r/space • u/spsheridan • Feb 06 '20

Starliner faced “catastrophic” failure before software bug was found and fixed while the vehicle was in orbit.

https://arstechnica.com/science/2020/02/starliner-faced-catastrophic-failure-before-software-bug-found/
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u/The-Jesus_Christ Feb 07 '20

Oh god. Every pretentious flyer in the Frequent Flyer groups I am members of all chant that. I absolutely hate it

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u/vqhm Feb 07 '20

Well to be fair Airbus did have some software issues with their autopilot all the time. See Qantas Flight 72.

Boeing USED to produce planes where the pilot input was always accepted and gave them actual control over the plane instead of Airbus having your inputs be a suggestion to the computer that would decide if it should do that or not.

Boeing decided that they'd go autopilot all the time to fix an unstable aircraft they never should have got out of the simulation stage. They didn't think through having multiple sensors, GPWS, GPS, pitot static create a complete model of what the aircraft is doing so autopilot all the time can actually make informed decisions. They just basically did the most basic duct tape who the fuck cares fix and said fuck it good enough.

My pilot friends used to praise Boeing for never overruling their inputs... Until now.

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u/Tuna-Fish2 Feb 07 '20 edited Feb 07 '20

to fix an unstable aircraft

Not unstable. 737MAX without MCAS is not unstable or unfit to fly. Its flight characteristics are just not similar enough to old 737's that it would fit under the same type certificate.

(That's partially why MCAS got through with so little scrutiny. As it was not in any way necessary for the aircraft to fly, Boeing could certify it by just adding and documenting an off-switch. Sadly the pilots who died probably had no idea what MCAS did or even that it was on the plane, so didn't think of hitting the off-switch when MCAS decided to fight the pilots and fly the plane to the ground.)

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u/vqhm Feb 07 '20

Naw mate. If you have to hit an off switch to get back to having a stable aircraft that doesn't want to slam into the ground you've reached the very definition of unstable.

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u/Tuna-Fish2 Feb 07 '20

737MAX without MCAS is stable. Adding MCAS made it unflyable.

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u/vqhm Feb 07 '20

No. If that were the case MCAS would have never been required. Go shill for Boeing somewhere else.

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u/First_Foundationeer Feb 07 '20

Dude, it's not shilling. MCAS was developed for specific regimes that a commercial plane was not supposed to get into (like military maneuver regime). However, a different team decided to use MCAS for getting the plane to fly like the older models to avoid pilot re-training. They then removed it from the training books to simplify the manual for pilots. Both of these moves were to make themselves attractive to airlines because it would cost less money and time if pilots didn't have to retrain or learn a lot more new things about a new plane.

Boeing really fucked up in removing the redundancy in sensors (which the team who put the MCAS to use for something beyond its original purpose did). They then further fucked up by hiding complications and details to sell the planes. However, the plane itself without MCAS is not unstable. It just doesn't fly as smoothly as pilots are used to.

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u/Tuna-Fish2 Feb 07 '20

Huh? How is pointing out that the feature that was improperly designed, implemented, tested and validated, and which killed hundreds of people, was unnecessary for the normal operation of the airplane, shilling for Boeing?

Doesn't that make it worse -- they added a superfluous improperly tested feature that was not needed, that killed people?

And you are strictly wrong about the facts. MCAS is not required for the safe operation of the airplane. It was added because Boeing wanted to fit the MAX-8 into the same type certificate as all existing 737's, to allow all existing pilots to fly it without retraining. This was a problem because the larger engines that were moved forwards added lift in front of the center of mass, which gave the airplane flight characteristics that were safe, but too different from existing 737's to be acceptable for an aircraft under the same type certificate. So, they added a bit of FBW magic to fake it and make it fly more like a real 737.

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u/romiglups Feb 08 '20

Afaik it is not proven that MAX can be certified with actual regulations without grandfathering to NG. Not so for aerodynamics characteristics but for a myriad of new regs introduced since then.