Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash • Hacker News Board

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

#121

Post by tyingq » Wed, Mar 20, 2019, 3:07 AM UTC

twblalock wrote: post #87

inferiorhuman wrote: post #71

Earlier quoted context omitted.

Every pilot on that plane should have been trained on the new system. How is that supposed to work when Boeing didn't inform any of the airlines of this system?

Boeing did inform them. Otherwise how would the third pilot have known what to do when he saved the plane?

Various pilot unions aren't mincing words. Here's one quote:

"This is the first description you, as 737 pilots, have seen,” the message from the pilots association at American reads. “It is not in the American Airlines 737 Flight Manual … nor is there a description in the Boeing FCOM (Flight Crew Operations Manual). It will be soon.”

It doesn't seem unreasonable to me that the jumpseat rider made an educated guess based on some prior experience. Aided by the fact that he didn't have other things to do besides observing.

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

#122

Post by inferiorhuman » Wed, Mar 20, 2019, 3:09 AM UTC

twblalock wrote: post #112

inferiorhuman wrote: post #104

Earlier quoted context omitted.

He knew what the system was How would he know something that was undisclosed? It's not conjecture here, no airlines and no pilots knew of the presence of MCAS before the Lion Air 610 crash.

The article says that all of the pilots were supposed to know what to do in this situation: > The so-called dead-head pilot on the earlier flight from Bali to Jakarta told the crew to cut power to the motor driving the nose down, according to the people familiar, part of a checklist that all pilots are required to memorize. This guy didn't go off script. It seems like he was the only one of the three who knew the scr…

This guy didn't go off script. It seems like he was the only one of the three who knew the script.

The script says to stop if the trim adjustments stop when you counter with manual trim input. MCAS, by design, stops. You can see where MCAS stops trimming nose down on the preliminary Indonesian report (they graph both the fatal flight and the previous flight).

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

#123

Post by inferiorhuman » Wed, Mar 20, 2019, 3:11 AM UTC

Someone1234 wrote: post #102

inferiorhuman wrote: post #81

Earlier quoted context omitted.

They were saying you cannot counteract MCAS's control inputs with the elevator alone. Pulling on the yoke is not how you counteract a runaway stabilizer on the 737. I've pasted the relevant part of the QRH in a few previous comments. Yes, the stabilizer ultimately has more pitch authority under some circumstances. That may be what happened here, but if I'm interpreting the graphs on the preliminary report correctly I…

> Pulling on the yoke is not how you counteract a runaway stabilizer on the 737. I've pasted the relevant part of the QRH in a few previous comments. It is how pilots learn to counteract nose down day one of pilot training. In many aircraft hard elevation will overpower even a faulty horizontal stabilizer. If the QRH was a panacea we would have 348 fewer loses today. > That may be what happened here, but if I'm inter…

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 interesting failure mode, especially in two separate sensors (Lion Air replaced the alpha vane before flight 610), and even more interesting as it's the same alpha vane used in the 737 NG. The left alpha vane was being interpreted as almost exactly twenty degrees higher than the right.

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

#124

Post by Someone1234 » Wed, Mar 20, 2019, 3:13 AM UTC

js2 wrote: post #119

Someone1234 wrote: post #116

Earlier quoted context omitted.

US pilots say they didn't either. The training wasn't out there.

The runaway stabilizer trim procedure is how it was expected to be handled: https://www.flightglobal.com/news/articles/faa-order-tells-h... https://www.youtube.com/watch?v=3pPRuFHR1co The specifics of MCAS weren't out there because Boeing expected the pre-existing procedure to have been sufficient. That procedure wasn't sufficient, or the Lion and Ethiopian Air pilots were somehow not aware of it, or they forgot thei…

Runaway stabilizer feels nothing like MCAS. They likely didn't associate the training they received with the problem at hand.

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

#125

Post by js2 » Wed, Mar 20, 2019, 3:17 AM UTC

Someone1234 wrote: post #124

js2 wrote: post #119

Earlier quoted context omitted.

The runaway stabilizer trim procedure is how it was expected to be handled: https://www.flightglobal.com/news/articles/faa-order-tells-h... https://www.youtube.com/watch?v=3pPRuFHR1co The specifics of MCAS weren't out there because Boeing expected the pre-existing procedure to have been sufficient. That procedure wasn't sufficient, or the Lion and Ethiopian Air pilots were somehow not aware of it, or they forgot thei…

Runaway stabilizer feels nothing like MCAS. They likely didn't associate the training they received with the problem at hand.

