
Third Pilots' Union Raises Concern About Boeing 737 Max Jet - swznd
https://www.bloomberg.com/news/articles/2018-11-15/third-pilots-union-raises-concern-about-boeing-s-737-max-jet
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WalterBright
The pilots would have seen the nose down action as an uncommanded stabilizer
trim movement. The solution is to shut off the power to the stab trim. This
would work and would require no knowledge of the stall avoidance mechanism.

~~~
sokoloff
Exactly this. Following the existing memory items and QRH checklist items
taught to every 737 pilot is (very, very likely) enough to overcome this
contemplated scenario of a runaway trim from a flaw in the stability system.
(It's remotely possible that the crew holds no blame in that they followed the
checklist properly and the cutout switches were defective or the checklist
response was otherwise insufficient.)

~~~
bronco21016
Would runaway trim be the thing they were reacting to? It seems to me the trim
was pitching down due to the design of the stall system. I’m imagining they
were getting erroneous stall warnings due to the AOA sensor feeding bad data.
If I’m in an aircraft and I’m getting stall warnings, stick shakers, and stick
pushers I’m definitely not going to run runaway trim memory items.

~~~
sokoloff
It's pretty likely that they _weren 't_ reacting to runaway trim; on that we
agree.

The trim wheels are large, painted mostly black with alternating, offset white
stripes (so the motion is quite visible), and have a very distinctive clacker
on them.
[https://www.youtube.com/watch?v=cQirIH_DuAs](https://www.youtube.com/watch?v=cQirIH_DuAs)

It's possible that the crew fought to keep the airplane in a basic attitude
flying configuration for several minutes without ever noticing the trim in
motion unexpectedly, but that seems unlikely, particularly when the act of
holding the nose up to hold attitude was accompanied by increasing nose down
trim.

Minor note: there is no stick pusher in the 73. Those tend to only be
installed on T-tail aircraft. Synthetic elevator feel increases, but no pusher
only a shaker.

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A2017U1
The preliminary investigation report is due out 29th Nov.

Boeing is already being sued.

A bit OT but how hasn't the cockpit voice recorder been found yet? It's been
weeks while giving off a detectable ping and is in 30m of water, that's
recreational level diving. You simply follow signal strength.

Given the big economic hit that occurred last time when Indonesian carriers
were banned from Europe you have to wonder whether they actually want to find
it.

~~~
cyberferret
I think I read somewhere that they are not getting the 'pings' from the
Cockpit Voice Recorder like they did the Flight Data Recorder, which was
recovered.

I believe the force of impact, which was almost vertically nose down at high
speed just caused such a shattering of the airplane that it might have fatally
destroyed the CVR, or else driven it under many feet of mud and silt.

Re: Your last point - I think this time around the CVR could vindicate the
crew and point the blame at Boeing, so it may seem in their best interest to
recover it and have extra proof for the court case. Then again, the level of
corruption in Indonesia could affect what happens with the recovery process.

~~~
userbinator
The CVR is mounted next to the FDR so they should search in approximately the
same place, and it probably won't be damaged if the FDR wasn't. It's more
likely to be buried, as you note.

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capkutay
Would it be overly cautious to avoid flights on Boeing 737 MAXs?

edit: of course with the downvotes for an honest question. this site can be
ridiculous.

~~~
JshWright
Yes. This is a very specific failure mode, and given the publicity of this
event, it's not going to catch anyone else out.

Now, that doesn't mean I didn't double check the aircraft types for some
upcoming flights flights...

~~~
SteveNuts
I've got an upcoming flight on a 737-800, is it safe to assume that model
isn't affected by this?

~~~
JshWright
Correct, the 800 is a "Next Generation" series jet, not a MAX, and so it
doesn't have the MCAS that is suspected to be related to this accident.

