Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

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A346Dude
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by A346Dude »

I'm a little surprised by the number of pilots willing to defend a system as poorly thought out as MCAS. With a single point failure, it will actively yet subtly try to kill you, while providing multiple, possibly conflicting warnings. It has a foreseeable and severe failure mode that never should have made it into a production airplane.
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FICU
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by FICU »

Regardless of the faults in the design of the MCAS AoA input it should not have resulted in 2 hull losses.
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Eric Janson
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by Eric Janson »

FICU wrote: Sun Mar 17, 2019 7:12 pm It’s exactly the same. If the stab trim is running on its own in the opposite direction you want it to, you treat it as a runaway. Dont try to analyze why it is doing what it is in the moment just cut power to it.

As an FYI the stab trim runaway QRC is all memory action right to moving the cut off switches to the cut off position.
So you're going to use the cut-out switches when the Speed Trim and/or Mach Trim move the Stabilser?

In the Lion Air crash the stickshaker was operating continuously which would mask the sound of the trim wheel moving. This in addition to multiple Master Cautions giving failures messages that may add to the confusion (just look at the message list on the Boeing advisory). All this while the crew is fighting to control an aircraft that is getting nose heavy.

Don't forget this crew knew nothing about MCAS - a previous write up incorrectly identified this as a problem with the Speed Trim.

I can see why a crew would become overloaded in this situation and once the stabiliser reaches full nose down the nose down input cannot be over-riddden by elevator input. If you are low then you won't have enough time to recover.

I'm surprised that people continue to believe this failure is nothing to worry about. Fortunately the decision makers at various Airlines and Regulators around the World hold a different view.
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FICU
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by FICU »

Eric Janson wrote: Mon Mar 18, 2019 2:47 am So you're going to use the cut-out switches when the Speed Trim and/or Mach Trim move the Stabilser?
We are talking uncommanded runaway not normal operations of minor trim inputs.

Let's try to use some common sense here.
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J31
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by J31 »

FICU wrote: Mon Mar 18, 2019 4:43 am
Eric Janson wrote: Mon Mar 18, 2019 2:47 am So you're going to use the cut-out switches when the Speed Trim and/or Mach Trim move the Stabilser?
We are talking uncommanded runaway not normal operations of minor trim inputs.

Let's try to use some common sense here.
TWO hull losses with nearly 350 people dead! Common sense is there is something really wrong here!

Have you flown the 737 with speed trim? Lots of us have and can easily see how this scenario can overwhelm a crew.
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LittleNelly
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by LittleNelly »

Gino under

Sorry if my post came across as hostile, I didn’t intend it to.

My main point is these are not my opinions but the facts, not as reported by random news agencies, but from investogators and regulators.

The idea that uncommanded stab trim movement(regardless of what system is creating the movement) is actioned by the stab trim runaway checklist is not my opinion. It is the opinion of Boeing, the FAA, Transport canada, EASA, CAA of China, every other aviation regulator around the world, as well as every airline in the world that operates the Max.

After Lion air all those people were aware that the Max stall protection system utilizies trim but they also concluded that it was a reasonable assumption that flight crews would action their memory items and emergency checklist for trim runaway in the event of uncommanded trim movement. Whether it’s the MCAS or the flight control system giving eranous commands is irrelevant to our actions. That’s the opinion of all those regulators, they all agreed with Boeing.

What changed with Ethiopian. Well now maybe we can’t assume flight crews will preform their emergency actions. So how does that get remedied. Well once we figure that out, it’ll be an autonomous airliner.

But anyway every single issue being discussed right now in regards to the Max has already been discussed. Every regulator accepted pilots should know how to recognize uncommanded stab trim movement.

Boeing for sure will want to make whatever updates and changes to help out but that in no way puts the cause on them anymore than Airbus changing the pitot tubes on the 330s after Air France 447.
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goingmach_1
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by goingmach_1 »

Not a Boeing pilot, all corporate stuff for me. The trim “runaway” is quite manageable as soon as it is recognized on the current machine I am flying F-900LX. The Falcon has no stick shaker or pusher, though the Challenger 601/605 I have also flown did.

Read most of the informative posts on this thread, skipped the irrelevant stuff, so might have missed a piece of info.

I have a couple of questions for those in the know.

1. Does the MCAS only function with autopilot off? (In other words, when being hand flown)

2. Does the MAX have a stick shaker/pusher?
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by C-GGGQ »

1 yes autopilot off, flaps up, high AOA
2 yes
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FICU
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by FICU »

J31 wrote: Mon Mar 18, 2019 6:23 amHave you flown the 737 with speed trim? Lots of us have and can easily see how this scenario can overwhelm a crew.
I have been for many, many years.

