hirowan · HackerTrans

I'm just grateful I'm not a core Python dev after reading this thread. I've never seen so much negativity concentrated in one place in quite some time, for a feature of a programming language which is fairly innocuous.

hirowan

7년 전discuss

The issue with this and `singledispatch` is that they no longer support pseudo-types from the `typing` module [1] so you can't use them with containers of type `x`, e.g. `List[str]`, or protocols like `Sequence`.

[1] https://bugs.python.org/issue34498

hirowan

7년 전discuss

That doesn't mean it can't use the same _jetway_ (we were discussing jetways, not gate spacing) you'd use on a 737 or that a 737 can't park at a stand wide enough to fit an A380.

hirowan

7년 전discuss

I can assure you you can use the same jetway on a 737 that you can use on an A380.

hirowan

7년 전discuss

I think it's a little bit of everything (stairs, tech, loading/unloading) but the main reason prrrobably was being able to throw bags into the cargo hold without the need for GSE - the airstair could've easily been made taller.

hirowan

7년 전discuss

The 737 rudder hardover wasn't discovered until the mid-to-late 90s, a long, loooong time after the 737 entered into service. That does not quite speak to the benefit of a mature product (how mature is 'mature'?). Case in point: the 737 trim wheel and pitch trim assembly. The deficiencies of their design were put on full display in 2018, because of MCAS. Why do you think it is that (other) modern airliners do not have a stabilizer runaway non-normal checklist? There's a whole host of issues that are inherent to the 737 precisely because of how... mature it is. I think there's probably a crossover point, when a design ceases to be mature and becomes obsolete.

(Engines on newer models can be - and usually are - iterations of older designs. The A380's RR engines are built on the same platform as the Tristar's, introduced in 1972!)

hirowan

7년 전discuss

There is no other modern airliner with a software bodge for static stability. No, Airbuses are not comparable (Airbus FBW control laws are _not_ for stability control) and they are (to the best of my knowledge) positively stable throughout the flight envelope in direct law.

Emulation is incidental. Redesigning the 737 with FBW is not something that Boeing would've considered, even for a moment.

hirowan

7년 전discuss

I don't know which one you imagine MCAS to be but see [1]; specifically:

   MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation. ... This new location [of the engines] and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA. As the nacelle is ahead of the [centre of gravity], this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) "Stall characteristics". Several aerodynamic solutions were introduced such as revising the leading edge stall strip and modifying the leading edge vortilons but they were insufficient to pass regulation. MCAS was therefore introduced to give an automatic nose down stabilizer input during elevated AoA when flaps are up.

> Airbus

Airbuses operate in C* law (they are not positively stable) [2] and the stick is just that, a spring-loaded.... stick; it meets regulations by default.

[1] http://www.b737.org.uk/mcas.htm

[2] https://www.skybrary.aero/index.php/Fly-By-Wire

hirowan

7년 전discuss

> After an incident like this ...

Clearly, that didn't happen, or a second MAX wouldn't have crashed under very similar circumstances.

> Southwest installed additional gear on their planes to help prevent this when the first plane crashed.

Southwest ordered the MAX with an AoA indicator; it wasn't retrofitted.

> ... to help prevent this ...

It's questionable whether the AoA indicator would've made a difference. However, an AoA disagree alert that is standard in the previous 737 gen was "accidentally" made part of the AoA indicator extra feature set on the MAX, and the AoA disagree just _might_ have made a difference. [1]

> It’s not far fetched that companies in countries with lesser regulations might skip out on training or plane enhancements that would lessen the chances of this problem.

An AoA indicator is not mandatory anywhere in the world.

[1] https://www.aviationtoday.com/2019/05/06/boeing-angle-of-att...

hirowan

7년 전discuss

You're putting the safety record into chauvinist context, to be exact. An AoA failure is sufficiently rare for it to have only occured in a couple of occasions in - shockingly - only a couple of countries.

hirowan

7년 전discuss

MCAS has absolutely nothing to do with maintaining commonality. An aircraft with decreasing stick force on approach to stall in its normal mode of operation would've never been certificated.

hirowan

7년 전discuss

> A brand new design would probably introduce more serious flaws than an interation of a mature design

As evidenced by the ever-crashing 787s and A350s.

hirowan

7년 전discuss

I think you've misunderstood. The system you're describing kicks in when (a) the aircraft is on the ground, (b) commanded thrust is idle and (c) the engines continue to produce thrust above idle (when there is an overthrust condition). Boeing does not cut power to the engines to prevent reverse thrust application in air - that would be absurd.

On this particular occasion the system is thought to have malfunctioned in some way (e.g. it might have not registered the application of reverse thrust) triggering a shutdown.

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