After Reading the Preliminary Report, A Change of Heart on the 737 MAX Grounding

737, Accidents/Incidents

After Ethiopian 302 crashed on takeoff from Addis Ababa, I thought the decision to ground the airplane was hasty. But now after reading the entire preliminary report that came out last week, I’ve changed my tune. Now that we have more complete information, I would agree that grounding the airplane is the right thing to do.

I would recommend a read through the entire preliminary report from the Ethiopian authorities to get a full sense of what is known, but I’m going to focus on what I found so concerning here.

There’s nothing overly surprising about how the flight started. The take-off roll was normal, but once the airplane took flight, things started to go wrong instantly.

The Angle of Attack (AOA) sensors started showing extremely different numbers. The right sensor was correct showing the airplane at around 15 degrees to the air flow, but the left sensor dropped to 11.1 degrees and then spiked as high as 74.5 degrees. That data is obviously incorrect, but Boeing’s problematic MCAS system — a perfect example of awful design — only looks at the one sensor, and that is the sensor it used. Thanks to that bad data, the pilots were about to be thrust into a nearly-impossible fight for their lives, despite Boeing saying it should have been easily over-ridden.

Less than two minutes after departure, the flaps were retracted and the auto-pilot disengaged. (It’s unclear from the report why the latter happened.) That paved the way for MCAS to do its thing for nine long seconds. It saw the false angle-of-attack and changed the pitch trim from 4.6 to 2.1 to push the nose down. That may not mean anything to you, but put it this way. That stopped the airplane from climbing and put it into a slight descent. Once the MCAS stopped, the pilots recovered and pointed the nose up.

A mere 11 seconds after MCAS stopped pushing the nose down, it tried to do it again. This time pitch trim went down to 0.4 and the airplane descended more quickly.

Only 15 seconds later, the pilots did what they were trained to do in a situation like this, just as Boeing said after the Lion Air accident last year.

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

This should have prevented the MCAS from forcing the nose down again, and indeed, it did.

At 05:40:41… a third instance of [Aircraft Nose Down] 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

The MCAS tried to push the nose down again, still based on the faulty sensor data, but the operative word is “tried.” This time, with the automatic trim disabled, the MCAS efforts did nothing. Good news, right? Well, yes and no.

The pilots at this point were trying to stabilize the airplane and continue climbing. But while they were doing that, the airplane started going faster and faster. Though the two airspeed indicators showed different numbers, the lowest one showed them accelerating to 340 kts. I don’t know Ethiopian rules, but in the US airplanes are supposed to be under 250 kts when they are below 10,000 feet. At those high speeds, manually trimming the airplane is exceedingly difficult thanks to the airflow over the surface.

The pilots continued to try to get the airplane to pitch up, and the Captain even asked the First Officer for help. One minute after the trim cutout was flipped, the First Officer said that he could not manually trim the airplane despite multiple attempts.

While we don’t know from the preliminary report what exactly happened in the next minute and a half, it appears that the auto-trim was somehow reactivated. Presumably the pilots, realizing that they weren’t able to manually trim the airplane, tried to flip the auto-trim back on. The cynic in me says that Ethiopia left this detail out of the preliminary report because it would have implicated the pilots in having done something wrong, but of course, we don’t know that. All we know is that the simple solution of flipping the trim cutouts did not save this airplane. It left the pilots with an airplane that was way out of trim and going far too fast. Boeing’s easy fix was anything but.

Looking at the flight data recorder (FDR) data shown on page 26 of the report, at this point it looks like the airplane was relatively level but that’s not good enough when you’re at such a low altitude.

Below you’ll see the end of the flight. In the top chart, look at the black line as showing the airplane’s altitude. Then look at the pink spikes at the bottom which show the pilot efforts to pitch the nose up. It didn’t have a big impact, and the airplane remained level. At this point, the auto-trim went back on, and you can see what happened in turquoise at the bottom. That’s where the MCAS kicked in and pushed the nose down, putting the airplane on its final descent into the ground.

The preliminary report confirms as much.

At 05:43:20… an [Aircraft Nose Down] automatic trim command occurred and the stabilizer moved in the [Aircraft Nose Down] 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.

