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Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

bbc.co.uk

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Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#191

Post by VBprogrammer »

peteradio wrote: post #175
VBprogrammer wrote: post #162

Earlier quoted context omitted.

If someone connected a big industrial stop switch to a solenoid and pointed that solenoid at the trigger of a rifle aimed at the person pressing the button I don't think you would expect anyone to look particularly hard at the person who manufactured the switch. If it was indeed a bird strike which took out the sensor then they seem to be completely beyond all possible blame. Even if it wasn't I'm sure they could poi…

So you are saying this was probably not spec'd for this criticality? I guess I'm curious for more information on this. Obviously don't blame the sensor manufacturer without cause but why are these things so buggy?

The sibling comment says it better than I ever could. It's a mechanical device exposed to 500mph wind speeds and temperatures from 40c to -50c. It's a wonder that they work at all.

I don't think they are particularly prone to failure though. MCAS aside, having the stick shaker activate along with a host of other indications would probably be cause for a precautionary diversion by most pilots.

Having no autopilot and / or an unreliable altitude would most likely disqualify the aircraft from entering RVSM airspace which is where these aircraft would normally operate.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#192

Post by saiya-jin »

jfk13 wrote: post #53
vfinn wrote: post #46

Every time I read about these plane accidents, I wonder why planes don't have any emergency features to save these people. Couldn't you build a plane that would eject the cabin as a parachute module or something. Yes, I'm sure this is naive, but why? Edit: My point is that almost anything is better than crashing down with the plane.

Can you imagine the scale of parachute that would be needed to safely bring an airliner cabin to earth? Could a parachute on that scale actually be made sufficiently strong (and light), and successfully deployed? I doubt it.

Imagine 500m wide parachute. Would probably weight few tonnes, be very complex to deploy (say only above 1-2km altitude), very hard to inspect regularly etc.

The other problem is, a lot of death/damage is done after plane hits the ground and starts to burn. You wouldn't be able to prevent that, since emergency parachute falls are hard ones. So you might still end up killing everybody on plane.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#193

Post by sokoloff »

JshWright wrote: post #186
sokoloff wrote: post #129

Earlier quoted context omitted.

I am one of those people. If in fact the stab trim cutout switches were set to cutout early in the incident sequence, as required by the memory items on the checklist, I will absolutely retract my criticism of the crew and the blame falls much more squarely/exclusively on Boeing. I’ll make it a point to retract and apologize on all three forums where I made those comments (two tech and one aviation). I don’t read the…

Shouldn't that be the other way around? You're the one making the claim that the pilots acted inappropriately. Now you're saying you require evidence contradicting your claim before you retract it?

IMO, no. There is a released fact (via photographs) that the jackscrew on the stab trim was run to the extreme. That's strong evidence to suggest that the non-normal checklist for stab trim runaway was not correctly followed.

The aviation minister's comment today does not carry weight in excess of the photographic, factual evidence, IMO. There are too many "loopholes" that she could be exploiting without leaving her statement technically incorrect.

The good thing, such as it is, is that the facts are almost surely going to emerge here. The CVR transcript, FDR dump, and analysis of whether there's a mechanism for the electric trim to run even with the stab trim cutout switches in cutout and whether that can exceed the crew's ability to stop and reverse the trim setting manually will be telling. I do admit that the minister has greater access to that information than you or I do at this time. It is possible, but not decided, that she's had time to review all that information, knows with certainty the crew is blameless, and has chosen to not make a specific enough statement to support that for any number of valid reasons.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#194

Post by [deleted] »

DanielBMarkham wrote: post #16

There you have it, folks, programmers killing people. No, it wasn't on-purpose, but that doesn't mean it didn't happen. This, of course, has been happening for a long time, it's just getting more and more obvious now. I feel strongly that AF 447 was an example. It's important to understand that this is the natural result of two trends. One, software/hardware systems continue to become more and more complex, many time…

[deleted]

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#195

Post by CaptainZapp »

Shank wrote: post #160
alkonaut wrote: post #145

Earlier quoted context omitted.

I'm an armchair non-expert at best: but shouldn't planes always be controllable by the column so long as the plane is mechanically OK? I.e. max power + pull stick should always just take the plane up, regardless of any amount of misconfiguration such as being out-of-trim etc? Isn't that a reasonable expectation? That is: a pilot in panic at low altitude should never be required to do anything more than he basically c…

> but shouldn't planes always be controllable by the column so long as the plane is mechanically OK? The problem is that you can easily exceed the aircraft flight specifications if you enable unlimited control. If you pull the stick back at max power you can seriously risk the creation of a stall, which is why MCAS exists in the first place. The whole goal Boeing had was to create a safe plane by letting software ens…

The problem is that you can easily exceed the aircraft flight specifications if you enable unlimited control. If you pull the stick back at max power you can seriously risk the creation of a stall, which is why MCAS exists in the first place.

That's manifestly wrong.

MCAS was introduced because of the design decision to place the larger and more powerfull power plants further in front and higher up.

