B737MAX [Grounded as of 13 March 2019]

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Old May 20, 19, 1:23 am   -   Wikipost
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United does not fly the 737MAX8 that has been involved in two recent crashes, but it does operate the 737MAX9.

How to tell if your flight is scheduled to be operated by the MAX 9:

View your reservation or flight status page, either on the web or on the app. United lists the entire aircraft type. Every flight that is scheduled to be on the 737 MAX will say "Boeing 737 MAX 9." If you see anything else -- for example, "Boeing 737-900," it is not scheduled to be a MAX at this time.

The same is true in search results and anywhere else on the United site.

For advanced users: UA uses the three letter IATA identifier 7M9.

All 737MAX aircraft are currently grounded, with exceptions for non-passenger-carrying positioning flights (e.g., to move them to a storage area until the grounding is lifted).
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Old Mar 22, 19, 3:13 pm
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Originally Posted by exwannabe View Post
More complicated than this, The FAA required the MCAS for certification. W/o MCAS, it was deemed to unstable to be airworthy.

So why could Boeing not design it right in the first place? It is easy for people to just assume they made stupid mistakes, but that is very unlikely to me. I presume they made engineering decisions and tradeoffs based on issues we do not know. And if so, can they implement a system that does not push the risk elsewhere?

Do agree that the true next gen mid-size (whatever it is) is needed ASAP. Even if they fix this issue, the 737 kind of sucks.
It actually is fairly straightforward.

The single-input is a huge engineering mistake - that needs to be corrected. The fix is basically done; just has to be qualified. That'll reduce the rate of occurrence to more acceptable levels.

It's not a matter of "moving the risk elsewhere" - it's a matter of the pilots knowing the proper procedure for responding to a runaway stabilizer. This is a situation that is trained for -- and has been trained for -- for decades. But, because of MCAS, it can occur at a different phase of flight than is usually trained for. But the response is exactly the same -- slap the stab trim cutout switches, and everything is back to normal.

Fast forward to 2:45 to see the proper procedure:

But that's all that has to happen ... and at this point, I'd guaran-freakin-tee that ANY 737 pilot would respond by hitting the stab trim cutouts right away. I'd argue that the 737MAX is plenty safe to fly as it sits; since any pilot will know what to do now.
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Old Mar 22, 19, 3:25 pm
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Originally Posted by LarryJ View Post
When you're hand-flying an airplane you are trimming frequently. Even more so in a transport jet as you are operating over a much wider range of speeds and configurations than smaller, slower airplanes. As conditions change, the nose either starts dropping below where you want it or it starts rising above it. You react by holding pressure to keep the nose in the desired position then re-trim to remove the pressure. This reaction is a normal part of hand-flying an airplane and should be an automatic response to an out-of-trim condition.

[...]


After three, maybe four, cycles the pilot should notice that everytime he trims the nose back up the airplane is trimming it back down. This is a stabilizer runaway. He can continue to counter the MCAS activations with his electric trim indefinitely or accomplish the stabilizer runaway procedure which will disable the system for the remainder of the flight.

The procedure is; 1. Grasp control wheel firmly. 2. Disconnect Autopilot (it's already off or MCAS wouldn't be operating) and autothrottle. 3. Stab Trim switches to Cutout.

AoA Disagree messages, or in-depth knowledge of MCAS , doesn't really help because you're busy controlling the airplane and don't have time for detailed thought on system interaction. That would come later when you're writing up the problem in the logbook for maintenance to fix. You fly the airplane. The key factor in identifying a stabilizer runaway is the repeated, or increasing, abnormal need to retrim.

[...]
Thanks for your clear description of techniques and issues in this and other posts.

As a layperson, I'm wondering if there was a typo (in red): would MCAS only be operating when autopilot is on rather than off? The former makes intuitive sense to me, but if it's the latter — I am curious why would MCAS only operate when autopilot is off? From what I have understood so far, the MCAS was added to give the MAX a manoeuvring feel consistent with the non-MAX, but if it's primarily intended as a manual pilot aid, I don't understand why disconnecting the autopilot is part of the corrective action.

