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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 4th Apr 2019, 13:24
  #3101 (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
  #3102 (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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Old 4th Apr 2019, 13:47
  #3103 (permalink)  
 
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Originally Posted by ecto1 View Post
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)
Fair point, I should have written crews were overwhelmed instead of too easily overwhelmed. Nonetheless, despite all the stress and confusion that was surely occuring, the "only thing" that was happening is that the airplane was trimming nose down. According to Boeing this can be overriden with the electric trim switch and I have not seen any proof yet that this isn't the case. As I already wrote in an earlier post it is just very puzzling to me why a pilot would let his/her aircraft get to an extreme nose down state if it is possible to counter this with electric trimming. We obviously need more information to be able to understand what truly happened.
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Old 4th Apr 2019, 14:02
  #3104 (permalink)  
 
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Originally Posted by mryan75 View Post

If you're not a pilot, why are you posting on a professional pilot's website?
I would suggest that his input has been far more valuable that yours...

Ultimately, this crash will come down to design and engineering so, let’s not be too precious about pilot only input into this forum.
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Old 4th Apr 2019, 14:34
  #3105 (permalink)  
 
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Anyone consider the old "pitch for airspeed" and how counter intuitive slowing down might have seemed?
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Old 4th Apr 2019, 14:36
  #3106 (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.
This^^^.

Not one word more is necessary. Thanks.
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Old 4th Apr 2019, 14:40
  #3107 (permalink)  
 
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Originally Posted by 737mgm View Post
Nonetheless, despite all the stress and confusion that was surely occuring, the "only thing" that was happening is that the airplane was trimming nose down.
Not quite the only thing - also Stick Shaker, elevator feel shift, IAS disagree and ALT disagree to deal with.

Regardless, there is a simple way of proving whether an average crew will be overwhelmed - test it in the sim. During the likely extent of the MAX grounding there must be enough NG/MAX crew getting a sim check anyway to give you a large dataset to be sure.

If the average crew is overwhelmed, either the system isn't safe or the training isn't good enough, or both. If the average crews cope just fine, then these crashes are just pilot error, nothing to fix, move along...

Of course, the industry can't do that because sims that can replicate mcas are rare as rocking horse sh*t outside of Boeing itself, because they aren't needed, because you can learn all you need to know about the MAX from an NG sim. All except how not to crash.
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Old 4th Apr 2019, 15:05
  #3108 (permalink)  
 
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Referring to the same post
And perhaps you could remind us how US crews were somehow able to fly this dangerously designed airplane for two full years without a single MCAS activation.
Isn't there a report by an AA pilot concerning MCAS causing problems in the safety reporting database (can't remember the name of it just now)?
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Old 4th Apr 2019, 15:11
  #3109 (permalink)  
 
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Originally Posted by FakePilot View Post
Anyone consider the old "pitch for airspeed" and how counter intuitive slowing down might have seemed?
I have repeatedly suggested that excessive airspeed may have played a role, particularly based on the ADS-B data for the ET302 crash. Given the simultaneous stick shaker and other warnings, reducing speed may not have been the first choice, and was certainly not on any checklists.

The downside of reducing thrust with underslung engines, is that this reduction produces a slight nose down pitch. It is unlikely that a reduction in speed would have been sufficient in the time available, given the low altitude and 'point of no return' reached by ET302

Last edited by GordonR_Cape; 4th Apr 2019 at 18:03.
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Old 4th Apr 2019, 15:23
  #3110 (permalink)  
 
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Sim pilots also put Sully plane back on a runway.

In this and many other scenarios, figuring out what to do is a lot more challenge than doing it. That sim test is worth nothing if you know which specific failure is going to happen at your specific flight.
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Old 4th Apr 2019, 15:26
  #3111 (permalink)  
 
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Preliminary Report

http://www.ecaa.gov.et/documents/204...8-d7af1ee17f3e

- GY
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Old 4th Apr 2019, 15:32
  #3112 (permalink)  
 
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CNN say they have a copy of the preliminary Report - see their website - and have quoted some interesting facts.
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Old 4th Apr 2019, 15:34
  #3113 (permalink)  
 
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Hi Gordon,
Your post surprises me a bit. I can't see that I suggested a checklist for AoA disagree here...
I did say that the much touted so called "correct" checklist for Stab trim runaway was unsuitable for the rogue MCAS cases which have occurred and that a dedicated checklist should be made for that.But there can't be checklist, study or training until Boeing has the final (final...) design.
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Old 4th Apr 2019, 15:56
  #3114 (permalink)  
 
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FDR ET302


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Old 4th Apr 2019, 15:58
  #3115 (permalink)  
 
