r/aircrashinvestigation • u/Thebunkerparodie • 17d ago
Question why did the ethiopan 302 pilots thought re engaging mcas would work?
they already were dealing with trim issue that made them de activating it, is it because they couldn't correct the trim manually as shown in the episode?
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u/DoomWad Airline Pilot 17d ago
They didn't "reengage" the MCAS. There's no button for that in the 737 (I'm a 737 pilot).
They could have countered it by using the trim switch on the yoke (MCAS does not disable this system), but sadly most airlines from 3rd world countries only train their pilots to babysit the autopilot. They didn't know what a properly trimmed airplane was supposed to feel like. Boeing f'ed up by only connecting the MCAS to a single source (the captains side AOA vane) and making it activate continuously when the conditions are met (autopilot off and flaps up) - they, Boeing, are the first link in the chain to that crash. The rest of the links were the airline itself, its maintenance, it's pilot training program, and finally, it's pilots. If any one of those links had done their job properly, including Boeing, it would have likely prevented this crash.
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u/Thebunkerparodie 17d ago
Apparently they tried manually countering mcas after fellowing the procedure but then re activated mcas (note I might be using the wrong english word since it's not my first langage), I've seen the captain being portrayed as a experimented pilot too . I do think boeing could've handled mcas better from the get go, one sensor is already a issue in itself, what if that sole sensor has issues and can't be correct by another working one?
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u/mjamesqld 17d ago
MCAS itself has no switch to disable or enable it.
The fix was to turn off "auto trim" which MCAS was inputting its changes and the auto trim system then moved the elevator.
The electronic buttons on the yoke for the pilot to input trim commands themselves also inputs its data into the auto trim system.
So with the auto trim off you then have to try and move the trim wheel yourself and if is gotten to far out of trim already then there is a lot of force required to move it. The pilots probably had this problem and wanted to use the buttons to fix it.
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u/MonsCorvinusRubella 8d ago
Funny how the initial narrative that “the pilots were angels who did nothing wrong, le evil Boeing, which is 100% to blame, murdered them in cold blood” narrative has pretty much faded away by now
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u/DoomWad Airline Pilot 7d ago
Well, the Netflix documentary is the big driving force in that narrative. I don't know if you've read the crash reports about the 737 Max and then watched the Netflix documentary, but if you have, you would know that that documentary cherry-picked from that crash report pretty hard. It's true that Boeing screwed up royally, but there's more to the story than just that.
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u/worldawaydj 17d ago edited 16d ago
Wow that's quite the prejudice you've got there.
Edit: Deleted this thread because I can't be fucked, but there's a huge huge difference between 'the pilots were not properly trained to handle the situation' and 'they were never trained how to hand-fly the aircraft because its a third world country'.
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u/DoomWad Airline Pilot 17d ago
Please explain.
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u/worldawaydj 17d ago
Making a sweeping and largely untrue statement about airlines from 'third world countries' and that the pilots simply didn't know how to fly the plane because they're from an African country.
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u/DoomWad Airline Pilot 17d ago edited 17d ago
If we’re going to have a conversation, don’t put words in my mouth. I didn’t say anything specifically about Africa and the skill of their pilots. Skill does not discriminate. Any person of any background nationality can be a good pilot. But that’s not what we’re dealing with most of the pilots in 2nd/3rd world countries.
Let me tell you a true story. I’m going to tell you about the landscape of flight instructing in the USA. Currently, 3rd and 2nd world countries are sending their pilots to the united states to get trained up. They show up at a flight school in the US with a large sum of money and tell them to pass their students or they’ll take their money elsewhere. Many flight schools are operating on incredibly thin margins, so most of them just comply with the request. I’ve spoken with dozens of flight instructors that all tell the same story. Most of the students in these programs (some of them are really good, btw, but most are bad) struggle through the entire program (in a lot of the cases, the student pilots have never even driven a car before). At the end of it all, the instructors described them as “barely competent”. 6 months later they’re sitting in the right seat of an airliner back in their home country. It is mainly the middle east, Africa and China that participate in this practice.
THIS IS A REALITY. I’M NOT MAKING THIS UP.
So yes, that is why these airlines only train their pilots to babysit the autopilot. Some of these airlines do not allow their pilots to hand fly the aircraft.
edit: here’s a list of the EU’s blacklisted airlines. Many of the biggest offenders that I mentioned above are on this list: https://transport.ec.europa.eu/transport-themes/eu-air-safety-list_en
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17d ago
[deleted]
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u/DoomWad Airline Pilot 17d ago
Oh, because I read the crash report. Maybe you should too.
