
Before 737 Max, Boeing’s Flight-Control System Included Key Safeguards - bookofjoe
https://www.wsj.com/articles/before-737-max-boeings-flight-control-system-included-key-safeguards-11569754800?mod=rsswn
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heisenbit
Here is some non pay-walled content: [https://qz.com/1718506/boeings-737-max-
mcas-has-better-desig...](https://qz.com/1718506/boeings-737-max-mcas-has-
better-designed-military-forerunner/)

The key quote from there:

Notably, pilots of the KC-46 are able to override the MCAS—or Maneuvering
Characteristics Augmentation System—simply by pulling on the controls, the
Journal reports. It quotes an Air Force procurement chief as saying, “We have
better sensor data. But most importantly, when the pilot grabs the stick, the
pilot is completely in control.”

~~~
cjbprime
It's weird to see an article writing about this without mentioning the
regulatory and training aspect. Previous MAX MCAS *couldn't" allow the pilot
to override with the stick, because previous MCAS both needed to prevent a
pilot-induced stall and needed to require no training or knowledge from the
pilot in order to maintain the type rating.

A better way to write the article would be "Boeing and the airlines have given
up on trying to do MCAS without telling pilots anything about it."

~~~
mlyle
> previous MCAS both needed to prevent a pilot-induced stall

MCAS is there mostly because of certification requirements for hands-off
stability. It is not a mechanism to prevent the pilot from stalling the
aircraft.

~~~
msbarnett
> MCAS is there mostly because of certification requirements for hands-off
> stability

I don’t believe this is correct. During testing the MAX was discovered to have
an inverted force curve on the stick approaching a stall — as the aircraft
approaches stall angle, forces flip around and it becomes easier to pull the
stick back (into the stall) than forward (out of the stall angle).

This violates a fundamental airworthiness requirement — commercial aircraft
cannot be certified as airworthy if the stick forces invert.

MCAS “solves” this by commanding the stabilizers down as the airplane
approaches stall — effectively using the stabilizer to put the forces on the
stick that are “missing” due to the MAX’s aerodynamics, ensuring the force
curve never inverts.

MCAS is entirely about generating force on the stick to meet airworthiness
regs, not hands-off stability. It actually _can’t_ disengage when the pilot
pulls back on the stick, as that would defeat its entire purpose re: the
airworthiness force-on-stick requirement.

The WSJ kind of muddled things here. The KC-46A does mid-air refueling, and
its semi-similar MCAS system _is_ about hands-off stability — compensating
automatically as the weight and balance of the plane dynamically changes as
fuel is offloaded. The pilot can override it with the stick because its
purpose isn’t to provide stick force.

~~~
GhettoMaestro
Is there a summarized list somewhere of fundamental airworthiness requirements
such as the one you listed?

~~~
mlyle
It's 14 CFR 25.173 and 14 CFR 25.175.

~~~
GhettoMaestro
Thanks

------
anon91831837
Remember the 2010 Ducommun 737 NG (-600 to -900) scandal? Boeing subcontracted
key structural components to them to be CNC machined, instead they were
crudely hand-fabricobbled and out-of-spec, but Boeing management ordered them
installed anyhow. Furthermore, when a Boeing blue-ribbon panel reported its
findings, they were ignored. As a result, several aircraft fuselages have
broken up on hard landings and runway overruns, killing several passengers. In
the past, aircraft fuselages remained intact in similar situations. There are
an unknown number of substandard airframes flying around that have the
potential to spontaneously break up in heavy turbulence, accelerated fatigue
damage, hard landings, and runway overruns. If the flying public and
professional pilots were smart, they would avoid aircraft designed,
manufactured, or overhauled within the past 20 or so years because of the
pervasive, systematic deficiencies introduced by regulatory capture. Older
aircraft, if maintained properly, are demonstrably safer until regulators get
back on the ball to insist on depth and breadth of safe, proper engineering
and manufacturing.

~~~
JonathonW
Actual accident rates don't appear to back that up; accident rates (per
million flights) are _drastically_ higher for both the original 737 and 737
Classic versus the 737 NG:
[http://www.airsafe.com/events/models/rate_mod.htm](http://www.airsafe.com/events/models/rate_mod.htm)

------
tus88
But presumably the pilots of both downed MAXs were pulling back as hard as
possible.

~~~
kart23
So scary. It's like driving a car, trying to slow down, slamming on the brake,
but it just keeps accelerating. Cant imagine everyone's feelings on those
flights.

~~~
blattimwind
The good thing with cars is that the time to avert a crash is generally very
low (<1 second - <10 seconds), so while you're bending the supports of your
seat pushing down on the brake pedal in panic, that state is not going to last
very long.

~~~
toss1
Well also with a car, you can jut put it in Neutral and let the engine rev and
throw a piston while you coast off to the side

~~~
PhantomGremlin
I don't know if it works that way any more.

Nowadays with CVT or with PDK it seems to me that you're merely making a
"suggestion" to put the transmission into Neutral. If the transmission
software is borked, you're screwed?

But I'm not sure, maybe there is some fail safe override that occurs when you
physically move the transmission control stalk into the neutral position?

I'd say that you could always turn the engine off. But Toyota made a mockery
of that. Q: Who knew that you needed to press and hold the OFF button for a
full five seconds before the car decided to comply? A: Not everyone knew ---
people died!

~~~
blattimwind
> Nowadays with CVT or with PDK it seems to me that you're merely making a
> "suggestion" to put the transmission into Neutral. If the transmission
> software is borked, you're screwed?

Nice thing about a standard transmission is that unless the linkage breaks you
can always pull it out of gear, even under load.

> I'd say that you could always turn the engine off.

You can't necessarily turn a Diesel off [1], and I would not be surprised if
modern very-high compression gasoline engines are able to pull the same
runaway off.

[1] Big Diesel generators have countermeasures for runaway, but cars don't.

------
bookofjoe
[http://archive.is/h5ejA](http://archive.is/h5ejA)

------
jwildeboer
Moderators: please add [paywalled] or [$] to paywalled content so I can ignore
instead of wasting time. Thanks.

~~~
chrisseaton
[https://news.ycombinator.com/newsfaq.html](https://news.ycombinator.com/newsfaq.html)

> But please don't post complaints about paywalls. Those are off topic.

~~~
droithomme
Please post the whole rule. You neglected this bit:

> It's ok to post stories from sites with paywalls _that have workarounds._

Where's the workaround? I don't find workarounds for WSJ. WSJ is locked out.
Please post the workaround, or kindly stop badgering people as it is not
productive.

If there is no workaround that allows us to view WSJ articles, then WSJ
article are NOT allowed here, per the rules you yourself selectively cited.

The rule about paywalls are that paywalled articles must come with a
workaround, and that people should not post complaints about paywalls. His
post did not complain about paywalls themselves nor does mine. He requests
that paywalled articles be tagged as such, a much more relaxed rule than the
official rules which are that paywalled articles without workarounds, such as
WSJ articles (unless someone would like to post a legal workaround allowing us
to view WSJ articles), are not allowed.

~~~
chrisseaton
If you don’t know how to workaround WSJ paywalls then ask someone - the rules
allow for that. They didn't ask - they just complained. Or pay up and
subscribe to the WSJ!

~~~
craftinator
"Moderators: please add [paywalled] or [$] to paywalled content"

That is asking.

~~~
chrisseaton
No, ask them for the workaround we mean.

