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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 5th Apr 2019, 12:52
  #3301 (permalink)  
 
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Originally Posted by fgrieu View Post
and pristine extracts of images in appendix 1 (improving on these in post 3161)
- preliminary FDR data
- general overview of the flight
See posts #3139 and #3147.

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Old 5th Apr 2019, 12:54
  #3302 (permalink)  
fdr
 
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Originally Posted by BluSdUp View Post
FDR
NO No, we have all been there!
I am just stating a FACT.
This Young Commander was experienced , just not as a Commander.

And according to Ethiopian propaganda he did all correct.
NO he did not!!
Engage AP at 400 feet with the stick shaker going : WRONG
Never controlling PWR and Speed WRONG
Retracting Flaps as per standard Ops when possible in a stall : WRONG
I feel so bad for him!

But sad to say, he was set up by Murphy, FAA and Boeing and I see only panic in the action and reaction.
After 4000+ hrs in 4 sims I have seen a bit, and it is all down to a confusing flight deck with this fail mode!
Something like this I have never encountered in a Sim

But , please
Were do You see experience? . Sorry to be so blunt.

Sincerely
Cpt B
BSU,

Before the big bang there is no experience, after the big bang there is experience. The individual chance of a critical system event occurring is unassociated with experience. The risk of a bird strike, engine failure, trim runaway is equally distributed across the career of the crew member. The recovery method suggested by the FCTM is apparently problematic given recent history, and the wording is hardly confidence inspiring. If the pilot was old enough to have had training that included the gems on this that are coming out now, then that is wonderful, and all would still be right in the world. Reading the FCTM alone would not necessarily result in competency in conducting the implied manoeuvre, one which assumes that there are two pilots in the seat at the time, and that sufficient altitude exists to recover the aircraft from the trim problem.

The more reflection on the recovery technique, the less it appears to be reasonable to be conducted, and at the very least the more necessity there is to undertake the training in the simulator. A yo-yo manoeuvre is not what one expects to be needed in a Part 25 transport, it is likely to spill the champagne in the front and to end up with a flight attendant shaped dent in the overhead lining down the back. The calendar indicates this is now 2019, and the FCTM suggests in rather vague terms a procedure that is essentially aerobatic, and Wilbur and Orville would have not been so happy with in 1903.

The design standard and the design is unlikely to be changed any time soon, but anyone considering that the crew of these two accidents were deficient in dealing with the trim condition needs to take a look in the mirror, and think seriously about the situation they were placed into. Post hoc, it is quite easy to say "I woudn't have done that" or "I would have done this", but I can say that I trained late in my jet career on the 73, under an FAA 142, and the implied procedure of the FCTM was not a takeaway, conceptually or in practice. Having flown some rather lousy designs where jack stall could occur, the concept in the unloading is not alien, but when the procedure calls for both pilots on the controls at the same time, and to undertake a ballistic flight path either upwards or downwards as determined by the in trim speed that has been established by the uncommanded motion, that just doesn't appear to gel with the spirit of RPT jet transport certification by the leaders of the worlds aerospace regulators.

The recovery technique that is implied in the FCTM, and which is not incorporated in the QRH as a recall item, is rather depressing, no matter how much lipstick is put on it.

In respect to the "errors" suggested to have occurred, the alternative observation is the pilot had ascertained that the stall warning was spurious, and therefore engaged the A/P, and retracted flaps. Perhaps he had a compelling reason to maintain speed, perhaps arising from the fact that the AOA outputs to the ADIRU and alters that sides IAS as a function of the sensed AOA, a refinement of the air data system... therefore having both AOA and IAS issues, the pilot elected to prudently maintain power to gain separation from the hard stuff. Perhaps. Equally as likely, under the assault of information and task demands that confronted the pilots, they were cognitively overloaded. Perhaps. Getting into a situation where you are leaving teeth marks on the elevators is never fun, and even less when there is a risk of catastrophic outcomes. The next crew to experience such conditions will have been gifted the insight that sober reflection on the situation that befell these crews. Whether the pilot had 1.5 years or 150 years is unlikely to be a factor in the outcome of the event, IMHO.

Last edited by fdr; 5th Apr 2019 at 13:14.
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Old 5th Apr 2019, 12:54
  #3303 (permalink)  
 
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Originally Posted by MemberBerry View Post
"They seem to mean that the safety added by not being able to trim with the thumb switches until you hit the mechanical stops compensates not being able to do that when you actually need it."
Still gobbledygook to me.

