Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

nytimes.com

Post reply on HN
Print view View original

51–60 of 83 posts

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

#51

Post by loeg »

callmeal wrote: post #35
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…

>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 p…

Drivers aren't trained to follow checklists and usually don't have dozens of seconds to respond to mechanical emergencies. Cars also don't fall out of the sky if they break down. It's not a great metaphor.

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

#52

Post by peteradio »

lmm wrote: post #40
peteradio wrote: post #11

Earlier quoted context omitted.

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.

Who knows? Have you ever been taught an undocumented procedure by the expert and been told to use it regardless of what the manual states? Happens all the time? Is a pilot in a position to affect Boeing beauracracy?

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

#53

Post by kirykl »

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…

Southwest has added enhanced AOA indicators to its Max fleet as a result [0].

Lion Air didn't even have the basic (optional) AOA Disagree alert[1]

[0]https://theaircurrent.com/aviation-safety/southwest-airlines...

[1]https://www.reuters.com/article/us-indonesia-crash-boeing-ao...

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

#54

Post by richardhod »

callmeal wrote: post #35
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…

>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 p…

Indeed, any pilot will respond to nose down with ,pulling back on the yoke, or on the joystick, in other and older aircraft. This is a basic flying control, as basic as steering wheel and brakes, making this an excellent analogy. Any system that complicates this in the way described is a terrible system, for the reasons explained above.

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

#56

Post by twtw »

loeg wrote: post #51
callmeal wrote: post #35

Earlier quoted context omitted.

>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 p…

Drivers aren't trained to follow checklists and usually don't have dozens of seconds to respond to mechanical emergencies. Cars also don't fall out of the sky if they break down. It's not a great metaphor.

> have dozens of seconds to respond

12 minutes, in this case.

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

#57

Post by kirykl »

Animats wrote: post #36
danielvf wrote: post #29

Earlier quoted context omitted.

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…

There wasn't a "sensors disagree" alert in the Lion Air plane because they didn't have installed the optional AOA Disagree indicator.

As comparison, Southwest had the indicator but has now also installed an enhanced AOA Disagree indicator as a result of the Lion incident

https://theaircurrent.com/aviation-safety/southwest-airlines...

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

#58

Post by sokoloff »

twtw wrote: post #50
Someone1234 wrote: post #49

Earlier quoted context omitted.

Accurate but irrelevant. This assumes the pilots knew they were dealing with a runaway stabilizer, and considering M.C.A.S. wasn't behaving similar to their previous training/experience/simulations with Runaway Stabilizers, it isn't clear they'd know they should follow this checklist. Now had they been actually trained on M.C.A.S. inc. faults, they may have known to do exactly this and we wouldn't even be discussing…

It's not really possible to not know that you are dealing with a runaway stabilizer. MCAS (and every other automatic system to adjust trim) causes large physical wheels at the side of the pilot's knee to spin.

And these large wheels have small bell/clackers on them so you get a distinctly audible signal in addition to the large black wheels with white stripes on them.

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

#59

Post by crooked-v »

LoSboccacc wrote: post #44
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…

> That's how it's always worked and you've gotten used to this but still, instead of going trough the full checklist they stopped and tried repeatedly whatever fixed the issue in the past/on the simulator. a more complete analogy: "follow these ten step do diagnose a bug on the software" "but last time it was just a compilation flag, I'll check the compilation flags" "bug persists" "last time it was just a compilatio…

From what I understand, part of the problem was that it helped temporarily... and then the system pointed the nose down again.

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

#60

Post by acklenx »

LoSboccacc wrote: post #44
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…

> That's how it's always worked and you've gotten used to this but still, instead of going trough the full checklist they stopped and tried repeatedly whatever fixed the issue in the past/on the simulator. a more complete analogy: "follow these ten step do diagnose a bug on the software" "but last time it was just a compilation flag, I'll check the compilation flags" "bug persists" "last time it was just a compilatio…

"system halts"

That's one heck of an analogy! Brutal

Post reply on HN