
Pilots offer insights on Boeing 737 crashes - internalfx
https://www.aopa.org/news-and-media/all-news/2019/march/14/faa-grounds-boeing-737-max-fleet
======
burlesona
Money quote is as the end, from a Max pilot:

“Tecce did not fault the FAA for taking a wait-and-see approach. “A lot of
people throwing a lot of rocks at the FAA. Since 2010 we’ve had one aviation
fatality” in the United States. “Our safety record is astonishing,” he said.
“I don’t think there’s anything wrong with the airplane. If you talk to the
pilots who fly them, they’ll tell you it’s not the airplane so much as whether
or not the manual properly describes what’s going on.””

Seems more and more consensus is forming around this idea, that the MCAS
system generally did what it was supposed to do, _and_ has an appropriate
safety cutoff for the pilot if needed, but that Boeing did not focus a lot of
attention on this new system in their training/documentation when in fact they
needed to.

~~~
briatx
Even if training would have prevented the crashes it's still bad design for a
critical change in flight control.

Computers should never overrule manual controls. If the autopilot is on and
the pilot makes an manual adjustment to the yoke, the autopilot shuts off.

They should have designed the MCAS system to recognize when the pilot was
fighting it and to disable itself.

It's like the runaway Prius problem. Turning off the car might be considered
an appropriate safety cutoff, but not everyone thinks of that in an emergent
crisis.

~~~
deelowe
> Computers should never overrule manual controls.

The aoa system was put in place specifically to keep pilots from stalling
planes. By design, it has to override manual controls. This is like saying ABS
shouldn't override the brakes on a car.

~~~
briatx
Well, how well does that work whenever the AoA sensors are faulty?

All it really had to do was decrease the sensitivity of the controls not
override it. Once the manual controls were pulled back all the way the
computer should have disengaged.

> This is like saying ABS shouldn't override the brakes on a car

Remind me, does the ABS system make the car speed up?

~~~
y4mi
> _Remind me, does the ABS system make the car speed up?_

Irrelevant. Cars don't crash on deacceleration .

And ABS does override the controls - especially if the user just presses as
hard as he can.

~~~
SomeHacker44
Take a hard, stable turn and tap the brakes. You will soon see that you are
wrong. Heck, if you are at the limit of adhesion, even lifting a little off
the gas will cause a novice to crash.

------
hencq
It seems like there's a never ending barrage of 'news' around this. All of
this is speculation at this point though. Investigation takes time, which is
almost unusual in a time of minute by minute updates on absolutely everything.

I would not be surprised if the cause ends up being more complicated than the
currently suggested causes. There's definitely a lot to suggest that the cause
of the Ethiopian and Lion Air crashes is the same, but the current explanation
seems overly simplistic.

The failure modes in the leading theory for the Lion Air crash were a broken
AOA sensor causing the MCAS to kick in erroneously, combined with the pilots
not reacting properly to a runaway trim situation. From what I understand,
while MCAS is new, the process for reacting to runaway trim is not new to the
737 Max. This is probably also why the FAA and airlines like Southwest were
confident their pilots would handle this situation correctly.

For the cause of the Ethiopian crash to be the same, the pilots would also
need to be unfamiliar with the runaway trim process. This seems unlikely
though after the Lion Air crash since it put so much attention on that
scenario. That suggests to me there might at least be other contributing
factors to both these crashes. I think we just need to wait and see what the
investigations of both these crashes find.

~~~
linuxftw
> This is probably also why the FAA and airlines like Southwest were confident
> their pilots would handle this situation correctly.

It's interesting to note that American Airlines released a statement that they
have not observed any MCAS related malfunctions in any of their fleet data.

In particular, there is only one account of (alleged) MCAS malfunction
(possibly due to a faulty AoA sensor, which was subsequently replaced...
hmmm.... new part still didn't fix it?) where the plane wasn't destroyed. And
that account notes several drops in altitude before being able to stabilize.

So, you better hope MCAS malfunctions at 8k feet about ground instead of 800.

