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The Egg
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Re: DYMT: Imi's Legacy

Thu Mar 14, 2019 10:55 am

derFunkenstein wrote:
The Egg wrote:
No.....I know parents use it when talking to their kids; I'm mainly referring to its use in weather forecasting. My fault for not really clarifying that.

Downstate too. Also old people say it all the time. Guess who watches TV over the air still. ;)

I've noticed older people using it alot as well. That doesn't really bother me (because we're all kids to them), it's moreso when the word is used in a professional application such as forecasting (especially in the written form).

Similar to if they had a doctor on TV diagnosing someone with "a case of the sniffles".
 
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Re: DYMT: Imi's Legacy

Thu Mar 14, 2019 11:26 am

I think you just need to chill out. :wink:
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Re: DYMT: Imi's Legacy

Thu Mar 14, 2019 11:42 am

just brew it! wrote:
I think you just need to chill out. :wink:

I heard they make a pill for that.
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Re: DYMT: Imi's Legacy

Thu Mar 14, 2019 12:55 pm

superjawes wrote:
just brew it! wrote:
I think you just need to chill out. :wink:

I heard they make a pill for that.

There's a cool plant that was legalized in Canada recently that's p solid too ;)
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Re: DYMT: Imi's Legacy

Thu Mar 14, 2019 1:06 pm

The Egg wrote:
derFunkenstein wrote:
The Egg wrote:
No.....I know parents use it when talking to their kids; I'm mainly referring to its use in weather forecasting. My fault for not really clarifying that.

Downstate too. Also old people say it all the time. Guess who watches TV over the air still. ;)

I've noticed older people using it alot as well. That doesn't really bother me (because we're all kids to them), it's moreso when the word is used in a professional application such as forecasting (especially in the written form).

Similar to if they had a doctor on TV diagnosing someone with "a case of the sniffles".

I've seen this episode of House I think.
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Re: DYMT: Imi's Legacy

Thu Mar 14, 2019 3:55 pm

TIL: lots of CPU cores + a process with hundreds of threads that make heavy use of the heap + the version of malloc() in Debian 9 = bad news
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Re: DYMT: Imi's Legacy

Fri Mar 15, 2019 7:46 am

Interesting! Let me guess, malloc() has some locking going on while updating its lists and the performance just goes in the toilet?
 
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Re: DYMT: Imi's Legacy

Fri Mar 15, 2019 8:12 am

notfred wrote:
Interesting! Let me guess, malloc() has some locking going on while updating its lists and the performance just goes in the toilet?

Close. We're actually seeing memory bloat (ultimately resulting in OOM kills), but it is lock-related. If malloc() encounters lock contention on all existing heap arenas it creates a new arena, up to a limit of 8x the number of CPU cores. So lots of wasted RAM. Capping the arena count at a lower value prevents the bloat, but hurts performance.

The weird thing is, the heap arena management logic doesn't seem to have changed much. So this appears to be an indirect effect of something else which is causing us to contend on the heap locks more than we used to in Debian 8, causing the number of arenas to balloon. What we know is that the issue is definitely tied to the version of glibc being used, and the heap code is definitely a player in the mess.

Looks like this version may also be less aggressive about trimming unused space from the end of arenas and returning that unused space to the OS, which would also tend to aggravate the issue. If I had to speculate, maybe this was done to reduce the number of syscalls, to mitigate the performance penalty of the Meltdown patches...
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Re: DYMT: Imi's Legacy

Mon Mar 18, 2019 5:33 pm

The Egg wrote:
US grounds all 737 MAX 8 and 9 flights.
Some additional reading material for those interested (sorry for all the in-line videos).
Pilots Complained About The 737 MAX In A Federal Database

This isn't looking good for Boeing, if correct:

https://jalopnik.com/recent-boeing-737-max-crashes-may-be-the-result-of-a-si-1833380459
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Re: DYMT: Imi's Legacy

Mon Mar 18, 2019 7:43 pm

ludi wrote:
The Egg wrote:
US grounds all 737 MAX 8 and 9 flights.
Some additional reading material for those interested (sorry for all the in-line videos).
Pilots Complained About The 737 MAX In A Federal Database

This isn't looking good for Boeing, if correct:

https://jalopnik.com/recent-boeing-737-max-crashes-may-be-the-result-of-a-si-1833380459

Single point of failure is a big no-no for any critical flight control systems. Boeing and the FAA both share blame for this if it turns out to be correct.
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Re: DYMT: Imi's Legacy

Tue Mar 19, 2019 12:44 am

just brew it! wrote:
ludi wrote:

Single point of failure is a big no-no for any critical flight control systems. Boeing and the FAA both share blame for this if it turns out to be correct.