How is safety added by not being able to trim with thumb switches? In particular, until a mechanical stop is hit? I would think it is the other way around, that hitting a mechanical stop disables trimming? Furthermore, I would think that a mechanical stop should never be hit, that there should be some microswitches on the actuator to prevent hitting a mechanical stop.

How does not being able to trim when a mechanical stop is NOT hit compensate not being able to do that when you actually need it?
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Old 5th Apr 2019, 12:55
  #3304 (permalink)  
 
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Could someone more knowledgeable than me kindly explain why there appear to be 2 references to Flap retraction as below, or am I misreading the report?

At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33seconds later), the flaps were retracted and the pitch trim position decreased to 4.6 units.
and
At 05:39:45, Captain requested flaps up and First-Officeracknowledged. One second later, flap handlemoved from 5to 0 degrees and flaps retraction began.
Many thanks
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Old 5th Apr 2019, 13:00
  #3305 (permalink)  
 
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Originally Posted by industry insider View Post
Could someone more knowledgeable than me kindly explain why there appear to be 2 references to Flap retraction as below, or am I misreading the report?



and


Many thanks
Luc Lion did here. The first probably refers to gear retraction, or perhaps to partial flap retraction.

Bernd
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Old 5th Apr 2019, 13:00
  #3306 (permalink)  
 
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bsieker #3326, take care when interpreting the FDR trim. The switch position for ‘manual’ elect trim probably has a low sampling rate, thus a single data point would be displayed as a ramp up / down. The important aspect is that there is no change in the pitch trim position.

Thus the indications toward the end off the flight probably identifies reactivation of the elect trim, even two pulses recorded due to selecting the two switches back to an active state; either without further pilot elect trim input by choice, or due to a certification inhibit (? discussed elsewhere), or with manual elect trim, it was not strong enough to overpowered the tail forces (from the crew’s perception the latter situations were of an elect trim fail)
Thereafter, the trim command is only down - elect signal (MCAS), the actual trim position further nose down.

The other important aspect is that with the elect trim inhibited some time before, there was no change in trimmed position; i.e. the MCAS had no effect, but critically there was no nose-up trim from manual trim wheel operation, indicating the crew’s inability to move the trim.
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Old 5th Apr 2019, 13:04
  #3307 (permalink)  
THUNDERTAILED
 
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Originally Posted by DaveReidUK View Post
Of course not, you simply turn the manual trim wheel.

About 250 revolutions from full ANU to full AND ...
Maybe in a 737, But it's wasn't in other jets, like the Fokkers. The trim wheel is just geared ..again question the 737 design..are so many clack clack clack turns necessary?
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Old 5th Apr 2019, 13:05
  #3308 (permalink)  
 
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Originally Posted by StuntPilot View Post
Still gobbledygook to me.

How is safety added by not being able to trim with thumb switches? In particular, until a mechanical stop is hit? I would think it is the other way around, that hitting a mechanical stop disables trimming? Furthermore, I would think that a mechanical stop should never be hit, that there should be some microswitches on the actuator to prevent hitting a mechanical stop.

How does not being able to trim when a mechanical stop is NOT hit compensate not being able to do that when you actually need it?
Obviously hitting the mechanical limit disables trimming. It's a hard limit. But there are also electric switches preventing you from reaching the full nose down (and up) position using electric trim even before you hit the mechanical limit. Boeing regards this additional limitation as a safety feature. And indeed, in case of electric trim runaway, it can limit the amount of trim the runaway could apply, so it can improve safety in some situations.

Later edit:

You can read in more detail about that in the latest Satcom Guru article: https://www.satcom.guru/2019/04/stab...and-range.html

In that article there is a table describing the available ranges for the various types of electric trim, compared to manual trim with the trim wheels.

For example, for the 737-800, the full trim range available with the trim wheels is -0.20 to 16.9 units. For manual electric trim with the flaps retracted the range available is 3.95 units to 14.9 units, so far away from the mechanical stops.

That's what the EASA document was talking about. You can't access the full range of mechanical trim positions using manual electric trim. With the flaps retracted on the 737-800 you would only have access to a range of 10.95 units of trim out of the total range of 17.1 trim units available with the trim wheels.

Unfortunately MCAS doesn't use the same limits as manual electric trim, so it can bring the trim closer to the full nose down limit. In the Ethiopian flight it manages to bring it to 0.4 units of trim at some point.