------
scriptkiddy
I was waiting to hear something like this. Generally speaking, Airline pilots
who actually flew the plane are one of the best sources to consult when it
comes to determining any possible safety malfunction of an aircraft.

One thing to note is the mention of a "Runaway Trim Checklist". When piloting
an airliner, there is a checklist for almost everything. Sometimes there are
multiple checklists with branching paths. Most emergency/malfunction
checklists involve what are called "memory items". These are checklist steps
that the pilot must remember in order to react quickly to any possible
problem. After the memory items are completed, the pilots will break out the
checklist binder and follow the checklist procedure that comes after the
memory items.

Every procedure the pilots undergo has passenger safety as it's #1 concern.
Pilots are free to make whatever decision they deem necessary to ensure the
safety of their passengers, even at the detriment of the airline's bottom
line. They are free to make these decisions without question, even if the
problem seems small.

I believe it's important to note the above information whenever we look at
these horrible accidents and try to reason about them. Often, pilots are the
first line of defense against failures. Most aircraft have 2-3 redundant
systems for almost every control and feature. Pilots need to understand and
know how to work with and around these systems in order to react to emergency
situations. That's why I think the MCAS isn't really to blame here as much as
Boeing is to blame for not properly documenting it's operation in their
manuals.

~~~
outworlder
> One thing to note is the mention of a "Runaway Trim Checklist".

The pilots may not have recognized (in time) that it was a runaway trim issue.
Many such issues involve trim being continuously applied. The trim wheel spins
wildly.

MCAS will trim in increments of 10s. So it will trim, pause, trim some more,
pause. This may have confused the pilots. And they don't have much time to
begin with – MCAS engages with autopilot off and flaps retracted. Most
takeoffs have at least minimum flaps, so the plane will fly fine and then
start misbehaving while still relatively close to the ground.

> Most aircraft have 2-3 redundant systems for almost every control and
> feature.

Yes. MAX 8 has two AOA sensors. Only one needs to misbehave for this issue to
happen. But even with two, it is difficult to know which one is fault (for a
machine). With three, it would be possible to tell.

In any case, all of this is still speculation.

~~~
losvedir
> _MCAS will trim in increments of 10s. So it will trim, pause, trim some
> more, pause._

No, not quite. By itself MCAS will only trim once, I believe.

But if it's interrupted by a pilot manually trimming, then it will stop, wait
5 seconds, and then try to do its 10 second trim again.

The characteristic up-down pattern from the Lion Air flight I think was from
the latter scenario of MCAS starting to trim, the pilot manually trimming back
(disabling MCAS for 5 seconds) and then it activating again.

> _Yes. MAX 8 has two AOA sensors._

But I think the MCAS system only gets its input from one! (And it switches
each flight.) If true, that's just appallingly bad.

~~~
linuxftw
> No, not quite. By itself MCAS will only trim once, I believe.

Unfortunately, we don't know this is actually true. Certainly, it's what
Boeing wants us to believe, that their software is perfect in this regard.
Might be completely broken. Where's the independent verification. And,
allegedly, it's only supposed to trim just a little bit at each increment. If
you look at the accounts, there are roller coaster-like drops. Seems to me it
started nosing down really hard.

------
antirez
It almost looks like if it was an error to call this plane 737 MAX instead of,
let's say, 738, to communicate that it's quite a different plane because of
aerodynamic differences and electronic systems to require a training for the
pilots. Aircraft semaver.

~~~
cjbprime
Boeing fought extremely hard to avoid doing this because it would introduce
new costs in certification and new requirements for pilot training. It wasn't
accidental.

~~~
SketchySeaBeast
I blows my mind that a naming convention can be used to determine the
similarities between vehicles. "I don't need a licence as this isn't a bus,
it's clearly a tricycle, look on the side."

~~~
Obi_Juan_Kenobi
It's not the naming convention; the name just matches the certification/rating
scheme.

The substance of keeping the rating consistent has to do with how the plane
operates, the flight controls, etc.