The reason for this was that Boeing wanted to grandfather the 737 certification into this model and wanted to avoid pilot retraining in the simulator, which was an important sales argument.

The problem with this redesign was that the airframe tended to point the nose up, since its aerodynamical characteristics changed due to the redesign.

MCAS was introduced in order to simulate the same behavioral characteristics of the older 737s.

This is proven by the fact that the system was neither documented nor was it part of the scenarios in the 737 MAX simulator. The idea was that the functionality is completely transparent to the pilots so that the could fly the new plane after a minimal presentation on an iPad, which was less thank one hour if they were already 737 certified.

The problem was not pilots pulling the nose too high. The problem, which MCAS tried to correct was the tendency of the plane to pull the nose high and correct for it.

Boeing tried to cram a 50 year old airframe into a new plane with engines too big to fit that airframe and wanted to avoid recertification and retraining.

That's the whole issue we're discussing here.

edit: clarification

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#196

Post by Dirlewanger »

golergka wrote: post #40
guylepage3 wrote: post #35

I’m a social capitalist. IMO, it seldom happens that the free market does not punish companies who make serious errors. For those times, logic, common sense & societal regulation should step in, punish the company with fines ratcheting up until free market clearly loses confidence.

With this kind of publicity I don't see how can Boeing can possibly not punished by the market itself. Even before 737 Max fleet was grounded, I already started hearing, from a lot of different people, that they wouldn't fly on that plane.

Can one even accurately know what plane they will be on until mere hours before? Does flightradar help with this?

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#197

Post by JshWright »

treis wrote: post #190
JshWright wrote: post #184

Earlier quoted context omitted.

As we have now learned, switching to the manual control is useless when the aircraft is in this condition (high speed, stab down, elevator up). The Ethiopian pilots turned off the electric trim control, only to have to turn it back on again.

>As we have now learned, switching to the manual control is useless when the aircraft is in this condition (high speed, stab down, elevator up). That wasn't the position the Lion Air flight was in. I don't think there is much debate that the Lion Air flight was recoverable since the pilots on the previous flight recovered from the same issue: >As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8,…

It was recoverable in a similar situation. That does not mean it was recoverable in both situations.

Any incident like this is a chain of events (which in this case started back with the original design decisions). Many links in that chain aren't obvious, and no two chains are identical. Just because the chain was broken in one case doesn't mean it was reasonable to expect it to be broken in all of them.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#198

Post by JshWright »

sokoloff wrote: post #193
JshWright wrote: post #186

Earlier quoted context omitted.

Shouldn't that be the other way around? You're the one making the claim that the pilots acted inappropriately. Now you're saying you require evidence contradicting your claim before you retract it?

IMO, no. There is a released fact (via photographs) that the jackscrew on the stab trim was run to the extreme. That's strong evidence to suggest that the non-normal checklist for stab trim runaway was not correctly followed. The aviation minister's comment today does not carry weight in excess of the photographic, factual evidence, IMO. There are too many "loopholes" that she could be exploiting without leaving her…

The explanation put forward (which seems reasonable) is that the cutouts were disengaged because the aerodynamic forces were stronger than could be overcome by the manual control, so they had to turn the electrics back on in an attempt to move it (which allowed the MCAS to continue pushing the stabilizer to the extreme)

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#199

Post by carbocation »

DanielBMarkham wrote: post #42
carbocation wrote: post #20

Earlier quoted context omitted.

Why is this a software problem? Even if there is a software “fix,” doesn’t it seem that this tells us more about regulatory capture than using software to patch over bad hardware decisions?

I really didn't want to flame the room. As a commercially-rated small plane pilot and coder, I have a passion here and it both hurts me and makes me really angry. I said this was a programmers problem, not a software problem, and I identified one of the key causes as programmers being isolated from user outcomes. Probably not a big deal if your user can't get to the website for 10 minutes. Different thing entirely he…

I agree with much of what you say here. I don’t agree that programmers are at fault or are particularly well suited or intervene, since the core is not a software problem. This is the nature of systems problems. Nevertheless, I think that we have a core agreement.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#200

Post by Shank »

CaptainZapp wrote: post #195
Shank wrote: post #160

Earlier quoted context omitted.

> but shouldn't planes always be controllable by the column so long as the plane is mechanically OK? The problem is that you can easily exceed the aircraft flight specifications if you enable unlimited control. If you pull the stick back at max power you can seriously risk the creation of a stall, which is why MCAS exists in the first place. The whole goal Boeing had was to create a safe plane by letting software ens…

The problem is that you can easily exceed the aircraft flight specifications if you enable unlimited control. If you pull the stick back at max power you can seriously risk the creation of a stall, which is why MCAS exists in the first place. That's manifestly wrong. MCAS was introduced because of the design decision to place the larger and more powerfull power plants further in front and higher up. The reason for th…

> The problem with this redesign was that the airframe tended to point the nose up, since its aerodynamical characteristics changed due to the redesign.

Alas, I do appreciate your comment. This is what I was attempting (but failing) to say.

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