Ethiopian 737 Max Crash this morning

trafficinsight

Well-Known Member
MCAS type? Are you talking about the mach trim and auto trim? Pusher? Lots of planes have some type of auto trim or envelope protection, but usually the manufacturers tell people about it and provide an override.
Yeah, I get that. What was I told about it? That it exists. What do we train for? Stab trim runaway, and we always train for it at an altitude where a lazy recovery will still bring success.

I'm not convinced that, in the Lion Air case, knowing that it existed would have changed anything. One crew successfully recovered, maintenance pencil whipped, and the next crew wasn't as sharp or wasn't as lucky.

People seem to be offended that the system even exists in the first place. I think it's especially humorous when it's Airbus people.

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JeppUpdater

Well-Known Member
What do we train for? Stab trim runaway, and we always train for it at an altitude where a lazy recovery will still bring success.
I was 71% (yeah, I kept track) for killing people with uncommanded pushers below 500’ in the sim after a guy I knew had one in a situation the OEM said couldn’t happen (then quietly rectified with a software update).

In the sim. With fake negative G’s.
 

trafficinsight

Well-Known Member
Well, the FAA or at least the “Orange One” at the press conference just grounded the 737 Max in the US.
We kinda don't have a choice at this point, so it at least makes sense in that context.

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trafficinsight

Well-Known Member
I was 71% (yeah, I kept track) for killing people with uncommanded pushers below 500’ in the sim after a guy I knew had one in a situation the OEM said couldn’t happen (then quietly rectified with a software update).

In the sim. With fake negative G’s.
That's kinda cool that you were given the opportunity to try. I have a list of things I want to try if blessed with a few extra minutes of sim time rather than the usual hurr durr let's see if it'll loop.

This has certainly made the list.

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Ecl!pse

Well-Known Member
Could the FAA have received pertinent info recovered from the FDR?
It’s my understanding the black boxes are still in Ethiopia and have not been sent out for analysis. FAA is supposed to give a press conference this afternoon so we should know more, at least on what information they have or don’t have, then.
 

woutlaw

Well-Known Member
We don't have the MAX, but my understanding is MCAS only takes input from the onside AOA sensor. So, if that puppy starts sending out bad data weird things can happen. I'd have thought it would compare onside and offside and if they were reading different things it'd either not activate at all or look to a third source as a tie-breaker.

I would love to be wrong about that, btw.



Yeah the stab trim brake is still there. Run the trim nose up and push forward and it stops the trim and vice versa. The thing with MCAS is that it is bypassed because if the airplane is stalling and you are causing it by pulling up, it needs to trim down to help push the nose over due to the changes with the LEAP engines being different. MCAS is supposed to only work under very specific conditions, flaps up, autopilot off, and high AOA. It is in addition to the elevator feel shift which just ramps up force required to pull up during a stall.

MCAS can be turned off with the stab trim cutout switches on the pedestal next to the start levers. That takes out power to the stab trim and then it is time to break out the crank like it is the 1950s again.

I don’t have all the specifics right in front of me but that is how it works off the top of my head.

The spoilers are fly by wire and have things programmed into them for things like jammed elevator, landing attitude modifier and auto speed brake extension while at idle with the flaps extended. There are a few other things that they do now as well like turbulence dampening.
 

deadstick

Well-Known Member
I'd have thought it would compare onside and offside and if they were reading different things it'd either not activate at all or look to a third source as a tie-breaker.
I was wondering about this too.
How many AOA sensors are there on the Max?
If there are multiple sensors, how does this input with the MCAS?
Is there a flag if there is more than x difference?
 

exneophyte

Well-Known Member
What’s up with the black box game of hot potato? Has it happened like this before where they have the box, but no one to analyze it?

I can’t imagine the list of places capable of analyzing these is that long. I’m guessing there might be a few people interested in what they reveal.
 
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