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Boeing CEO ousted as 737 Max crisis deepens

reuters.com

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Re: Boeing CEO ousted as 737 Max crisis deepens

#631

Post by gomijacogeo »

konspence wrote: post #588
CydeWeys wrote: post #565

Earlier quoted context omitted.

It needs three AoA sensors, like Airbus planes have. Two isn't enough for such a safety-critical system. When one malfunctions, you still need to know what the correct value is.

Three AoA sensors is still not enough to generate a confident consensus to allow an autopilot system capable of crashing the plane to function On Lufthansa 1829, two of the three AOA sensors on an A321 erroneously agreed, causing a system similar to MCAS to kick in[1] The sensors can fail due to being frozen, or also be damaged by birds traveling in flocks [1] Third bullet point under the A321 heading: https://en.wik…

The thing is 1829 didn't crash, the pilots got an alert, figured out the problem, took manual control, and flew the plane. Defense in layers.

It would be ideal to use different technologies for the AoA sensors to help minimize common-mode failures. Integration and crosschecking against other systems (IMU, radar altimiter, DGPS, an open-loop model of the plane based on engine settings and control surface positions, etc) could give the pilots and flight envelope protection systems a better understanding of their situation. Also, the signature of a failed/frozen vane-type AoA sensor is pretty obvious and I'm surprised the software doesn't take that into account.

Good writeup on LH-1829: http://avherald.com/h?article=47d74074

Re: Boeing CEO ousted as 737 Max crisis deepens

#632

Post by SAI_Peregrinus »

AdrianB1 wrote: post #407
rosybox wrote: post #394

Earlier quoted context omitted.

> There is no normal height. There more certainly is a statistically average height. > Out of 4,063 pilots, not a single airman fit within the average range on all 10 dimensions. This article is comparing 10 dimensions of variability and we're talking about just one here, the one you yourself mentioned, height.

Statistically or mathematically average height does not equal normal height, it has no relevance in this discussion. If you read the article, the average does not fit most people even if you take a single dimension, height.

Within one standard deviation of the mean does, by definition, fit most people for a normally distributed factor like height. (64% > 50%, thus most). "Within 1 standard deviation of the mean" is a decent (if possibly overly strict) definition for "normal" in this context.

Re: Boeing CEO ousted as 737 Max crisis deepens

#633

Post by themeiguoren »

kevin_thibedeau wrote: post #275
jonplackett wrote: post #236

Earlier quoted context omitted.

Reminds me of the news coverage of SpaceX’s first landing attempts, where they crashed into the barge and exploded and everyone was like “it’s a failure, it will never work”. Yeah but so much went right. I think it’s just the (well deserved) media narrative Boeing is in now. When you kill hundreds of people and then pretend it wasn’t your fault, you get what’s coming to you.

That negative messaging was driven by ULA in a desperate bid to close the door on their new competitor. If they could kill off enough contracts, SpaceX might have run out of runway before they established their business model.

Citation? That’s the first I’ve heard of it and that’s a pretty big accusation.

Re: Boeing CEO ousted as 737 Max crisis deepens

#634

Post by AdrianB1 »

SAI_Peregrinus wrote: post #632
AdrianB1 wrote: post #407

Earlier quoted context omitted.

Statistically or mathematically average height does not equal normal height, it has no relevance in this discussion. If you read the article, the average does not fit most people even if you take a single dimension, height.

Within one standard deviation of the mean does, by definition, fit most people for a normally distributed factor like height. (64% > 50%, thus most). "Within 1 standard deviation of the mean" is a decent (if possibly overly strict) definition for "normal" in this context.

Read the article in the link and then explain your comment.

Re: Boeing CEO ousted as 737 Max crisis deepens

#635

Post by inferiorhuman »

WalterBright wrote: post #622
inferiorhuman wrote: post #620

Earlier quoted context omitted.

Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT. If the graphs are to be believed neither the electric commands nor hand crank…

I don't know what graph you're looking at. The reports I saw was that the EA pilots did not follow the procedure: 1. trim to normal with the electric trim switches 2. cut off the stabilizer trim What the EA pilots did was: 1. cut off the stabilizer trim 2. try to use the hand cranks to trim to normal

I don't know what graph you're looking at.

Graphs of the FDR data from the (preliminary) accident reports. The Ethiopian authorities even annotated theirs with things like "automatic trim command with no change in pitch trim". You can see quite plainly the stabilizer was not moving as intended.

2. try to use the hand cranks to trim to normal

Per Boeing's documentation this should've worked. Unfortunately Boeing's documentation is mostly wishful thinking. Boeing's also suggested that a pilot try unloading the stabilizer with a roller coaster type maneuver. Unfortunately Boeing removed detailed instructions on this maneuver decades ago and the FAA's already demonstrated that with the altitude that the Ethiopian crew had, unloading the stabilizer would've just flown the plane into the ground.

There's a reason Boeing's largely backed off of the whole pilot error nonsense: the 737 MAX crashed due to shitty design not pilot error.

Re: Boeing CEO ousted as 737 Max crisis deepens

#636

Post by inferiorhuman »

WalterBright wrote: post #616
inferiorhuman wrote: post #597

Earlier quoted context omitted.

Whatever you read about that is simply wrong. (I've seen a LOT of misinformation in popular print about this.) You're correct that the hand cranks were unusable. But the electric thumb switches WERE usable and were pointed out in the AD. And if you enable the electric trim switches on a 737 MAX you get MCAS activation. MCAS, of course, trims faster than the switches. Using the electric switches is fighting a losing b…

> And if you enable the electric trim switches on a 737 MAX you get MCAS activation. The electric trim switches override MCAS. That is why the steps are: 1. use the electric trim switches to set the trim to normal 2. cut off the electric trim That's all there is to it. > MCAS presented counter to how Boeing defines runaway trim. That's simply false. (And runaway trim does not need definition, Boeing does not define i…

The electric trim switches override MCAS.

They pause MCAS but do not disable or override it it. The trim switches move the stabilizer slower than MCAS activation thus as seen by the Ethiopian and Lion Air crews using the electric trim switches is tantamount to fighting a losing batle.

1. use the electric trim switches to set the trim to normal

What happens when the electric trim switches don't work? They didn't in the Ethiopian crash.

runaway trim does not need definition, Boeing does not define it.

Sure they do, it's in the QRH plain as day.

Condition: Uncommanded stabilizer trim movement occurs continuously.

MCAS activation isn't continuous, especially not if you're pausing it with the trim switches.

Re: Boeing CEO ousted as 737 Max crisis deepens

#637

Post by temac »

ferzul wrote: post #629
temac wrote: post #361

Earlier quoted context omitted.

Giving up things like modern medicine would not be reasonable. Giving up air travel, or at least reducing it vastly, would be merely an inconvenience. Well yeah, giving up air travel entirely would be somehow a mess, but even there it is completely sure we can make it work. In France the train is ~50 x more carbon efficient. We will not be able to keep emitting like crazy forever (we actually should have stopped comp…

If trains are so much better, why is it cheaper to fly?

I'm not sure this is cheaper to fly, but part of the reason this is too cheap is that fuel for airplane is not taxed...
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