Now, had the auto-trim not been reactivated, could the airplane have been saved? If the data is right and it was flying mostly level AND if there were no obstacles that required the airplane to climb to clear them, then yes, they could theoretically have pulled back on the throttles, slowed the airplane down, and returned to the field. But with all these problems going on, that very well could have required some super-human piloting efforts. No perfectly-flyable airplane should ever put its pilots in that position.

You have two pilots overwhelmed by a host of problems right after takeoff that were caused by the airplane itself. Had the cutout returned the airplane to normal operations and they could have manually trimmed it and continued on their way, then fine, this works. That’s what Boeing said should have happened, and it’s what we’ve all been operating under. But the manual trim didn’t work, and the pilots were forced to try to fix a complex issue with little room between them and the ground.

To me, this goes back to the shockingly poor design of the MCAS system. I talked about this a couple weeks ago, and now I find it even more unconscionable that this system was allowed to fly on an airplane. Boeing designed this poorly and the FAA’s lack of oversight failed to stop it. In the short run, the software fix that Boeing is putting together will solve the problem. Then at least these airplanes can get back in the air. But in the long run? It’s going to be a very rough ride for Boeing and the FAA.

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63 comments on “After Reading the Preliminary Report, A Change of Heart on the 737 MAX Grounding

  1. thanks for the writeup; You are right, this is shockingly bad for the FAA and for Boeing. Hubris and good old cheapness.

  2. Quick note: I believe auto-pilot shuts off when it’s getting discordant readings, which is why it shut off two minutes into the flight, most likely. Basically, the computer says “I have sensors telling me different things so I can’t do this properly, it’s up to you.”

    1. Enc – Thanks for that. The report didn’t say explicitly why it shut off, but that would certainly make sense.

      1. But this makes the failure of MCAS to empoy two sensors even less defensible. Basically, autopilot says “woah, two important sensors disagree by more than an acceptable amount — I’m outa here”. And then in manual mode (with flaps up), MCAS kicks in. But MCAS just looks at one sensor — rather than the two that the autopilots looks at.

        It’s so obvious that MCAS is a badly designed, badly implemented system. It’s just shocking. People at Boeing need to walk the plank on this.

        1. Right, I am really looking forward to reading (in a court trial filing?) the design document explaining the decision making around the use of only one sensor. If they can fix that via a software patch, the cost savings of not implementing some logic to check both would seem negligible. So was it just not considered and then missed in any review?

  3. While there is no question that MCAS needs the software update the evidence presented is indicative of shockingly bad flying on the part of the pilots. Forget the rules on 250 below 10. In their situation you do NOT want to be at 340 plus knots. That’s insanity. Especially with a nose down trim issue. They should never have allowed the speed to get that high. Note that the thrust stays high all through the event. Those guys lost control of the Jet well before it crashed. Ethiopian is wrong in stating that their pilots followed proper procedures and still could not save the airplane. They didn’t.

    There is no doubt that MCAS started the chain of events that led to this accident. But the final nail in the coffin wasn’t MCAS it was pilot error. Had the crew slowed down they would have had the control authority to climb away. Had they not violated proper procedure by turning Stab trim back on that final fatal nose down trim input would not have happened.

    The MAX grounding is unique in the annals of types that have been grounded. Never before has a type been grounded over an issue that could be addressed by proper pilot applied procedures and technique.

    1. But for the MCAS, would a reasonable pilot in the same situation have been able to keep the plane from crashing?

      Also, would a reasonable regulator in the same circumstances issue a flight certification?

      1. From 121Pilot’s tone, he/she could have easily dealt with all of these issues, and multiple birdstrikes, too….

        Jesus, no-one on that plane should have been put in the position that the poor design of the 737MAX put them in, regardless of how shite you think the pilots were. Sounds like they fought ridiculously hard to keep their passengers and crew alive – and lost.

    2. Agree. One pilot trouble shoots, the other flies the plane. (Which was which? The 8K hour pilot flew while the 200 hour pilot tried to troubleshoot?) Troubleshooting at 340 kts is unnecessarily difficult.

      1. Especially when you’re manually trimming a plane that, regardless of airspeed, has a center of gravity damn near the nosecone thanks to the engine placement.

