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ams6110 commented on Boeing CEO Dennis Muilenburg Addresses the Ethiopian Airlines Flight 302 Report   boeing.mediaroom.com/2019... · Posted by u/kaboro
pcurve · 6 years ago
I think lack or major crashes in recent years made them complacent and emboldened them to roll the dice. Then hit snake eyes. Then also may have looked down on the foreign pilots are the airline. Had this been a Southwest plane they may have grounded the plane.
ams6110 · 6 years ago
I do think the complacency issue might be a component here. Humans tend to quickly accept recent history as "normal" and over time forget the lessons learned by past disasters.

"Those who don't remember history are doomed to repeat it"

It's been a couple of decades I think, maybe more, since an engineering screwup affected a passenger airliner like this. You could argue that the 787 LiIon battery thermal runaway thing was a red flag. That also resulted in an FAA grounding, but that was fairly easily remedied and nobody died.

ams6110 commented on Boeing CEO Dennis Muilenburg Addresses the Ethiopian Airlines Flight 302 Report   boeing.mediaroom.com/2019... · Posted by u/kaboro
makomk · 6 years ago
The reason this preliminary report is so damning is that it's evident that the pilots on flight 302 knew this - they realised what was happening, took the necessary steps to disable MCAS, and still couldn't stop the plane from crashing and killing everyone on board.
ams6110 · 6 years ago
Read the narrative in the report. Why do you suppose that after they got the same initial signs of trouble that the Lion Air flight had (stick shaker on left side, disagreement in airspeed values, etc. immediately after takeoff) that the captain tried to engage autopilot and instructed the first officer to retract flaps and inform controllers they were proceeding to climb to FL 320 (32,000 ft). Why not instead turn back and land and hand the aircraft over to maintenance?

From the report:

At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in ¾ seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.

...

At 05:39:06, the Captain advised the First-Officer to contact radar and First Officer reported SHALA 2A departure crossing 8400 ft and climbing FL 320.

...

At 05:39:42, Level Change mode was engaged. The selected altitude was 32000 ft. Shortly after the mode change, the selected airspeed was set to 238 kt.

At 05:39:45, Captain requested flaps up and First-Officer acknowledged. One second later, flap handle moved from 5 to 0 degrees and flaps retraction began.

Bear in mind stick shaker and divergent instrument readings all this time.

Why not just return and land, leave the flaps configuration alone (which would have inhibited MCAS), especially since this is exactly how the Lion Air flight started.

I know this is easy to critique from the comfort of my chair, and the pilots are not here to defend themselves, but some things in this narrative just don't make sense.

ams6110 commented on Boeing CEO Dennis Muilenburg Addresses the Ethiopian Airlines Flight 302 Report   boeing.mediaroom.com/2019... · Posted by u/kaboro
acqq · 6 years ago
Now read again what Boeing issued to the airlines and the pilots after the first crash:

https://www.avm-mag.com/faa-issues-emergency-ad-for-boeing-7...

"An erroneous AOA input can cause some or all of the following indications and effects:"

"IAS DISAGREE alert."

The whole "what to do" is then:

"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. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."

We know now that the pilots performed what was there laconically written, and that even these actions couldn't save the plane.

Which means either:

- Boeing never actually tested how to really handle the situation described then or

- Boeing indeed tested that and knew that IAS DISAGREE procedures would also be followed and which would guarantee to make the plane uncontrollable (for details see here: https://leehamnews.com/2019/04/03/et302-used-the-cut-out-swi... how one pilot recently reconstructed that and made a video about it, which was later withdrawn on the demand of the pilot's company -- note a single pilot here did what Boeing, which is supposed to sell hundreds of billions USD worth of these planes didn't want to do), but bet on "it won't happen soon enough, we can get away with it."

I can't find that anybody can excuse either of these.

ams6110 · 6 years ago
The pilots didn't actually do that. They did not use electric stabilizer trim to "neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT" in fact the trim had been run markedly down by MCAS by the time they switched off the electric trim.
ams6110 commented on What Is Idempotence?   lispcast.com/what-is-idem... · Posted by u/tdurden
js2 · 6 years ago
At 13:45 in this interview from 2003, Sergey Brin and Larry Page try to explain idempotence to Terry Gross (NPR's Fresh Air host):

http://www.npr.org/2003/10/14/167643282/google-founders-larr...

(It does not go very well.)

Edit: I can't find a transcript, so I just transcribed that portion of the interview myself, starting at 13:45:

TG: Now I'll tell you, in preparing for this, I decided, let me Google Google, so I typed in "Google" into the Google search, and I came up with a lot of Google things in the regular search, but in the "Are you feeling lucky?" search, I got nothing.

LP: Well you just got Google itself.

TG: Yeah, I just got Google itself. Oh, I see, Google was giving me itself.

LP: Yeah.

TG: Oh.

LP: In computer science, we call that recursion. [laugh].

