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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 4th Apr 2019, 11:14
  #3081 (permalink)  
 
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Originally Posted by Quentin
They might notice that the stick shaker was operating on a single side only.
No, the columns are interconnected so a single shaker will be felt through both or so my old FCOM says.
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Old 4th Apr 2019, 11:23
  #3082 (permalink)  
 
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Originally Posted by Capn Bloggs View Post
No, the columns are interconnected so a single shaker will be felt through both or so my old FCOM says.
You might be right. The faa ad though says the stick shaker on one side only, is an indication of angle of attack disagreement.
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Old 4th Apr 2019, 11:31
  #3083 (permalink)  
 
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Originally Posted by fotoguzzi View Post
(Not a pilot) This random internet grab from 2009 (authenticity unknown to me) does say to use electric trim and does not say to apply it again if runaway continues.

As these are terse instructions, if one might soon be grabbing a rotating wheel, and not long after that, hand cranking it, [would he] not want to do the best possible work with the electric trim before cutout?

Hello Foto,

Thanks for posting the checklist page.
It is good to follow a non normal or emergency checklist to see what the writer had in mind, before taking to the air sometimes.
In this case the items in point 2. about operating main electric trim are provisional to the autopilot having been on before. Here the writer covers
the case where the autopilot could have been causing the runaway.
Having disengaged the AP there is now the choice of the runaway having stopped, which allows manual flight with normal trim inputs OR if it doesn't stop, no longer is electric trim desired - but stab trim cutout switches off.
Now in these accidents the AP was not engaged, so point 2. did not apply - and as the stab movement continues, pass point 3. and you are left with point 4. - no trim, cutoff switches off.
This is where the "recommended checklist" does not properly cover the case of rogue MCAS operation, despite claims to the contrary. A dedicated checklist is required. A checklist which, if studied on the ground would provide insight into dealing with this complex failure.
And to answer the point further up about, how do the pilots recognise rogue MCAS operation? - at the first accident, they couldn't, since nobody knew of the system - at the second accident after the publicity they may well have realised what was wrong but the runaway checklist is insufficient alone to deal with it (reasons above) and that checklist is what they had.
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Old 4th Apr 2019, 11:32
  #3084 (permalink)  
 
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I'm sorry, but this is a complete hose job by the Ethiopian CAA authority (which has an annual budget of $89,000) and Ethiopian Airlines. "We did everything perfectly". Well RELEASE THE REPORT. Turning MCAS back on 4 times is not following the AD or the standard trim procedure. They're laying all the blame on Boeing, and then once 18,000 news articles have repeated that, they'll release the report tomorrow. Absolute crap.
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Old 4th Apr 2019, 11:45
  #3085 (permalink)  
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Originally Posted by wheelsright View Post
It is not known that the pickle switches are the solution. It is just a theory.
You might have to explain that further. The LionAir crash FDR clearly shows short bursts of uncommanded nose-down trim (from MCAS), each one counteracted by PF-commanded nose-up electric trim, maintaining level flight at 5000 feet for roughly six minutes. The uncommanded nose-down trim is never coincident with the PF's nose-up electric trim. They are clearly interleaved, which is exactly the MCAS behaviour described by the updated advice.

The erroneous AoA / AP disconnect / MCAS response chain may have manifested differently on the EA flight, but we'll have to wait for the FDR / CVR data in the report to know one way or the other.
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Old 4th Apr 2019, 11:45
  #3086 (permalink)  
 
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Originally Posted by mryan75 View Post
I'm sorry, but this is a complete hose job by the Ethiopian CAA authority (which has an annual budget of $89,000) and Ethiopian Airlines. "We did everything perfectly". Well RELEASE THE REPORT. Turning MCAS back on 4 times is not following the AD or the standard trim procedure. They're laying all the blame on Boeing, and then once 18,000 news articles have repeated that, they'll release the report tomorrow. Absolute crap.
It maybe complete crap, or it may not. But if it is a hose job, where did they learn it, and who said they were unsophisticated?
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Old 4th Apr 2019, 11:50
  #3087 (permalink)  
 