I think this question is complementary to zdog2x's post just above; it seems like an odd pattern that both of the problem flights crashed soon after takeoff.

———

Also, NPR's All Things Considered did a pretty nice summary of the market pressures (fuel) and design constraints (frame dimensions vs. engine size) that led to the conception of MCAS.

Link to summary:
https://www.npr.org/2019/03/22/70597...s-737-max-jets

Link to audio:
https://ondemand.npr.org/anon.npr-mp...7_max_jets.mp3

(This isn't UA specific, but I'm posting here for continuity of discussion.)
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Old Mar 22, 19, 3:34 pm
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Originally Posted by emcampbe View Post

Guaruda just canceled their MAX orders, and their statement cited customer confidence in the aircraft.
Garuda had deferred almost their entire order well before the first crash. They are in a extreme financial pinch.
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Old Mar 22, 19, 3:42 pm
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Originally Posted by Yellowjj View Post
Garuda had deferred almost their entire order well before the first crash. They are in a extreme financial pinch.
That’s called “taking advantage of a situation”... no way could Boeing penalize them for it if they throw the safety card right now. The optics would be awful.
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Old Mar 22, 19, 3:46 pm
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Originally Posted by zdog2x View Post
I haven't seen this asked so far, but apologies if it has.

Why have MCAS operational during an initial climb? Both flights had issues within the first 2 minutes. How much risk of a stall is there during the climb while accelerating?
I read somewhere (I don't recall where and I am sure someone will correct me if I am wrong) that this could be one of the phases of flight where MCAS is most important.

Because of the higher / farther forward mounting of the MAX's engines and their location relative to the center of gravity compared to non-MAX 737s, a nose-high attitude like that experienced during initial climb makes the engines themselves in effect lift devices (as the oncoming air pushes up at the bottoms of the engines), leading to an even more nose-high attitude and a more critical AoA that may not be responded to adequately enough by the pilots. Boeing determined during flight testing that the MCAS solution was necessary to counteract that effect.
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Old Mar 22, 19, 5:18 pm
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Originally Posted by spin88 View Post

and P.S. This news really makes Boeing look slimy and ugly....

"Attorney Steve Marks, who is representing the families of 20 Lion Air crash victims, said relatives of people who died were pressured by airline employees to sign agreements shortly after the disaster. The agreements stipulated a payment of 1.3 billion rupiah ($91,600) and barred family members from suing the airline. "
https://www.washingtonpost.com/world...=.6b4fbae50092

Boeing was hoping that they could force grieving families to take an ultra-cheap pay-off before the truth of Boeing's own gross negligence came out. Really a dirt-bag move in light of subsequent developments.

It says airline employees asked victims' families to waive suing the airline.

I don't see where it says Boeing employees asked that they waive the right to go after Boeing.
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Old Mar 22, 19, 5:40 pm
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Originally Posted by cerealmarketer View Post
It says airline employees asked victims' families to waive suing the airline.

I don't see where it says Boeing employees asked that they waive the right to go after Boeing.
you are 110% right, my bad. The paragraph talks about Boeing's liability and I just read it wrong... will remove from my post so as not to confuse anyone. Gott'a admit when you got it wrong.
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Old Mar 22, 19, 5:44 pm
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Originally Posted by fumje View Post
———

Also, NPR's All Things Considered did a pretty nice summary of the market pressures (fuel) and design constraints (frame dimensions vs. engine size) that led to the conception of MCAS.
Ya, pretty good.

And it is radio, but hopefully NPR would not show picture of front of 737 from two generations ago that still shows the "eyebrow" windows (that were used to navigate by stars IIRC) like ABC news showed for the SECOND night in a row in their video
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Old Mar 22, 19, 5:51 pm
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Originally Posted by EmailKid View Post
Ya, pretty good.

And it is radio, but hopefully NPR would not show picture of front of 737 from two generations ago that still shows the "eyebrow" windows (that were used to navigate by stars IIRC) like ABC news showed for the SECOND night in a row in their video
Pretty sure no one ever navigated 737 Classics by the stars.
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Old Mar 22, 19, 7:04 pm
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Originally Posted by cmd320 View Post
Pretty sure no one ever navigated 737 Classics by the stars.
That's because the moonroof option is too expensive for the airlines.
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Old Mar 22, 19, 7:36 pm
  #716  
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Originally Posted by clubord View Post


Also facts:

One carrier has had a history of maintenance and training issues which included a ban of flying into EU airspace.

