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Ethiopian Airlines 737 MAX Investigation Preliminary Report

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Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#321

Post by cjbprime »

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…

We don't want pilots to be creative. Air safety is so good because pilots learn memory items and checklists and actually follow them instead of making stuff up.

If the checklist doesn't mention flaps and the plane crashes if you keep the flaps up, that's on Boeing.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#322

Post by cjbprime »

kayfox wrote: post #102
proctor wrote: post #63

Earlier quoted context omitted.

this video[0] from "mentour pilot" on youtube explains the stabilizer system quite well. it seems the trim wheels are connected manually to the trim mechanism in the back, but when the trim stabilizers are in an extreme position the wind loading on them makes it very hard/impossible to rotate the trim wheels manually. from what i understand, one way to relieve/lessen the wind loading so that the manual wheels can be…

Its possible and I think it was demonstrated in one of Mentour Pilot's videos that both pilots can work together to manually trim. Boeing put notes in the manual that this may be needed and it would not break the manual trim system to apply that much force to the trim wheels.

Recall that at the same time it's taking the strength of both pilots on the yoke to keep the plane approximately level. You're saying they should both let go at low altitude and see if they can crank a trim wheel together?

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#323

Post by cjbprime »

pdonis wrote: post #126
Rooster61 wrote: post #60

Earlier quoted context omitted.

> MCAS is specifically designed for an edge case Source? That's the first I've heard that it's only for edge cases.

> That's the first I've heard that it's only for edge cases. It's only supposed to activate in a specific edge case (high angle of attack, manual flight, no flaps, low airspeed). That's been discussed plenty online (including previous threads here at HN). But that assumes that the angle of attack sensors are accurate. If the AoA sensors are inaccurate, as they were on this flight (more specifically the left one), MCA…

I don't agree with "low airspeed". You can exceed critical AoA (and therefore stall) at any airspeed.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#324

Post by kalleboo »

paulmd wrote: post #188
holler wrote: post #74

Earlier quoted context omitted.

this may be a naive question but with all of the advanced technology on these planes, why isn't there a check for altitude before any automated command runs which says "hey we just took off, are 400ft above ground, MCAS is saying nose down, we will crash if that command runs, CANCEL"

Because right after takeoff is the single most common point at which you might stall the aircraft. What's more, at that point it is likely to be a power-on stall, which is the specific situation that MCAS is intended to fix (because the 737 MAX has a tendency to pitch upwards in power-on scenarios). Really there should just have been a separate cutout for MCAS itself, but that would have triggered retraining requirem…

And the AoA disagree needs to be actually used and not just an "option feature pilot warning". AoA disagree on ground = plane doesn't take off. In flight = MCAS cuts out.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#325

Post by cjbprime »

aeternus wrote: post #212
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?

Icing is a possible culprit. Most likely covering the static port which will cause incorrect pressure altitude and airspeed. >the First-Officer mentioned Master Caution Anti-Ice.

The plane was taking off from Addis Ababa. I don't think it's ever freezing near ground level there?

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#326

Post by cjbprime »

bbojan wrote: post #285
Osiris wrote: post #80

Do we know of any documented situations in which MCAS actually did it's job correctly, that is, preventing a stall from too large AoA?

Preventing a stall is not what the job of MCAS is. (edit: clearer language)

This language is not clear, at least to me. MCAS is absolutely an anti-stall system. There's some correlation with yoke handling, but it's still with the goal of affecting yoke handling in order to prevent stalls.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#327

Post by cjbprime »

kalleboo wrote: post #324
paulmd wrote: post #188

Earlier quoted context omitted.

Because right after takeoff is the single most common point at which you might stall the aircraft. What's more, at that point it is likely to be a power-on stall, which is the specific situation that MCAS is intended to fix (because the 737 MAX has a tendency to pitch upwards in power-on scenarios). Really there should just have been a separate cutout for MCAS itself, but that would have triggered retraining requirem…

And the AoA disagree needs to be actually used and not just an "option feature pilot warning". AoA disagree on ground = plane doesn't take off. In flight = MCAS cuts out.

You can't have an AoA disagreement when stationary on the ground. It is a wind vane.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#328

Post by djmips »

cjbprime wrote: post #327
kalleboo wrote: post #324

Earlier quoted context omitted.

And the AoA disagree needs to be actually used and not just an "option feature pilot warning". AoA disagree on ground = plane doesn't take off. In flight = MCAS cuts out.

You can't have an AoA disagreement when stationary on the ground. It is a wind vane.

You don't know that. If it's malfunctioning it could be in the electronics and nothing to do with how it operates.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#329

Post by dang »

ummonk wrote: post #140
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…

Why is that getting downvoted? What the heck.

It got extremely heavily upvoted. Unfortunately, though, that wasn't for good reasons in terms of the HN guidelines: https://news.ycombinator.com/newsguidelines.html.

This subthread is clearly about gratifying rage, not intellectual curiosity. That makes it off topic for Hacker News. Yes, the rage is understandable and there are reasons for it. Nevertheless what's going on in this vortex of the discussion is not in keeping with the values of the site. To a weird extent actually.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#330

Post by djmips »

Imagine MCAS was never created. Instead pilots had to deal with the nose up stalls themselves. Would that have ended up being the outcome? Instinctively I feel like pilots could deal with the situation where MCAS was supposed to help, especially a lot better than when MCAS is dooming these two planes. What do you think?
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