What you're saying does not contradict that the trim switches override the MCAS. Hence, trim could be restored by using the trim switches and throwing the cutouts when not using the trim switches.
I read about this in the newspaper, it wasn't a secret. I do not have inside information.
Again, if I was an MCAS pilot I'd be very interested in following what happened with the Lion Air crash, to ensure it wouldn't happen to me. I'd still follow the procedures set out by Boeing - but when they didn't work I'd do what did work.
It's a little hard to discern from the erratic newspaper reports, but during the time the pilots were fighting the MCAS they were using the trim switches and surely would have noticed that those switches overrode the MCAS.
The reason we have pilots, and not a fully automated airplane, is we need them to think outside of the procedures when the procedures aren't working. This is not impossible as the pilots in the flight prior to the LA crash did have MCAS runaway and did successfully deal with it.
It can be overridden, yes, but releasing the switch also resets the MCAS activation timer, resulting in an activation 5 seconds after the switch is released.
You would have to pulse the switch in sub-5 second increments depending on the way the switch works.
If it's a direct switch, I.e. switch held down->motor moves, then they'd have to hold it down until trim was neutralized, then cut it out.
If it's a discrete toggle, I.e. each toggle increments/decrements a set point the motor then follows; a pilot would have to be very conscious of their timing on the switches, and how much the stabilizer had actually managed to travel.
Both of these would constitute new, MAX specific skills, that Boeing cannot show any acknowledgement or foreknowledge of without opening a massive can of worms.
> It can be overridden, yes, but releasing the switch also resets the MCAS activation timer, resulting in an activation 5 seconds after the switch is released.
That's why I suggested in this thread to activate the cutoff switches when the trim is in the correct position.
The electric trim switches are a hold down => motor moves. It's not a MAX specific skill. Neither are the cutoff switches.
>The electric trim switches are a hold down => motor moves. It's not a MAX specific skill. Neither are the cutoff switches.
Neat!
>It's not a MAX specific skill. Neither are the cutoff switches.
Well, the cutoff switches functionality was changed according to the Seattle Times, so while the procedure may be shared, the semantic significance of the switches did, in fact, change for MAX.
Do you recall when you learned that the trim switches could be used to override MCAS (so long as you did not toggle the trim cutouts, if flying a Max?) I don't believe the switch issue was raised in the FAR.
While we certainly hope that pilots will be able to extemporize a solution to a situation, even if that involves going beyond or against the documented procedure, and while it is certainly possible that there was a course of action that could have saved ET302 (though the success of the Lion Air pilots does not necessarily prove that, as there were differences), I do not accept the implication that if such a course of action existed, there is nothing to be concerned about. Reliance on pilots' problem-solving skills should be a last resort, not a planned-for solution, and those skills certainly are not helped by withholding information about aircraft systems.
It was in one of the Seattle Times articles about it after the LA crash. I've never seen it since, although if you read the sequence of events it's pretty clear that's the case, as the pilots had been overriding the MCAS commands with the trim switches.
> I do not accept the implication that if such a course of action existed, there is nothing to be concerned about.
I did not suggest that. Nearly all crashes are the result of a string of failures, including these crashes, and each point needs to be corrected.
> and those skills certainly are not helped by withholding information about aircraft systems.
After the LA crash, that was no longer the case. I reiterate that my information comes from the newspaper. If I was a MAX pilot you bet I'd be much more diligent in finding things out, if only just to save my own hide.
I further find it very strange that after the prior LA flight successfully dealt with the MCAS failure, that the airplane was still deemed flight-worthy and nobody even bothered to inform the next flight crew?
There's plenty of failure that needs to be dealt with all around with those accidents.
With regard to why the Lion Air airplane was deemed flight-worthy, we have to take into consideration that, because MCAS had not been disclosed, some important information was missing from the analysis. It is unfortunate that the maintenance crew incorrectly thought that they had fixed the sensor, and perhaps felt that was enough to deal with the problem, but they may not have known how aggressively this undisclosed system could mis-trim the airplane, and the pilots certainly did not (it was even a surprise to many at the FAA involved in the Max certification.)
Maybe the crew of the earlier Lion Air flight were lucky and had the airplane temporarily back in trim at the point where the deadheading pilot recognized that they had an ongoing trim runaway situation, for which toggling the trim cutout switches was the documented response [1].
I think it is unreasonable to suggest that the EL302 pilots were negligently unprepared. After using the trim cutout switches to disable MCAS, they found they were unable to correct the trim manually, so they did exactly what you suggested in your first post: they re-engaged the electric trim and attempted, unsuccessfully, to re-trim the airplane before it crashed. This suggests a familiarity with the AD issued after the Lion Air inquiry. Maybe if they had not switched the trim off initially, they would have prevailed, but the message from Boeing after the Lion Air crash was that its pilots were at fault because they failed to use the cutout switches.