The other had a pilot at the controls with less flight experience than a United Airlines Intern.
Your facts don't counter my facts. And my facts deal with human beings.

Too many people around here in love with machines and companies, finding all sorts of ways to apologize for them. Not so much with actual people.
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Old Mar 22, 19, 8:02 pm
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Originally Posted by DenverBrian View Post
Your facts don't counter my facts. And my facts deal with human beings.

Too many people around here in love with machines and companies, finding all sorts of ways to apologize for them. Not so much with actual people.
The loss of life is tragic. I don’t think anyone is attempting to disagree.

Yet, the situations are not so simple. Although there are no reports, I can almost guarantee neither accident will have been caused by one or even two factors. Almost every airplane crash is caused by a chain of events, which often includes faults with equipment that may or may not have been overcome if it were not for other factors.

Unequivocally pointing the finger at the aircraft without all of the facts is not respecting the lives that were lost. Neither Boeing nor the regulators nor the operators are interested in operating an aircraft with any type of fault and you can guarantee that the 737 MAX and it’s pilots will be safer when the airplane returns to device than before it was grounded. That is the least Boeing, the regulators and operators can do for the families of the 346 people that were lost.
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Old Mar 22, 19, 8:12 pm
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Originally Posted by exwannabe View Post
More complicated than this, The FAA required the MCAS for certification. W/o MCAS, it was deemed to unstable to be airworthy.

So why could Boeing not design it right in the first place? It is easy for people to just assume they made stupid mistakes, but that is very unlikely to me. I presume they made engineering decisions and tradeoffs based on issues we do not know. And if so, can they implement a system that does not push the risk elsewhere?

Do agree that the true next gen mid-size (whatever it is) is needed ASAP. Even if they fix this issue, the 737 kind of sucks.
Even more complicated, Boeing in their filings w/ the FAA reported that MCAS would be able to make a maximum adjustment of 0.6 degrees. However when they realized that would not be enough to compensate for the stall-risk, they adjusted MCAS to be able to make 2.5 degrees of adjustment. Except they neglected to mention that change to the FAA, so the final FAA analysis/approval was done using incorrect numbers.
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Old Mar 22, 19, 8:13 pm
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Originally Posted by fly18725 View Post


The loss of life is tragic. I don’t think anyone is attempting to disagree.

Yet, the situations are not so simple. Although there are no reports, I can almost guarantee neither accident will have been caused by one or even two factors. Almost every airplane crash is caused by a chain of events, which often includes faults with equipment that may or may not have been overcome if it were not for other factors.

Unequivocally pointing the finger at the aircraft without all of the facts is not respecting the lives that were lost. Neither Boeing nor the regulators nor the operators are interested in operating an aircraft with any type of fault and you can guarantee that the 737 MAX and it’s pilots will be safer when the airplane returns to device than before it was grounded. That is the least Boeing, the regulators and operators can do for the families of the 346 people that were lost.
The only place where we disagree is that I do think Boeing and/or the regulators have an interest in operating an aircraft even with faults, as long as they can rationalize the faults to minor or not dangerous or hazardous to people's lives. "What can possibly go wrong?" We've seen, twice in five months, what can possibly go wrong.

I want my manufacturers and regulators to be absolutely ruthless about safety, and in this case, I think the foot went ever so slightly off the gas.

Absolutely, the MAXes will be safer when they return to service. They damn well ought to be. And it shouldn't have taken stalling on the part of Boeing to ground 'em on the second crash, let alone the first. Abundance. of. caution. Not abundance of profits.
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Old Mar 22, 19, 10:08 pm
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It looks terrible on United's part to be such a huge, international carrier and cheap out on some safety features that they probably could have bargained hard for to bring it under that $80K (assuming list price) especially since AA and WN ordered the warning light. Typical cheap United and typically bad PR/executive response.

I've flown on United's MAX 9 2x before the accidents.
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