Thread: Lion Air

Apparently, the correct procedure wasn't in the manual.

New Questions Swirl Over Boeing on Updated 737 Model that Crashed - The New York Times

Hi Bob,
I don’t have much info on the MCAS. Does it work through the stab trim, or is it a version of stick-push?

If it runs the stab trim, MCAS intervention might present as a runaway stabiliser (memory checklist for that). Stick push? - well that’s an entirely different animal......

Yes, it works through stab trim. See, for example, Indonesia 737 crash caused by “safety” feature change pilots weren’t told of | Ars Technica

We know the answer to the question... "How many 'hands-on' pilots are there in the Boing team that thought of, designed and signed off on that little add-on "Safety Feature"... the one that's lurking in the background even when the autopilot is turned off. ?
Or was it driven by the Sales Dept...

And it's not just airliners that are going overboard with computers gate-keeping between the Pilot and controlled surfaces.
Over on this side of the island, an iron ore train decided to go for a ride, while the driver was performing a routine (visual, out of cabin) carriage check. Cause of BHP runaway train | CEO says 'systems' - Australasian Mine Safety Journal
and, How mining company BHP remotely derailed a runaway train - Create News

My spy in the industry speculates that "they" may have been trialling a version of (Autonomous?) driverless train software, playing catch-up with another big company that has been successfully running theirs...
Not a Good Look when a software error takes over and buggers off with your expen$ive hardware !

Automobiles are not immune to 'automation mishaps', but being on the ground at a slower speed helps..
2002 Lexus LX 470 Anti-Skid Engage: My Lexus, without Warning, ... and the same model here - Lx 470 2001 skid control malfunction:The vehicle suddenly - Fixya


Point is, it's a philosophy or 'Direction' of thinking that is driving this, - over-thinking, resulting in unexpected, obscure, UN-intended consequences.

Originally Posted by JDNSW

Yes, it works through stab trim. See, for example, Indonesia 737 crash caused by “safety” feature change pilots weren’t told of | Ars Technica

I did some research today, and confIrmed it, JDNSW.

It looks like the MCAS drives the stab trim to meet its parameters - obviously nose down.

Boeing’s copout is the Runaway Stabiliser checklist. I admit that if I saw the stab trim running nose down for an unknown reason, I would be straight into that checklist.

It’s verging on criminal to include a totally new protection or system and not incorporate it into the manual suite for the people who operate this variant. It’s interesting that when Boeing introduced RCAS (roll protection) to the 737 fleet, there was a new section in the manuals, as well as a training module and a sequence in the simulator that needed to be completed. Someone seriously has dropped the ball here...

I get the impression that it was deliberate, so that no additional training was needed for pilots of earlier 737s.

This of course is separate from the issue of what exactly was the malfunction. The angle of attack sensor was replaced, so presumably not this. Sounds to me like it was a software error of some kind, either a coding error, or failure to design for some unusual set of parameters.

Originally Posted by Hugh Jars

Hi Bob,
I don’t have much info on the MCAS. Does it work through the stab trim, or is it a version of stick-push?

If it runs the stab trim, MCAS intervention might present as a runaway stabiliser (memory checklist for that). Stick push? - well that’s an entirely different animal......

A very good question. Above my pay grade, I'm afraid.

Interesting conundrum.
Here’s why, The runaway is a ‘Sensed’ Airspeed Unreliable(I.e low IAS approaching stall)........A completely different beast to ‘Runaway Stabilizer’.
I’m not conversant with this new system as I’ve only flown the classics and NG’s, where at least the runaway can be felt/seen in A/H and rapid descent but also recognized by trim wheel running continuously.
Does the trim wheel run continuously in the MAX with this failure? Because if not it would be hard to pick up(particularly close to the ground soon after T/O).
What’s also interesting is that this will only present itself when flying manually as the system is inactive/disarmed when A/P is engaged.

Also I’m gobsmacked that a manufacturer would integrate a system and make no mention within the FCOM?