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

[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.

[FICU]

Regardless of the faults in the design of the MCAS AoA input it should not have resulted in 2 hull losses.

[Eric Janson]

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.

[FICU]

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.

[J31]

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.

[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.

[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?

[C-GGGQ]

1 yes autopilot off, flaps up, high AOA
2 yes

[FICU]

Have 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.

[Heliian]

Have 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!

[FICU]

Well, just put a sticky label on the dash and call er good!

Not needed.

As a professional pilot it is your job.

[digits_]

Well, 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.

[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.

[digits_]

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?

[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.

[digits_]

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.

[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

[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.

[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.

[C.W.E.]

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

[BTD]

.....
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.

This is indeed the crux of the issue I think. It is to identify that it is in fact a runaway. Once that is known the solution is straightforward. Any basic human factors/crm courses will discuss the limitations to human multitasking. Throw in the sticker shaker, egpws warnings etc, and life just got more challenging. 2 10 second bursts of trim or more smaller ones if you interrupt them and it’s full nose down. Throw in that sts trim is running often at this time anyway and it is easy to see how it gets missed.

The first Lionair flight that made it back had an IAS disagree that could have helped lead the crew to the problem. Do we know if the same message appeared in the accident flight? I don’t recall reading that in the report. Maybe I missed it. And we don’t know if it was there or not in the Ethiopian accident.

Keep in mind to, when the Lionair preliminary report was issued, they still didn’t have the CVR. Who knows the distraction in the flight deck from all the noise at this point.

[sportingrifle]

.....

I think that this is going to be way bigger than the 737, definitely way bigger than the sub-system in the airplane that caused the problem. First of all, it calls into question Boeing's competence and approach to aircraft certification in general.

A quick read of the Far.25 certification standards shows that the MCAS system isn't even close to meeting it. As it originally was designed, it may have been. But as installed, not even close. Many engineers in Boeing would have raised a red flag on this and yet were overruled by higher ups. The problem is that this corporate culture is probably more pervasive than just in the 737 flight control division. This is not the first time that Boeing have rushed an airplane thru certification only to have the fleets grounded.

But the bigger problem, is that the FAA couldn't work as fast as Boeing wanted them to. So Boeing convinced very senior people in the FAA to delegate certification review work back to Boeing. Work that is normally done by the FAA. It takes a very robust safety and QA culture to allow somebody to wear an FAA hat but cash a Boeing paycheck. Obviously it didn't work here.

So the first problem Boeing has is to devise a fix that will satisfy the FAA. A band aid, for a band aid, for an airplane with bad aerodynamics. But the world has already pretty much lost faith in the FAA certification office in Renton. So Boeing is going to have to convince TC, the European JAA, and everybody else, one at a time. This has already started to happen as of about an hour ago. This will add weeks to getting the airplanes back in the air.

The second problem that hasn't happened yet, is that some certification authorities may decide that they want to look at the whole airplane again. If the FAA got the trim system wrong, what else in the airplane doesn't meet FAR25. If this happens, expect the airplanes to be grounded for a year.

But the biggest problem for Boeing going forward is the erosion of trust. Every airplane they build going forward will be getting the fine tooth comb going over at certification. Especially the growth of airplanes under previous grandfathered type certificates. The 787-10, 777X, everything. Boeing better get used to the process taking a long time, and having lots of suits with slide rules looking over their shoulders. And as this drags on, the Airbus sales team will be filling the order books with NEO's and A350's.

And to top it all off, the Justice Dept. criminal division has started taking an interest in the whole affair. This is going to get waaay worse for Boeing before it get better. And so it should, 349 people died. Getting the Max back in the air is the easy part.

[BTD]

I have a feeling a few years down the road, with perspective, this entire debacle will share numerous similarities to the Challenger and Columbia shuttle accidents.

[goingmach_1]

I have reached out to a good friend of mine who is very much in the know, believe me, and he has let me know there is no stick shaker or pusher on this machine.

It has stall strips on the inboard wings. "it really causes the column to shake at high angles of attack."

Three electric systems help with stall of high AOA in addition to the MCAS.

1. Yaw damp reduces rudder movement
2. More hydraulic pressure is sent to the actuator to double pitch control feel in the cockpit, so as the the AOA builds the stick is harder to pull back.
3. Further, the "Speed trim system", (not the MCAS) trims the nose down to further increase control stick pressure to make it even harder to pull back. This system also helps the other way when accelerating to help offset trim requirements.

Forth system is MCAS.

If the MCAS senses a high angle of attack and as a precaution IN FLIGHT MANUAL ONLY trims nose down for 10 seconds then waits for 5 seconds and if the problem is still there trims another 10 seconds nose down the waits 5 seconds and the system just keeps repeating until the high AOA is reduced.

The only way to stop this nonsense is to shut off the trim system completely. Then use the manual trim wheel thereafter.

Seems like such a simple solution to a otherwise complicated add on. Is it just me, or are 737's stalling all over the skies?

Thinking you might get into fight with the thing before you would react to shutting the whole thing off. Cannot imagine the shenanigans in cockpit as the wrestle begins. Damn thing thinks your stalling, pilot goes WTF, and hits the electric trim on the yoke to stop the MCAS (problem solved?). Sensor says high AOA, and it trims nose down again. Pilot trims from the yoke again. and on and on. I can just see them wrestling this demon by fighting now with the control column till you have no strength to overcome the forces on the elevator.

Its not intuitive what to do thats for sure.

[Daniel Cooper]

If the MCAS senses a high angle of attack and as a precaution IN FLIGHT MANUAL ONLY trims nose down for 10 seconds then waits for 5 seconds and if the problem is still there trims another 10 seconds nose down the waits 5 seconds and the system just keeps repeating until the high AOA is reduced.

That sounds like an absolute nightmare and it makes me wonder if they kept it out of the flight manual on purpose because any pilot reading that should be very concerned.