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After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

seattletimes.com

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Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#21

Post by 1101010010 »

Lots of blame to pass on the software, but the real culprit is spelled out clearly in the middle of the article:

> the computer then calculates just the right amount of engine thrust so the pilots don’t use more than necessary. “The goal is to lower the power used on takeoff,” he said. “That reduces engine wear and saves money” on fuel and maintenance.

This is not an accident, but rather a feature of capitalism, this time it is human lives that are commodified and have costs externalized unto.

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#22

Post by hansvm »

Tempest1981 wrote: post #11

Curious about the actual bug: > the update to the DynamicSource software had been tested over an extended period, the bug was missed because it only presented when many aircraft at the same time were using the system > the data was on the order of 20,000 to 30,000 pounds light. With the total weight of those jets at 150,000 to 170,000 pounds, the error was enough to skew the engine thrust and speed settings. Multithr…

Could be something as simple as the first concurrency 101 example: atomic addition. The += operator behaves poorly on concurrent access.

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#23

Post by Game_Ender »

1101010010 wrote: post #21

Lots of blame to pass on the software, but the real culprit is spelled out clearly in the middle of the article: > the computer then calculates just the right amount of engine thrust so the pilots don’t use more than necessary. “The goal is to lower the power used on takeoff,” he said. “That reduces engine wear and saves money” on fuel and maintenance. This is not an accident, but rather a feature of capitalism, this…

In a competitive industry saving money can mean lower fares for customers. It can also mean fewer total planes or engines produced reducing environmental side effects of that activity.

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#25

Post by zaroth »

1101010010 wrote: post #21

Lots of blame to pass on the software, but the real culprit is spelled out clearly in the middle of the article: > the computer then calculates just the right amount of engine thrust so the pilots don’t use more than necessary. “The goal is to lower the power used on takeoff,” he said. “That reduces engine wear and saves money” on fuel and maintenance. This is not an accident, but rather a feature of capitalism, this…

Calculating the appropriate amount of liftoff thrust based on the weight of the plane is universal for flight ops.

This feature of capitalism caused the money to be invested to achieve this efficiency, and also the systems and processes in place to ensure it was implemented properly; with sanity checks, authoritative oversight to halt ops when something was determined to be off, manual backup systems in place and well trained on, a fix rapidly deployed, and new testing put in place to detect any similar bugs in the future.

Yes indeed the stench of capitalism is strong here!

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#26

Post by hn_throwaway_99 »

sudhirj wrote: post #10

> Peyton added that even though the update to the DynamicSource software had been tested over an extended period, the bug was missed because it only presented when many aircraft at the same time were using the system. That seems horribly wrong to me. I can understand software being slow under load, but being wrong under load sounds like a horrible internal architecture problem.

> but being wrong under load sounds like a horrible internal architecture problem.

Tons of software can be "wrong under load" - things like race conditions and memory leaks are common problems, and they don't necessarily point to a huge architectural defect. E.g. Cloudflare had a bug years ago that caused highly sensitive data to leak, but only for a teeny (relatively) portion of their site. Similar issue happened to GitHub: https://github.blog/2021-03-18-how-we-found-and-fixed-a-rare...

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#27

Post by ceejayoz »

justinclift wrote: post #14

With Boeing's recent 737 family history (MAX fiasco, etc), it's very concerning to see "software errors" still happening in operation. :(

How does a "SaaS Founder, Senior DevOps Engineer" get the idea that software errors are entirely avoidable?

This story is about the system working well. Detected immediately via well-trained and alert humans, someone had and used their individual authority to ground the entire airline for safety reasons, mitigated with a workaround 20 minutes later, permanently fixed within five hours, and new tests implemented to account for the root cause.

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#28

Post by pixl97 »

1101010010 wrote: post #21

Lots of blame to pass on the software, but the real culprit is spelled out clearly in the middle of the article: > the computer then calculates just the right amount of engine thrust so the pilots don’t use more than necessary. “The goal is to lower the power used on takeoff,” he said. “That reduces engine wear and saves money” on fuel and maintenance. This is not an accident, but rather a feature of capitalism, this…

I mean yes, would you rather flights are $10,000 or $100,000 each so the engines are taken apart and rebuilt each time after a flight? Reducing the maintenance interval requirements 'safely' is good for everyone.

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#29

Post by nop_slide »

This other article linked near the end of the source article is even sketchier!

It basically boils down to “this flight started nosediving, almost hit the ocean, and we don’t know why”.

https://www.nytimes.com/2023/02/13/us/united-maui-flight.htm...

Re: After Alaska Airlines planes bump runway, a scramble to ‘pull the plug’

#30

Post by djanogo »

cratermoon wrote: post #15
sudhirj wrote: post #10

> Peyton added that even though the update to the DynamicSource software had been tested over an extended period, the bug was missed because it only presented when many aircraft at the same time were using the system. That seems horribly wrong to me. I can understand software being slow under load, but being wrong under load sounds like a horrible internal architecture problem.

Concurrency is hard. Thread unsafe operations that end up getting executed in multi-threaded contexts are a huge source of heisenbugs

This wasn't really a concurrency problem as I understand it, the requests for calculations didn't need to share any data between them.

"the bug was missed because it only presented when many aircraft at the same time were using the system"

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