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Originally Posted by gmx View Post
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.
Quite simply the LionAir data does not establish that it is possible to win the battle between Electric Trim and MCAS (particularly if time is of the essence). With combined opposing authority it may only have have a marginal effect on trim. While that may be sufficient to maintain control if the trim is close to optimum it may not be enough if the trim is already way off. Like you say, the data on Ethiopian has not been released yet. However, the published information on the LionAir incidents is not sufficient to draw firm conclusions. I will concede that in the LionAir incident it would appear to be the case that the situation could have been resolved by acting sooner; as in the previous flight. It is not clear that the same is true in the Ethiopian accident. It also may be of some importance that the situation developed at a later stage in the previous LionAir flight. Despite reading most of what is available, I still have more questions than there are answers. In the LionAir incident (crash) stick-shaker started at the beginning of the take-off roll... it is a stage that puts particular stress on the crew to properly interpret and react.
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Old 4th Apr 2019, 16:03
  #3116 (permalink)  
 
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Preliminary report and FDR data are out.

It appears MCAS did in fact make several Stab Nose-down inputs.

Pilots trimmed back up and selected switches to CUTOUT. But the stab remained in a nose down angle. Crew seen pulling back on elevator continuously. They decide to re-energize the stab cutouts so as to trim nose up again (only slightly). It is then when MCAS goes "I've had enough" and adds another 2,5degs nose down. Airplane dives.

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Old 4th Apr 2019, 16:04
  #3117 (permalink)  
 
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Originally Posted by 737mgm View Post
Fair point, I should have written crews were overwhelmed instead of too easily overwhelmed. Nonetheless, despite all the stress and confusion that was surely occurring, the "only thing" that was happening is that the airplane was trimming nose down. According to Boeing this can be overriden with the electric trim switch and I have not seen any proof yet that this isn't the case. As I already wrote in an earlier post it is just very puzzling to me why a pilot would let his/her aircraft get to an extreme nose down state if it is possible to counter this with electric trimming. We obviously need more information to be able to understand what truly happened.
"Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.
In those cases, longitudinal trim is achieved by using the manual stabilizer trim wheel to position the stabilizer. The trim wheel can be used to trim the airplane throughout the entire flight envelope.
In addition, the autopilot has the authority to trim the airplane in these conditions.
The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane
throughout the flight envelope."
Reference: Explanatory Note to TCDS IM.A.120 - Boeing 737 Issue 10 page 15 [Ref 1]. My reading of this, and the preceding paragraph in the referenced document, plus an equivalent safety issue on the 747-8 / -8F [Ref 2], is that the aisle stand trim switches can be use throughout the flight envelope, but the yoke trim switches cannot.

Ref 1 - http://www.easa.europa.eu/sites/defa...20ISS%2010.pdf
Ref 2 - http://www.easa.europa.eu/sites/defa...ESF%20B-13.pdf

Last edited by Semreh; 4th Apr 2019 at 16:43.
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Old 4th Apr 2019, 16:09
  #3118 (permalink)  
 
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"The crew performed all the procedures repeatedly provided by the manufacturer, but was not able to control the aircraft," said Ethiopian Transport Minister Dagmawit Moges, unveiling results of the preliminary probe into the crash.
Presumably Moges refers to "STAB TRIM CUT OUT switches (both) ... CUT OUT" on the Runaway Stabilizer Checklist.
Does the ET302 Preliminary FDR data support the assertion that the crew did this, and if so, when?
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Old 4th Apr 2019, 16:11
  #3119 (permalink)  
 
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Narrative of the flight from the preliminary report:

1 FACTUAL INFORMATION

1.1 HISTORY OF FLIGHT

On March 10, 2019, at about 05:44 UTC (All times listed is Universal Coordinated Time (UTC), as recorded on the FDR.), Ethiopian Airlines flight 302, a Boeing 737-8 (MAX), Ethiopian registration ET-AVJ, crashed near Ejere, Ethiopia, shortly after takeoff from Addis Ababa Bole International Airport (HAAB), Ethiopia. The flight was a regularly scheduled international passenger flight from Addis Ababa to Jomo Kenyatta International Airport (HKJK), Nairobi, Kenya. There were 157 passengers and crew on board. All were fatally injured, and the Aircraft was destroyed.

The following is based on the preliminary analysis of the DFDR, CVR and ATC communications. As the investigation continues, revisions and changes may occur before the final report is published.

At 05:37:34, ATC issued take off clearance to ET-302 and to contact radar on 119.7 MHz.

Takeoff roll began from runway 07R at a field elevation of 2333.5 m at approximately 05:38, with a flap setting of 5 degrees and a stabilizer setting of 5.6 units. The takeoff roll appeared normal, including normal values of left and right angle-of-attack (AOA). During takeoff roll, the engines stabilized at about 94% N1, which matched the N1 Reference recorded on the DFDR. From this point for most of the flight, the N1 Reference remained about 94% and the throttles did not move. The N1 target indicated non data pattern 220 seconds before the end of recording. According to the CVR data and the control column forces recorded in DFDR, captain was the pilot flying.

At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in ¾ seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.

