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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’

#81

Post by Aloha »

jg42 wrote: post #70
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.

The key here seems to be the word "many." Alaska Airlines has 289 airplanes (per wikipedia). All the other arguments seem to assume a large consumer type of load - tens of thousands of users, etc... I just can't see an undue strain being placed on a well designed system from Also, to somewhat change the topic, didn't Alaska Airlines disband their QA org a few years ago as part of cost cutting? IIRC, they did this to…

They also mentioned American was using the same system too. So it may have been load from more than one company.

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

#82

Post by lowbloodsugar »

My fucking washing machine can sense how big a load is in it. Surely the plane could measure how fast it is actually accelerating given its thrust and thus derive its actual mass. If it doesn’t match what it’s been told it should alarm.

Also shocking that the system gives an incorrect answer when it is under load. Lack of load testing is a problem, sure, but an architecture that allows the answer to just be wrong is fundamentally flawed.

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

#83

Post by hodgesrm »

CPLX wrote: post #31
guitarbill wrote: post #19

Earlier quoted context omitted.

Agreed, although it takes an individual with a huge amount of integrity or a culture that values and promotes integrity to make a call like this: > “At that point, two in a row like that, that’s when I said, ‘No, we’re done,'” said Peyton. “That’s when I stopped things.” Hats off to Peyton, and possibly Alaska. I would also love to hear about times when something similar happened, and it was discovered that nothing w…

Amazingly, this really is the approach that has characterized all aspects of aviation for decades. It’s incredibly admirable and worth emulating in many other situations. It’s also fragile, and the fact that it strikes many as an uncommon level of integrity for a business decision is precisely why aviation needs to be shielded from having the prevailing business culture sneak in, like we have seen happen at Boeing in…

This type of judgment call by a single person has also helped avoid nuclear war on at least two documented occasions. [0,1] Again, food for thought.

[0] https://en.wikipedia.org/wiki/1983_Soviet_nuclear_false_alar...

[1] https://en.wikipedia.org/wiki/Able_Archer_83

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

#85

Post by renewiltord »

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…

Concurrency is one source, yes, but integration is another possible source. If the vendor software interfaced with Alaska's software then the interfacing layer could imperfectly handle pagination, assume ordering where there is none, and other such data source problems.

A trivial error could be "list all active planes", "list current luggage weight for all these plane IDs", and have the latter give responses in a different order than the input list. Or perhaps "fuel load" returns in a different order. Or something.

Concurrency seems like the obvious one, but it's not the only source I can imagine here. And ultimately, the max is under 300 planes. You can do that serially unless the integration layer is slow.

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

#86

Post by mmcconnell1618 »

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…

I'm surprised there wasn't any human or general guardrail around the calculation that would have flagged such a significant weight difference. No one looked at the passenger count and the weight calculation and thought "whoa, that doesn't look right?"

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

#87

Post by ww520 »

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…

The fix was probably just a rollback to the previous version.

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

#88

Post by lordnacho »

Merad wrote: post #53

I was under the impression that SOP for most aircraft was to take off at full power, and if you happen to be lightly loaded you just get into the air faster. Was I wrong, or is this a recent change? If so, it seems like a concerning way for airlines to cut costs. Having excess power available at take off means there's a greater margin for error to handle emergencies (engine failure, bird strike, etc.).

I'm surprised too. I would have thought the take-off system would incorporate some sort of feedback about how close the tail was to touching the ground and either tell the pilot or correct for it and tell the pilot.

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

#89

Post by renewiltord »

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…

Any fool can build a bridge. You need an engineer to build a bridge that can barely stand.

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

#90

Post by hn_throwaway_99 »

jki275 wrote: post #79
hn_throwaway_99 wrote: post #26

Earlier quoted context omitted.

> 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…

That's still an architecture defect. Software's accuracy being affected by load is completely unacceptable.

Please let us know where these software magicians are that write perfect, bug-free code.
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