        Saying “If the system that we designed to automatically trim the plane because we thought the plane would be to hard to trim manually fails, just turn it off and trim the plane manually” is HIGHLY circular reasoning – if the plane wasn’t hard to trim, they wouldn’t have needed MCAS.

        It’s like saying “if you’re skidding on the road and your anti-lock breaks don’t work, just turn them off and brake manually.” I mean, sure, but it ignores the time horizons and the fact that the system is only there BECAUSE of something that’s hard to do manually.

    3. A 737 driver who has flown almost every type told me that hes had to drop his gear before to help regain control of the airplane (to slow it down), and he believed theres a serious design flaw in the tailplane.

      As you said, speed is everything.

      However, MCAS goes against Boeing’s main principal of stick & rudder skills vs Airbus: Boeing has always, ALWAYS, required the pilots to fly the plane- its systems will only *recommend* what to do- as Airbus’s systems will prevent pilots & the plane from doing dangerous behaviors.

      I think Boeing needs to scrap MCAS & come up with something different, or stop having 3 AOA sensors as an optional product & make it mandatory.

  4. Hi Cranky,

    Interesting post again. There is a whole lot of talk about the MCAS and faulty sensors. Indeed faulty sensors are strange on a brand new plane.

    However, what I’m missing in discussions everywhere is the need for a MCAS system in the first place. The 737MAX is based on a 50-year old airframe, with low ground clearance for the engines. This is why the new, efficient engines with larger diameter have been positioned in front of the centre of gravity of the plane. Subsequently, the aircraft starts to pitch up when a certain angle of attack has been reached and near-to-full throttle is applied (i.e. take-off). Boeing tried to fix this behaviour with MCAS.

    This leads me to question: shouldn’t Boeing have worked out a way to get more ground clearance and properly fit the engines under the wing? Should Boeing have used a 50-year old airframe? Should aircraft manufacturers start to focus more on zero-emission engines, rather than slightly more efficient engines?

    1. Guy – Well, that’s the (multi) million dollar question. Of course, had Boeing gone with a clean-sheet design, it would have taken longer. That would have meant more time without a real response to the A320neo program, and Boeing feared that happening. So it took the risk and won some orders because of it (notably from American, who demanded the airplane). But that was short term gain for long term pain. A clean-sheet design certainly would have been preferable. It was just a timing and cost issue.

      1. I have a feeling we will be hearing stories from engineering about how this was a project that management drove and kept a very strict timeline causing a series of design shortcuts to be taken all in order to keep the orders from falling off the books.

        1. To be fair, they WERE caught relatively flatfooted by how well the Neo sold, which really constrained the time they had to respond.

          You could argue that Boeing SHOULD HAVE had a replacement plan in the works much earlier, but they thought (probably correctly) that they had a paradox: The 737NG sold because it was a quick, easy, direct replacement for older 737s – meaning keeping legacy customers like Southwest was all but certain. A new airframe would have meant more pilot training, new infrastructure (for maintenance and potentially even gate infrastructure at small airports), and that’d have essentially meant an open competition.

          1. True. It’s pretty clear the MAX was a rush job to try to catch up to the neo. Boeing had a lot more reworking to do to their air frame in order to fit those newer larger engines and we have seen what happened.

    2. AFAIK, the ground clearance issue is constrained by the 50 year old design. The emergency exit design requires that the airplane be low to the ground. The window exits don’t have a slide on the 737 like the A320. The evacuees are expected to slide down the wing near the root. If Boeing increased the ground clearance they’d have to redesign the emergency exits to the extent that the FAA might not be willing to consider it to be the same type..

  5. Yes, terrible for Boeing and likely to cost them dearly. Have read some stories about info leaking out of Boeing that the MAX was rushed to market to keep pace with Airbus. Not surprising that it has problems and not making me want to step onto one even when they do come up with the fix. We’ve already discussed how the 737 is the proverbial barbie doll of aircraft. It’s overdue for a replacement which my crystal ball says will happen not because Boeing wants to do the right thing – but because faith in this aircraft is forever tarnished and the A320 series will see double digit more sales over the 737 from now to eternity.