As bad as it would be (and that’s to say, really really bad), I think changing a core flight characteristic of the #1 selling commercial passenger jet while saying almost nothing is worse still. Reason being, even with a single point of failure going out, it likely would not have resulted in a crash if the plane behaved as all previous versions had, or if the pilots were aware and/or had been retrained.

The only thing Boeing seems to have had redundancy with is 10/10 scale failures.
 
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Re: DYMT: Imi's Legacy

Tue Mar 19, 2019 4:48 am

The Egg wrote:
just brew it! wrote:
ludi wrote:

Single point of failure is a big no-no for any critical flight control systems. Boeing and the FAA both share blame for this if it turns out to be correct.

As bad as it would be (and that’s to say, really really bad), I think changing a core flight characteristic of the #1 selling commercial passenger jet while saying almost nothing is worse still. Reason being, even with a single point of failure going out, it likely would not have resulted in a crash if the plane behaved as all previous versions had, or if the pilots were aware and/or had been retrained.

Yes, this definitely exacerbates the initial poor design decision. Especially when the system in question is one where a failure during takeoff requires quick, decisive action by the pilot to avert a fatal mishap.
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Re: DYMT: Imi's Legacy

Tue Mar 19, 2019 7:37 am

just brew it! wrote:
Especially when the system in question is one where a failure during takeoff requires quick, decisive action by the pilot to avert a fatal mishap.
It's not operating during takeoff, it only operates once the flaps are up.

In a way this is worse because takeoff is such a critical phase of flight that the pilots are primed and ready to respond. They have to do a number of simulator exercises regularly including failures around takeoff. Once they've taken off and are cleaning up the aircraft for the climb, they are beginning to relax a bit on the aircraft trying to kill them and are now thinking about where they are going in terms of flying the departure and climb.

They really messed up with the single sensor! There are 2 sensors present but the MCAS switches from one side to the other on each flight. I believe the updated software was going to take the input from both sensors and if there was a significant difference then it would disable MCAS. Critical stuff on aircraft have 3 sensors so you know which is correct and which is wrong.
 
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Re: DYMT: Imi's Legacy

Wed Mar 20, 2019 3:08 am

https://www.bloomberg.com/news/articles ... er-crashed

Now a new detail emerges about the Lion Air flight that crashed previously, looks like the MCAS on that plane had malfunctioned on an earlier flight but a dead-head pilot riding in the jumpseat recognized the symptoms and told the flight crew how to defeat it.
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Re: DYMT: Imi's Legacy

Wed Mar 20, 2019 7:39 am

ludi wrote:
https://www.bloomberg.com/news/articles/2019-03-19/how-an-extra-man-in-cockpit-saved-a-737-max-that-later-crashed
Now a new detail emerges about the Lion Air flight that crashed previously, looks like the MCAS on that plane had malfunctioned on an earlier flight but a dead-head pilot riding in the jumpseat recognized the symptoms and told the flight crew how to defeat it.

Wow.....well he's a hero for everyone aboard, regardless of whether it crashed the following day.

After the Lion Air crash, two U.S. pilots’ unions said the potential risks of the system, known as the Maneuvering Characteristics Augmentation System, or MCAS, hadn’t been sufficiently spelled out in their manuals or training. None of the documentation for the Max aircraft included an explanation, the union leaders said.
“We don’t like that we weren’t notified,’’ Jon Weaks, president of the Southwest Airlines Pilots Association, said in November. “It makes us question, ‘Is that everything, guys?’ I would hope there are no more surprises out there.’’

That's a damn good point. What else did they change that we don't know about yet? What else wasn't important enough to tell the pilots? I wouldn't go near one of those planes until they have about 10 years of vetting.
 
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Re: DYMT: Imi's Legacy

Thu Mar 21, 2019 11:18 am

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Re: DYMT: Imi's Legacy

Thu Mar 21, 2019 3:44 pm

Arstechnica: Safety Feature Which Could Have Prevented 737 MAX Crashes Sold By Boeing As An Expensive Option.
:o




Edit: LOL at some of the comments:
Urist wrote:
570rmy wrote:
"I'm sorry, your current plan doesn't include flight safety. You'll have to call our upgrade line to speak with a representative to see if that feature is available on your model and in your area. Thank you for flying with us, have a nice day"
The next logical progression is offering loot crates to the pilots.

For just 100 BoeingCrystals you have chance to unlock cool skins for the aircraft, various unique pilot's hats to impress your friends, and if you are very lucky you could even get an Ultra-Rare Shiny Legendary Purple Tier critical flight control system that will help you keep the plane in the air!
 
