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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’

#151

Post by AdrianB1 »

dandandan wrote: post #148
AdrianB1 wrote: post #145

Earlier quoted context omitted.

Rotating at a slower speed is a bad idea. Indicating a lower weight, resulting in a lower calculated rotating speed, is the root cause of the problem. There is no "slower rotation", one does not just pull the yoke slowly, raise the nose wheel and wait for the plane to take off by itself when it will be fast enough, that you can do on a light prop plane where rotate speed is so low some planes will take off by themsel…

I interpreted "slower" as "later," ie wait longer before rotating.

That means rotating at a higher speed than calculated Vr, this is also bad as you put more wear in the tires and use more fuel (rolling on the tires vs flying in the air) to take off. The Vr is an optimal speed, below is dangerous, above is wasteful.

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

#152

Post by seabird »

basch wrote: post #117
mnw21cam wrote: post #116

Earlier quoted context omitted.

> The purpose of telling pilots thrust was to save money and fuel. No, it's more that using lower thrust during take off saves on engine wear and noise levels around the airport. It doesn't really have that big an impact on fuel use, at least that's not the primary purpose. The article concentrates far too much on the thrust setting. The important bit is the speed where the plane should be rotated to take off, which…

> saves on engine wear Which is saving on money

I'm cracking up at the thought of an airline telling their pilots "fuck it, run em however hard you think you need to."

There's a difference between dumping toxic waste into a river to save money and keeping a plane engine in safe operating conditions to save money.

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

#153

Post by tbrownaw »

exabrial wrote: post #47
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.

I was just about to post the _Exact_ same thing. Each execution of the program should be completely independent from other calculations. Something is _Horribly_ wrong with their architecture.

... Call to the baggage-tracking service returned 429 and an empty body, and that was treated as "there are no bags" because some dweeb [dev, but I'm leaving in what autocorrect said] had been reading to much design guidance from Netflix/Facebook/etc that assumes missing features on a fraction of page loads are NBD?

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

#154

Post by klyrs »

AdrianB1 wrote: post #150
klyrs wrote: post #91

Earlier quoted context omitted.

A proper transactional database would suffice. You could do this safely and performantly on '00s hardware in PHP3 for crying out loud, serving thousands of planes per second.

Bad coding happen even in transactional databases, see my example in the other comment.

Note that I didn't say you couldn't write bad PHP3.

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

#155

Post by mgsouth »

AdrianB1 wrote: post #151
dandandan wrote: post #148

Earlier quoted context omitted.

I interpreted "slower" as "later," ie wait longer before rotating.

That means rotating at a higher speed than calculated Vr, this is also bad as you put more wear in the tires and use more fuel (rolling on the tires vs flying in the air) to take off. The Vr is an optimal speed, below is dangerous, above is wasteful.

I think the more important factor is that it eats runway and takes longer to reach safe speeds. If there is a problem at rotation you want as much runway available as possible. If you delay rotation not only are you further down the runway before "really rotating", but you're traveling faster. A 10-knot increase in speed means 20% more energy to disipate. And you're even further above the brake's certified performace. And you've dawdled in getting to safe climb speeds; you accelerate more slowly rolling than flying.

Edit: Actually, that probably doesn't even come into it. Not a pilot, but don't imagine "barely rotate so the nosewheel is in the air but still have negative angle of attack so no lift" is very easy, or very stable if possible. Even if you could do it, you'd risk slamming the nosewheel back into the runway.

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

#156

Post by wlonkly »

basch wrote: post #4
Aloha wrote: post #2

This seems like mostly how it ought to work - * There were two unusual events in very short order * Someone quickly noticed and gave the order to go to ground stop * The problem was figured out quickly and a work-around was developed * Flights Resumed after successfully deploying the work around to the 'production process' * A patch was quickly developed and deployed once the underlying bug was uncovered. I think eve…

The purpose of telling pilots thrust was to save money and fuel. It’s a “least viable” optimization. >“The goal is to lower the power used on takeoff,” he said. “That reduces engine wear and saves money” on fuel and maintenance. >Flights to Hawaii are typically full, with lots of baggage and a full load of fuel for the trip across the ocean. The planes are heavy. > That morning, a software bug in an update to the Dyn…

Based on my experiences reading aviation accident and safety reports, air transport pilots have a _lot_ of divorces.

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

#157

Post by dehrmann »

> Flights to Hawaii are typically full, with lots of baggage and a full load of fuel for the trip across the ocean. The planes are heavy.

Interesting that baggage weight changes by destination. I'm sure passenger weight does too, but for different reasons.

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

#158

Post by forgottenlogin9 »

jki275 wrote: post #98
hn_throwaway_99 wrote: post #90

Earlier quoted context omitted.

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

Who said anything about that? You're arguing against a straw man nobody has set up but yourself.. There's no such thing as perfect software, but there is definitely software that doesn't make up a false value if it can't work.

And if there is a bug in the logic that determines if it can or can’t work?

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

#159

Post by _moof »

Aloha wrote: post #2

This seems like mostly how it ought to work - * There were two unusual events in very short order * Someone quickly noticed and gave the order to go to ground stop * The problem was figured out quickly and a work-around was developed * Flights Resumed after successfully deploying the work around to the 'production process' * A patch was quickly developed and deployed once the underlying bug was uncovered. I think eve…

If it makes you feel any better, the people providing these calculations to the pilots are FAA-certified airline dispatchers. That means they've passed the same exam that airline pilots have to take, minus the flying. They may not have personal experience flying the airplane but they do have to know it inside and out. And if the dispatchers weren't running the numbers, the pilots would be running them using the same software and/or tables, so there really isn't much difference.

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

#160

Post by Dylan16807 »

richwater wrote: post #133
KennyBlanken wrote: post #126

Earlier quoted context omitted.

In what scenario would you anticipate data for the calculation of rotation speed and engine thrust for one particular plane to be based on a value that is not only shared and writable, but changing each time a plane's performance data is calculated? "multiple data streams feeding in weight data per aircraft"? What does that word salad even mean? Even if what any of what you said was true: these developers are writing…

I fucking cracked up at: "multiple data streams feeding in weight data per aircraft" it's literally some integers (floats at the worst?).

You can send integers from multiple sources, dude.
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