Ethiopia issues preliminary report of ET302 accident

April 4, 2019: Ethiopian aviation crash investigators today issued the preliminary report into the Ethiopian Airlines ET302 crash.

The report may be downloaded here: Preliminary Report B737-8 MAX (ET-AVJ).

LNA will have a report on the finding today or tomorrow.

30 Comments on “Ethiopia issues preliminary report of ET302 accident

  1. Norwegian has just sold a couple of 737 NG,I bet they got a really good price.

  2. ref: page 26, Appendix 1 ( is this reprenting the values at the sensor or after some system pass through?

    Interesting : beyond being off the right AoA shows much less noise than the left one.
    Static pressure left/right shows growing divergence ending 2200ft apart.
    There is more to this than just defective AoA.

  3. Muilenberg proudly proclaiming that Boeing know how fill the hole in one slice of Swiss cheese when we know that there were at least 4 slices lining up. Not convincing enough to get me up in one of those things again.

  4. I don’t belive they are more dangerous now that before.

    Key issue is the inability to manually trim the stabilizer regardless of the malfunction that has it out of position in the first place.

    For all the comments, too much has focused on the engine location and have missed the fact that it was a cascade affect that stems in large part to the old legacy system.

    That system is at the heart and core of backup for the stab trim no matter what generation and its not been trained on correctly for the aerodynamic load on the the stabilizer.

    And that is the core issue, its so in build to the 737 that you can’t change it.

    Engine change meant a hashed up change and MCAS added which in turn has shown up the weakness of the backup (or outright failure)

    Having backup is the hearts and sole of redundancy be it FBW Envelope protection or the old systems.

    Backup is supposed to be the reliable last resort to a failure in the 737 setup or the the Airbus philosophy.

    Boeing has failed in that.

    • It’s not Boeing’s fault pilots ignored overspeed warnings and accelerated to the point that aircraft was not controllable.

      • The pilots were keeping the airspeed high because of their very high takeoff altitude and because it’s part of Boeing’s checklist for “unreliable airspeed” (there was a 20-25 kt difference between left and right airspeed indicators). It’s Boeing’s fault for not updating the MCAS checklist with information on what to do when faced with unreliable airspeed.

        • They still had overspeed warnings on both sides and it should have been obvious they had too much thrust for level flight, on top of the obviously increasing cockpit noise from the rush of air.

    • “Boeing has failed in that.”

      They did not fail their objective: keeping up with the joneses.
      today a micrometer over any regular use case and you are in free fall over an abyss. Ever safety feature has been whittled down to paper thinness. If you hit on one issue you create stampeding herd syndrome of follow on problems.

      Schroedinger’s Airplane: only unsafe if you lift the lid and look inside the box.

    • Uwe, I agree.

      TransWorld, it’s the engine mounting that is causing/requires excessive use/deflections of the stabiliser/elevator. So as usual, you have the logic back to front.

      Uwe, I think you are right, there is a lot more going on. Working it out will take some time.

      As the CEO of Boeing said, MCAS is just one link in a chain of events. I agree, but I think we have different reasons. The report shows two pilots who were consummate professions, but verybody still died.

  5. From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND (nose down) direction from 2.3 units to 2.1 units.
    This was after the “stab trim cutouts” confirmed.
    Can somebody confirm if the stabilizer in the 737 has at least independent braking systems that would maintain the stabilizer in its position without input?
    Does this mean that pulling on the yoke at a certain speed range would lead to a failure of the braking system and move the stabilizer?
    This MCAS problem (besides the scandal of the architecture and the obscure reasons for its implementation) could reveal significant weaknesses in the 737 design particularly the stabilizer design.

  6. Grandfathering has got to be better managed. Consider, the Max includes design elements from the original certification in 1968. Now 50 years ago. The 737NG was manufactured for 20 years assuming the same for the MAx and an aircraft life of 20 years then the last 737 will stop flying in 40 years. Passengers on that flight will be in a craft conforming to 90 year old safety standards. 90 year old safety standards! In something that is often assumed to embody the latest in technology and safety.

  7. The preliminary accident report shows left-side/right-side discrepancies in AOA readings, altitude readings and airspeed readings. It is not clear from the report (at least to me ) whether the AOA difference indicator was installed on this aircraft.

    Uwe’s comment above that there is more happening here than just AOA discrepancies appears correct. What is the possibility that there was some kind of electrical system/flight instrument ensemble failure?

  8. Something to ponder about.
    The preliminary report mentions the crew could not move the Stab manually (By turning the wheel), with high speed, and stab in extreme trim position. So they decided to reengage the electric trim, which also reactivated the MCAS.
    On earlier aircraft before the NG, there were two Stab Trim motors. One for Manual electric, and other for Auto pilot and other systems like STS. There were also two switches marked for each motor on the pedestal and pilot can switch off the trouble maker. But from NG onward we have a single motor and when it is cutoff you have lost all powered movement of stab trim.
    So did this design switch reduce the redundancy on the MAX?
    Just a thought.