      1. It has been modified so far beyond it’s original 1960’s design that it now needs computer helpers to keep the thing in the air. Just like Barbie who has proportions so unrealistic that if she were a real person she’d have a serious case of lower back pain, let alone be able to stand up.

  6. Presumably aviation regulators are going to be all over any kind of fix, with the FAA I imagine in particular wanting to be seen as being especially tough so as to try to rescue their reputation.

    When might we expect to see the 737 Max flying commercially with passengers again ?
    July ? Xmas ? 2020 ? Later ?

    1. One airline I work with has removed them from their schedules until the IATA Winter schedule- so October 26… wouldnt surprise me.

      I can’t see the worlds aviation authorities agreeing to a “software” fix. I think Boeing is gonna have to add in the 3rd AOA sensor for free on all the planes that dont have them.

      1. Can you elaborate on what a 3rd sensor would do?

        From what I have read so far, each MAX has two physical sensors, but MCAS uses only one and trusts it to be correct. The software fix is supposedly changing that to use both sensors (big question is why that wasn’t done originally).

        Some aircraft apparently have an optional $80k indicator lamp telling the pilots if the two sensors disagree.

        What would the third sensor do? 2:1 vote? What if all three show different values? (two broken)

        1. No system is 100% perfect, but one sensor can obviously fail (and it LOOKS LIKE the AoA sensors on the 737 aren’t particularly reliable, since this has now happened twice).

          A 3rd sensor means that MCAS could theoretically be engaged even if one sensor has failed (using the mean of the 2 working sensors, and ignoring the divergent reading). Its MUCH less likely that 2 sensors will fail at the same time, but if they do, that puts us in the situation we’re in today, where MCAS can disengage and let the pilots trim the plane (which is NOT easy to do, hence the need for MCAS in the first place).

  7. It’s easy to Monday morning quarterback a situation like this one and point out things that were done wrong, but there is one GLARING issue I see here that, as a pilot, I cannot understand. According to all indications, the thrust was never reduced from climb thrust during the entire accident sequence. This seems a massively egregious error when taken into consideration of pilotage. Even if African rules allowed flight at greater than 250KIAS below 10,000 feet, 320 knots is not a profiled climb speed and at that altitude is right around VMO, or maximum operating speed. Clearly the crew was dealing with a lot but not exceeding structural limits is somewhat of an automatic response. I’d have expected one of them to at least move thr throttles at some point.

    Clearly Boeing screwed the MCAS deal up, both from an engineering standpoint and from a training standpoint (most pilots were completely unaware of this system when the plane was delivered). Serious questions need to be answered, for sure, but I can’t get it out of my head that if the crew would have taken steps to manage their airspeed they would have survived the incident. Clearly mistakes were made.

    1. Well don’t forget the captain’s stall shaker was going off the entire time- so along with the airspeed indicators being off, they probably thought they were close to stalling…

      maybe its time for a 3rd airspeed/groundspeed source??

      1. There actually are 3 sources; the Captain’s, the FO’s and the standby. They are all driven by independent air data computers deriving data from their own set of sensors. If the Captain’s indications were in disagreement with the other 2 a master caution would have triggered along with an air data flag on the Captains side. Either way, given the multiple suspicious indications from the captains side I would have thought he’d have at least looked over to the standby to corroborate the data he was seeing.

  8. The question needs to be asked (and investigators in the US government are doing it) why US airlines all managed to figure out that they needed to buy optional equipment that would have alerted them if the same AoA failures had occurred on their flights but many foreign operators including Lion and Ethiopian did not.

    Boeing offered two levels of safety to its customers with the safer level sold at a higher price.

    That is beyond belief and to a great extent why the FAA’s role in all of this is being questioned by aviation authorities around the world and why those same foreign aviation authorities have much less urgency to get the MAX back in the sky.

    1. In short order we will find out how Boeing got this Barbie doll aircraft certified & it ain’t going to be pretty for them or the FAA.

    2. I believe all the US, Canadian, and Panamanian carriers ordered their planes with the extra redundancies.

    3. My understanding is that United did not buy the optional equipment. Source is a United spokesperson

    4. United did not order either of the options, and I don’t believe it would have made a difference in the accident. The stick shaker going off with an indicated airspeed of about 300 knots already indicates that there is a sensor disagreement. Providing an AOA gauge or a disagreement light would have told them nothing new, and wouldn’t have changed the outcome.