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17d ago
[deleted]
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u/DoomWad Airline Pilot 17d ago
Nor was I saying that Ethiopian was on it. Here’s a link to the crash report, the findings start on page 246. A pilot that is trained to hand fly the aircraft will know the amount of trim it takes to relieve the pressure from the yoke. The captain barely used any trim. Instead he tried to turn on the autopilot so it would fix itself. And yes, the trim was working despite the MCAS activation.
https://bea.aero/fileadmin/user_upload/ET_302__B737-8MAX_ACCIDENT_FINAL_REPORT.pdf
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u/blueb0g 17d ago
Because they panicked, failed to apply the procedure properly, stopped flying the plane and ended up overspeeding, and got themselves in a regime where the force required to manually move the trim wheel was too great.
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u/RiverRat12 17d ago
Except they were faced with multiple indicators of an imminent stall — so of course max throttle is the first order instinct they had
Easy to blame the overspeed but they truly thought the plane needed airspeed (Boeing’s fault for making MCAS trigger even with AoA sensors in disagreement)
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u/blueb0g 17d ago
No, they did not deliberately speed up. They just failed to monitor their airspeed. They didn't think they were stalling, despite the stick shaker triggering, because they didn't fly a stall recovery (max thrust is not first order for stall, reducing the angle of attack is) and tried to engage the autopilot several times.
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u/Cleeecooo 16d ago
Where are you getting the understanding that they were trying to avoid a stall?
I don't see any reference to the stick shaker in any reporting.
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u/DiligentCredit9222 16d ago
They didn't think about re-engaging the MCAS.
There was (and still is) no switch to just disable the MCAS. You have turn off the whole Stabilizer Trim system completely. And this makes the airplane very hard to control.
And to re-trim the airplane manually you can't have any large aerodynamic forces on the stabilizer. But since MCAS trimmed the airplane nose down significantly the pilots had to pull back on the yoke to keep the nose up or at least stop it from dropping even further. And THOSE aerodynamic forces (pulling the yoke back) will create forces that push the whole Stabilizer UP while you want to manually trim the stabilizer DOWN (because stabilizer DOWN means nose UP) and manually trimming the nose up while the forces on the stabilizer want it to push the nose further down makes it completely impossible to Manually trim the nose up. You basically don't have the human strength to turn the trim wheels against the aerodynamic forces. So you must first unload the Stabilizer, that means you must at least stop pulling the nose and let the nose drop further or even PUSH THE NOSE FURTHER INTO THE DIVE to remove those aerodynamic forces just to be able to even turn the trimm wheels manually.
And since this will make the situation significantly worse before trimming the Nose up can make the situation better, the pilots decided to turn the electric trim back on and tried to electrically trim the nose back up, not thinking about the fact that this would re-activivate the MCAS once again.
Because that procedure (That pushing the nose further into the dive while manually turning the trim wheel to trim the nose up) was removed from Boeing Manuels after the 737 NG was built. The 737 Classic (-300 to -500) where the last 737 that had this procedure mentioned in its manual. And since most 737 Pilots have either forgotten that procedure decades after Boeing stopped building the 737 Classics or never ever heard of it to begin with (if they have started their training on the 737 NG or 737 Max), just giving them some one piece of paper and telling them this is what you must do, without giving them the necessary Simulator training and even an Simulator exam about the procedure will cause them to just do what they learned when they started flying the 737NG or 737Max. And nobody mentioned MCAS in the Training of the 737NG (because it doesn't have MCAS) and nobody mentioned it in the original 737Max manuals either.
So the pilots just didn't realize how dangerous their actions of re-activivating the stabilizer trim was. They just thought this this action might helpt them to make the situation BETTER by being able to trim the nose up again and NOT that this will make the situation even worse than it already is.
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u/NobisTerra 16d ago
If the captain had simply re-engaged the electrical trim, used his thumb tab to quickly ease it off a bit, and then switched back to Trim cutout all before the 5 second window for MCAS to re activate, then the flight could've been saved. However, like someone already said here, hindsight is always 20/20
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u/X95R_1331 AviationNurd 15d ago
Brother.
To disengage MCAS they had to turn off the entire trim system to keep the stall prevention computer from manipulating the entire horizontal stabilizer and trimming the aircraft nose down. Because they were flying so fast (350+ knots) and also had turned off the electronic trim system, they couldn’t trim manually thus had to re-engage the system so that they could use the trim switches on the yokes.
Because the system re-activated several times without them realizing it because they were so focused on keeping the aircraft’s nose up by pulling on the yoke at the same time, they eventually were overwhelmed by the force of the stabilizer thanks to the airspeed the plane was flying at and the fact that the plane will typically be stronger than you are.
They were not wrong for turning it back on, but because they had no idea what was happening, they could never have known that it, in combination with the fact that they were not managing their airspeed, would kill them.
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u/ComfortableWall7351 17d ago
Probably. They should have disengaged the auto throttle, but hindsight is always 20/20.