Last edited by MemberBerry; 5th Apr 2019 at 13:47. Reason: adding more details
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Old 5th Apr 2019, 13:07
  #3309 (permalink)  
 
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Why does ANU stop at 2.3?

I usually don't contribute anything to a discussion, preferring to listen more to what everyone has to say. This is reflected in my posts on here too, which are non-existent. However, I have been following this thread very keenly and am very grateful to all the amazing insights and points of view provided. I'm a NG/Max driver and coincidentally, flew a Max on both the crash days.

Generally, my attitude towards any incident / accident is "They should have done this. But, I wasn't in that hot seat. Maybe I would've done the same". However, I've been struggling a lot trying to get that attitude and the posts on here have helped. Especially the ones which have been downright condescending of the operating crew. They have helped me get my perspective.

One thing that I have noticed in the preliminary report of the ET is that the pilot ANU stopped at exactly 2.3 units on three separate occasions. The first one was a shallow pick-up after the first MCAS activation. The second one was a more agressive pick-up immediately following the second MCAS activation, suggesting that the pilot(s) now knew what they were dealing with. As soon as the ANU stopped at 2.3 units, FO asked if he should cut-off the stab trim. The third was when they, presumably, reactivated the stab-trim to get some leverage with the electric trim and ended up with short bursts, instead of a long ANU activation.

With discounts given to adrenalin not allowing you to feel the AND for the first one and coincidence being the second, the third ANU also stopping at 2.3, suggests there was something else at play and not merely pilots not knowing how much to trim. The clue is provided in the timing of the FO suggestion for stab-trim cut-off.

Or am I reading too much?
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Old 5th Apr 2019, 13:18
  #3310 (permalink)  
 
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Originally Posted by fdr View Post
BLU, do we stop using captains that have less than 1.5 years in command?
Also, do not let new type aircraft fly until they have made 15.000 flights
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Old 5th Apr 2019, 13:19
  #3311 (permalink)  
 
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Originally Posted by industry insider View Post
Could someone more knowledgeable than me kindly explain why there appear to be 2 references to Flap retraction as below, or am I misreading the report?
and
Many thanks
There are 2 typos in the report "History of Flight"
So please read:
...
At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the GEAR was retracted and the pitch trim position decreased to 4.6 units.

The DFDR diagram shows that it was indeed the gear retraction that happened at that time.

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Old 5th Apr 2019, 13:22
  #3312 (permalink)  
 
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Game Over? Muilenburg statement

April, 4, 2019
We at Boeing are sorry for the lives lost in the recent 737 MAX accidents. These tragedies continue to weigh heavily on our hearts and minds, and we extend our sympathies to the loved ones of the passengers and crew on board Lion Air Flight 610 and Ethiopian Airlines Flight 302. All of us feel the immense gravity of these events across our company and recognize the devastation of the families and friends of the loved ones who perished.
The full details of what happened in the two accidents will be issued by the government authorities in the final reports, but, with the release of the preliminary report of the Ethiopian Airlines Flight 302 accident investigation, it’s apparent that in both flights the Maneuvering Characteristics Augmentation System, known as MCAS, activated in response to erroneous angle of attack information.
The history of our industry shows most accidents are caused by a chain of events. This again is the case here, and we know we can break one of those chain links in these two accidents. As pilots have told us, erroneous activation of the MCAS function can add to what is already a high workload environment. It’s our responsibility to eliminate this risk. We own it and we know how to do it.
From the days immediately following the Lion Air accident, we’ve had teams of our top engineers and technical experts working tirelessly in collaboration with the Federal Aviation Administration and our customers to finalize and implement a software update that will ensure accidents like that of Lion Air Flight 610 and Ethiopian Airlines Flight 302 never happen again.
We’re taking a comprehensive, disciplined approach, and taking the time, to get the software update right. We’re nearing completion and anticipate its certification and implementation on the 737 MAX fleet worldwide in the weeks ahead.
We regret the impact the grounding has had on our airline customers and their passengers.This update, along with the associated training and additional educational materials that pilots want in the wake of these accidents, will eliminate the possibility of unintended MCAS activation and prevent an MCAS-related accident from ever happening again.

Boeing: 737 MAX Update
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Old 5th Apr 2019, 13:24
  #3313 (permalink)  
 
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It was a great idea to have 2 cutout switches (up to the B737 NG) ; one acting on the yoke trim switches and the other acting on the autopilot and STS.
It was a not so great idea to replace them with a primary cutout switch and a backup cutout switch, both switches acting on both electrical channels of the trim.
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Old 5th Apr 2019, 13:24
  #3314 (permalink)  
 
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Originally Posted by industry insider View Post
Could someone more knowledgeable than me kindly explain why there appear to be 2 references to Flap retraction as below, or am I misreading the report?