If the trim is trying to drive you into the ground regardless of what system is running it... Kill the trim.
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Heliian
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by Heliian »

FICU wrote: Mon Mar 18, 2019 8:58 am
J31 wrote: Mon Mar 18, 2019 6:23 amHave you flown the 737 with speed trim? Lots of us have and can easily see how this scenario can overwhelm a crew.
I have been for many, many years.

If the trim is trying to drive you into the ground regardless of what system is running it... Kill the trim.
Well, just put a sticky label on the dash and call er good!
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FICU
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by FICU »

Heliian wrote: Mon Mar 18, 2019 9:37 amWell, just put a sticky label on the dash and call er good!
Not needed.

As a professional pilot it is your job.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by digits_ »

FICU wrote: Mon Mar 18, 2019 10:03 am
Heliian wrote: Mon Mar 18, 2019 9:37 amWell, just put a sticky label on the dash and call er good!
Not needed.

As a professional pilot it is your job.
Let's look at it from a different perspective. They add the MCAS because Boeing/FAA(via certification requirements) doesn't think pilots can recover from a stall in this airplane. A stall which (almost) never happens. Yet they build a system to deal with this bad stall in such a way that causes more trouble than it prevents in a way that is much harder to correct than an actual stall.

Sounds like a fairly bad design to me.

If your safety system costs more lives than what it tries to prevent, something's off. The pilots probably should have been able to deal with it, but the fact is they weren't. Could have been for multiple reasons, maybe system related, maybe not. Hard to say.
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FICU
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by FICU »

I'm not disputing a fault in the design. I question why 2 planes crashed. The Ethiopian one especially if it's due to the same problem as Lion Air after Boeing issued a notice to operators about what can happen and how to deal with it.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by digits_ »

FICU wrote: Mon Mar 18, 2019 10:23 am I'm not disputing a fault in the design. I question why 2 planes crashed. The Ethiopian one especially if it's due to the same problem as Lion Air after Boeing issued a notice to operators about what can happen and how to deal with it.
I might have missed it in the previous posts, but have they found out yet after how many seconds the MCAS trim because unrecoverable with just the yoke?
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FICU
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by FICU »

The MCAS trimming can be stopped by using normal electric trim on the wheel. As long as the pilot is trimming the MCAS is disabled.

There are some good references in this thread as to how MCAS works.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by digits_ »

FICU wrote: Mon Mar 18, 2019 11:23 am The MCAS trimming can be stopped by using normal electric trim on the wheel. As long as the pilot is trimming the MCAS is disabled.

There are some good references in this thread as to how MCAS works.
Yes I read that, but that doesn't answer my question. How many seconds do the pilots have before the MCAS puts the airplane in a state where recovery is impossible with just the yoke? How many seconds before the pilots have to intervene before recovery is extremely unlikely?

If that's 2 seconds, I don't blame the pilots for being unable to do so.
If it's 200 seconds, you could probably expect them to prevent it.

I don't find it unlikely that they won't start trimming right away if the stick shaker goes off. If anything, with a stick shaker, your first instinct would be to trim nose down, not nose up. I could easily see them lose 5 - 10 seconds dealing with that before they end up at a trim runaway conclusion.
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sportingrifle
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by sportingrifle »

Digits....
That is a great question. Since there are no simulators with MCAS programmed in to them, hard to know definitively. But the guess is about 20 seconds...ie 2 cyles of MCAS takes the stab to near full nose down. It depends on how much reverse trimming is done in between.

Originally the system was only going to move the stab a little over 1/2 a degree, but flight testing showed this to be insufficient so the range was increased by over 4 times that.

sportingrifle
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by C.W.E. »

Try this for a test of your cognitive abilities.

Look at the seconds hand of a clock for twenty seconds then decide how long that is to observe something for.

That may give you a better grasp of time.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by sportingrifle »

.....
Now try looking at the clock while flying a simulator close to the ground with a stick shaker activated, aural warnings of "stall," "too low", don't sink," differing indicated airspeeds, some warning messages on the EICAS, and the mis-trimming happening intermittantly. Time flies when you are having fun! And if you don't catch it in the first 10 seconds, you will have serious difficulties manually trimming the airplane after you do get the stab cutout switches selected.

There are no simulators set up to replicate this fault but a well known 737 operator tried to mimic this scenario with a number of their crews. It did not end well for many. These were experienced North American line pilots who had some idea what to do after Lion Air.

Cheers sportingrifle.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by C.W.E. »

For sure it would be challenging sportingrifle , and for sure Boeing has a problem on their hands.
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