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Re: DYMT: Imi's Legacy

Wed Mar 27, 2019 8:15 am

Scientists should really be studying oatmeal (quick oats) for its adhesive properties. Left on a surface overnight, it hardens into one of the strongest substances known to man --- a type of organic concrete. That it's able to do this with so few ingredients (just oats and water) is pretty impressive.

Of course, it will completely loosen if left submerged in water for a period of time, but absent water, I'd be interested to know what it would take.
 
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Re: DYMT: Imi's Legacy

Wed Mar 27, 2019 9:44 am

The Egg wrote:
Scientists should really be studying oatmeal (quick oats) for its adhesive properties. Left on a surface overnight, it hardens into one of the strongest substances known to man --- a type of organic concrete. That it's able to do this with so few ingredients (just oats and water) is pretty impressive.

Of course, it will completely loosen if left submerged in water for a period of time, but absent water, I'd be interested to know what it would take.

Why would you wait for scientists to do that?
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Re: DYMT: Imi's Legacy

Wed Mar 27, 2019 2:31 pm

The Egg wrote:
Scientists should really be studying oatmeal (quick oats) for its adhesive properties. Left on a surface overnight, it hardens into one of the strongest substances known to man --- a type of organic concrete. That it's able to do this with so few ingredients (just oats and water) is pretty impressive.

Of course, it will completely loosen if left submerged in water for a period of time, but absent water, I'd be interested to know what it would take.


On the counter? Pretty much requires a hammer and chisel.
Trying to remove it from a mug or bowl or measuring cup? Boiling water, industrial strength solvent, and a lot of elbow grease.
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Re: DYMT: Imi's Legacy

Wed Mar 27, 2019 3:40 pm

MileageMayVary wrote:
The Egg wrote:
Scientists should really be studying oatmeal (quick oats) for its adhesive properties. Left on a surface overnight, it hardens into one of the strongest substances known to man --- a type of organic concrete. That it's able to do this with so few ingredients (just oats and water) is pretty impressive.

Of course, it will completely loosen if left submerged in water for a period of time, but absent water, I'd be interested to know what it would take.


On the counter? Pretty much requires a hammer and chisel.
Trying to remove it from a mug or bowl or measuring cup? Boiling water, industrial strength solvent, and a lot of elbow grease.
I was thinking binding two surfaces with holes for breathing like a mesh would work the best. I might try it this weekend.
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Re: DYMT: Imi's Legacy

Thu Mar 28, 2019 6:15 pm

Do not meddle in the affairs of archers, for they are subtle and you won't hear them coming.
 
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Re: DYMT: Imi's Legacy

Mon Apr 01, 2019 2:01 pm

Just getting caught up on a couple of weeks of posts...
DancinJack wrote:

LOL... though I have to ask, if it is designed to be both, how well-optimized can it be for either task?

"It's a floor cleaner... it's a dessert topping!"

The Egg wrote:
Scientists should really be studying oatmeal (quick oats) for its adhesive properties. Left on a surface overnight, it hardens into one of the strongest substances known to man --- a type of organic concrete. That it's able to do this with so few ingredients (just oats and water) is pretty impressive.

Of course, it will completely loosen if left submerged in water for a period of time, but absent water, I'd be interested to know what it would take.

In keeping with the brewing theme, I can attest that brewing high oat content beers is also a PITA. Really gums up (literally!) the mash.
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Re: DYMT: Imi's Legacy

Wed Apr 03, 2019 2:21 pm

Ars: Ethiopian Air Pilots Turned Off 737 MAX Anti-Stall System, Then It Turned On Again

"The pilots of Ethiopia Airlines Flight 302 apparently followed the proper steps to shut down an errant flight control system as they struggled to regain control of the 737 MAX aircraft shortly after takeoff. But according to multiple reports, data from the ill-fated aircraft’s flight recorder revealed that the anti-stall feature of the aircraft’s Maneuvering Characteristics Augmentation System (MCAS) was triggered at least three times—and at least one time after the pilots followed the correct steps to shut it down."
 
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Re: DYMT: Imi's Legacy

Wed Apr 03, 2019 2:48 pm

The Egg wrote:
Ars: Ethiopian Air Pilots Turned Off 737 MAX Anti-Stall System, Then It Turned On Again

"The pilots of Ethiopia Airlines Flight 302 apparently followed the proper steps to shut down an errant flight control system as they struggled to regain control of the 737 MAX aircraft shortly after takeoff. But according to multiple reports, data from the ill-fated aircraft’s flight recorder revealed that the anti-stall feature of the aircraft’s Maneuvering Characteristics Augmentation System (MCAS) was triggered at least three times—and at least one time after the pilots followed the correct steps to shut it down."



See, the issue is they they only blew it apart with a stick of dynamite. You really need to get it crushed in a hydraulic press to actually stop.