There are potentially perverse incentives here, but it's not as trivial as
that.

~~~
darkpuma
If Boeing had chosen to name it the 738, would that really have had no
psychological impact on the humans involved in the process of determining
whether or not Boeing should be permitted to consider it the "same" aircraft
for certification/rating?

~~~
jcoby
It's not really a psychological question. Boeing had no option to change the
name and meet the requests of its customers.

The FAA says you have to have a B-737 rating to fly any 737, regardless of
revision [1]. The MAX series is the maximum number of changes the FAA would
permit and still allow it to be called a 737. In theory, someone who is type
rated and familiar with the -100 series should be able to safely operate the
MAX 8.

Most likely the airlines have rules above and beyond that (like requiring sim
or right seat time in a particular revision), but this is the motivation
behind the aircraft. If they had made a 738, it would have needed to go
through certification as if it were a new design. By making it a revision, the
certification process is significantly reduced in both time and costs.

1\.
[https://registry.faa.gov/TypeRatings/](https://registry.faa.gov/TypeRatings/)
(note the MAX isn't present on this list; I assume due to it being grounded)

~~~
darkpuma
I _presume_ that if Boeing arbitrarily decided that all new production 737NGs
were to be renamed 738 with no engineering changes, on just the whim of some
marketing team, the FAA would recognize it as the same airplane despite the
different name. Perhaps they'd be quite annoyed with Boeing for doing that,
but I can't imagine they'd actually require all pilots to retrain.

That's just my presumption though.

------
jahewson
How hard is it to flip through a binder while fighting against the trim system
by putting significant force onto the stick and overriding the trim system
every 10 seconds? Seems excessively challenging.

~~~
ralph84
The pilot flying (PF) controls the aircraft while the pilot monitoring (PM)
calls out the checklist items. It's very manageable with an experienced crew.
But apparently the first officer in the Ethiopian crash only had 200 hours of
experience, so it will be interesting to see if his inexperience was a
contributing factor.

~~~
dragontamer
But the captain had 8000 hours of experience. But I agree, maybe the less-
experienced pilot was a contributing factor. The black box recording should
provide insight if there were any cockpit squabbles...

~~~
vt240
But he had only been a 737 Captain since Nov 2017 [1]. And graduated from
flight school in 2010. It's unknown what the distribution of the 8000 hours
are. For all we know, he had 6000 hours on the Q400.

[1]:[https://outline.com/dMNAS5](https://outline.com/dMNAS5)

~~~
dragontamer
The plane has only been in operation since 2017. No one has more than a two
years of experience with this plane.

If there are significant deviations of the Max8 with the previous 737 models,
that would constitute a safety risk IMO. Banning the plane probably wouldn't
be the appropriate response, but we would at least ask Boeing to develop
proper simulators and training so that Pilots would be more familiar with
whatever the issue is.

~~~
kayfox
Yes, but the 737 has been around since 1967, which is what the person your
replying to was talking about.

Going between the 737 NG and the 737 Max would not be a big change even if
they were different type ratings, but going from say some turboprop to a 737
would be a big change.

