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

Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

bloomberg.com

Post reply on HN
Print view View original

151–160 of 269 posts

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#151

Post by spricket »

tntn wrote: post #148
spricket wrote: post #141

The fact that "AoA disagree" light and logic was an optional feature seems criminal enough to me. A sensor with no failover unless you pay for an option. Who the hell thought this was a good idea or approved it? WTF! 500 people are already dead. Boeing should be brought to the coals. It probably takes longer to go through the checklist than it does for everyone to die. I promise if the audio recordings are ever relea…

The checklist in question has three steps. Step two is "move stab trim to cutout," which disables automatic systems that adjust the stabilizer. The pilots in lion air had ~10 minutes to do this. It is extremely unlikely that the pilots were trying to work through the checklist. More likely they simply did not know what to do.

This doesn't make jive with disaster being averted by a third pilot. Assuming the third was totally dedicated to checklist vs preventing the plane from diving, it was only his insight that stopped the plane from going down.

The MCAS system apparently increased downward trim without any speed considerations, to over 2.5 degrees in 10 seconds. I don't have the full flight control details but it sure sounds like pilots would lose control within minutes at most. In the LionAir crash the pilot reported control problems and asked to return to airport within 3 minutes, and they slammed into the ocean in 12.

Not sure where you're getting this info but I'm more than sure they knew something was wrong in the last 2 minutes (while they were heading into the earth at almost the speed of sound).

You really think they have ten minutes to react when by then everyone on LionAir was doomed to die?

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#152

Post by Diesel555 »

flashman wrote: post #23

So a single point of failure (malfunctioning sensor) can engage the horizontal stabilizer without notifying pilots, in a way that the control yoke can't override. What the hell did Boeing think was going to happen?

All fly by wire jets have movements based on sensors. In the F-16 a faulty AOA probe is okay. 2x Faulty AOA probes are okay as long as they disagree. 2x faulty AOA probes that agree (frozen) are a very bad thing. But the loss is just a jet with an ejected seat if it can't be fixed, not nearly 200 people which is terribly sad. The worst part is from a previous Hacker News post listed below. In particular, the "Economic Problem" which states "Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737MAXes that crashed were delivered without this option. No 737MAX with this option has ever crashed."

https://twitter.com/trevorsumner/status/1106934369158078470?...

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#153

Post by js2 »

inferiorhuman wrote: post #130
js2 wrote: post #125

Earlier quoted context omitted.

Can you explain how they are different? Both cause the stabilizer to tilt. Both cause the stabilizer wheels next to the pilot/co-pilot to turn. If the plane is pitching down, and you pull back the yoke and that still doesn't recover, don't you at some point check the stabilizer angle? If it's wrong, you use the stabilizer trim switch on the yoke under your thumb to correct it. Won't you see the stabilizer wheel turn…

Also, how did the off-duty pilot figure it out if they are nothing alike? My assumption is that the jupmseat guy took a very generous interpretation of the checklist. But there may have been more panic about the trim on the earlier flight. If you compare trim inputs on flight 610 to the previous flight, the pilots on the earlier flight were making much shorter, more rapid inputs than the pilots on flight 610. The pla…

Thank you for the preliminary report link. It’s the first I’ve seen it.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#154

Post by cjbprime »

cryptonector wrote: post #135
zaphirplane wrote: post #106

Earlier quoted context omitted.

This is very important, as it shows the ratio of pilots aware of the mitigation is low, and/or the stress of fighting with the the computer makes you forget you training amendments Edited to add it’s a training amendment

It also shows that pilot awareness (and therefore training) should have been sufficient. The key deficiency here was Boeing's. The agency not disclosing this detail is a problem too.

That.. sounds like the literal opposite of what it shows, no?

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#155

Post by cjbprime »

Someone1234 wrote: post #94
sterlind wrote: post #89

Earlier quoted context omitted.

Seems like pilots are overburdened by so much automation, as alluded to by the famous "Children of the Magenta" video[0]. I don't get why the plane doesn't just say what it's doing, and why it's doing it, and have a big red button to put the plane into a safe-mode alternate law. 737s already say warnings like "BANK ANGLE", couldn't it just say "DANGEROUS CLIMB DETECTED, TRIMMING NOSE DOWN. PRESS RED BUTTON TO CANCEL.…

Boeing offered that, but it was a paid extra that few airlines purchased. https://theaircurrent.com/aviation-safety/southwest-airlines...

