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Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

reuters.com

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Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#181

Post by strunz »

mlindner wrote: post #89
t0mas88 wrote: post #84

Earlier quoted context omitted.

The same applies to the trim in a 737 and any other transport class aircraft. If you move the control column in the opposite direction of trim, the electric trim and autopilot trim will cut out. The same applies to the autopilot in all types I've flown, it disconnects if you override it manually (except for CWS mode, but that's known and expected) I don't fly the 737, so I haven't read the aircraft specific books and…

Why didn't the pilots adjust the trim manually? I don't understand how any pilot would consider increasing control pressure to be normal and not automatically respond by manually adjusting the trim.

> It's just that concluding the trim is the issue, without knowing MCAS, under high pressure and with the wrong (autopilot) conclusion already on your mind is not very likely.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#182

Post by achandlerwhite »

petilon wrote: post #180

This is the most revelatory news for me: The MAX has larger engines than previous 737s, and they are in a slightly different position. As a result, the plane has a tendency to pitch its nose up. To keep that from getting out of control if pilots flying manually aren’t attentive, MCAS automatically pushes the nose down if the sensor says the nose is too high. See: https://www.wsj.com/articles/what-you-need-to-know-abo…

Not a really a hardware flaw--a design choice/hardware compromise so that existing 737 infrastructure could be used. The low ground clearance of a 737 is one of its main selling points. It's customers have a large investment in infrastructure around this capability--Think of things like loading ramps, luggage carts, servicing vehicles, etc.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#183

Post by js2 »

_s wrote: post #177
zaroth wrote: post #150

The previous flight had exactly the same issue. This is what that pilot wrote in the logs; After parking, the PIC informed the engineer about the aircraft problem and entered IAS (Indicated Air Speed) and ALT (altitude) Disagree and FEEL DIFF PRESS (Feel Differential Pressure) light problem on the Aircraft Flight Maintenance Log (AFML). The PIC also reported the flight condition through the electronic reporting syste…

It probably is a memory item, but it's not something they got to immediately, and I'm guessing here because runaway trim symptoms are slightly different to what MCAS was doing. This happened to me a while ago involving trim, and I'll try and go through my thought process and why it takes a little while in the cockpit to figure things out: - Autopilot is engaged, holding a heading of X, altitude of Y and I've got a po…

Thank you for a pilot's perspective. Here's my bit of confusion though. Once you realized the stab trim was the issue, you were able to reset it and get back to normal flight. Had the problem recurred that flight, you'd probably have recognized it immediately.

In the Lion flight, the pilots realize the stab trim is off because they correct it. Once they realize that, regardless of what keeps setting the stab trim to pitch down, and even if they've forgotten there's cut-out switches, why don't they keep resetting the stab back to 0? And how do they not eventually notice the stab wheels turning?

It's almost as if the pilots weren't even aware of the stab wheels and stab indicator, and how those related to the electronic trim switch and the stabilizer itself. But I can't beleive that.

The thing that would be most helpful is knowing what their mental model of the plane was, but I'm not sure the investigation will be able to tell us that.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#184

Post by [deleted] »

oldgradstudent wrote: post #76
matt4077 wrote: post #42

Earlier quoted context omitted.

How would it even be possible for US pilots to sustainably have „much higher levels of experience“? Do non-US pilots fly only two days a week? Do they all die before age 40? This stereotype of dingy third-world airlines with incompetent, untrained pilots borders on racism. At the very least, one should notice that flying the world’s newest airliner in significant numbers is incompatible with one‘s preconceptions.

The first officer in Ethiopian Airlines Flight 302 was confirmed to have 350 flight hours, which is much lower then the US standard for the large carriers. Southwest Airlines, for example requires: > Flight Experience: 2,500 hours total or 1,500 hours Turbine total. Additionally, a minimum of 1,000 hours in Turbine aircraft as the Pilot in Command* is preferred. Southwest considers only Pilot time in fixed-wing aircr…

[deleted]

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#185

Post by petilon »

achandlerwhite wrote: post #182
petilon wrote: post #180

This is the most revelatory news for me: The MAX has larger engines than previous 737s, and they are in a slightly different position. As a result, the plane has a tendency to pitch its nose up. To keep that from getting out of control if pilots flying manually aren’t attentive, MCAS automatically pushes the nose down if the sensor says the nose is too high. See: https://www.wsj.com/articles/what-you-need-to-know-abo…

Not a really a hardware flaw--a design choice/hardware compromise so that existing 737 infrastructure could be used. The low ground clearance of a 737 is one of its main selling points. It's customers have a large investment in infrastructure around this capability--Think of things like loading ramps, luggage carts, servicing vehicles, etc.