Also, WTF?!?
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Re: DYMT: Imi's Legacy

Wed Apr 03, 2019 3:01 pm

MileageMayVary wrote:
The Egg wrote:
Ars: Ethiopian Air Pilots Turned Off 737 MAX Anti-Stall System, Then It Turned On Again

"The pilots of Ethiopia Airlines Flight 302 apparently followed the proper steps to shut down an errant flight control system as they struggled to regain control of the 737 MAX aircraft shortly after takeoff. But according to multiple reports, data from the ill-fated aircraft’s flight recorder revealed that the anti-stall feature of the aircraft’s Maneuvering Characteristics Augmentation System (MCAS) was triggered at least three times—and at least one time after the pilots followed the correct steps to shut it down."

See, the issue is they they only blew it apart with a stick of dynamite. You really need to get it crushed in a hydraulic press to actually stop.

Also, WTF?!?

One of the stories I read indicated that the pilots may have assumed they mis-diagnosed the issue when switching it off had no obvious immediate effect, and switched it back on.
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ludi
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Re: DYMT: Imi's Legacy

Wed Apr 03, 2019 10:07 pm

Yeah, it's still not clear on why the system was turned on again. The pilots were under severe stress at that point and may have reactivated it by intent or mistake. Once a system stops behaving as expected, the risk of user error goes way up.
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Re: DYMT: Imi's Legacy

Thu Apr 04, 2019 8:27 am

You can't actually turn off MCAS. MCAS is just one of a number of systems that feed trim commands to the horizontal stabiliser (tail plane). What you actually do is you turn off the power to the trim motors. There are 2 switches to turn off the trim motors, one for autopilot and one for manual. MCAS actually goes through the manual trim path. Normally the pilot trims by pushing buttons on the control column. If you turn off the manual trim you now have to trim the aircraft by winding the trim wheel round and round by hand.

If the trim is very nose down and you are pulling back on the control column to keep the plane level and the plane is flying fast enough then you may not be able to actually move that wheel by hand, the aerodynamic forces on it will be jamming it. There is a technique where you have to get the nose high with both pilots pulling on the control columns together (60lbs of pull force) and then you let the nose drop. As the nose drops then the aerodynamic load comes off the horizontal stabiliser and you can now wind a few turns of nose up trim on before you need to do the both pulling together to stop it nose diving in to the ground. I've read reports of pilots doing it in a simulator and they said it's a real rollercoaster ride. It's not something that's part of the standard simulator training, they had completed all their standard simulator training and were trying some "what if..." type things, so most pilots wouldn't normally be thinking of this.

The Ethiopian flight was actually flying very fast - they had normal takeoff and climb power set but were not actually climbing so all that power went in to the aircraft speed. They may have decided to turn the manual trim back on to get the motors to help trim the nose back up, but this then let the MCAS drive the trim nose down again and kill them.

One of the other things that I haven't seen reported on but I have seen pilots chat about, is what this would look like in the cockpit with one of the Angle of Attack sensors reading high. As soon as the wheels came off the ground, the aircraft would see the high AoA on one side and that would set the stick shaker rattling and trigger stall warnings. The cockpit would go from a normal takeoff roll to a cacophony of sound telling you that you are stalling. Without an AoA disagree warning light (optional) and a screen menu to compare AoA readings (optional), the only symptom that this is a false warning triggered by a sensor failure is that the stick shaker is only shaking on the side with the failed sensor - the other control column isn't shaking. At this point MCAS isn't active - it only comes in once the flaps are up. The response to a stall warning is to lower the Angle of Attack (i.e. nose down, but if you have the ground right there you are going to crash) and increase speed. As the speed increases you need to bring the flaps up - they have a max speed before they get ripped off the wing, and when you do that then the MCAS kicks in and tries to kill you. You can use the trim buttons to trim it nose up which stops MCAS for a few seconds - making you think that you don't have runaway trim, but after a little while it starts trimming nose down again. Also because you are now travelling fast, you have that large aerodynamic load on the trim. It's a nasty place to be.
 
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Re: DYMT: Imi's Legacy

Thu Apr 04, 2019 8:34 am

IOW it looks like we may have a situation where incredibly bad UI design has literally killed hundreds of people.
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Re: DYMT: Imi's Legacy

Thu Apr 04, 2019 8:56 am

just brew it! wrote:
IOW it looks like we may have a situation where incredibly bad UI design has literally killed hundreds of people.

Apparently because Boeing and the airlines didn't want to retrain 737 NG pilots on the MAX 8/9 by claiming that there were no differences in their flight characteristics and/or control laws.
What we have today is way too much pluribus and not enough unum.

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