  9. Obviously, in hindsight, MCAS should not have been fed from data of only one sensor. However, how often do these sensors disagree? Lots of talk about MCAS’ flaws, but I don’t have a good understanding on how often sensor failures happen and why (AOA, pitot tubes, etc).

    1. Spacie – Well, we know of at least 3 flights so far with disagreement. But these things should be highly reliable in general. Still, if they aren’t, then there shouldn’t be an effort to crash the airplane.

      1. But given that the autopilot apparently looks at both indicators and kicks back to manual mode if they disagree by too much (which I believe is true), you have to wonder why MCAS wasn’t built the same way. First thing it should do is compare indicators, and if one is way off from the other, MCAS should sideline itself with a message to the pilot that it’s doing so based on AoA indicator mismatch.

      1. Exploiting disaster for ones own gain usually isn’t a wise idea. It’s seen as cold and opportunistic. Even though it is, still, there are some lines that just shouldn’t be crossed. This being one of them.

        Furthermore, you have any idea how badly that could blow up in their face if anything ever happens with an A320/A321 or ERJ 170/190?

        Not a good idea bro.

      2. That would be classless and tempting fate – next time it might be you. Airbus has been admirably quiet. Besides, there’s a saying that’s highly applicable here – when your opponent is engaged in digging himself into a hole, don’t interrupt. Almost every other day has brought horrendous headlines for Boeing. All Airbus needs to do is keep quiet.

        Meanwhile, my guess is Airbus is engaged internally in figuring out how they can boost production of the A320 (and A220) yet further. Boeing was supposed to go to 57 737s/month, now that’s down to 42 – so that’s 180 narrowbodies per year that are out of the market – and that’s assuming the 737 returns to schedule. So my guess is Airbus is figuring out how do they squeeze an additional A320 out of Toulouse, out of Hamburg, out of China and above all, how to ramp up Mobile much faster than before.

        TL;DR – Boeing competitors and those who fly them need do absolutely nothing at this point to benefit from the Seattle (sorry, I mean Chicago) company’s massive, gargantuan, mind-bogglingly awful screw up.

      3. I thought it was an unwritten law in the airline industry to never ever “we are safer” as a marketing message after an accident?

      4. Stvr, as other commenters mentioned, its bad business to exploit disasters of your competitors.

        AFAIK, it used to be a traditional procedure that if there was a crash of an airliner in the US, all US airlines would pull their advertisements for around a week, so as to be respectful to those who have lost their lives.

  10. Heads should start rolling in Chicago over this abomination of an airplane. The fact they created something that has played a role in two crashes in under a year without taking action (at least in public) until after the plane was grounded should be frowned upon in a heavily regulated environment.

    I always felt that the 737 MAX really was lipstick on a pig since the original 737 hails from the 1960’s and it had a common fuselage to the 1950’s 707. I really feel they should have come up with something new that would compete with the A320neo and the C-Series (now A220). Right now, Airbus is on track to completely dominate the narrow body market until Boeing comes up with something new.

    1. By “heads rolling” do you mean handcuffs and prison sentences for manslaughter? I’ve seen it said on other forums and while I think everyone should have their day in court the body count here deserves much more than a “software fix.”

      I’ve also heard from some people out in Seattle that hear more over water cooler talk than I do that Boeing blew their wad on the 787 and doesn’t have the $$$ to do a clean sheet anything right now. On top of that the 737 is the only aircraft they’re really making money on at the moment. Right now the smart money is on shorting BA stock.

      1. Step 1 is to get those responsible out of the company so they don’t cause anymore harm to other projects. Step 2 is to perform a criminal investigation if there is a reason to do it (I’m not a lawyer, so I don’t know what is legal or not).

        1. I endorse this suggestion. The men and women ( including the test pilots and the FAA officials) who had no qualms about allowing a flawed passenger aircraft to be airborne and certified should not be allowed inside any aircraft manufacturing company/certifying authority. And criminal action must be taken against all those who so casually played with precious lives in this case.