------
gargravarr
Okay, I've never sat in the cockpit of an aircraft, but the one thing I don't
understand - if the nose of a plane suddenly drops, isn't the pilot's first
instinct to pull back on the controls to raise it? From what I've read, in
Boeing aircraft at least, the pilot's controls can always override the
automatic systems.

~~~
JshWright
Pulling back on the controls moves small control surfaces (elevators) on the
horizontal stabilizer (the "tail wing"). The way the anti-stall measure works
on the MAX (and many other planes, to be fair) is by adjusting the pitch trim.
Adjusting the trim changes the angle of the entire horizontal stabilizer.

[https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi...](https://en.wikipedia.org/wiki/Stabilizer_\(aeronautics\)#/media/File:Tail_of_a_conventional_aircraft.svg)

It's very possible for the effect of the extreme trim condition to be more
than the elevators can overcome. The pilot can certainly override the trim
setting, but the issue here is that they weren't expecting that to change,
since they weren't trained on the fact that the plane might do it
automatically (in those flight conditions).

Here's a good video explaining how trim works (in normal operation) on a
(slightly older) 737:

[https://www.youtube.com/watch?v=l62NvkRWa5E](https://www.youtube.com/watch?v=l62NvkRWa5E)

~~~
danielvf
A 737 and a 737 MAX has big wheels in the cockpit that move as the stabilizer
trim changes. This lets the pilots see what the autopilot is doing with the
stabilizer, and/or override stabilizer changes by grabbing and holding the
wheel or rotating it. You also have two switches to disallow control of the
stabilizer, one for blocking other stabilizer controls in the cockpit, and one
for blocking control by the autopilot.

In theory then, solving the stabilizer problem that caused the crash is as
simple as flipping both switches to cutoff, then using the wheel to set the
stabilizer back to a sane value. Handling a stabilizer runaway is a standard
part of US 737 training, and the updated Emergency Airworthiness Directive
just says to follow the stabilizer runaway checklist. Again, in theory, this
should have been a no-brainer, "common" emergency, and following the usual
checklist would have fixed the issue.

However, pilot's mental model of the aircraft has been broken. In the previous
generation of 737's, there were exactly two things outside the wheel that
could control the stabilizers - the cockpit trim switches, and the autopilot,
and each had it's own cutoff switch. Now we have three systems that can
control the stabilizer wheels, and the new one doesn't have a labeled switch,
nor was anyone told it existed.

~~~
inferiorhuman
> In theory then, solving the stabilizer problem that caused the crash is as
> simple as flipping both switches to cutoff, then using the wheel to set the
> stabilizer back to a sane value.

[https://www.youtube.com/watch?v=rxPa9A-k2xY](https://www.youtube.com/watch?v=rxPa9A-k2xY)

The issue for the Lion Air pilots was time. At 5,000 ft you don't have time to
adjust the trim before you hit the ground. While I think that the stabilizer
trim can be adjusted more quickly than the video shows you'd still be looking
at somewhere around the order of 30 seconds end to end.

~~~
VBprogrammer
The elevators still have some authority, you don't have to wind it from end to
end to regain control. Also, the full range of mechanical motion is only
available via the trim wheel, the electronic trim doesn't drive it to either
extreme (although it can move it back to the centre from an extreme).

~~~
inferiorhuman
> The elevators still have some authority, you don't have to wind it from end
> to end to regain control.

If you're at a low altitude and managing other problems will you have enough
time to even recognize the problem and then wind the cranks and recover before
you hit the ground?

> Also the full range of mechanical motion is only available via the trim
> wheel, the electronic trim doesn't drive it to either extreme (although it
> can move it back to the centre from an extreme).

Can MCAS drive the trim full down? What I've read suggests that if you give it
time, it can.

~~~
VBprogrammer
> If you're at a low altitude and managing other problems will you have enough
> time to even recognize the problem and then wind the cranks and recover
> before you hit the ground?

My suspicion is that it would probably have required a well drilled crew to
have handled the problem correctly. But I don't think we're up there with the
extraordinary levels of piloting which we've seen demonstrated previously e.g.
Flight 1549 (the miracle on the Hudson).

> Can MCAS drive the trim full down? What I've read suggests that if you give
> it time, it can.

I'd be surprised if it can drive it outside the normal range of electronic
motion. There aren't really enough details out there for me to be sure though.

~~~
inferiorhuman
Yeah. I suspect that if MCAS played a deciding role in JT 610 the flight would
have been survivable if the pilots were made aware of how the plane handles
with faulty AoA data.

Although it may simply turn out that the MAX is a much more delicate plane to
fly, something along the lines of DC-10 vs MD-11.

> I'd be surprised if it can drive it outside the normal range of electronic
> motion. There aren't really enough details out there for me to be sure
> though.

Yep. There are a lot of questions (at least in my mind) including why the
Brazilians and Europeans (LOT, TUI) knew about MCAS and the Americans (US +
Canada) and Indonesians did not.