Given that Boeing was still holding to the line that MCAS failure should be handled as if it were just another case of trim runaway, and that the procedure for that was the same as on previous variants, the pilots could reasonably consider themselves to be well-prepared for the situation - they now knew about the problem, and they had trained for recovering from trim runaway on NG simulators. The AD issued after the Lion Air inquiry says "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", but it says nothing about this differing from the NG, where one can disable faulty inputs while retaining trim-switch control. It also says "If relaxing the control column causes the trim to move, set stabilizer trim switches to CUTOUT" - and it seems quite possible that, in the case of MCAS runaway, relaxing the control column could coincide with the trim continuing to move (and the crew is not in a position to determine causation), at which point, using the cutout switches is prescribed. Finally, this checklist [1] says "If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) [to] CUTOUT." None of this says anything directly about getting the airplane back in trim before toggling the cutout switches, if that is what is necessary to regain control if this happens close to the surface.
> so they did exactly what you suggested in your first post: they re-engaged the electric trim and attempted, unsuccessfully, to re-trim the airplane before it crashed.
The critical question here would be would be did they use the electric trim switches, and did they cut off the trim after re-trimming the stabilizer?
> None of this says anything directly about getting the airplane back in trim before toggling the cutout switches,
The FAD did say that directly, and you quoted that part.
> if that is what is necessary to regain control if this happens close to the surface.
It obviously was necessary. It's why they re-engaged the trim system.
Pilots are not robots blindly following procedures - if they were, we wouldn't have pilots on the airplanes, it would be run be a computer. Pilots are expected to have understanding of what the switches do and how to use them.
The wording of the FAD could be improved, but it is not that hard to understand. The electric trim switches override any other inputs to the stab trim, and the cutoff switches prevent powered movement of the stabilizer. Those two facts are all one needs to know to regain control.
First, a note: the link I provided in my previous post is now broken, and its target has been replaced by something that is not germane to this discussion, but you can currently find the relevant part of the checklist in [1].
On first reading, I also thought the quoted passage from the AD was an instruction to use the yoke switch to re-trim before cutting out the stabilizer trim, but the following sentence (also quoted above) makes it clear that it is not: it is actually part of a statement about what options are available to adjust the trim before and after the switches are set to cutout. I feel sure you will try to argue this point, but I am pretty confident that this is the correct reading, because the checklist has no mention of delaying trim cutout. This is very significant, because the checklist is what pilots are trained and expected to follow (and, furthermore, I believe this checklist is a 'memory item' - one of the procedures that pilots are required to be able to perform from memory.) Nothing in a checklist should be incomplete or ambiguous, nothing of consequence should be taken as read, and if anything is, it is a more serious matter than poor wording.
And the checklist is unambiguous about what to do: if the problem persists after the autopilot is disengaged, use the trim cutout, and thereafter, trim manually - this is what the crew experienced, and this is what the crew did.
It is quite clear from the documentation that the manual trim wheels were regarded as an adequate means of adjusting the trim if the electric trim was cut out. Once the pilots found that this wasn't working, they did extemporize - they re-enabled the electric trim - showing that, contrary to what you insinuate, they did understand what the switches do.
You have set up a false dichotomy between pilots acting as robots and being able to extemporize a solution to every problem from first principles. The reality is that aviation has achieved its unprecedented level of safety by, in part, by considering a great many things that could go wrong and figuring out the optimal responses, taking into account that these responses must be made in a stressful and often degraded (informationally, functionally, physiologically) situation. Pilots are trained, and expected, to execute the documented procedures promptly, and only deviate when the situation demands: extemporize on a check ride, and you are likely to fail. This is not mindless bureaucracy at work: it is the rigorous application of hard-learned lessons. At the same time, they are also expected to know their airplanes thoroughly so that they can respond to unanticipated problems, and this is precisely why they were annoyed at not being told about MCAS.
So, to summarize: 1) by their actions, the crew demonstrated that they were up-to-date on the procedures that nominally incorporated the lessons from JT610; 2) by their responses to a problem with this procedure, they demonstrated that they did understand what the switches did and how to use them. Undoubtedly they did not figure out what they needed to do as rapidly as you would have in their place, but it is unreasonable to fault them for that.
I recently learned that, prior to the Max, the trim wheels were so rarely needed that their use was no longer part of simulator training, and the diameter of the wheels was reduced on the Max, yet here we have an AD saying you can use these wheels to trim the airplane when the electrical mechanism is cut out, and item 6 on the checklist explicitly says to do so. Elsewhere in the AFM it notes that the trim wheels can be hard to move in some circumstances, but if you are going to fault the pilots for not connecting the dots, then it applies doubly so for the people at Boeing and the FAA tasked with writing and certifying the procedures for handling an MCAS failure, who all apparently overlooked something that was obvious to you just from reading some newspaper articles.
At this point, the more you argue that an effective procedure for dealing with MCAS runaway was obvious following the JT610 inquiry, the more you indict Boeing and the FAA for not making it explicit in their response.
I read about this in the newspaper, it wasn't a secret. I do not have inside information.
Again, if I was an MCAS pilot I'd be very interested in following what happened with the Lion Air crash, to ensure it wouldn't happen to me. I'd still follow the procedures set out by Boeing - but when they didn't work I'd do what did work.
It's a little hard to discern from the erratic newspaper reports, but during the time the pilots were fighting the MCAS they were using the trim switches and surely would have noticed that those switches overrode the MCAS.
The reason we have pilots, and not a fully automated airplane, is we need them to think outside of the procedures when the procedures aren't working. This is not impossible as the pilots in the flight prior to the LA crash did have MCAS runaway and did successfully deal with it.