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 when you do that? If you let go and the wheel immediately starts turning again the wrong way (pitching the plane down), doesn't that look like runaway stabilizer?

Also, how did the off-duty pilot figure it out if they are nothing alike?

BTW, when you write "runaway stabilizer feels nothing like MCAS" are you speaking from personal experience?

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

#126

Post by arcticbull » Wed, Mar 20, 2019, 3:19 AM UTC

zaphirplane wrote: post #106

Someone1234 wrote: post #91

Earlier quoted context omitted.

It didn't need to be included in the preliminary report since it is contextual/background information. They did include in the report that on a previous flight the same sensor error occurred and the pilots resolved it by disabling auto-trim. The fact there was a third pilot there is definitely interesting, but they didn't make anyone less safe by not including it in the report. There's no bombshell here. Previous pro…

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.

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

#127

Post by inferiorhuman » Wed, Mar 20, 2019, 3:23 AM UTC

js2 wrote: post #119

Someone1234 wrote: post #116

Earlier quoted context omitted.

US pilots say they didn't either. The training wasn't out there.

The runaway stabilizer trim procedure is how it was expected to be handled: https://www.flightglobal.com/news/articles/faa-order-tells-h... https://www.youtube.com/watch?v=3pPRuFHR1co The specifics of MCAS weren't out there because Boeing expected the pre-existing procedure to have been sufficient. That procedure wasn't sufficient, or the Lion and Ethiopian Air pilots were somehow not aware of it, or they forgot thei…

That procedure wasn't sufficient

Winner, winner, chicken dinner. The existing runaway stabilizer trim checklist does not fit the MCAS failure to a T. The procedure dictates that you stop if the trimming action stops when you counter it with the switches (MCAS pauses when you do this). Unfortunately when you're taught to only think inside the box, you'll go as far down that checklist as you need to and no further.

Beyond that, just after takeoff is one of the busiest part of the flight. In fact, if you look at the graphs you'll see that the stick shaker on the left side was going crazy almost immediately after takeoff (and before MCAS kicked in as a result of retracting the flaps). The pilots of flight 610 were able to reign in MCAS with the trim buttons and almost certainly continued to do so in order to focus on the other failures and their relevant checklists (stick shaker, unreliable airspeed, elevator feel system non-op).

[One thing I've been wondering: somehow the pilots were able to bring the nose back up... it was only (apparently) after multiple nose downs that they eventually failed to recover the plane. What was going on there? It's as if they understood how to correct the stabilizer trim, but weren't aware of the cut-off switches.]

Yep, to me, that looks an awful lot like some sort of hardware failure. Something to look for in the subsequent and final reports.

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

#128

Post by Someone1234 » Wed, Mar 20, 2019, 3:24 AM UTC

js2 wrote: post #125

Someone1234 wrote: post #124

Earlier quoted context omitted.

Runaway stabilizer feels nothing like MCAS. They likely didn't associate the training they received with the problem at hand.

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…

Runaway stabilizer causes a more dramatic sudden movement than MCAS. MCAS's start, wait 5 seconds, re-start, motion is more gradual. For example you could look at the wheel and it has stopped, only to re-start after you look away (add noise cancelling Bose headphones and you may not hear it)

Pilots are trained well for runaway stabilizer, MCAS was essentially the same thing, but it didn't FEEL like the same thing, so a stressed pilot's mind may not immediately go to that solution/memory item.

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

#129

Post by 6nf » Wed, Mar 20, 2019, 3:27 AM UTC

inferiorhuman wrote: post #123

Someone1234 wrote: post #102

Earlier quoted context omitted.

> Pulling on the yoke is not how you counteract a runaway stabilizer on the 737. I've pasted the relevant part of the QRH in a few previous comments. It is how pilots learn to counteract nose down day one of pilot training. In many aircraft hard elevation will overpower even a faulty horizontal stabilizer. If the QRH was a panacea we would have 348 fewer loses today. > That may be what happened here, but if I'm inter…

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

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

#130

Post by inferiorhuman » Wed, Mar 20, 2019, 3:29 AM UTC

js2 wrote: post #125

Someone1234 wrote: post #124

Earlier quoted context omitted.

Runaway stabilizer feels nothing like MCAS. They likely didn't associate the training they received with the problem at hand.

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 plane also pitched down far more dramatically than on flight 610.

The graphs for flight 610 seem to indicate that the pilots thought they had the trim situation under control (and they did right up until they didn't).

https://reports.aviation-safety.net/2018/20181029-0_B38M_PK-...