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

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

#61

Post by kayfox »

jimktrains2 wrote: post #32
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?

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…

The trim adjustments by MCAS can be disabled by setting the two stabilizer trim cutout switches[1] to cut-out. The recognition that trim is being automatically adjusted outside of their ability to control the aircraft and how to correct it is considered so important to be a "memory item" or something pilots should know how to do without referring to the quick reference handbook.

1. https://aviation.stackexchange.com/questions/58798/why-doesn...

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

#62

Post by JMTQp8lwXL »

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…

Even if the US doesn't choose to do much (though I find it embarrassing the FAA was one of the last regulatory bodies to respond), Boeing will face a reckoning globally from other regulatory agencies.

Stock is down 15% since March 1. Hard to know what an executives there are thinking, but I hope some folks in the organization genuinely feels some sort of empathy for the families of the deceased on these flights.

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

#63

Post by nas »

jquery wrote: post #22

Runaway trim is supposed to be part of the "memory checklist" for pilots. The symptoms of MCAS are the same as runaway trim and the fix is the same (which is why Boeing didn't feel like extra pilot training was needed), so I'm curious to see the most recent investigation and hear the black box voice recorder. Did they not know they were dealing with runaway trim? Did they think it was something else? Did they forget…

This Seattle Times article is quite informative:

https://www.seattletimes.com/business/boeing-aerospace/faile...

It seems the MCAS had a flawed design where it would move the trim further than expected and would also trigger multiple times. Based on my understanding, the MCAS would have been quite safe if it didn't have these flaws (pilots deal with a failed AoA sensor as another case of "runaway trim").

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

#64

Post by chrisseaton »

dsfyu404ed wrote: post #54
ajxs wrote: post #48

Earlier quoted context omitted.

I'm fairly certain that the characteristic "If this component malfunctions loss of life is one potential outcome" is a solid case for the component actually being safety critical. The pilots would never have needed to disable MCAS had it not malfunctioned in this manner. I'm not sure what redundancy has to do with this, but clearly there was a failure in a safety-critical system.

>I'm fairly certain that the characteristic "If this component malfunctions loss of life is one potential outcome" is a solid case for the component actually being safety critical. The same thing can be said for literally tons of components on a plane. You can't have them all be redundant. At some point you have to pick and choose. A sensor for an obviously supplemental feature seems like a pretty obvious one to choo…

> You can't have them all be redundant.

Why not?

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

#65

Post by jimktrains2 »

dsfyu404ed wrote: post #57
jimktrains2 wrote: post #53

Earlier quoted context omitted.

> 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. In flight entertainment, non-emergency lighting, food prep, &c aren't "safety critical" any more than the TVs in hospital rooms are. As a layman, I'd've imagined that all avionics and control surface control was redundant. Don't most large planes have redundant hydraulic…

But this isn't really "avionics and surface control" more than automatic lane keeping is a critical control system for the car. MCAS is a convenience feature that counteracts the plane's tendency to pitch up more than you want when climbing. Sure it can improve safety, so can lane keeping in a car. Neither are critical to operation. You can fly/drive perfectly safely without them so they need not be super hardened ag…

> MCAS is a convenience feature that counteracts the plane's tendency to pitch up more than you want when climbing.

It's still controlling control surfaces.

> Sure it can improve safety, so can lane keeping in a car. Neither are critical to operation. You can fly/drive perfectly safely without them so they need not be super hardened against failure because you can just switch them off.

I'm not quite sure where to begin. Just because the absence of something would make the plane flight worthy doesn't mean the addition of it keeps the plane flight worthy.

Take your lane following example. Sure, they can be turned off, but that didn't help the person whose Tesla ran straight into a jersey barrier because it got confused by it and where the lane was. (https://www.popularmechanics.com/technology/infrastructure/a...)

If a mechanisms can control the vehicle, it is safe critical. It needs to fail safe under all conditions. The requirement to fail safe is part of what makes it a safety critical system.

In the most extreme of examples, adding a lane following module to a car that randomly swerves into jersey barriers once at speed and if the barrier is close enough would be a clear example of a situation where the automatic controls can cause a situation that a human could not possibly react to; hence, the system itself needs to be held to much higher standards.

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

#66

Post by yeukhon »

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…

IMO, I don't want MAX to be resurrected. If the design is flawed, let it be and shut it down. But this ain't gonna happen because how expensive aircrafts are.

Oh well.

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

#67

Post by twblalock »

It also seems like this was not properly reported to safety agencies at the time, nor was it reported when that plane crashed in a subsequent flight.

Say what you will about Boeing, but this could have been avoided if the airline had better safety practices. Every pilot on that plane should have been trained on the new system. And the malfunction, if reported properly, should have caused that particular plane to be grounded for a mechanical inspection. Instead it flew again and hundreds of people died because they weren’t lucky enough to have one of the pilots who was trained properly.

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

#68

Post by inferiorhuman »

dralley wrote: post #51
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?

The pilots know that the trim is moving, it's connected to a wheel in the cockpit that's super obvious. But the normal way of stopping it (the yoke) doesn't necessarily work, and the pilots wouldn't necessarily think to physically stop the wheel with their hands.

But the normal way of stopping it (the yoke) doesn't necessarily work, and the pilots wouldn't necessarily think to physically stop the wheel with their hands.

Well, no. Pulling on the yoke traditionally moves the elevator. MCAS adjusts the horizontal stabilizer. You can adjust the stabilizer with switches on the yoke or with the trim wheels by your knee. MCAS will pause for five seconds if the pilot hits one of the switches on the yoke (and the Lion Air pilots did this until that stopped working).

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

#69

Post by argd678 »

ricardobeat wrote: post #47
jquery wrote: post #22

Runaway trim is supposed to be part of the "memory checklist" for pilots. The symptoms of MCAS are the same as runaway trim and the fix is the same (which is why Boeing didn't feel like extra pilot training was needed), so I'm curious to see the most recent investigation and hear the black box voice recorder. Did they not know they were dealing with runaway trim? Did they think it was something else? Did they forget…

> [MCAS] it’s not stopped by the pilot pulling the yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors This implies that 'normal' runaway trim can be stopped by pulling the control yoke. Maybe pilots simply have no idea what is going on once they realise that action has no effect with the MCAS?

> “After this horrific Lion Air accident, you’d think that everyone flying this airplane would know that’s how you turn this off,” said Steve Wallace, the former director of the U.S. Federal Aviation Administration’s accident investigation branch.

I suspect the other factors will answered when this question is answered too.

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

#70

Post by inferiorhuman »

dsfyu404ed wrote: post #57
jimktrains2 wrote: post #53

Earlier quoted context omitted.

> 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. In flight entertainment, non-emergency lighting, food prep, &c aren't "safety critical" any more than the TVs in hospital rooms are. As a layman, I'd've imagined that all avionics and control surface control was redundant. Don't most large planes have redundant hydraulic…

But this isn't really "avionics and surface control" more than automatic lane keeping is a critical control system for the car. MCAS is a convenience feature that counteracts the plane's tendency to pitch up more than you want when climbing. Sure it can improve safety, so can lane keeping in a car. Neither are critical to operation. You can fly/drive perfectly safely without them so they need not be super hardened ag…

MCAS is a convenience feature that counteracts the plane's tendency to pitch up more than you want when climbing.

Nope, MCAS is required to meet the requirements set forth by the FAA. That's not a convenience thing. Various nannies may seem like convenience things in a well balanced car, but they become far more important in a powerful, poorly balanced car like a Porsche 911 or Dodge Viper — cars that have earned reputations as widowmakers.

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