~~~
VBprogrammer
> Although it may simply turn out that the MAX is a much more delicate plane
> to fly, something along the lines of DC-10 vs MD-11.

Ha, yes that it possible.

Out of interest, where are you from and what do you do? If you find yourself
in London at some point let me know. I'm sure it would be interesting to have
a coffee or a pint. My email is in my profile.

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smaddox
> Pilots on the Lion Air flight were receiving erroneous speed readings, a
> problem that had occurred on three previous flights, according to the
> Indonesia National Transportation Safety Committee. They had radioed air-
> traffic controllers to say they intended to return to land.

Was that three previous flights of the same aircraft? And if so, why was it
still in service?

~~~
mtw
The aircraft was serviced just the night before. Somehow, that failed.

If the company knew about this issue, I doubt they would have authorized
putting the aircraft in service.

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StreamBright
If this is true I am going to lose all my confidence in Boeing.

~~~
dingaling
I have less ire for Boeing than I do the FAA.

There was an interesting comment on airliners.net that the USSR operated new
airliners on freight services for several _years_ before putting them on
passenger services. So far I've confirmed that for the Tu-154 trijet, for
example, which flew freight for two years before taking a revenue passenger.

But in the West there has always been a tension between certificating for
safety versus commercial imperative. Why hasn't the 737Max been grounded
pending investigation? Because that would lead to companies losing money. Why
would the FAA care about that? Because it considers manufacturers and airlines
as 'stakeholders'.

~~~
WalterBright
> Why hasn't the 737Max been grounded pending investigation?

Because jumping to conclusions is not helpful. Let the NTSB do their job and
find out what went wrong.

~~~
simion314
>Because jumping to conclusions is not helpful. Let the NTSB do their job and
find out what went wrong

We are used from previous cases that aircrafts will get grounded until we are
sure the airplane is not at fault. So why in the past this happened before the
investigation was complete but in this case the risk is considered t be
minimal? I am not saying that it is right or wrong but I want to understand
the algorithm that is used to decide what to do in this cases.

~~~
ubernostrum
_We are used from previous cases that aircrafts will get grounded until we are
sure the airplane is not at fault._

To be clear: you're suggesting that grounding an entire type of aircraft,
either worldwide or even just within US airspace, is a common response to
accidents?

I ask because the last general grounding of a type was in 2013 to remedy the
787 battery issues. Prior to _that_ , the last such grounding was the DC-10 in
1979.

~~~
simion314
Sorry, my experience was with incidents in my country and my memory could also
play tricks on my.

Anyway the question still stands, who and how decides if we should ground some
airplanes?

~~~
ubernostrum
Airlines can voluntarily ground their planes. Manufacturers can recommend it.
Generally, only a government agency can _force_ it and they only do so in
truly extreme circumstances (often requiring multiple serious incidents). More
commonly in the US, a directive will be issued to airlines telling them to
carry out some remedy (fix/replace a part, change a procedure, etc.) and a
window of time in which to complete it. They don't speculatively ground entire
air fleets every time there's a potential problem.

For example, in 1991 a Boeing 737-200 crashed in Colorado with the loss of all
lives on board. In 1994 there was another crash of a 737, in Pennsylvania,
again killing everyone on board. In both accidents the investigation pointed
to unexpected movement of the rudder.

Several other cases were identified where pilots claimed the rudder was moving
unexpectedly, but they were able to land safely.

The follow-up took several years of investigative work, and eventually
identified a situation where a servo could jam and deflect the rudder.

Despite two severe crashes and many other suspected non-fatal incidents, that
generation of 737s was not grounded; the remedy, once the cause had been
determined, was an order from the FAA to replace the servos, with a timeline
by which the replacement had to be completed.

------
anticensor
Is this third union of pilots or union of third pilots?

------
isostatic
If it's Boeing, I 'aint going

~~~
jsjohnst
“I’d rather be hit by a bus than fly in an Airbus”

There’s versions of these type of statements for all aircraft manufacturers.
Does it add anything to the conversation to state them? Not in my opinion.