TG: Oh, you even have a name for it. [laugh]. I didn't quite get that. I kept thinking it was just repeating itself. I didn't realize it was giving me itself. [laugh].

LP: [laugh]

TG: And what's the name for it?

LP: Uh, recursion. It's... kind of... Sergey is giving me a dirty look.

TG: Why?

LP: It's a loose definition. [laugh]

TG: Lighten up Sergey. [laugh]

LP: It's a loose interpretation of... [laugh]... recursion.

TG: Sergey, what's the more literal interpretation?

SB: The technical term is you got itself back.

TG: Right?

SB: There's not really much beyond that. [laugh]

TG: Okay.

SB: Idempotence. How about that.

TG: Say it again.

SB: Idempotence.

TG: What is it?

SB: That's when you uh... [laugh]... Maybe I should stop while I'm ahead...

TG: ...You're just making this up, aren't you...

SB: ...Before I dig a deeper hole. Idempotence is when you do something and you get the original thing back.

TG: Oh, so that's a real word?

LP: It's a mathematical term.

SB: Yeah, yeah, but it's also just as loose an interpretation as Larry's was of recursion.

ams6110 · 6 years ago
Classic illustration of why conversations between geeky technology people and "normal" people usually and in awkward silence after about two minutes.
ams6110 commented on Boeing CEO Dennis Muilenburg Addresses the Ethiopian Airlines Flight 302 Report   boeing.mediaroom.com/2019... · Posted by u/kaboro
xiphias2 · 6 years ago
,,We remain confident in the fundamental safety of the 737 MAX.''

Am I irrational for not wanting to be on the first 1-2 years of flights on 737 MAX after it gets its software update?

ams6110 · 6 years ago
I see this playing out in a couple of possible ways. One is that it ends up like the DC-10. Public confidence is lost, even though the problem is fixed. The aircraft end up going into freighter service.

The other is that they make a convincing case that the problem is resolved. I don't know if that's possible given today's default hate for big corporations, we'll see. They've done it before with the 737 and the rudder problem it had in the 1990s or so. That problem led to a few fatal crashes, but I'm not sure it ever got the attention that this story is getting. The news cycle was different then.

I would absolutely fly on one once the problem is corrected.

ams6110 commented on Ethiopian Airlines 737 MAX Investigation Preliminary Report   ecaa.gov.et/documents/204... · Posted by u/kunkurus
msbarnett · 6 years ago
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 Boeing/FAA directive does not instruct them to deviate from this and extend flaps. They have a checklist memory item instructing them to in fact do the exact opposite, and not touch flaps.

ams6110 · 6 years ago
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 autopilot off, flaps up, at high indicated AoA.

You mention unreliable airspeed, that was actually their first problem. Flaps were extended at that point, as according to the narrative they were not retracted until after the AoA disagree, stick shaker, and airspeed disagree. In fact it almost reads like they were intending to continue the flight, engage autopilot, and climb to 32,000 ft with the stick shaker going the whole time. That seems very odd to me.

ams6110 commented on Ethiopian Airlines 737 MAX Investigation Preliminary Report   ecaa.gov.et/documents/204... · Posted by u/kunkurus
snuxoll · 6 years ago
> reading the manual

Runaway stabilizer is a memory item, there should be no reading of the manual involved.

Unfortunately the design of MCAS defeated the checklist of this particular memory item when in lower flight altitudes - which goes back to the argument that the 737 MAX never should have been given the same type rating as the older models.

ams6110 · 6 years ago
At the very least it seems that some specific "differences training" on MCAS should have been included. I don't know at what point the differences are enough to require a new type designation.
ams6110 commented on Ethiopian Airlines 737 MAX Investigation Preliminary Report   ecaa.gov.et/documents/204... · Posted by u/kunkurus
simion314 · 6 years ago
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.

ams6110 · 6 years ago
Pilots should have known that MCAS is inactive with flaps extended, per information from Boeing.
ams6110 commented on Ethiopian Airlines 737 MAX Investigation Preliminary Report   ecaa.gov.et/documents/204... · Posted by u/kunkurus
wereHamster · 6 years ago
> Aerodynamic loading prevented manual trimming using the trim wheels.

Are the trim wheels mechanically connected to the trim mechanism in the back? Is there no way to trim the horizontal stabilizer electrically without also enabling MCAS? What would happen if the pilots continually pressed the trim up switch on the yoke? That should've prevented MCAS from activating, right?

I thought Boeing airplanes were built such that "the pilot is always in control". That doesn't seem to be the case anymore, if by cutting the power to certain subsystems you can't control the airplane anymore.

ams6110 · 6 years ago
Yes, pilots selecting "up" on the trim switch should stop and override MCAS. But it also "resets" MCAS so that it will pitch down again on its next cycle. So you'd have to be constantly correcting it, or switch the electric trim off entirely (i.e. treat it as runaway trim).

u/ams6110

KarmaCake day28057March 1, 2009View Original