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Ethiopian Airlines 737 MAX Investigation Preliminary Report

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Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#261

Post by simion314 »

ams6110 wrote: post #190
msbarnett wrote: post #168

Earlier quoted context omitted.

Nope. The Boeing/FAA directive re: MCAS does not instruct them to extend flaps. Further, there's other things going on in the cockpit due to the malfunctioning AoA sensor that's the root of all this. Specifically one of the effects is that they get an Unreliable Airspeed Indication, and run that checklist. That checklists memory items include maintaining the current flap configuration (in this case, flaps up). The Bo…

You're correct that the AD and runaway trim procedure does not instruct them to extend flaps. What I was addressing was the statement upthread that "Flaps out supposedly would have kept MCAS off but the pilots weren't expected to know that." If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with aut…

>If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA.

And in a crisis situation you skip the checklists and think fast and apply your instincts because you read something on a forum? Sure if you have a lot of time you can try thinking but this is not debugging a bug where you have hours to observe the issue, try different inputs, observe again, Google some questions etc..

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#262

Post by acqq »

Phrodo_00 wrote: post #250
geofft wrote: post #223

Earlier quoted context omitted.

The "greedy bunch of assholes" are the Boeing execs who optimized for profit over the lives of those pilots and their passengers. (I thought that was pretty clear from the comment, fwiw.) I think it's been pretty thoroughly established at this point that an underlying design constraint in the MCAS was that it was easier for Boeing to get a 737-with-modifications approved than a new airplane, despite the engines being…

It's not just Boeing, though (not that this exculpate them in any way), but cheap airlines insist in flying 737, but also have demand for more efficiency. This plane was trying to satisfy that impossible "I want the exact same plane but better" demand, so that the other greedy bunch of assholes that are airline execs wouldn't have to spend in training mechanics and pilots because the plane they're flying has another…

No. The redirection of demand would just give some more clients to Airbus and reduce the speed of the growth of the total number of planes flying.

Nobody should accept this attempt to excuse Boeing of its responsibility and even less the possible variant of it "we are all guilty we will buy the cheapest flight."

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#263

Post by darkpuma »

Zak wrote: post #247
darkpuma wrote: post #230

Earlier quoted context omitted.

> "A stick pusher, or a pilot pushing forward on the stick is not enough for the aerodynamics of the 737 MAX in certain circumstances. The position of the engines means the thrust tends to push the nose up, and at low speed, the elevator controlled by the stick alone is not enough to push the nose down when nearing a stall. Instead, the trim must be used, which moves the whole horizontal stabilizer rather than just t…

All jets with low wings and underslung engines (most modern airliners) experience a pitch-up moment from engine thrust, and trim is used to compensate. When the plane is being flown in some steady state, pilots adjust the trim until no force on the controls is required to maintain that state - they're not getting a specific setting from a table or memory. What's different is that at low speed, high thrust, and high a…

> "What's different is that at low speed, high thrust, and high angle of attack, the elevator of the MAX does not always have enough pitch moment to reduce the angle of attack."

It's my understanding that for the 737 NG as well, there are stall scenarios at particular speeds, levels of thrust and angles of attack where trimming the stabilizer is necessary to recover. That the difference between the NG and MAX is what those particular values are, not whether or not that scenario exists ever.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#264

Post by msbarnett »

davepage wrote: post #259
cjbprime wrote: post #71

Earlier quoted context omitted.

> sufficient nose up trim was not selected by the yoke manual trim switch prior to pulling the trim cutouts The EAD/service bulletin doesn't talk about sufficient nose up trim or caution against performing the cutout with even a slight mistrim. > And then they did not work the mechanical trim wheel hard enough to reset the residual nose down trim. It's possible that aerodynamic load (of the stabilizer opposing the el…

The Boeing/Ethiopian ETH-2 bulletin quoted in the above linked AAIB preliminary report on page 33 says "Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT ..."

> Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT ..

Which really under explains the situation. In reality the STAB TRIM CUTOUT must be switched to CUTOUT within 5 seconds of using the electronic stabilizer trim, or the MCAS will re-establish the forces.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#265

Post by late2part »

rdiddly wrote: post #119

Reading through the chronology in section 1.1, it feels like a movie where the aircraft is a malevolent entity that's trying to kill them. So if I were in the cockpit I'm sure it would've been some mix of fear and anger. My life's not in danger though, so I'm only left with the anger, on their behalf, knowing some greedy bunch of assholes were effectively that malevolent entity, whose will was expressed via the aircr…

I generally support your first paragraph and the first sentence of your second. But your final sentence is illogical and immature. If you want @dang and mods to ban you; just erase your account.

