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Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

nytimes.com

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Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#31

Post by PedroBatista »

Someone1234 wrote: post #20

Makes one wonder if the FAA is too close to Boeing. Not only did they green light this but they also put considerable pressure on EASA to do the same. The FAA's first priority should be safety, not Boeing's bottom line or their ability to more quickly deploy an aircraft update. Pilots are pretty unhappy about this M.C.A.S. situation. They're literally expected to fly an aircraft, and not even being told how that airc…

The revolving door between FAA and cushy positions at Boeing is not a secret. The shortcuts Boeing has been making with the blessing ( or willful omission of the FAA ) have been discussed but with many interests in the middle, like strong competition from Airbus, geopolitics, internal politics, States outbidding each other to create more jobs, national ego, and straight up greed.

"Word on the street", is that Boeing has lost most their safety reputation and most people just do their job and try to not get burned when the planes start to crash. I want to believe most are just blowing of steam, but I don't know..

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#32

Post by CydeWeys »

twtw wrote: post #26
CydeWeys wrote: post #8

Earlier quoted context omitted.

To use a car analogy ... You can always override cruise control by stomping hard on the brake (like to avoid an imminent crash). That's how it's always worked and you've gotten used to this, and done it on occasion when warranted. Now imagine that the next generation of adaptive cruise-control/"auto-pilot"/whatever comes out, and stomping on the brakes no longer does anything. You have to first disable the cruise con…

I do not think this is a good analogy. Firstly, there is no single equivalent to "slamming on the brakes" for uncommanded nose-down. This could be caused by a variety of faults, and pilots are trained to respond in a fashion that will be effective for even those in which the first thing to try doesn't work. There is a standard procedure in place to use in this type of situation - arguing that the pilots should only b…

Their response would have worked to return to level flight in non-MAX variants of the plane, though. Regardless of what the manual or checklist says, they had years of experience flying 737s that behaved in a specific way, they developed an unconscious/intuitive mental model of the plane based on those behaviors (that is faster and quicker to react than consulting checklists), and then a significant and deadly change was made to those behaviors and not communicated to them for cost-cutting reasons.

There's clearly a problem on Boeing's end here.

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#33

Post by llukas »

twtw wrote: post #30
llukas wrote: post #18

Earlier quoted context omitted.

More training and experience is a problem as previous plane model behaved differently. Pilot trained this situation and plane did X and now does Y - you don't really see the problem? - now pilot has extra burden to quickly determine if something else is wrong as plane behaves differently than pilot was trained to. And you are writing this after many, many accidents that root cause was pilot not exactly knowing what o…

> Pilot trained this situation and plane did X and now does Y - you don't really see the problem? - now pilot has extra burden to quickly determine if something else is wrong as plane behaves differently than pilot was trained to. The pilots did not train for a specific root cause of a fault. They trained for a symptom (uncommanded nose down), and the procedure for that situation was unchanged. > extra burden to quic…

They did train recovery scenario on simulator and know how plane should behave (based on old model knowledge) - now it behaves differently. All you wrote is they should ignore it as not important detail and stick to the checklist.

Unexpected situations are always extra cognitive burden.

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#34

Post by danielvf »

CydeWeys wrote: post #27
lolc wrote: post #21

Earlier quoted context omitted.

From a UX perspective what should have happened is the plane telling the pilots: "I've detected the danger of a stall and corrected for it!" with the pilots being able to answer either "Ooops thank you!" but also "Don't do this for the rest of the flight!" I'm a bit baffled about how the previous flight had the problem, apparently misdiagnosed but resolved it, and the new crew had the same problem but was unable reso…

Yes, there should definitely be visual and auditory warnings as well when MCAS is engaged. When the autopilot is doing something so important as struggling to prevent a stall (and in its mind, failing, because of the faulty AoA sensor), it definitely needs to be raising alarms. Also, given how important the AoA data apparently is, it may not be displayed prominently enough. In clear weather, level flight flying, it s…

When anything in a 737 moves the stabilizers, physical wheels in the cockpit loudly turn right next to the pilots. In the case of a stabilizer runaway, it's really obvious. (See https://www.youtube.com/watch?v=3pPRuFHR1co&t=154)

MCAS is just one of many different systems on a 737 that can automatically adjust the stabilizer. Because there are so many things that could be the cause of the problem, the checklist procedure for any runaway is just to cutout automatic control of the stabilizers.

Here is Boeing official update to all 737 MAX operators after the crash, which boils down to saying "follow the checklist, dummies".

http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC...

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#35

Post by callmeal »

twtw wrote: post #26
CydeWeys wrote: post #8

Earlier quoted context omitted.

To use a car analogy ... You can always override cruise control by stomping hard on the brake (like to avoid an imminent crash). That's how it's always worked and you've gotten used to this, and done it on occasion when warranted. Now imagine that the next generation of adaptive cruise-control/"auto-pilot"/whatever comes out, and stomping on the brakes no longer does anything. You have to first disable the cruise con…

I do not think this is a good analogy. Firstly, there is no single equivalent to "slamming on the brakes" for uncommanded nose-down. This could be caused by a variety of faults, and pilots are trained to respond in a fashion that will be effective for even those in which the first thing to try doesn't work. There is a standard procedure in place to use in this type of situation - arguing that the pilots should only b…

>Firstly, there is no single equivalent to "slamming on the brakes" for uncommanded nose-down.

Actually in the "old" version, there is.