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Originally Posted by quentinc View Post
Yes... but as we know now, the MCAS system will keep cutting in... So the pilot reaches (4) in the check list. That step is clear... operate the the CUTOUT... If already trimmed down and speed a little high, the pilot is now in a very dangerous position. All following the FAA AD and Boeing check list.
(Still not a pilot) Thanks. It is understandable that one would not want to remove his hands from the yoke. MCAS seems to give five seconds after the last electric trim, and I presume it does not operate while the trim switch operates. My contention is that if they are reading ahead, they know some cranking is coming, and would naturally trim before cutout. That is, one argument is that MCAS trims faster than the trim switch can, but (unless I am wrong) MCAS will give you as much time as needed to trim before it tries to undo your work.

At what point the combination of nose down and overspeed makes hand cranking unreasonable (or makes even the idea of letting go of the yoke unreasonable), seems yet unclear. The penultimate Indonesian flight continued to destination while the Ethiopian flight lasted minutes.



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Old 4th Apr 2019, 11:54
  #3088 (permalink)  
 
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Originally Posted by Just This Once... View Post
So in sum, we have a non-DAL A system integrated with a secondary control system with no redundancy, monitoring, crew warnings or a dedicated means to disengage. Strap it to an aircraft where the trim system is more powerful than the primary controls and give it authority to move the stab at a far faster rate than normal trim and give it no limits of travel other than mechanical end-stops. If it goes wrong, force the crews to disable all powered stab control and equip them with manual trim wheels that are difficult and slow to operate at the best of times. Modify said wheels to make them slightly smaller and insert a more powerful damper to counteract the spring and backlash effect of the stab being moved at a faster rate than ever before - requiring an undocumented increase in physical effort. Finally inform the crews of this system's existence and get the company test pilots to retest all of this after a quick fatal crash, but do so only at a relatively slow speed. Second accident crew become the unexpected test pilots collecting a datapoint that suggests the trim wheel is impossible to move when at a higher airspeed. Cumulogranite awaits.

Apart from the flight envelop defining the configuration, CofG, AuW and airspeed/mach beyond which the manual wheels cannot be moved at an effective rate, what are we missing?
OTOH:

* build it all in a rush after being caught out by the competition
* while maxxed out on the rush job, expend some precious resources on changing stuff that didn't need to be changed (bigger displays must be better, must-have new feature, just like on phones )
* take a marketing claim - differences training will not need sim time - and turn it into a design requirement
* sign a sales contract that turns it into a financial requirement so we can beat the engineers with that one as well
* screw up the aero modelling of the effect that lead to the system in the first place, find it is much worse in flight tests, make the system several times more powerful to fix it
* don't tell the regulator what you just did
* don't tell aircrews anything because they don't need to know because of the no-training requirement above
* make all failure cases for the system the crew doesn't know about be handled by existing procedures, however mismatched or badly, because can't train any new procedures
* hang it all off a single sensor because if it used two it would need a warning if a disagree caused it to disable itself, and new warning means new training so it can't be done that way
* rewire the cutout switches, which have been the same for decades, so that now a really clever crew cannot turn off just the automatic trim and leave the manual electric on to regain control

And between both of us we've probably still missed something.
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Old 4th Apr 2019, 11:57
  #3089 (permalink)  
 
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I'm sorry, but this is a complete hose job by the Ethiopian CAA authority (which has an annual budget of $89,000) and Ethiopian Airlines. "We did everything perfectly". Well RELEASE THE REPORT. Turning MCAS back on 4 times is not following the AD or the standard trim procedure. They're laying all the blame on Boeing, and then once 18,000 news articles have repeated that, they'll release the report tomorrow. Absolute crap.
I don't think you can point the finger at the Ethiopian CAA here, as they appear to have had control seized by the Govt so the choice of timing is probably not down to the investigators . A UK colleague who flew with the ET302 captain told me he was a very competent operator, but I think many of us could be caught out by the effort required to manual trim at higher speeds and with a significant stick forces involved as well. He may well have opted to try further electric trim inputs to try to manage a situation that only 2 other crews had faced, but that is speculation. We won't know exactly what he was dealing with until the final report is released, when perhaps we will have proper FDR and CVR information to speculate with.

