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Ethiopian Airlines 737 MAX Investigation Preliminary Report

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Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#81

Post by geofft »

smaili wrote: post #24
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…

Just out of curiosity, will there actually be any punishments handed out beyond just a slap on the wrist? Or is Boeing far too large of a corp to take on?

Incidentally, Boeing has received billions of dollars in illegal tax subsidies from the US (as in, anti-competitive with non-US manufacturers like Airbus): https://www.bbc.com/news/business-38131611 So it's hard to imagine fines or market penalties actually conveying any productive sense of punishment.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#82

Post by daddylonglegs »

jordache wrote: post #69

>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. How can the sensors record such different readings?

The reading from the pitot tubes (pressure sensors) for a particular airspeed varies with the sensors angle to the airstream so the airspeed value is adjusted based on the angle of attack (AoA). If the AoA sensor is on the fritz on one side the airspeed reading for that side changes.

For redundancy, each pilot receives separate instrument readings from independent sensors. When the airspeed readings disagree a warning is activated and the pilots are expected to follow a prescribed and memorized procedure. The warning that the AoA sensors disagree was a paid option before this crash and the Lion Air crash.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#83

Post by [deleted] »

davepage wrote: post #43
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…

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)…

[deleted]

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#84

Post by mgazzer »

smaili wrote: post #24
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…

Just out of curiosity, will there actually be any punishments handed out beyond just a slap on the wrist? Or is Boeing far too large of a corp to take on?

Still too early to tell, this report is just the first step and inevitably will invoke conversation around who's to blame.

Boeing's bottom line would like this is be crew or operating procedure.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#85

Post by simion314 »

ams6110 wrote: post #41
dsfyu404ed wrote: post #27

Earlier quoted context omitted.

Flaps out supposedly would have kept MCAS off but the pilots weren't expected to know that.

Post Lion Air, they should have known that.

Why exactly? if Boeing did not updated the manuals and checklists how would pilots know that? from internet forums? Should a pilots ignore the checklists and try steps he read on the internet ?

I could not find if Boeing updated their manuals/checklists after the first crash.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#86

Post by cjbprime »

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…

> 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.

Are they talking about manual electric trim, or physically moving the trim wheel with its handle?

I would expect manual electric trim to stop working after you STAB TRIM CUTOUT, since that kills the trim motor. Did the pilots try physically moving the trim wheel?

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#87

Post by AnabeeKnox »

smaili wrote: post #24
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…

Just out of curiosity, will there actually be any punishments handed out beyond just a slap on the wrist? Or is Boeing far too large of a corp to take on?

This is an absurd comment. The rule of law works in the USA as much as it does in other developed countries. There is no such thing as "too large to take on". I note though that there is not yet any evidence of a crime having been committed.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#88

Post by kayfox »

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…

> It's possible that aerodynamic load (of the stabilizer opposing the elevator) made it physically impossible to manually trim given any mistrim at the time the cutout happened, given the airspeed they had.

Its been noted in previous discussions that while it would be difficult, the load can be overcome if both pilots were to operate the manual trim wheel at the same time.

Not that its a good situation to be in.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#89

Post by cjbprime »

msbarnett wrote: post #75
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)…

> And, the crew left the power setting at climb throughout almost the entire sequence, so they oversped the airframe. I believe that's correct given that they had an Unreliable Airspeed Indicator warning (due to the malfunctioning AoA sensor), per the memory items on the UAI checklist. It makes the forces on the trim wheel much worse, which explains why they couldn't turn it, but it's the correct checklist response t…

I think they couldn't turn the trim wheel because STAB TRIM CUTOUT unpowers it.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#90

Post by sdenton4 »

jordache wrote: post #69

>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. How can the sensors record such different readings?

Q: How do you use a barometer to accurately measure altitude? A: Drop it, and count the seconds until it hits the ground.
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