Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

E.U.’s Biggest Economies Ban Boeing Max 8 Jets

nytimes.com

Post reply on HN
Print view View original

91–100 of 365 posts

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#91

Post by opencl »

rixrax wrote: post #89
anaphor wrote: post #5

Earlier quoted context omitted.

The engines are larger than previous models and had to be moved forward, which causes it to (potentially) stall, so they implemented an anti-stalling mechanism called MCAS which relies on a particular sensor, which can malfunction potentially. They also didn't inform pilots that this system even existed which means they have trouble diagnosing the problem and will potentially only make it worse by trying other things…

Are there any statistics available for how often there has been a need for a pilot to disengage MCAS? If we speculate (e.g. before the facts are in) that this was similar in cause to Lion air incident, then I would be curious to know how often AoA sensor has malfunctioned and|or MCAS has otherwise gone haywire and pilots have needed to revert to manual control during the two years of service MAX8s have had.

The Lion Air plane that crashed had suffered from the exact same failure on its previous flight, though obviously the pilots managed to recover from that one.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#92

Post by hencq »

anaphor wrote: post #5
Areading314 wrote: post #3

Does anyone actually know or suspect what's wrong with these planes? Hardware issue? Software issue?

The engines are larger than previous models and had to be moved forward, which causes it to (potentially) stall, so they implemented an anti-stalling mechanism called MCAS which relies on a particular sensor, which can malfunction potentially. They also didn't inform pilots that this system even existed which means they have trouble diagnosing the problem and will potentially only make it worse by trying other things…

As you say, most of the speculation seems to focus on MCAS in combination with faulty sensor data. While, as a layman, pilots being unfamiliar with MCAS seems like a reasonable explanation, doesn't this theory still require 2 planes in 6 months to have faulty AOA sensor data? That seems unusually high to me as well. I haven't really seen any comments on that.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#94

Post by Brakenshire »

ConceitedCode wrote: post #85
Brakenshire wrote: post #76

Earlier quoted context omitted.

I mean, initially pilots were not informed this system existed. Certainly the assumptions that went into that decision seem to match up with what the person above you is describing.

In theory (not saying I agree), the "regain control checklist" is very similar before and after this change which is apart of why they did not see a need to communicate this until after the 1st crash. Reviewing the video below - it appears to still line up with this. He doesn't mention the actual memory items changing. His explanation is the pilots starting using the wrong memory items because of information overload…

That appears to be contradicted in this video which was linked above, around the 8:45 minute mark, it's a different set of memory items ("Runaway stabilizer") which should be enacted in the case this system was coming into force outside of a stall situation.

https://www.youtube.com/watch?v=zfQW0upkVus

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#95

Post by anaphor »

kawfey wrote: post #74
anaphor wrote: post #5

Earlier quoted context omitted.

The engines are larger than previous models and had to be moved forward, which causes it to (potentially) stall, so they implemented an anti-stalling mechanism called MCAS which relies on a particular sensor, which can malfunction potentially. They also didn't inform pilots that this system even existed which means they have trouble diagnosing the problem and will potentially only make it worse by trying other things…

The linked article also mentions the plane was smoking, and fire was coming from the engines. This is new information to me that I think is being overlooked, because if MCAS was enabled erroneously, it's unlikely the plane would have caught fire. The Lion Air Max 8 wasn't reported to be smoking/on fire. If something else made the engine(s) catch fire and become inoperative, and the MCAS system enabled correctly due t…

I hadn't heard that, but that's exactly why he says (in his latest video and here) to avoid too much speculation, because there are other things that could go wrong under similar conditions. Takeoff and landing are the most risky parts of a flight so it's no surprise that if there is going to be an issue, it would be during takeoff.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#96

Post by Theodores »

anaphor wrote: post #5
Areading314 wrote: post #3

Does anyone actually know or suspect what's wrong with these planes? Hardware issue? Software issue?

The engines are larger than previous models and had to be moved forward, which causes it to (potentially) stall, so they implemented an anti-stalling mechanism called MCAS which relies on a particular sensor, which can malfunction potentially. They also didn't inform pilots that this system even existed which means they have trouble diagnosing the problem and will potentially only make it worse by trying other things…

The bottom of the engines are a mere 40cm of so above the ground when the plane is on the runway. Hence the tight fit and need to move the engines forward so they would fit. Then the auto-fix-the-stall software isn't something the pilots are told about.

They didn't come up with a common sense solution, doing so would have costed many billions for a new airframe with longer legs for the landing gear. This is how I understand the problem, coming from a design compromise and organisational groupthink.

Clearly this is my armchair speculation however I suspect there will be lessons to be learned from this that run along the lines of the 'Vasa' rather than the 'Comet'.

https://en.wikipedia.org/wiki/Vasa_(ship)

The Vasa story crops up on HN from time to time, it was a top heavy Swedish ship that sank after launch in light winds many centuries ago. The spec had changed with more gun decks added and groupthink drove the 'pride of the fleet' project forward. The launch date happened and it sunk.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#97

Post by tivert »

jsty wrote: post #79
gizmo385 wrote: post #28

Earlier quoted context omitted.

Yikes. How would ya like to be a passenger on one of those planes: "We're returning to our departure airport because this airplane has been grounded."

Although if you'd realised it was a 737 MAX, you might already be clutching a medicinal gin & tonic ...

> Although if you'd realised it was a 737 MAX, you might already be clutching a medicinal gin & tonic ...

I wouldn't, haven't all the problems so far have been during takeoff? So once you're cruising you're safe from them?

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#98

Post by lozaning »

aunty_helen wrote: post #39
ak217 wrote: post #32

Earlier quoted context omitted.

Wow. This is pretty ridiculous considering all three of these planes seem to have been closer to their destination than the origin, making it safer to just finish the planned flight.

Both incidents have been in the first few minutes of flight and this is also a 'long term safety' thing. They're relatively safe to fly still. On the other hand, if your plane gets stuck in a foreign country the bill just for parking the thing could be massive. Better to get it back while you still can.

Eventually the bill can get so high that it doesn't make financial sense to still attempt to claim to be the owner. As of January there was a McDonnell Douglas MD87 in Madrid thats abandoned. Three 747 were sold for scrap in 2017 after they were abandoned at Kuala Lumpur.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#99

Post by foobarbazetc »

aunty_helen wrote: post #39
ak217 wrote: post #32

Earlier quoted context omitted.

Wow. This is pretty ridiculous considering all three of these planes seem to have been closer to their destination than the origin, making it safer to just finish the planned flight.

Both incidents have been in the first few minutes of flight and this is also a 'long term safety' thing. They're relatively safe to fly still. On the other hand, if your plane gets stuck in a foreign country the bill just for parking the thing could be massive. Better to get it back while you still can.

It can happen any time if it’s the MCAS issue again. Which we don’t know yet.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#100

Post by bryondowd »

Svip wrote: post #38
jka wrote: post #34

Earlier quoted context omitted.

Do you have a reference to confirm that this was a knee-jerk/optics reaction, out of interest? (definitely curious to see how airlines/authorities are reaching these decisions) The MCAS system and the way it was introduced sound a little like a patch, and slightly haphazard. While training & runbooks and procedures are important, take-off is a busy time, and the Max-8 is (afaik) intended to operate very-nearly-like a…

Over 300 people dead sounds pretty serious to me. It's probably safest to ground the plane model until we know more.

I've seen a number of people pointing at this likely being more an issue with untrained pilots than the plane itself. EI, the flight crew on the crashed planes may have had considerably less experience than the minimum requirements most major airlines and all US airlines set for flying these planes.
Post reply on HN