Ethiopian Airlines Crash; Another 737 Max

TCABM said:
No hard numbers.
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Ok, let me ask you this. Vno for that airplane is 340kts. A quick eyeball of the timeline makes it appear airspeed at the time the cutouts were engaged was 290-300kts. Would it be reasonable for the Captain to assume the trim wheel should still turn manually then?
 
dmspilot said:
So we have, going back to the 60s:
  1. a decision by Boeing engineers to design an airplane low to the ground
  2. an aircraft design that requires a so-called "roller-coaster" technique to relieve enough aerodynamic force on the stabilizer to use the manual trim wheels
  3. a decision to remove the "roller-coaster" technique from flight manuals starting with the 737-300 despite it still being
  4. to not purchase the AoA disagree warning light
  5. a failure of an AoA sensor, that just so happens to be the one that feeds the MCAS system
  6. pilots not keeping the airplane in-trim with the manual electric trim following an unwarranted MCAS activation due to point #12
  7. pilots not following the MCAS stab-trim-cutout procedure quickly enough, possibly due to point #3
  8. pilots unable to manually retrim the airplane due to points #2, #3, and #14
  9. pilots then re-activate a malfunctioning electric trim system due to point #15
  10. pilots are timid re-trimming the airplane due to violent reactions from small trim movements at the aircraft's current speed,
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Where in the above list are you going to put lack of training, to the extent of not even informing pilots the MCAS system existed until recently, only after a catastrophic crash?
 
Chip Sylverne said:
Where in the above list are you going to put lack of training, to the extent of not even informing pilots the MCAS system existed until recently, only after a catastrophic crash?
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It's not exhaustive, I'm sure I left some other things out and maybe more will be discovered in the course of the investigation. Put it in there somewhere.
 
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Chip Sylverne said:
Ok, let me ask you this. Vno for that airplane is 340kts. A quick eyeball of the timeline makes it appear airspeed at the time the cutouts were engaged was 290-300kts. Would it be reasonable for the Captain to assume the trim wheel should still turn manually then?
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I truly don’t know, for a variety of reasons. I’ve never flown a 737, so take the following for what it’s worth.

I’m going to guess the CA had no idea the amount of force that would be needed and when, except that it would probably have to be a lot.

As I go back and review the ET prelim, I truly wonder if he didn’t consider, however briefly, that he needed to stay out of a condition in which MCAS inputs would occur....as soon as the shaker started going off.

If that was the line of thinking, combined with a desire to free up some brain bytes to work the abnormal condition, it might have led to the decision to try the AP early, so that means flaps up, which loses some lift. And with sink rate going off, power + pull is a natural response that should result in a higher AoA and MCAS operates in a high AoA regime. Then the AP kicks off and MCAS commanded AND occurs, without interruption, taking out half the nose up trim. *** I think at this point they were dead men flying ***

I wonder if they had hit the stab trim cutout during the 30 or so seconds the AP was engaged, would that have changed the outcome.

That’s conjecture and puts the crew squarely in test pilot mode. But if the known fleet history for stick shaker at rotation in a Max jet is 0-1, I personally would consider hitting the stab trim cutout first thing, just to prevent the jet from entering an unsurvivable condition.

I’m okay with those that disagree with that line of thought. I’m also okay with the biggest lesson learned out of these two crashes is AoAs are delicate and the ground environment in some places isn’t exactly easy on those things.
 
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Maybe a Boeing engineer can weigh in here, but...

Are all 737 Max 8 & 9 control surfaces strictly fly-by-wire, or is there some sort of purely mechanical cable actuation system as a backup?
 
Larry in TN said:
I don't think so. The pitch-up from full thrust isn't all that much. They were flying roughly 150kts faster than they needed to, though, which adds a lot of authority to the mis-trimmed stabilizer and increases the air loads on it making manual trimming much more difficult. I think the excessive airspeed was a lot bigger problem than the nose-up moment from thrust was a help.
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I'm not experienced in B-737s, although I jump seated on one once (and only once—not too comfortable there). I had a seminal moment in Lear training, though, back in 1976. Given a simulated (not in a sim) nose up trim runaway, the head of training at EJA (NetJets now) told me, "If this ever happens, you want to put the airplane in a configuration where you normally need nose-up trim, like in a steep turn, while you configure for another time it's normal to have it, like for landing." We slowed down in the turn, put out the flaps and gear and, Voila! That LR24D was tamed. He said just the opposite for nose-down trim—you speed it up. So, I'm thinking the aerodynamics are probably the same.
 
ircphoenix said:
Boeing's CEO
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Haha, wouldn't that be cool! What's moronic to me (and something I did not know) is that there scenarios where the aerodynamic loads are such that you cannot reasonably control or trim the plane
 
SoCal RV Flyer said:
Are all 737 Max 8 & 9 control surfaces strictly fly-by-wire, or is there some sort of purely mechanical cable actuation system as a backup?
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There are no fly-by-wire primary flight controls on any version of the 737. The controls are normally hydraulically powered with manual (cables) revision.

dtuuri said:
He said just the opposite for nose-down trim—you speed it up. So, I'm thinking the aerodynamics are probably the same.
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What is forcing the nose down? What happens to the tail-up/nose-down force as airflow is increased over a stabilizer in the full nose-down position?
 