Many thanks
The first is suspected to be a typo and should read "gear".

- GY
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Old 5th Apr 2019, 13:25
  #3315 (permalink)  
 
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Originally Posted by Luc Lion View Post
There are 2 typos in the report "History of Flight"
So please read:
...
At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the GEAR was retracted and the pitch trim position decreased to 4.6 units.

The DFDR diagram shows that it was indeed the gear retraction that happened at that time.
So the gear was raised at 1000'AGL? No doubt this crew was overwhelmed by the lights and shakers coming on....
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Old 5th Apr 2019, 13:27
  #3316 (permalink)  
 
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Originally Posted by safetypee View Post
bsieker #3326, The important aspect is that there is no change in the pitch trim position.


Yes there is. The creep in the lines is too consistent for it to be random sampling errors (which are also there and clearly visible as jitter.)

Thus the indications toward the end off the flight probably identifies reactivation of the elect trim, even two pulses recorded due to selecting the two switches back to an active state; either without further pilot elect trim input by choice, or due to a certification inhibit (? discussed elsewhere), or with manual elect trim, it was not strong enough to overpowered the tail forces (from the crew’s perception the latter situations were of an elect trim fail)
True, these low-resolution traces need to be read very carefully, but I think a slight nose-up trim change is clear from the trace around the time the two manual trim switch inputs are recorded. Yes, we don't know the sampling frequency for pitch trim position, but as can be seen from the areas in the graph where it changes rapidly, it cannot be less than once per seconds, so that very very slow decrease from 5:30:45 to 5:43:10, and the following very slight increase between 5:43:10 and 5:43:20 are real. Both these movements are also mentioned in the textual part of the report.

The mention of failure of both electric and manual trim was much earlier, during the time where we assume that the cutout switches were in the cutout position. That to me is the most scary part that even for these moderate control column loads that can be held for several minutes, manual trim would not work at all. I had always assumed that in all but extreme out-of-trim situations, mechanical trim would be available.

Bernd
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Old 5th Apr 2019, 13:37
  #3317 (permalink)  
 
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Originally Posted by TTail View Post
So the gear was raised at 1000'AGL? No doubt this crew was overwhelmed by the lights and shakers coming on....
Sorry, confirmation bias ; I positively checked that it wasn't the flaps and then I misread another line for being the gear (was probably the AP).
So something was retracted, but it wasn't the flaps and probably not the gear.
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Old 5th Apr 2019, 13:44
  #3318 (permalink)  
 
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Thanks Bernd. But if, even with the wheel handle, the pilots can not turn the wheel fast enough? I understand that the elevator is the primary pitch control, but this is supposing the aircraft is trimmed accordingly. If, for some reason, the stabilizer does the opposite of what the pilot wants, the elevator becomes the secondary pitch control. An unwanted dive can only be corrected by using trim (on the 737). But with no electric trim it will take some precious time too bring the aircraft back to an atitude where the elevator is the primary pitch control again. And time was exactly what those pilots didn't have...
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Old 5th Apr 2019, 13:48
  #3319 (permalink)  
 
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Originally Posted by Rob21 View Post
Thanks Bernd. But if, even with the wheel handle, the pilots can not turn the wheel fast enough? I understand that the elevator is the primary pitch control, but this is supposing the aircraft is trimmed accordingly. If, for some reason, the stabilizer does the opposite of what the pilot wants, the elevator becomes the secondary pitch control. An unwanted dive can only be corrected by using trim (on the 737). But with no electric trim it will take some precious time too bring the aircraft back to an atitude where the elevator is the primary pitch control again. And time was exactly what those pilots didn't have...
The problem is not so much trim-wheel-motion speed (which I guess at light loads can be up to 5 revolutions per second), but that the sheer force required cannot be exerted by a human "without exceptional strength" if the aircraft is more than just a bit out of trim and nose-up control input needs to be held continuously because of low height above ground, which exacerbates the required force.

Bernd
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Old 5th Apr 2019, 13:49
  #3320 (permalink)  
 
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MCAS seems to be a cure that is much worse than the disease. And if you are having to resort to the manual trim you are really on a wing and a Prayer. Actually the prayer works better.
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