  9. How can they fix the manual stabilizer trim on all 737s? A bigger wheel? Different sprockets? Power assist? This is going to have to be redesigned on all MAx and NG. Its not as risky on NG that you’ll get into tha situation ,but if you do you are equally in deep peril.

    • I don’t seem to be able to get a answer about whether some of this is what happened to flyduabi. I’m not knowledgeable enough, so I’m assuming that if it was someone would have mentioned it by now.

      • If the same problem is present in the NG,it would explain why mentorpilot took down the vidio, he would be in a sticky place.

        • It’s quite possibly in the NG as well, the difference is that in the NG you can kill the trim buy pulling back on the yoke.

          So if you don’t get into a nose down situation that you can’t remedy you’re not likely to see a point where manual trim won’t work due to aerodynamic forces.

          So MCAS 2.0 will allow the pilots to recover from nose down, and they don’t need to address the manual trim issue. (what I suspect will happen, not what I think SHOULD happen).

          I still don’t get why the yoke back to kill the auto trim was changed in the MAX, there must have been a reason for it.

          They tried to change as little as possible in order to maintain the common type rating, even to the point of not having the AOA warning light, so if they changed yoke back trim cutout, there was a reason !

  10. Why the enormous speed?Too busy?Totally confused?Or did they feel they needed the energy for the climb they were trying to achieve in a desperate struggle for height?

    • They did not run the trim run away checklist correct, they did not disengage the auto throttle. It is I think the key to the catastrophe. See my comment down for more information. I do think they were panicked and I do think the “addition training after lion air” that Ethiopian airlines said they had was kind of “look if you see nose down just switch off these and everything is ok” it’s scary to say it but I don’t see why an experienced pilot would the checklist and perform only one line of it

  11. The tone of Muilenbergs latests statement has improved. He had to. Still there are carefull disclaimers, trying to spread responsibility. The cain of events, “profesional” pilots are still in, other ‘pilots’ told us, “associated training and additional educational materials that pilots want”. Noticed.

    • Oh, I get it now. I found the claim that Boeing could fix one link absolutely terrifying, but what he’s trying to imply is that all the other links are not dont belong to Boeing.

  12. Yes I know, but I’m wondering if all the problems with trying to move the stabilizer trim are similar. Perhaps JakDak has answered the question, the yoke cuts out the trim in the 800.

    • Peter Lemme pointed that out, and I agree it could have made a big difference. I still don’t really understand why they changed it.

      The closest answer I could find was by Marcus with a comment on https://www.satcom.guru/2019/03/ethiopian-et302-similarities-to-lion.html

      “It is impossible to restore the aft-column cutout switches. MCAS will activate in a high AoA regime where the column is fulled aft pretty heavily. Therefore keeping the aft switches would render MCAS functionless & useless.”

      I would have thought at that point the pilot would be pitching the nose down but this just takes me back to my question “why is MCAS so necessary” it’s as if the pilots can’t be trusted to react quickly enough ?

      Also MCAS 1.0 was ferocious in it’s action, why is MCAS 2.0 much less so if it was deemed so necessary the first time around ?

  13. All experts gathered here I see or more like all wanna be Sherlock Holmes.

    The report is very general and incomplete, it also does NOT state certain things that happened while more or less it means them.

    1) the trim cut out happened BUT NOT according to the checklist. The checklist requires the a/t (for the Sherlocks that don’t know what is that it’s the auto throttle) to be disengaged. Clearly the engines remained on 90+ % thus for sure the checklist wasn’t run completely. The report doesn’t state that clearly though it means it (over speed warning, co pilot calling trim cut out without calling the checklist one by one items he should have called for a/t disengage first)

    2) the trim cut out switches were re engaged (turned on again). This is evident by the electric trim and obviously the final nose down application. Again the report does NOT state that clearly though it means it when it says that the co pilot asked to try the electric trim and the captain agreed. That can happen by switching on the auto trim.

    3) you should NOT be victims of the media before the final report emerges. You should NOT comment and make assumptions when you do NOT Have even basic aviation knowledge and training.

    4) my comments do not accuse the pilots nor Boeing and do not have a target to give the blame as in my opinion it is a combination of things: a) panic in cockpit, b) inadequate training c) poorly designed automation. Could they have saved it if the checklist was done correctly and the a/t was disengaged and the speed lower ? May be. Could they have saved it by taking control fly low and low speed manually with flaps down which anyway removed the interference of MCAS ? May be. From our comfortable seats typing all these yes may be it was possible…up there though the things can be different for some.

    5) do not forget the pilots of the previous-to-crash lion air that got exactly the same problem. They did run correctly the checklist and they did land safely.

    6) wait for the final report, leave the media with their ignorance to do their propaganda. You will be surprised if they get sued from Boeing in the end…

    • If we are going to aviod speculating and wait for the final report, does that mean that the MAX shouldn’t fly until it’s out?1 or 2 years?We can’t prove anything at the moment but Boeing and the FAA have a lot more information and my scandal antennas are buzzing.

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