I find it ridiculous the plane was certified by the FAA when it is unflyable using manual trim.

Electric trim should be a “nice to have” not a “you’ll die without it” kind of thing.

....and if it really is a “you’ll die without it” thing, there needs to be another way to disconnect MCAS.
 
dans2992 said:
I find it ridiculous the plane was certified by the FAA when it is unflyable using manual trim.

Electric trim should be a “nice to have” not a “you’ll die without it” kind of thing.

....and if it really is a “you’ll die without it” thing, there needs to be another way to disconnect MCAS.
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There are quite a few airplanes that don't have manual trim, only electric. In fact I was surprised that the 737 had a manual trim wheel.
 
Something else that people might not be aware of is that the heavy forces on the control column are simulated by the elevator feel computer, a separate system with it's own airspeed. Without it there would be no "force" on the control column as the flight control surfaces are hydraulically actuated. You could pull it back with two fingers but also you could bust the whole tail clean off.
 
Everskyward said:
There are quite a few airplanes that don't have manual trim, only electric. In fact I was surprised that the 737 had a manual trim wheel.
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Ok, but if the manual trim is needed to fly with MCAS off.... it should at least work.
 
LongRoadBob said:
Some others have written similarly here, pointing out the situation in depth and the difficulty because you went into the details of what is happening instead of fragmented pieces of information. Instead of bullet points. Great post.

The pilots did the procedures, reportedly, several times but it didn’t help.

Then folks asked why the flaps were retracted. This doesn’t definitively prove it, but just read that another different (unrelated to MCAS) software bug was in the system, and it had to do with flaps. They don’t get more specific, but here is the story

https://www.washingtonpost.com/worl...ory.html?noredirect=on&utm_term=.c4b3e0e6b216
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Again, according to the linked story, there was another bug found in the software, having to do with the flaps.
I think there too, that information seems possibly important. Anyone seen more details on that?

Of a list of possible bugs in software having to do with flaps, not many seem trivial.
 
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Larry in TN said:
What is forcing the nose down? What happens to the tail-up/nose-down force as airflow is increased over a stabilizer in the full nose-down position?
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Gravity pulls the nose down, lift is a function of speed and AoA, the tail sets the AoA. If the tail is set for a low AoA (full nose-down trim) it's another way of saying it's set for high-speed flight. Pulling against that force may be impossible, but speeding up to an even higher speed would reverse the pull force to a push force. As the speed increases, the pull becomes less and finally it becomes a push. If you don't run out of altitude first.
 
AKiss20 said:
And even with that light, if pilots aren’t even informed that MCAS exists and how it works and it’s limited fault tolerance, they would not be able to deduce the possible consequences of an AOA disagree.
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But should they be able to recognize what is, in effect, a trim runaway? We know that at least one crew (yeah, +1) did. I do tend to play the devil's advocate, but if it's true that MCAS has never activated in the US under the proper conditions (where it would actually be needed/useful), how many times has it activated with non-US operators? And does the system let you know when it activates?
 
Chip Sylverne said:
Curious if that's something trained for in the sim?
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@Sluggo63 mentioned they did it in the pattern on the -135.

In the E-3, the flying characteristics due to the rotodome are significantly different than a ‘stock’ 707 platform, which is why I hesitate to rely on that knowledge.

For example, level flight can require 5* or more nose up attitude.
 
Chip Sylverne said:
Curious if that's something trained for in the sim?
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Won't speak for SWA or UA, but we don't. I'm not even sure if our sims are capable of adjusting the force required to move the trim wheel.
 