And as for the Ethiopians laying all the blame on Boeing, could someone remind me which manufacturer produced an aircraft that was vulnerable to a catastrophic outcome from a single point of failure and which has been grounded across the globe because, pending modification, the design is currently viewed by regulators as being unsafe?
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Old 4th Apr 2019, 12:03
  #3090 (permalink)  
 
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100% Agree

Originally Posted by mryan75 View Post
I'm sorry, but this is a complete hose job by the Ethiopian CAA authority (which has an annual budget of $89,000) and Ethiopian Airlines. "We did everything perfectly". Well RELEASE THE REPORT. Turning MCAS back on 4 times is not following the AD or the standard trim procedure. They're laying all the blame on Boeing, and then once 18,000 news articles have repeated that, they'll release the report tomorrow. Absolute crap.
I agree 100%. Can we actually read the report and judge for ourselves if the pilots achieved "full compliance with the emergency procedures." Also I find it incredible to read that some people here are suggesting it is too much of pilots to ask if they should trim out the aircraft with the electric trim switch first before setting the stab trim cut out switches to cut out. Boeing pointed out the need for this and it is also obvious that it isn't a good idea to set the stab trim cut out switches to cut out when the airplane is already in a nose dive at more than 250 knots (I am not saying that is what happened with ET 302). Of course in hindsight Boeing is largely to blame for these two accidents because apparently crews are too easily overwhelmed if MCAS malfunctions. Nonetheless, it doesn't make the aviation world safer to always claim the pilots couldn't have done anything. There are plenty of accidents in which a lack of flying skills is the main cause. Systems will continue to fail and then it will be up to the pilots to regain control of the airplane. If pilots are lacking in their ability to do so there needs to be just as much of a focus on dealing with that as there needs to be a focus on making systems less prone to fail.
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Old 4th Apr 2019, 12:07
  #3091 (permalink)  
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Originally Posted by fotoguzzi View Post
(Still not a pilot) Thanks. It is understandable that one would not want to remove his hands from the yoke. MCAS seems to give five seconds after the last electric trim, and I presume it does not operate while the trim switch operates. My contention is that if they are reading ahead, they know some cranking is coming, and would naturally trim before cutout. That is, one argument is that MCAS trims faster than the trim switch can, but (unless I am wrong) MCAS will give you as much time as needed to trim before it tries to undo your work.

At what point the combination of nose down and overspeed makes hand cranking unreasonable (or makes even the idea of letting go of the yoke unreasonable), seems yet unclear. The penultimate Indonesian flight continued to destination while the Ethiopian flight lasted minutes.
I think it is generally accepted that full nose-down stabilizer position at high airspeed, low altitude may be unrecoverable via the manual trim wheel.

We think we know that the ET302 crew activated the STAB TRIM CUTOUT, leaving them in a potentially vulnerable position if the stabilizer was already at or near its maximum nose down position. We also think we know that the crew re-enabled the electric trim at some stage -- the FDR should therefore show whether the crew subsequently attempted to level the aircraft via the electric trim after re-enabling it (and by extension) MCAS. I think that will be a key indicator as to the crew's understanding of what the cause of their flight control problem was, and what they understood they needed to do to recover from it.

By that I mean -- when the crew re-enabled electric trim, did they attempt to recover the dive using the electric trim switches ?
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Old 4th Apr 2019, 12:16
  #3092 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
There were actually two failures on the MAX: The faulty AOA sensor data which triggered a whole range of spurious warnings, put the pilots in a high workload situation, which on its own was hazardous. Then MCAS comes along, and administers the coup-de-grace while the pilots are busy trying to make sense of the aircraft and their checklists.
Excellent summation, Gordon.
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Old 4th Apr 2019, 12:27
  #3093 (permalink)  
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Originally Posted by HundredPercentPlease View Post
It could take years, but it may be more like the rudder hardover problem. Two fatal accidents, keep the thing flying, quite a few hairy moments, then find and fix the problem years later.
The outcome of the UAL585 and USAir 427 jammed servo/rudder reversal problem owns a great deal to one certain manager in USAir who doggedly refused to accept the conclusions being drawn on the Aliquippa event. Eventually that led to the in-depth investigation and the surprise revelation of thermal shock from hot hydraulic fluid interacting with a cold actuator. I still have an issue on the rate of roll recorded in 427's case, which is consistent with autorotation, which needs a high AOA to exist in such cases; the rudder alone did not have the secondary roll authority to achieve the rates recorded.
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Old 4th Apr 2019, 12:52
  #3094 (permalink)  
 