If what you mean to say is "if what I am saying is wrong, then ban me for saying it," you should say that.

Regardless you've created a little drama for your biologically degrading snowflake, and it's unlikely they'll want to make you a martyr, but does your second sentence really add much value except to air your protestations?

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#267

Post by calecon323 »

cjbprime wrote: post #71
davepage wrote: post #43

Earlier quoted context omitted.

It does not appear to be "precisely" the procedure, in that sufficient nose up trim was not selected by the yoke manual trim switch prior to pulling the trim cutouts. And then they did not work the mechanical trim wheel hard enough to reset the residual nose down trim. And, the crew left the power setting at climb throughout almost the entire sequence, so they oversped the airframe. And, when they (against procedure)…

> sufficient nose up trim was not selected by the yoke manual trim switch prior to pulling the trim cutouts The EAD/service bulletin doesn't talk about sufficient nose up trim or caution against performing the cutout with even a slight mistrim. > And then they did not work the mechanical trim wheel hard enough to reset the residual nose down trim. It's possible that aerodynamic load (of the stabilizer opposing the el…

You're right that the service bulletin doesn't talk about selecting selecting a sufficient nose up trim because control of the aircraft using manual trim is a continuous action performed in combination with the pitch up command of the control yoke. Just pulling up on the control column and activating momentary manual trim isn't sufficient or intended. I understand why people think the checklist implies that performing a STAB TRIM cutout occurs instantly after the autopilot is disengaged because of the "if runaway continues" language.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#268

Post by geofft »

VBprogrammer wrote: post #251
cjbprime wrote: post #231

Earlier quoted context omitted.

Agree on the consensus. There's a piece of additional flavor, which is that as I understand it Boeing proposed building a new type of plane as an a320neo competitor, and the airlines announced that they'd only buy it if it's a 737 subtype to avoid having to retrain their pilots. It's not just "Boeing doesn't want to pay for certifications", but also -- and perhaps primarily -- "Airlines don't want to pay for training…

Just to add an extra element to what you've already said. It's quite likely that the pilots themselves would have been reluctant to accept another entry level narrow body jet. In the current climate it's often the pilots themselves who are paying for the type rating, at least the first one they acquire.

That's fair, but also, salaries for pilots are not great, and Boeing's former CEO got a salary of $865K/year + $1.3M/year bonus + stock and now that he's retired gets a pension of $730K/year. I'm sort of curious what exactly it would have cost Boeing to say, "This is not a 737, but we will pay to retrain any 737-trained pilot who's interested." (Which still would have given them a negotiating advantage over Airbus!)

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#269

Post by dboreham »

Rooster61 wrote: post #7

> The crew performed runaway stabilizer checklist and put the stab trim cutout switch to cutout position and confirmed that the manual trim operation was not working. This is very damning to Boeing. It's precisely the procedure they prescribed and intended to mitigate possible MCAS caused trim runaway. In light of the fact that they put this in place as a justification for moving the engines forward without reclassif…

Wondering why Boeing stock went up today...

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#270

Post by cjbprime »

bbojan wrote: post #255
tuna-piano wrote: post #238

Earlier quoted context omitted.

Just to put their "mistakes" in context - Sully, America's favorite hero pilot, accidentally put his airplane into an almost stall as he was performing the Miracle on the Hudson (due to the A320's design philosophy, the airplane prevented the stall...). It goes to show- even great pilots doing good work in a stressful time can make critical oversights.

Do you have a reference for that statement? Because the story that I heard is that he purposefully commanded max pitch knowing that alpha protection would prevent the airplane from stalling, as his landing speed would be lowest at max AoA.

And I heard a third story, which is that the aircraft nearly botched his deliberate attempt at flaring for the water landing due to envelope protections he hadn't known about:

> I was commanding for more, pulling back full aft on the stick and the flight control computers prevented me from getting more lift therefore we hit harder than we would have (...) It turns out there's a little-known software feature known only then to a few Airbus software engineers, and to no pilots to no airlines that was the case. It's called a phugoid mode. And it was not the way we were trained the airplane should work, apparently it is the way the airplane does work. But that was not apparent to us.

https://aviation.stackexchange.com/questions/52147/why-cant-...

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