And I know what I’m talking about.

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#49

Post by ams6110 »

7952 wrote: post #45
zaxomi wrote: post #22

Earlier quoted context omitted.

No, it is not unstable without MCAS. MCAS is only designed to change the trim if the airplane is hand flown in flaps-retracted, low-speed, nose-up flight. This is something almost everyone is missing: A normal flight should not encounter this.

I agree that normal flight should not encounter these conditions. Although, does it actually check for air speed before activating MCAS?

As I understand it, no. But airspeed, actually Mach, is an input to the calculation of how much nose down to apply. I.e. the higher the speed, the less trim change is needed to achieve the desired effect.

Re: Preliminary conclusion MCAS misfired in Ethiopian's 737 max crash

#50

Post by chopin »

VBprogrammer wrote: post #37
cm2187 wrote: post #29

Earlier quoted context omitted.

I am not talking about these specific pilots about which I know nothing. But not every single commercial pilot is passionate about his job. For some it is just a day job and until they are asked to do a particular training, may not even be aware that MCAS even exists. Think professional developers (granted the bar is infinitely lower). You would assume no one would introduce a SQL injection vulnerability in new code…

That would be a huge failing on behalf of the airline. There was an emergency airworthiness directive which should have brought this to the attention to all pilots of these aircraft even if they somehow missed all of the other coverage.

But this directive said "handle like a trim runaway". However MCAS may present itself differently from a trim runaway when failing. Furthermore a failing sensor may activate the stick shaker and the last thing a pilot is trained to do is pull up in such a situation. So you might get:

- unreliable airspeed warning

- stick shaker (=stall is imminent)

So you don't know your airspeed (otherwise you can conclude you're safe for your current pitch and vertical speed) and a stall warning. The last thing you do is to look for horizontal trim.

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