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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 5th Apr 2019, 13:18
  #3301 (permalink)  
 
Join Date: May 2016
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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
  #3302 (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At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the GEAR was retracted and the pitch trim position decreased to 4.6 units.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
  #3303 (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, its 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. Its 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, weve 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.
Were taking a comprehensive, disciplined approach, and taking the time, to get the software update right. Were 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
  #3304 (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
  #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?

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
  #3306 (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
  #3307 (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
  #3308 (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
  #3309 (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
  #3310 (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
  #3311 (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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Old 5th Apr 2019, 13:57
  #3312 (permalink)  
 
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- After autopilot engagement, there were small amplitude roll oscillations accompanied by lateral acceleration, rudder oscillations and slight heading changes; these oscillations also continued after the autopilot disengaged.
Originally Posted by YRP View Post
So what is the significance or cause of this item in the report? Is this the result of the AoA sensor issue leading to the autopilot trying to track spurious inputs?

Or is it an unrelated problem, something else wrong?
I would think it's normal turbulence. The report lists everything happens, whether it may be a problem or not
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Old 5th Apr 2019, 13:58
  #3313 (permalink)  
 
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Having read most of the comments on this thread, my general conclusions are:

1. The crews flying JT610 and ET302 were reasonably well trained and experienced in flying B737 aircraft. Their flying skills could be characterised as representative of the "Average Pilot" within the total population of B737 type-rated pilots.
2. The MCAS system, as implemented on the B737 MAX, is extremely dangerous and should never have been certified on a passenger carrying aircraft. If it activates due to a sensor or system fault at the 'wrong' or disadvantageous moment during a flight, the aircraft can become unrecoverable.
3. Any automatic system that is permitted to control the horizontal stabiliser of a passenger aircraft should be required to have a fully redundant (triplicated) sensor/control system.

To make the B737 MAX safe/certifiable, the FAA and Boeing should consider the following steps:

1. Remove the MCAS system in its entirety.
2. To comply with FAR regulations concerning stick force as the aircraft approaches a stall AoA, Boeing should:

(a) consider aerodynamic changes to the airframe;
or
(b) develop a 'stick pusher' solution.

In addition to fixing the B737 MAX, Boeing should set their designers and engineers to work on building a completely new state-of-the-art replacement for the B737.
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Old 5th Apr 2019, 13:59
  #3314 (permalink)  
 
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Originally Posted by JesusonAHarley View Post
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?
I understand where you are coming from. I, too, was appalled at the attitude of some on here- stating the pilots must have been wrong based on where they came from. I also hypothesised a very similar scenario on 13th March- post 1171- all that I hadn't mentioned was the difficulty in turning the trim wheel at higher speeds, but I'd assumed that would be obvious if anyone looked at the indicated airspeed from the ADS-B data that was available at the time! (Put your hand out the window of your car when you're driving at 60mph/100kmh- it's a lot easier to move back and forward than at 100mph/160kmh!) The roller coaster movement I had never heard of before- and not sure if this would have been an option on this flight given the speeds and altitudes involved.

Mentour pilot's video was fantastic, it was uploaded prior to the publication of the preliminary report, it's a shame he has removed it. He also stated the reason for doing the test was because too many people instantly blamed the pilots just because of the geographic location of where they worked!

I also have a couple of queries about the data:

All the electric trim inputs from the pilot are short throughout apart from one...:

At 05:40:27 the Captain advised the First-Officer to trim up with him.
On this occasion, the trim moved 1.9 units ANU over a period of 8 or 9 seconds! This is the only occasion in the entire flight where the pilots were able to command ANU trim for any longer than 2-3 seconds. Possibly your point and my point are related to the 2.3 unit mark. Otherwise, is there some reason that the Captain's trim switches were compromised? It is the only time in the transcript where the Captain requested the FO to trim up with him. With the Captain's stick-shaker activated etc. would this possibly cause any complication to his trim commands being tripped out so soon each time? Is there another hidden 'safety' system that limits the pilot trimming up when stick-shaker is activated? Or is it simply just a case of the motor not being able to operate due to the increased forces at the given airspeed (when considering the blips later on)?






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Old 5th Apr 2019, 14:02
  #3315 (permalink)  
 
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Originally Posted by fdr View Post
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.
This sums it up nicely as far as I can judge. No matter the outcome of the investigation, the mere suggestion of the above scenario should send shivers through everyone's spine.

Regarding the thrust, whatever the reason they were still producing 94% thrust, may I add the sobering thought that reducing the thrust would have lowered the nose even further...
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Old 5th Apr 2019, 14:02
  #3316 (permalink)  
 
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Besides having made time during the 6+ minutes of flight to navigate (setting and resetting altitudes/headings) and to communicate multiple times with ATC, it's hard to conceptualize how at low altitude in day VMC neither pilot had reacted to the obvious increasing cockpit noise from the rush of a air in the slipstream as the jet zoomed to 458 kts IAS and beyond clacker speed to 500 kts. The 29 year old captain's purported 8000 hours' experience level obviously lacked depth in situational awareness and manual control of the thrust levers.
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Old 5th Apr 2019, 14:14
  #3317 (permalink)  
 
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I am just a glider guy and frequent SLF, I am very surprised every time I read about the low number number of hours in these posts. My clubs insurance wanted to me to have 500 hours total time plus 250 hours tail wheel to fly a clapped out agwagon dragging gliders around. Do insurance companies not set standards in the airline world?
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Old 5th Apr 2019, 14:45
  #3318 (permalink)  
 
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Originally Posted by Luc Lion View Post
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.
Autopilot engages, gear must be up for that to happen, no?
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Old 5th Apr 2019, 14:45
  #3319 (permalink)  
 
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Originally Posted by positiverate20 View Post
With the Captain's stick-shaker activated etc. would this possibly cause any complication to his trim commands being tripped out so soon each time? Is there another hidden 'safety' system that limits the pilot trimming up when stick-shaker is activated? Or is it simply just a case of the motor not being able to operate due to the increased forces at the given airspeed (when considering the blips later on)?
Would the trim motor not be able to move the stab, we would still see the trim command from the pilot.

The same when trim cutout switches were off, we don't see any change in stab position but we still see MCAS AND command
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Old 5th Apr 2019, 15:06
  #3320 (permalink)  
 
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Originally Posted by jimjim1
I offer an explanation for the behaviour of the Left hand AoA indication throughout the flight.

If the vane had been lost the AoA sensor would become unbalanced about its usual axis or rotation. The internal balance weight** would then cause the axle to be subject to movement when the aircraft transitioned from +g to -g. +g would cause the indication of +AoA. (If I have got this the right way round
Originally Posted by MurphyWasRight View Post
Excellent post, the tracking is almost too perfect to be believed at first.

This fits with the AoA heater fault as well, whatever happened caused 2 symptoms that are hard to explain except as physical damage to the sensor since the heater supply is independent of the resolver.

Someone commented that the pilots would have heard a bird strike, given the lack of a full CVR transcript we don't know if anything was audible.
I would suspect that the press conference statement of 'no foreign object' would suggest but not prove none was audible.

Anyone know if a departing vane by itself would cause a heater open?

One other observation is that the flight deck actions seem to be mostly normal until the AP disconnect, almost as though the stick shaker was activated but not working or noticed.
If missing from CVR that probably would have been noted.
Yes, a broken (losing its "winglet" part) or departing vane would explain AoA vs. gees curve and AoA heater fault.

If not a bird strike, it could be a previous damage which would have almost broken the vane. The AoA disagree happens when vertical acceleration is at its maximum (1,5 g or so) at the rotation. This acceleration would have finished to break the vane...
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