
Boeing Pilots Detected 737 Max Flight Control Glitch 2 Years Before Deadly Crash - elorant
https://www.npr.org/2019/10/18/771451904/boeing-pilots-detected-737-max-flight-control-glitch-two-years-before-deadly-cra
======
dmix
[https://news.ycombinator.com/item?id=21292860](https://news.ycombinator.com/item?id=21292860)

[https://news.ycombinator.com/item?id=21293550](https://news.ycombinator.com/item?id=21293550)

[https://news.ycombinator.com/item?id=21293497](https://news.ycombinator.com/item?id=21293497)

[https://news.ycombinator.com/item?id=21298304](https://news.ycombinator.com/item?id=21298304)

------
missosoup
Title is incredibly misleading.

The text messages exchanged are about the unexpected (but normal for 737 max)
amounts of speed trim applied. I.e. during normal operation, MCAS was applying
more trim than a non-max 737 pilot would expect. The individuals exchanging
these text messages never encountered the MCAS anomaly that led to the two
crashes. The pilots explicitly did not encounter the 'glitch'. The simulator
that the pilots were using was not even capable of replicating the glitch, as
it didn't factor trim screw forces.

The text messages are evidence of a systemic lack of communication in the
testing and certification process, but they are not the 'pilots knew MCAS
would cause crashes' smoking gun that the mainstream media is about to start
misinterpreting them as.

Here's Juan Browne breaking it down. For those not in the know, he ranks
amongst the most experienced pilots in the country.

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

~~~
hrktb
Things are not so simple as the pilots knowing everything and just hiding the
truth. They still identified there was an issue, but couldn’t match it to MCAS
as they didn’t know about it, and misattributed the effects to a simulator
error.

> As the two pilots banter back and forth in the messages, Forkner says the
> system is "running rampant in the sim on me," then adding, "I'm leveling off
> at like 4000 ft, 230 knots and the plane is trimming itself like crazy."

For me this clears the bar of pilots detecting there is an issue.

~~~
bonzini
_The_ issue that resulted in the crashes was angle of attack sensors reporting
broken data, which caused MCAS to nose down the plane; this is absolutely not
what the pilots are talking about.

Everything else that has been discussed (whether the pilots should have been
told how to disable it and tried it in the simulator, whether Boeing should
have added the second vane or even a third one on all planes, etc.)
fundamentally depends on having incorrect data from the sensors and the plane
not being able to deal with that.

The exchange might hint that MCAS had an awful design history, but even a
perfect MCAS could have had issues if supplied with incorrect sensor data;
garbage in, garbage out. Now if there was somewhere an email about the lack of
a voting system on vane readings, that would be another story.

~~~
mannykannot
The issue is the undocumented (and obfuscated) behavior of the airplane after
the failure of a single AofA sensor.

~~~
bonzini
Right, and it has nothing to do with the issue reported by the test pilots in
the simulator.

~~~
mannykannot
I see what you mean - there is no evidence (at least in the transcript) that
the problems were in response to a simulated system failure, and the actual
MCAS seemed to work well enough when nothing was broken.

------
zaroth
This is now marked as a dupe, so not likely to garner much more traffic, but I
am curious what the “M.2” refers to in the transcript?

Also, it’s pretty clear to me that they are confused by the parameters of when
MCAS should be active and how much trim it should be applying. They are trying
to figure out if the sim code is broken or out of sync with the spec. They are
asking for spreadsheets identify exactly which flight envelopes it should be
activating under.

This transcript perhaps demonstrates a cultural problem at Boeing around a
safety critical system. What it doesn’t actually show is that Boeing knew
about the specific MCAS issue that contributed to crashing two planes.

A question in my mind is what happened between this exchange and the next time
this pilot went to the FAA to tell them to keep MCAS out of the docs.

I really hope they can trace this all the way to the top and not simply hang
this test pilot out to dry.

~~~
mannykannot
M.2 is mach 0.2 - the speed range in which MCAS was active had been expanded
downwards.

Your second paragraph is precisely to the point, and it is not clear to me
whether these two pilots were ever given enough correct information to make an
informed decision about the safety of MCAS.

------
known
Looks like
[https://en.wikipedia.org/wiki/Whistleblower](https://en.wikipedia.org/wiki/Whistleblower)
protection assurance is not efficient; Time to amend it;

~~~
dmix
There are no whistleblowers in this story... both pilots signed off on the
safety and the guys lawyer is arguing the conversation is being
misinterpreted.

> “If you read the whole chat, it is obvious that there was no ‘lie,’” David
> Gerger, a lawyer for Forkner, said in an email. “The simulator was not
> reading right and had to be fixed to fly like the real plane. Mark’s career
> -- at Air Force, at FAA, and at Boeing -- was about safety. And based on
> everything he knew, he absolutely thought this plane was safe.”