AKiss20 said:
Honestly, I do find it pretty disgusting how quickly some people in the US Aviation community jumped to the assumption that because these incidents occurred outside of the US or Western Europe that it was “obviously” due to poor piloting and training.
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Thanks, I can understand the sentiment, however it is not a racially motivated thing, if you looked at the known facts at the time we had large fleets of this aircraft type flying all over Canada Europe in the United States apparently quite safely. Either these crews were very lucky and never had an MCAS failure, or they were able to identify the problem early and stop the trim run away before the plane got hopelessly out of trim and unrecoverable by manual flying. I don't believe in luck, so it likely wasn't the former

You then had two accidents crop up from relatively small fleets from parts of the world that are not generally known for their aviation safety. The only real variable at the time that we knew was a different trained pilot flying the aircraft

If you can drive your car no problem but give it to your son and he wrecks it, I think it's obvious to look at the driver as the biggest variable as opposed to some new failure with the car

I do think it is however inexcusable that the aircraft can get into a situation where it is impossible to fly manually, however, the question still remains to me
A.) Why did they let the trim go full deflection before cutting it out
B.) Why were other crews not killed by this

No room in aviation for hurt feelings and safe spaces. If we are going to make flying safer *all* factors (human and machine) must be looked at. Our politically and clickbait motivated PC culture media made sure to go after Boeing with everything they had
 
Tantalum said:
I do think it is however inexcusable that the aircraft can get into a situation where it is impossible to fly manually, however, the question still remains to me
A.) Why did they let the trim go full deflection before cutting it out
B.) Why were other crews not killed by this

No room in aviation for hurt feelings and safe spaces.
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I doubt we will ever know the answer to A; for B, what needs to be known is how many times MCAS has activated. The subsets are with AoA disagree and without. Criteria is resolved or not.
 
dtuuri said:
Gravity pulls the nose down, lift is a function of speed and AoA, the tail sets the AoA. If the tail is set for a low AoA (full nose-down trim) it's another way of saying it's set for high-speed flight. Pulling against that force may be impossible, but speeding up to an even higher speed would reverse the pull force to a push force. As the speed increases, the pull becomes less and finally it becomes a push. If you don't run out of altitude first.
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Kind of like the concept of blowback, only instead of the pressure forcing the control surface down from above, it forces it up from below. Interesting. But to be honest, I'd just as soon leave that trick in the bag, thanks very much.
 
And just point of fact here, Ethiopia Airways has the largest most modern fleet on the African Continent, and has only had 18 crashes and 242 fatalitites on the continent, including this last one, since 1919. Backing out a handful of hijackings that ended badly, the actual flying record is pretty darn good.
 
Chip Sylverne said:
has only had 18 crashes and 242 fatalitites on the continent, including this last one, since 1919
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I saw that. There are certainly lessons to be learned here for both the manufacturer, the regulators, and the training culture and environment. I think it is safe to say that a half an hour iPad course is insufficient
 
Tantalum said:
...
Either these crews were very lucky and never had an MCAS failure, or they were able to identify the problem early and stop the trim run away before the plane got hopelessly out of trim and unrecoverable by manual flying. I don't believe in luck, so it likely wasn't the former
...
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The thing that seems common is a failed AOA sensor.

A third option is, "or, they had a failed AOA and kept the aircraft in the area of the flight envelope where MCAS never activated."

How many MAX had a failed AOA globally? We may know of three, two ended badly. From previous comments, AOA failure seems very low. Then 2 Lion Air and 1 Ethiopian Air.

When mx gets a squawk, how much of that info gets back to the mfg or other agency that can track trends?
 
Chip Sylverne said:
Kind of like the concept of blowback, only instead of the pressure forcing the control surface down from above, it forces it up from below.
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No, I don't think that's what happens. More like the degree of down force on the tail. The relative wind is still hitting the tail from above, assuming stable flight. This wasn't an "English bunt", which is what you describe.
 
Chip Sylverne said:
Ethiopia Airways has the largest most modern fleet on the African Continent,
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And the reason they could afford that fleet is because EA is one of the few Continent airlines that is approved for use by a large group of 1st world entities which was shown by the diverse pax listing. This is why EA and by extension Ethiopia itself has a lot riding on this. CEOs and elected officials are the last ones usually seen onsite at an airliner accident scene. And it is also why there is an internal collective push from EA and Ethiopia to show these pilots followed all the rules and procedures. However, the discussions have begun on EA and their method of operations while the rest of the industry debates MCAS and Boeing. At the front of these discussions is the 361 hr SIC. And there are parallels being drawn to the Lion flight as well.

While we can debate on the abilities of this crew, it is becoming more aware that the PIC may have been running a one man show in an aircraft designed for 2. And just as everywhere else, the supply of experienced and qualified pilots is dwindling and it's hitting the 2nd and 3rd world countries the hardest. Where ex-pat pilots were the norm years ago in most of these countries the local airlines can no longer compete in these times. So more of these particular airlines are turning to home-grown talent as replacements--and not as that is a bad thing. But country cultures and social issues differ greatly between what people in a 1st world country follow vs the 2nd/3rd world countries. It is what it is.