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Originally Posted by 737mgm View Post
I Of course in hindsight Boeing is largely to blame for these two accidents because apparently crews are too easily overwhelmed if MCAS malfunctions. Nonetheless, it doesn't make the aviation world safer to always claim the pilots couldn't have done anything.
Disregarding your choice of words, which I believe is unfortunate, we all agree that you need both things to fail (engineering and training) for most accidents to happen.

I also believe that the adequate level of engineering in this particular problem would have been a lot cheaper to achieve than adequate level of training for pilots. I mean, which is more understandable to you:

1) Assume that the new plane is not going to try to kill you (pilot) in a new way nobody explained you beforehand, (that was pilot error)
2) Assume that no crew is going to be "too easily overwhelmed" if the new system you designed, which is susceptible to failure as every other thing in the world, tries to kill them in a brand new way that you decide not to explain or mitigate beforehand. (that was boeing error)


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Old 4th Apr 2019, 12:55
  #3095 (permalink)  
 
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In a news conference in Addis Ababa, Ms Dagmawit (Ethiop.Transport Minister) said: "The crew performed all the procedures repeatedly [that were] provided by the manufacturer but were not able to control the aircraft." Her comments were based on a preliminary report into the crash, which has not been published yet, but could be released by the end of the week.

+

The preliminary report said:
  • The aircraft had a valid certificate of air worthiness.*
  • The crew had a licence and qualifications to conduct the flight.*
  • The takeoff appeared very normal.*
  • Pilots performed the necessary procedures, as provided by the manufacturer, "repeatedly" to bring the flight under control.But was not able to control the aircraft.*
  • Ethiopian Airlines Flight 302 experienced “repetitive uncommanded aircraft nose-down conditions” which "continued for the remainder of the flight” before the crash.
  • Boeing urged to review aircraft flight control system relating to control of the plane by accident investigators.
[Note A0283 - the lines with an asterix * were the literal words used by her during the press conference.]

The Ethiopian authorities did not attribute blame in their preliminary report and did not give detailed analysis of the flight.

Following the Ethiopian disaster, Max jets have been grounded worldwide pending a software fix that Boeing is rolling out, which must still receive approval from the US Federal Aviation Administration (FAA) and other regulators.

Boeing is now being investigated by the US Justice Department, the Transportation Department's inspector general, and congressional committees.

Investigations are also looking into the role of the Federal Aviation Administration in the US, which certified the Max in 2017 and refused to ground the jets after the crash back in October.

The FAA said in a statement it was continuing to work towards understanding what happened.

Last edited by A0283; 4th Apr 2019 at 13:10. Reason: Note and *'s added
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Old 4th Apr 2019, 12:57
  #3096 (permalink)  
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Originally Posted by quentinc View Post
I don't see the details in the preliminary report about who was flying and instructions to continue trimming, that you are reporting. Perhaps you have seen some other information. I will say the preliminary carries the same information in the appendices about operating CUTOUT. It does NOT say its fine to leave the electrical trim running, provided you are careful to trim up.
That's fair. I'll chase up a reference. Regardless, your characterisation of the FDR (that pilot-trim-up was involved in a losing tug-of-war with MCAS-trim-down) is incorrect. It is only the final 4 MCAS-commanded-nose-down trim commands that result in increasing nose-down attitude. The previous 21 such MCAS-commanded-nose-down trim commands are fully counteracted by the flight crew resulting in essentially level flight at 5000 feet for 6 continuous minutes.
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Old 4th Apr 2019, 13:16
  #3097 (permalink)  
 
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Originally Posted by gmx View Post
Also fair point. Maybe instead of "novel concept" I should have said "undesirable". Similar things are certainly not happening week to week. I'm not out to sink the boot into anyone at this stage. I'm keen to see the report and draw my own conclusions. My point at this stage is that the crew were obviously under stress, and the aircraft was working against them.
I think it is also important to note that both MAX crashes happened during day/VMC flight. I cannot imagine what it might be like to experience the same symptoms at night in IMC conditions.

