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Comment by 20after4 | Hacker News Reader

I think most recently developed large commercial passenger aircraft are completely fly by wire with most controls lacking any physically interlinked backup.

Thinking of this somehow reminded me of the most harrowing aircraft disaster that I've ever read about: https://en.wikipedia.org/wiki/United_Airlines_Flight_232

It's both tragic because half of the passengers were killed but also miraculous that anyone survived at all.

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Hopefully I am not too naive, but I think aircraft safety redundancy remains above retail car standards. Also, in aircraft they "have time to solve some problems", versus freeway bumper cars.

Indeed, but read the link I posted above if you're interested in a fascinating case of failed redundancy.

Engaging version by the incredible Admiral Cloudberg:

https://admiralcloudberg.medium.com/fields-of-fortune-the-cr...

Yeah

Also people say "oh what if fly-by-wire fails" well what if traditional hydraulic controls fail, which has happened plenty in the history of commercial aviation

Everything can and will fail at some point

No redundancy is redundancy enough in some %0.xx of cases. You can always reduce the number, but never make it 0

The reliability of software is so bad this is an absurd comparison.

This is a safety standards issue not a "software" issue. Standards for airplane software are very high

Most planes have been fly-by-wire for decades and aren't regularly falling out of the sky

Software is much easier to break accidentally than a valve.

I work for a medical device manufacturer, and software absolutely can be designed to be just as reliable as physical systems, but the development and testing process looks completely different than a developing a mobile app. Things slow WAY down: if you want to change one line of code, it'll take literally weeks before it makes it to a production environment because of all the testing, documentation, justification, and human approvals. I imagine flight safety systems are subject to a similar level of rigor.

Obligatory mention of SQLight going the DO-178B route.

https://corecursive.com/066-sqlite-with-richard-hipp/#testin...

"Richard Hipp: Getting that last 5% is really, really hard and it took about a year for me to get there, but once we got to that point, we stopped getting bug reports from Android.

"Richard Hipp: Yes, so we’ll do billions of tests."

> I imagine flight safety systems are subject to a similar level of rigor.

Not for cars tho. Cars can be expected to be as reliable as the average windows PC unless there are regulations made and accountability assigned

I also don't believe they install OTA updates while in flight.

Although if they did it would give a fantastic new meaning to "over the air" :-)

In service to the pun, there is a relatively famous demo of using erlang for embedded development where they show off hot code reloading of a drone's flight software while it's in flight.

https://www.youtube.com/watch?v=XQS9SECCp1I

More to the point, FAS regulations would absolutely forbid any such event. They probably mandate testing of the updates before returning to airplane to service.

Completely unlike the safety standards for cars.

Which has nothing to do with a bad update being installed during routing maintenance and only failing in flight. Or while driving.

I am assuming/hoping that testing from Boeing/Airbus is far more stringent than that of Jeep !

Boeing doesn't exactly have the best reputation.

Not for software. Hence airplanes needing reboots at certain time frequencies before they bug out in weird ways.

Large planes are all fly by wire. In a commercial airplane, you're talking about moving maybe a quarter-ton of metal for the rudder alone, and against high wind speeds. There is no way to move those without powerful servo motors.

They use hydraulics, not necessarily fly-by-wire and servos. But when they lose the engines, then they lose hydraulic pressure.

There's APU and/or RAT to fallback on in case of the rare dual engine failure.

I guess they are if you mean fly-by-piano-wire!

The (as of a this year) second-most popular airliner, the Boeing 737, has fully mechanical controls for the ailerons and elevator (with hydraulic boosting). Elevator trim is also mechanical.

The pilot needs to be built like a gorilla to fly it, but primary flight controls continue work, even with a total failure of all electrical and hydraulic systems.

I'm still stunned by Captain Haynes's grace under pressure:

Sioux City Approach: "United Two Thirty-Two Heavy, the wind's currently three six zero at one one; three sixty at eleven. You're cleared to land on any runway."

Haynes: "[laughter] Roger. [laughter] You want to be particular and make it a runway, huh?"

And here's a truly excellent long form article on the crash by the always excellent Admiral Cloudberg: https://admiralcloudberg.medium.com/fields-of-fortune-the-cr...

"The contamination caused what is known as a hard alpha inclusion, where a contaminant particle in a metal alloy causes the metal around it to become brittle. The brittle titanium around the impurity then cracked during forging and fell out during final machining, leaving a cavity with microscopic cracks at the edges. For the next 18 years, the crack grew slightly each time the engine was powered up and brought to operating temperature. Eventually, the crack broke open, causing the disk to fail."

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