  11. I now agree the aircraft should be grounded, but not because the incident would have required “super-human piloting efforts”. This event should have been survivable for any properly trained and qualified 737 crew, especially after the Lion Air accident. At that point, any crew should have realized what would happen with a stick shaker after rotation and responded accordingly.

    I recognize that MCAS put them in a difficult situation, and that there is a serious design deficiency with the aircraft that needs to be corrected. But I also think there are a lot of clues that point to an over reliance on automation and a lack of fundamental hand flying skills by the Ethiopian crew. First, there’s the attempted autopilot engagement at 400’ (I can’t imagine any pilot at my carrier attempting to engage the autopilot at 400’ with the stick shaker going off). The fact that the throttles weren’t moved from 94% would likely be due to them being dropped out of the flying pilot’s scan. If you always fly with the automation, you never need to touch the throttles until just before the flare. They likely had no awareness of throttle position (admittedly, the stick shaker and holding back on the yoke as hard as you could would be very distracting). Then there’s the lack of trimming – While hand flying, the captain allowed the MCAS to trim the aircraft nose down for 9 seconds without any intervention. This nose down input was followed by only a second or two of nose up trim, which was nowhere near sufficient. It should have been natural to react to the automatic nose down trim input while hand flying by trimming nose up. Taken together, these things lead me to believe the captain didn’t have a lot of proficiency hand flying (we know the F/O didn’t – the only way to learn to fly a 737 with only ~300 hours is to not do a lot of hand flying!).

    I don’t believe you would have needed extreme piloting skill to have survived this event. After the Lion Air accident, it was clear to 737 pilots that the MAX could respond with nose down trim to a faulty AOA indication. If I had rotated and gotten a stick shaker in the MAX, I would have likely had the trim turned off before the gear came up. Even without doing that, if they had countered the 9 seconds of nose down trim at any point with a manual trim input, or had pulled the throttles back from 94% before reaching VMO, they may well have survived. Surviving this incident would have taken solid hand flying skills, but in my opinion, not extreme skills. I worry that it’s yet another example of over reliance on automation.

    Having said that, there are large areas of the world where pilots have very little piloting skills and lots of skill in using the automation. Boeing sells airplanes to the entire world; grounding the airplane at this point is appropriate. But the best safety devices in the cockpit are still two well trained and competent pilots.

    1. Anonymous Delta pilot here. So glad Delta has no Max’s. It will take a long time before I can trust Boeing again.

    2. I am not a pilot.

      One thing that has always concerned me a bit when flying with US regional carriers is the level of experience of the guys and gals upfront. I trust that they can handle the aircraft under normal circumstances. But will they have the skills and experience to deal with unexpected emergencies?

      The MAX crashes, similar to the AF south Atlantic crash earlier in the decade, might be signals to invest more in pilot training. I’d be happy to pay more for my ticket.

      And none of that absolves Boeing from delivering a safe aircraft.

      And I continue to recognize that air travel is still the safest form of transportation in most parts of the world. Let’s make sure that continues.

    3. Even if a more experienced crew could have survived, MCAS created a failure mode that went thru the cockpit. No aircraft system should create circumstances that could cause a crash — such systems should, at worst, be neutral in that regard. MCAS does not appear to have been neutral.

    4. I presume this was an autothrottle take-off? It does seems strange they ignored the throttles but as you said I suspect they lost that part of the scan because they became fixated on problem-solving.

      1. Unless something is deferred, all takeoffs on all large transport aircraft are done with the auto throttle (737NG/MAX included).

    5. “But I also think there are a lot of clues that point to an over reliance on automation and a lack of fundamental hand flying skills by the Ethiopian crew.”