Originally Posted by gmx View Post
That's fair. I'll chase up a reference. Regardless, your characterisation of the FDR (that pilot-trim-up was involved in a losing tug-of-war with MCAS-trim-down) is incorrect. It is only the final 4 MCAS-commanded-nose-down trim commands that result in increasing nose-down attitude. The previous 21 such MCAS-commanded-nose-down trim commands are fully counteracted by the flight crew resulting in essentially level flight at 5000 feet for 6 continuous minutes.
Your overall description of JT610 is correct, but the airspeed was relatively low, so it may be premature to judge if electric trim would have had the same effects at speeds > 250kts, when both speed trim and horizontal stabiliser loading come into play.

FDR trace:



gmx The transition from captain to co-pilot is when the last four nose-up trim commands become short blips, instead of the long activation earlier in the FDR.

Last edited by GordonR_Cape; 4th Apr 2019 at 13:32.
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Old 4th Apr 2019, 13:23
  #3098 (permalink)  
gmx
 
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Originally Posted by GordonR_Cape View Post
Your overall description of JT610 is correct, but the airspeed was relatively low, so it may be premature to judge if electric trim would have had the same effects at speeds > 250kts, when both speed trim and horizontal stabiliser loading come into play.

FDR trace:

Thanks Gordon. Any help on the transfer of control from PF to FO at the time the aircraft attitude starts to go south ?
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Old 4th Apr 2019, 13:24
  #3099 (permalink)  
 
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Last year my first ever real in-flight incident was in my CAP-10, flying downwind 1000ft AGL in the circuit. The electric trim ran away to the end stop and suddenly I was pointing at the ground, After pooing myself, I worked out what it was quite quickly and returned the trim to neutral, where it promptly ran away to the end stop again. So I recentralised it, and disabled it. Problem solved, although had to land without flaps.
Gave me a real heart thumping moment until it was sorted.
The stick forces even in my small plane were quite high.
At the next opportunity I went up to 5000 ft and had a practice while slowly moving the trim to its end stops to see if the plane was controllable, which it was. Uncomfortable, but controllable.

I don't think anybody should second guess what the pilots should and should not have done, or did and didn't do, until the full report is made public and we can see the facts.

I think Boeing will have a lot to answer to with explanations and money before these planes are certified for flight again. And then you have the public relations problem of getting bums on seats again.
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Old 4th Apr 2019, 13:40
  #3100 (permalink)  
 
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Originally Posted by michaelbinary View Post
Last year my first ever real in-flight incident was in my CAP-10, flying downwind 1000ft AGL in the circuit. The electric trim ran away to the end stop and suddenly I was pointing at the ground, After pooing myself, I worked out what it was quite quickly and returned the trim to neutral, where it promptly ran away to the end stop again. So I recentralised it, and disabled it. Problem solved, although had to land without flaps.
Gave me a real heart thumping moment until it was sorted.
The stick forces even in my small plane were quite high.
At the next opportunity I went up to 5000 ft and had a practice while slowly moving the trim to its end stops to see if the plane was controllable, which it was. Uncomfortable, but controllable.

I don't think anybody should second guess what the pilots should and should not have done, or did and didn't do, until the full report is made public and we can see the facts.

I think Boeing will have a lot to answer to with explanations and money before these planes are certified for flight again. And then you have the public relations problem of getting bums on seats again.
Nobody is questioning that what they faced was a challenging situation. But these aren't recreational pilots out on a Sunday afternoon. These are professional revenue pilots, in theory trained to a very high standard. I agree, let's wait for the report, but you can't say "let's wait for the report, and Boeing is going to have a lot to answer for." I will bet anything that if we get a fair, complete report, it will cite design problems, single point of failure issues, yes - BUT I will eat my shoes if pilot training, adherence to standard procedures, maintenance practices, and even possibly parts sourcing and environmental factors (sand, high humidity, etc.) aren't all factors. I fully expect the end result to be a smorgasbord of issues. It usually is.
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