This is grossly overstating the optional feature. As I understand it, "AOA disagree" is a single light near the AoA indicator itself. It's not an explanation, or even an alert. It's not where anyone would reasonably look when trying to diagnose an uncommanded flight control problem.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#156

Post by cjbprime »

6nf wrote: post #129
inferiorhuman wrote: post #123

Earlier quoted context omitted.

In many aircraft hard elevation will overpower even a faulty horizontal stabilizer In the 737 you can get into situations where the elevator has insufficient authority to overcome a stabilizer. Excessive pitch up (leading to a potential stall) that you can't counter by pushing on the yoke is exactly what MCAS is designed to prevent. There was a mechanical failure, the AoA sensor. A fixed offset from reality is an int…

The left alpha vane was being interpreted as almost exactly twenty degrees higher than the right. Is that because the plane was in a banking maneuver at the time maybe? I dont know anything about planes but I heard that when you're turning the two sensors will disagree by some amount

I think it's been disclosed that in Lion Air the sensors were twenty degrees apart even when sitting on the runway before the flight. It is shocking that nothing checked for disagreement or communicated it to the pilots.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#157

Post by tomnm »

arcticbull wrote: post #126
zaphirplane wrote: post #106

Earlier quoted context omitted.

This is very important, as it shows the ratio of pilots aware of the mitigation is low, and/or the stress of fighting with the the computer makes you forget you training amendments Edited to add it’s a training amendment

It's a single data point / anecdote. These investigations are incredibly thorough, precise, and authoritative so it makes sense they'd seek to exclude that kind of information until they knew for sure.

> It's a single data point / anecdote.

A single data point is still a data point.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#158

Post by jquery »

WalterBright wrote: post #92
shiven wrote: post #43

From my point-of-view, two opinion points: 1. I am glad that 737 MAX has been grounded. May it stay that way, globally, until this issue is provably resolved. 2. The entire Boeing chain of management that resulted in these crashes should be publicly flogged, their remuneration & benefits clawed back & subject to a mandatory minimum prison sentence. Who the hell am I kidding! Neither is very likely to happen in the pr…

I'd fly on a 737 MAX tomorrow. But I might ask the crew during boarding if they're familiar with the stab trim cutoff switches.

I've flown on a 737 MAX a couple times this year. Smooth, comfortable, quiet flight. Although the failure of the MCAS system has been catastrophic, fortunately for Boeing the fix doesn't seem difficult... make an extra AoA vane or two mandatory and add a warning if they disagree, and require MAX pilots to sim train an MCAS failure.

The planes seem eminently airworthy, so far it appears they weren't brought down by anything that's terribly difficult to engineer out of. Unfortunately for Boeing and the FAA, nothing is more costly than an accident, it will take years to earn back the public's trust. Even if it's found the pilots were downright negligent in their handling of the MCAS failure, that won't make the general flying public feel any better about it, and it won't bring back the dead, may they rest in peace.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#159

Post by cjbprime »

dsfyu404ed wrote: post #44
jimktrains2 wrote: post #32

Earlier quoted context omitted.

Do we have a confirmed source that it can't be override by pilot input? My understanding was that using the stick could overcome it with other control surfaces and that the controls for trim can be set/reset by the pilot. I think Boeing has handled the aftermath (and much of the lead up since the release of the plane) very, very poorly. I, as a layman to aviation, am not willing to bet that Boeing knew the true likel…

>safety critical systems should always be redundant. That's east to say from an armchair but on an aircraft everything is "safety critical" to some extent and you have to choose what gets redundancy. Something where without it you can't fly the plane sure, that make sense. The argument for considering MCAS, a system which is not necessary to fly the plane safely, to be "safety critical" is much weaker. The Lion Air c…

But there are already two AoA sensors on the plane. They already made it redundant. They just didn't write code to perform an agreement check as an input to MCAS.

I don't think any aviation expert would agree that the case for requiring redundancy in the MCAS system is weak.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#160

Post by cjbprime »

gtirloni wrote: post #118
chrisseaton wrote: post #64

Earlier quoted context omitted.

> You can't have them all be redundant. Why not?

The usual, cost. But I wonder how much the redundant sensor costs for airlines to ditch it.

Every 737 has two AoA vanes. They are redundant and the redundancy is not optional. MCAS just doesn't take advantage of there being two sensors.
Post reply on HN