      Bingo! You just saved me from leaving the same comment. The supposedly “highly experienced” 8000 hour, twenty-nine-year-old Captain was another zero hour cadet from Ethiopian’s flight academy who was hired directly into the seat of a wide-body jet to do long haul flying with no experience. Any nascent hand flying skills that Captain may have gained from his cadet training withered on the vine of autopilot and auto thrust cruising at FL410. Six thousand hours of 15 and 16 hour blocks of autopilot babysitting was his only experience before he upgraded to 737 Captain. A far cry from grinding out flight time one hour at a time as a flight instructor followed by part 135 piston twin night cargo flying to build enough time to land your first regional FO gig. The tell tale sign of total automation dependance was evident in the bizzare and blantantly against norms and established procedures call to engage auto pilot at 400’ feet even as the stick shaker was going off. The automation dependent behavior was at its most bizzare and undeniable as the crew let the airplane fly them from take-off to 500 knots and forty degrees nose down into the dirt with take-off power set. That’s like letting cruise control drive you into a concrete wall at 150mph without ever tapping the brakes. Only a total auto thrust junkie, habituated to using auto thrust for all speed and thrust changes could do something like that without reflexively reaching to retard the thrust levers.

      Yes the Max was deeply flawed and unairworthy but it was excessive speed brought on by a lack of basic hand flying skills that caused Ethiopian 302 to crash. Had they keep the aircraft’s speed under Vmo the manual trim would have worked fine and they never would have been tempted to turn the faulty stab trim switches back in contradiction of procedure. That was the final unrecoverable mistake.

      1. I agree with everything you said, up until saying that turning the trim back on was the final mistake. If the manual wheel isn’t working, and you are having trouble controlling the airplane, turning the trim back on isn’t necessarily a huge mistake. You’d have to immediately start electrically trimming (overriding the MCAS). Once the aircraft was back in trim, you could turn the switches off again. But then you’d also expect them to pull the thrust back. In any event, there was no prolonged application of nose up trim, and activating the trim allowed MCAS to engage again, so it ended up being a mistake after all…

  12. Yup, it’s easy to blame the pilot… I would like to see how you would have responded in that situation that those pilots were in. Ultimately, they should have NEVER been in that position in the first place. In the past few weeks with all the coverage on the crash, it’s clear that both the plane itself and MCAS had issues to begin with, all due to a hasty process of bringing the MAX to “certification” in order to complete with the NEO.

    1. Unless you’re a pilot yourself you will never understand, but I thought my cruise control analogy might be relatable for the uninitiated.

      You are right, inflight emergencies are very stressful and have the ability to reduce your powers of reason and concentration to near zero. That’s exactly why habits and training matter so much, because that is what you fall back on in times of extreme stress. The crew of Ethiopian flight 302 was dealt a bad hand, but ultimately it was survivable. Sadly they lacked the basic hand flying skills they needed to survive their MCAS AOA vane/trim malfunction so everyone onboard died. That’s the professional, objective opinion of several experienced pilots here, so unless you have something material to counter those claims with I think you should just recognize that you’re way out of your depth and accept the unbiased professional opinions of others.

      Your sentiment seems to be a common one among online commentators of this tragedy, but air disasters are not either/or situations. Boeing AND the Ethiopian Pilots AND Ethiopian Airlines who trained both the pilots from scratch can all be at fault. There is plenty of blame to go around here. I personally have a lot of sympathy for the pilots and feel their skills deficit is 99% the fault of the airline that trained and hired them both. Pinning all the blame on one scapegoat allows guilty parties, bad procedures and bad behavior to go unchallenged and unchanged leading to more disasters later. Yes, Boeing is culpable and deserves a reckoning but the entire industry has an automation problem. It is most acute at these young, booming, developing world airlines and it needs to be addressed. There is an engineering solution for the faulty single sensor MCAS design. The crisis of automation over-dependence will be much harder to solve.

    2. As a 737 captain who’s flown a fair number of MAX flights, I’m also curious how I would have responded in that situation. But I can tell you two things:

      1. After the Lion Air accident, if I had gotten a stick shaker on rotation in a MAX, I would have disabled the stab trim immediately. Probably before the gear came up, and well before MCAS could have engaged.

      2. I would never, ever try to engage the autopilot at 400′ with the stick shaker going off. In fact, I wouldn’t ever engage the autopilot at 400′ on takeoff (I like to hand fly – my average is between 21,000-25,000′ on departure).

      Take that for what it’s worth, but I’m pretty confident I would have survived the Ethiopian scenario. I hope the Lion Air one too, but it’s hard to know how I would have reacted with no prior information.