Regardless, I hope the end result will be that the airlines will get away from supporting a "follow the magenta line" mindset with IPad recurrent and start mandating their pilots learn/re-learn how to physically fly the aircraft again.
 
Tantalum said:
Thanks, I can understand the sentiment, however it is not a racially motivated thing, if you looked at the known facts at the time we had large fleets of this aircraft type flying all over Canada Europe in the United States apparently quite safely. Either these crews were very lucky and never had an MCAS failure, or they were able to identify the problem early and stop the trim run away before the plane got hopelessly out of trim and unrecoverable by manual flying. I don't believe in luck, so it likely wasn't the former
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A few things.

1) It may legitimately not be racially motivated for you (and I do honestly believe you when you say it isn't), but I have seen many comments in various aviation forums (again not singling any person or forum out here) that were very clearly racially motivated, so to ignore that aspect entirely and claim it isn't a factor is a bit naive.

2) You claim that we have large fleets in the US and Canada but the US and Canada only represent 69 of the 376 delivered 737MAX aircraft (~18%) [1]. Given that, it isn't statistically unlikely that even if all things were equal, the first two crashes would be outside North America.

3) My issue is not when some people suggest that in all likelihood it was pilot error, which is statistically a valid thing to say given that the vast majority of accidents are due to pilot error, regardless of what country we are looking at. My issue is that some people insist from the very get go that it OBVIOUSLY MUST be pilot error and couldn't possibly be due to anything associated with the Boeing design without even the barest of facts available about the crash. Using statistics to make some statement about the probabilities of causes is fine, as someone who tends to think from a more Bayesian perspective that is what I tend to do anyway, but it is the insistence without fact that annoys me (and can often be tinged with underlying biases).

[1] https://en.wikipedia.org/wiki/List_of_Boeing_737_MAX_orders_and_deliveries

Tantalum said:
If we are going to make flying safer *all* factors (human and machine) must be looked at. Our politically and clickbait motivated PC culture media made sure to go after Boeing with everything they had
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I am actually in full agreement that all factors must be looked at and evaluated. That is exactly what I am advocating for. Waiting to evaluate the situation when all the information is available and not taking any party off the table in terms of improvement. The people I am referring to in my post did the exact opposite, they insisted that it couldn't possibly be a Boeing issue and absolutely had to be the fault of the crew. If you go in with that mentality, you will never improve the aircraft design, the aircraft documentation, or the training program because all the "fault" will be attributed to the crew without any flaws of the former being discovered.
 
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Larry in TN said:
That's because it isn't true.

The MAX has the same manual trim backup system as the B707, KC-135, B727, and all versions of the 737.
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Ok... so why couldn’t these guys properly operate the manual trim?
 
AKiss20 said:
A few things.

1) It may legitimately not be racially motivated
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How does one prove someone else’s unspoken thoughts?

As a retired military officer, America is being torn apart by the judgement of assumptions. We need to get past this.


AKiss20 said:
... My issue is that some people insist.
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That’s life, get over it.

AKiss20 said:
..... The people I am referring to in my post did the exact opposite, they insisted that it couldn't possibly be a Boeing issue and absolutely had to be the fault of the crew..
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That’s not really your problem, so ignore it.

I say this, because I know well and good most Americans haven’t set foot on the continent of Africa, much less are familiar with reality there. I have; on multiple occasions and for extended periods. There’s good and there’s bad, there professional and not. No different than here.

So why should I care about their opinion?

Just like most American pilots **** all over ab initio outfits in EMEA, yet they acknowledge the success of US military flight training programs, which is pretty much 100% ab initio, starting in turbo props and graduating to jets pretty early on. In formation, at low level, with aerobatics. But that’s insane. And done every single day. And then put them in a 585,000lb MGTOW jet as a co-pilot, doing aerial refueling at night, at under 300 hours. Sometimes with an IP at under 800 hours.

Number of ‘logged hours’ is irrelevant. Quality of training is.

And the best training program out there is still reliant on the knowledge available. If it ain’t provided, it can’t be taught.
 
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Tantalum said:
...Either these crews were very lucky and never had an MCAS failure, or...
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You're right, there hasn't been an MCAS failure outside of the two fatal incidents that both resulted in crashes and the fact that both were outside the United States doesn't have anything to do with it. It's odd enough that there were two apparently identical failures. That in itself should have been enough to ground the aircraft but everyone seemed to jump to the conclusion that because they were Indonesian and African pilots that was probably the reason. It wasn't. No American crew has yet survived an MCAS failure like this because no American crew has ever had one.
 
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