So in other words they designed it this way in order to make the 737 MAX is cheaper to operate, and therefore easier to sell. That's terrible. Boeing traded off safety for profits.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#186

Post by achandlerwhite »

t0mas88 wrote: post #84
zw123456 wrote: post #13

The thing I don't understand about that MCAS system is why it would continue to drive the nose of the plane down even when the pilot is reefing on the stick to pull up. The cruise control in my car automatically disengages when I hit the brakes, it doesn't continue to accelerate to keep the car going 60 while I am jamming on the brakes, in an emergency, I don't have time to find the off switch. Similarly, I would thi…

The same applies to the trim in a 737 and any other transport class aircraft. If you move the control column in the opposite direction of trim, the electric trim and autopilot trim will cut out. The same applies to the autopilot in all types I've flown, it disconnects if you override it manually (except for CWS mode, but that's known and expected) I don't fly the 737, so I haven't read the aircraft specific books and…

Since MCAS and autopilot are two different things and MCAS is only active when autopilot is off I think it is faulty to assume that something that disables autopilot would disable MCAS--but in the heat of the moment I can see room for confusion.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#187

Post by ProAm »

verytrivial wrote: post #62
RidingPegasus wrote: post #3

Earlier quoted context omitted.

Was the trim wheel not visibly spinning out of their control? Simply because the symptoms are different should mean that stopping it via taking manual control is a recurring option.

The Lion Air directive has instructions on page 41 of their preliminary report that include: 5. If the runaway continues after the autopilot is disengaged: STAB TRIM CUTOUT switches (both) ... CUTOUT If the runaway continues: Stabilizer trim wheel .... *Grasp and hold* This may be an overabundance of caution, or to cover other runaway events, but it reads like "you may need to physically fight the computer even when…

> you may need to physically fight the computer

This is the future I look forward to. AI/ML/Autopilot/Companies moving fast and breaking things.... Boeing took that one literally.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#188

Post by _s »

js2 wrote: post #183
_s wrote: post #177

Earlier quoted context omitted.

It probably is a memory item, but it's not something they got to immediately, and I'm guessing here because runaway trim symptoms are slightly different to what MCAS was doing. This happened to me a while ago involving trim, and I'll try and go through my thought process and why it takes a little while in the cockpit to figure things out: - Autopilot is engaged, holding a heading of X, altitude of Y and I've got a po…

Thank you for a pilot's perspective. Here's my bit of confusion though. Once you realized the stab trim was the issue, you were able to reset it and get back to normal flight. Had the problem recurred that flight, you'd probably have recognized it immediately. In the Lion flight, the pilots realize the stab trim is off because they correct it. Once they realize that, regardless of what keeps setting the stab trim to…

I think context is what helps -

- I’ve just taken off, and am going through the after take off checklist: Set the airspeed, power, climb rate, heading, talking to ATC, planning the next stage of the flight

- Perhaps I’ve just raised the flaps and the plane starts behaving erratically

- My first / immediate thought is that my previous action led to an undesired aircraft state.

- I work from that point on

- I touch the electronic trim as habit, which resets the system briefly, and all seems well for a few seconds. I don’t know that the system reset itself.

- It goes all weird again all on its own

- Now I’m even more confused

Etc

Edit: I'm a low time private pilot flying a LSA, I genuinely don't know the procedures or processes in place for a 737, but I can empathise with their situation as I know how quickly things can go start going amiss in a plane.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#189

Post by achandlerwhite »

petilon wrote: post #185
achandlerwhite wrote: post #182

Earlier quoted context omitted.

Not a really a hardware flaw--a design choice/hardware compromise so that existing 737 infrastructure could be used. The low ground clearance of a 737 is one of its main selling points. It's customers have a large investment in infrastructure around this capability--Think of things like loading ramps, luggage carts, servicing vehicles, etc.

So in other words they designed it this way in order to make the 737 MAX is cheaper to operate, and therefore easier to sell. That's terrible. Boeing traded off safety for profits.

Yes cost is a factor. The alternative might not be feasible economically. I don't think the failure here was reusing the 737 design, but the downstream due diligence of implying no significant changes. I also think airline training is a factor--both Boeing for the new systems and the airliners because runaway stabilizer trim has been in the aircraft emergency checklist for over 50 years and every pilot should know it. That same procedure would have saved these planes.

Re: Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

#190

Post by linsomniac »

AvE over on youtube has some speculation about what caused these crashes, and sums it up with: This was clearly a training issue, but now everyone is talking about it and every pilot is going to have this at the top of their mind. Would I hesitate to get on a Max 8 right now? Not for a second, pardner.

It's like how right after a bad health dept report is probably one of the safest times to go to a particular restaurant.

http://www.youtube.com/watch?v=1XCU__OEftU

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