      1. “…but it’s hard to know how I would have reacted with no prior information.”

        You would have reacted as you have previously stated… “I like to hand fly…” That’s what most pilots who elect to stay on the B737 say… because they like to hand fly, they stay on the B737. Those who do NOT like to hand fly switch to something with more automation.

        Hand flying the plane in these instances is neither difficult nor dangerous. A real PILOT would naturally counter the nose-down trim with nose-up trim. The second instance of unknown nose-down trim equates to activating the stab-trim cut-out switches and the resultant “oh crap, now I have to crank the handle the rest of this flight” but nothing more than that. Going fast, no matter the reason, always results in pulling the throttles back MANUALLY when hand flying. Those are simple natural instinctual actions for a PILOT!

        Of course, I’ve only been hand-flying military & commercial planes for 40+ years but heck: “you’re just a line pilot” (as told to me many times by management/union types).

  13. In reference to your statement “The cynic in me says that Ethiopia left this detail out of the preliminary report because it would have implicated the pilots in having done something wrong, but of course, we don’t know that.”

    Will we ever know? Will Boeing (along with other government’s agencies and independent analysts) get the data and be able to confirm or challenge the report?

  14. better late than never. MCAS or not, Boeing needs to be completely open regarding what’s available in the plane, then let the pilots decide how to leverage the systems. We can argue the merits MCAS all we want, but Boeing’s biggest problem here is the lack of disclosure, thus potentially giving the illusion that steering the MAX is by-and-large similar to the NGs when such a major feature (or is it “flaw”?) exists.

    Grounding *just* Lion Air would’ve been hysterical, and letting fear and panic rule the day. *Not* grounding after Ethiopian would’ve had all the fingerprints of a potential cover-up.

  15. A big question for me: if MCAS didn’t exist, how flyable is the aircraft?

    As for Cranky’s change of heart: the new key info is that the pilots did indeed cutout the stab trim, and still couldn’t recover. But I maintain that you didn’t need that info to ground the fleet well before the FAA actually did. The publicly available data already showed some aspects of this story. You don’t need total evidence that a plane is dangerous to ground it. The burden of proof is on the other side: a plane only flies if you have high confidence that it is safe. The FAA’s statements continue to show that they don’t understand this.

    Anyway, we’ve all known since the Lion Air tragedy that the design of MCAS was flawed, in that a single bad sensor could cause it to go haywire. Was Boeing putting enough urgency into fixing that much, at least, after the first crash?

    For years, the Space Shuttle Challenger disaster has been something of a textbook case in engineering ethics. I suspect that the Boeing 737 MAX will also become a matter for such case studies.

  16. As a regular air traveler,this line in the last para scares me: “In the short run, the software fix that Boeing is putting together will solve the problem. Then at least these airplanes can get back in the air”. How casually the temporary fix is mentioned. Instead of calling for redesigning the entire plane which obviously involves a lot of money and time, Boeing will be allowed to continue to endanger life with this patched-up plane. I for one will NEVER fly in this plane, no matter what reassurances are given. Even the FAA which was respected around the world till this report came out, has lost its credibility.

  17. Greetings from the world of U.S. airline maintenance.
    Some of us, myself included, KNEW that the plane should have been grounded. Frankly, it should have been grounded after the Lionair crash. Aside from the obvious ~170 lives that would have saved from the Ethiopian senseless tragedy, it was also completely warranted at that time. The design flaw was immediately obvious, and doomed to happen again, the very first time an AOA sensor got wonky.
    Amazing, it took about five months.

    What FRUSTRATES ME MOST is when people like YOU, who have a lot of public visibility and are periodically interviewed by media sources from outside the realm of travel-geekery, ERR ON THE SIDE OF “MEH”.
    As someone who has dedicated my career to making flying as safe as is humanly possible, it really grinds my gears when someone as influential as yourself come in with the attitude of “Two complete hull losses with over three hundred lives lost? Let’s wait for some better information.”

    I’m the last person to sensationalize or blow aviation events out of proportion.
    But the response by the FAA and Boeing was blatantly criminal negligence.
    And it’s unfortunate that you put yourself in that boat as well.

    Critically but respectfully,
    737 Mechanic

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Cranky Flier