If this pilot was moving up to the 737 from smaller aircraft (which nothing
says he did, its just speculation), it seems somewhat likely that he
transitioned from either their retired turboprops or the Q400 fleet they have.

~~~
dragontamer
Hmmm... this seems to address my confusion appropriately. Make sense.

------
gscott
The important part of the article \----------

“When Boeing built the MAX, in order to increase fuel efficiency, they went
with a different engine, explained Fred Tecce, a commercial aviation expert.
“Because the 737 sits pretty low on its landing gear, [Boeing] had to move the
engines up a little bit and move them forward a little bit” on the MAX
versions. “In order to compensate, they extended the nose gear by eight to 12
inches" and repositioned the engines which "affected the airplane’s pitch
characteristics and center of gravity.”

Tecce concurred that control inputs and the resulting pitch changes were
challenges that had to be overcome in the latest version of the world’s best-
selling aircraft.

“In order to compensate for what the engineers perceived to be an issue with
respect to pitch, they added this MCAS system that operates when the autopilot
is off and the angle of attack exceeds certain limitations and when the
airplane is banked pretty steeply.” He said the technology runs the stabilizer
pitch down for several seconds and it “reassesses and will start again until
it believes the airplane has reached a safe angle of attack, and it operates
without the pilots knowing [about it].”

Tecce noted that in the case of the Lion Air Boeing 737 MAX crash, “now the
airplane is pitching down and actually moving the control wheel will not stop
that system. If the pilot uses the trim system on the yoke, the [MCAS] system
will stop" but "if the airplane isn’t in the proper attitude it will
reactivate,” Tecce said, further forcing the aircraft downward if pilots fail
to recognize the situation and take proper corrective action.

A pilot familiar with the system pointed out that recognizing this scenario
was crucial to determine if there was a problem that warranted activating the
trim cutoff switches. Additionally, if the autopilot is engaged, activating a
yoke trim switch disconnects the autopilot and gives full control back to the
pilot immediately.

Tecce did not fault the FAA for taking a wait-and-see approach. “A lot of
people throwing a lot of rocks at the FAA. Since 2010 we’ve had one aviation
fatality” in the United States. “Our safety record is astonishing,” he said.
“I don’t think there’s anything wrong with the airplane. If you talk to the
pilots who fly them, they’ll tell you it’s not the airplane so much as whether
or not the manual properly describes what’s going on.”

------
tim333
There is some evidence that doesn't fit with the faulty angle of attack sensor
triggering MCAS hypothesis.

With the LionAir crash, they thought there was an a problem with the AoA
sensor and replaced it but problems continued. On the flight before the fatal
one and "Passengers in the cabin reported heavy shaking and a smell of burnt
rubber inside the cabin." (wikipedia) " The plane floor is hot. During the
flight, it's never been like that"
([https://news.detik.com/berita/d-4278530/kesaksian-
penumpang-...](https://news.detik.com/berita/d-4278530/kesaksian-penumpang-
soal-masalah-di-lion-air-denpasar-jakarta)) also "erroneous airspeed
indications were still present"

Then with the Ethiopian flight several witnesses reported smoke and a weird
sound from the plane. Also the pilots were aware of the Lionair crash and MCAS
issues.

I guess they'll figure it eventually.

------
United857
Refreshingly good analysis of the 737MAX from the pilot's perspective.

Most are focusing on the flaws of the plane (which I'm not discounting) but
pilot training is also a big part in recovering from unexpected situations,
overriding MCAS or automation in general when things go south, and hand-flying
the airplane.

The two crashes happened in developing countries, Indonesia and Ethiopia, with
local crew. While I don't know the specifics here, often times local airline
pilots in developing countries (i.e. no pool of experienced general aviation
or military pilots to recruit from) are trained ab initio to have a high
reliance on automation, not so much hand-flying the jet. That's how you get,
e.g. a first officer with 200 hours.

I do believe that the US civil and military pilot training pipelines, flawed
as they are, teach hand-flying and build up experience, and these crashes
would be very unlikely to happen with a US carrier and crew.

~~~
vkou
The Lion Air pilot had 6,000 hours of flight experience, and the co-pilot had
5,000 hours of flight experience.

Also, these same airline pilots in developing countries have managed to fly
the older 737 models just fine, for decades...

~~~
ralph84
To say Lion Air in particular has been flying 737s just fine simply doesn't
agree with the facts.

[https://en.wikipedia.org/wiki/Lion_Air#Incidents_and_acciden...](https://en.wikipedia.org/wiki/Lion_Air#Incidents_and_accidents)

~~~
mimixco
Wow. They've even had incidents with 737s _since_ the fatal crash.

------
cmurf
Not in any discussion I've read so far: what is the stall behavior of 737NG
compared to 737MAX _when MCAS is disabled_ via STAB TRIM set to cutoff?

We don't know, but will eventually find out, whether either plane was flying
during the final descent to crash. By that I mean, was the wing producing any
lift (dive to crash), or was the wing stalled (stall to crash) or some
combination of both and in which order? And the stall behavior very well may
become highly relevant.

It's a whole lot of ifs, a lot of questions, and not many answers.