From TFA:

Older 737s had another way of addressing certain problems with the stabilizers: Pulling back on the yoke, or control column, one of which sits immediately in front of both the captain and the first officer, would cut off electronic control of the stabilizers, allowing the pilots to control them manually.

Which makes the car analogy apt.

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#36

Post by Animats »

danielvf wrote: post #29
Animats wrote: post #22

From the article: "In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from only one of the two angle of attack sensors at a time, depending on which of two, redundant flight control computers — one on the captain’s side, one on the first officer’s side — happened to be active on that flight." They created a single point of failure that way. Why?

By having each redundant flight computer hooked to completely different sensors, in case of a bad sensor the crew can bypass not only the sensor, but also any computation done with that sensor. It's not a single point of failure as we think if it - if it starts acting up, you can easily disable the automatic stabilizer system, per the procedures. 737 stabilizer runaways take several seconds to take effect, and are re…

Using only one sensor at a time, there's no "sensors disagree" fault to tell the pilot there's a problem. Or to tell the flight control system it shouldn't be taking drastic action based on that sensor.

Airbus uses three angle of attack sensors and compares them. They've had at least one crash when two sensors failed in a consistent way.[1] The vulnerability of aircraft flight control systems to bad AOA data is well known.

[1] https://news.aviation-safety.net/2010/09/17/report-blocked-a...

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#37

Post by twtw »

CydeWeys wrote: post #32
twtw wrote: post #26

Earlier quoted context omitted.

I do not think this is a good analogy. Firstly, there is no single equivalent to "slamming on the brakes" for uncommanded nose-down. This could be caused by a variety of faults, and pilots are trained to respond in a fashion that will be effective for even those in which the first thing to try doesn't work. There is a standard procedure in place to use in this type of situation - arguing that the pilots should only b…

Their response would have worked to return to level flight in non-MAX variants of the plane, though. Regardless of what the manual or checklist says, they had years of experience flying 737s that behaved in a specific way, they developed an unconscious/intuitive mental model of the plane based on those behaviors (that is faster and quicker to react than consulting checklists), and then a significant and deadly change…

The point is that their response may have worked for this particular fault, but would not have worked in general. There is a reason that there are more procedures than "pull back on the stick" - pilots do not know what the fault is.

> they developed an unconscious/intuitive mental model of the plane

If the plane has a fault, it's frequently not going to behave like their unconscious model says it should. In the happy case, rely on your intuition. In the unhappy case, when things are working as they should, follow the emergency procedure.

Sorr, but this is a little like saying "follow standard procedure to put the landing gear down. If that procedure doesn't work, repeat your intuitive action over and over until hopefully the landing gear goes down." No - follow the emergency procedure in place for landing gear fails to descend.

> not communicated to them for cost-cutting reasons

Take it up with the FAA and the airlines?

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#38

Post by argd678 »

del82 wrote: post #4

Based only on what I read in this article, I can kind of see Boeing's point? From what I understand, the procedure/checklist for an uncommanded nose down didn't change from the old to the new version, even with the addition of MCAS. So from the Pilot's perspective, there is nothing that they should do differently in the new vs. the older 737s when this happens-- follow the checklist, which will (eventually) cause you…

The interface isn’t opaque in airplanes like in software, everyone learns about how the internals of the aircraft work in order to troubleshoot problems. So pilots are reasoning based how how they think it works under the hood.

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#39

Post by poof131 »

CydeWeys wrote: post #32
twtw wrote: post #26

Earlier quoted context omitted.

I do not think this is a good analogy. Firstly, there is no single equivalent to "slamming on the brakes" for uncommanded nose-down. This could be caused by a variety of faults, and pilots are trained to respond in a fashion that will be effective for even those in which the first thing to try doesn't work. There is a standard procedure in place to use in this type of situation - arguing that the pilots should only b…

Their response would have worked to return to level flight in non-MAX variants of the plane, though. Regardless of what the manual or checklist says, they had years of experience flying 737s that behaved in a specific way, they developed an unconscious/intuitive mental model of the plane based on those behaviors (that is faster and quicker to react than consulting checklists), and then a significant and deadly change…

From the article:

"Older 737s had another way of addressing certain problems with the stabilizers: Pulling back on the yoke, or control column, one of which sits immediately in front of both the captain and the first officer, would cut off electronic control of the stabilizers, allowing the pilots to control them manually.

That feature was disabled on the Max when M.C.A.S. was activated — another change that pilots were unlikely to have been aware of. After the crash, Boeing told airlines that when M.C.A.S. is activated, as it appeared to have been on the Lion Air flight, pulling back on the control column will not stop so-called stabilizer runaway."

If the above is true, it's near criminal that Boeing didn't notify pilots about the change. It's also not just about following checklists but understanding the systems of the aircraft.

Re: Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

#40

Post by lmm »

peteradio wrote: post #11
del82 wrote: post #7

Earlier quoted context omitted.

That's fair, but what does the checklist say? I mean, say there are a thousand different malfunctions that could cause an uncommanded nose-down. This one happens to be #359, but the pilots don't know that, they just know that they're pointed at the ground. Maybe it used to be the case that the first item on the checklist (pull back on the stick) fixed problem #359, and now it's the second. But there are several hundr…

Pull back wasn't in the original manual but was a relied upon method. Boeing fucked up years ago by not documenting the function so it was allowed to be dropped transparently. How is that defensible?

Why was a method that wasn't in the official checklist "relied upon"? Pilots following some undocumented, non-standard procedure sounds like their fault rather than Boeing's.
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