At 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.

At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.

At 05:38:58 and about 400 ft radio altitude, the flight director pitch mode changed to VNAV SPEED and Captain called out “Command” (standard call out for autopilot engagement) and an autopilot warning is recorded.

At 05:39:00, Captain called out “Command”.

At 05:39:01 and about 630 ft radio altitude, a second autopilot warning is recorded.

At 05:39:06, the Captain advised the First-Officer to contact radar and First Officer reported SHALA 2A departure crossing 8400 ft and climbing FL 320.

Between liftoff and 1000 ft above ground level (AGL), the pitch trim position moved between 4.9 and 5.9 units in response to manual electric trim inputs. At 1000 ft AGL, the pitch trim position was at 5.6 units.

At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the flaps were retracted and the pitch trim position decreased to 4.6 units.

Six seconds after the autopilot engagement, there were small amplitude roll oscillations accompanied by lateral acceleration, rudder oscillations and slight heading changes. These oscillations continued also after the autopilot was disengaged.

At 05:39:29, radar controller identified ET-302 and instructed to climb FL 340 and when able right turns direct to RUDOL and the First-Officer acknowledged.

At 05:39:42, Level Change mode was engaged. The selected altitude was 32000 ft. Shortly after the mode change, the selected airspeed was set to 238 kt.

At 05:39:45, Captain requested flaps up and First-Officer acknowledged. One second later, flap handle moved from 5 to 0 degrees and flaps retraction began.

At 05:39:50, the selected heading started to change from 072 to 197 degrees and at the same time the Captain asked the First-Officer to request to maintain runway heading.

At 05:39:55, Autopilot disengaged,

At 05:39:57, the Captain advised again the First-Officer to request to maintain runway heading and that they are having flight control problems.

At 05:40:00 shortly after the autopilot disengaged, the FDR recorded an automatic aircraft nose down (AND) activated for 9.0 seconds and pitch trim moved from 4.60 to 2.1 units. The climb was arrested and the aircraft descended slightly.

At 05:40:03 Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.

At 05:40:05, the First-Officer reported to ATC that they were unable to maintain SHALA 1A and requested runway heading which was approved by ATC.

At 05:40:06, left and right flap position reached a recorded value of 0.019 degrees which remained until the end of the recording.

The column moved aft and a positive climb was re-established during the automatic AND motion.

At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.

At 05:40:20, approximately five seconds after the end of the ANU stabilizer motion, a second instance of automatic AND stabilizer trim occurred and the stabilizer moved down and reached 0.4 units.

From 05:40:23 to 05:40:31, three Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.

At 05:40:27, the Captain advised the First-Officer to trim up with him.

At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.

At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.

At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position

At 05:40:44, the Captain called out three times “Pull-up” and the First-Officer acknowledged.

At 05:40:50, the Captain instructed the First Officer to advise ATC that they would like to maintain 14,000 ft and they have flight control problem.

At 05:40:56, the First-Officer requested ATC to maintain 14,000 ft and reported that they are having flight control problem. ATC approved.

From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position. The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left.

The data indicates that aft force was applied to both columns simultaneously several times throughout the remainder of the recording.

At 05:41:20, the right overspeed clacker was recorded on CVR. It remained active until the end of the recording.

At 05:41:21, the selected altitude was changed from 32000 ft to 14000 ft.

At 05:41:30, the Captain requested the First-Officer to pitch up with him and the First-Officer acknowledged.

At 05:41:32, the left overspeed warning activated and was active intermittently until the end of the recording.

At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

At 05:42:10, the Captain asked and the First-Officer requested radar control a vector to return and ATC approved.

At 05:42:30, ATC instructed ET-302 to turn right heading 260 degrees and the First-Officer acknowledged.

At 05:42:43, the selected heading was changed to 262 degrees.

At 05:42:51, the First-Officer mentioned Master Caution Anti-Ice. The Master Caution is recorded on DFDR.

At 05:42:54, both pilots called out “left alpha vane”.

At 05:43:04, the Captain asked the First Officer to pitch up together and said that pitch is not enough.

At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,4002 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.

At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording.

The left Indicated Airspeed increased, eventually reaching approximately 458 kts and the right Indicated Airspeed reached 500 kts at the end of the recording. The last recorded pressure altitude was 5,419 ft on the left and 8,399 ft on the right.
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Old 4th Apr 2019, 16:11
  #3120 (permalink)  
 
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However, you might add, at no point was thrust reduced from 94% N1, which allowed the airspeed to reach around 375kts.... which at the final ND trim was unrecoverable.

None of the crew trim inputs at any point were sufficient to counter the MCAS ND trim events, which is really where things went wrong. Had they trimmed sufficiently and hit the cutouts, we'd not be have this exact discussion.

Also, the AOA was not offset for the entire flight, it appears to an event that occured some8 seconds after takeoff. Bird strike maybe?

- GY
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