737 control check
https://www.youtube.com/watch?v=26-sSc2fJtw
At about the 1:30 mark you will see the elevator check and the trim tabs move in the opposite direction as the elevator.

Those are the ELEVATOR trim tabs, not the aircraft attitude trim tabs. As has been explained previously the B737 FAMILY (with the possible exception of the very, very, very first few) use the HORIZONTAL STABILISER to trim the aircraft. The purpose of the ELEVATOR trim tabs (which what you see moving at about 1:30) is to trim the elevators to neutral feel in flight and make it easier to move the elevators by giving some aerodynamic assistance.
MCAS, the pilot's trim toggles and the trim wheels all work by driving the HORIZONTAL STABILISER to a "nose up" or "nose down" aircraft attitude. With normal trim in flight is a few degrees nose up - the exact mount depending on altitude, load and a few other factors.

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

Stabilizer trim function.
https://www.youtube.com/watch?v=6hZQeTrmcjU
To me it looks like the pilots never trained the MCAS. Only learning the crash (no pun intended) course on an Ipad for about one hour.
That course, I'm quite sure, doesn't include how to handle the plane when getting errouness data from the AoA sensors.
The planes have two sensors. One is connected to the captains yoke on the left and the other one to the co-pilote's yoke on the right.
MCAS however only rely on one of the sensors at the time. Now that's must be very confusing to the pilots if the data doesn't correlate...
Is MCAS a "pilot memory item" btw?

And B737 Runaway Stabilizer. Grasp and Hold technique. Not included in the manual.
https://www.youtube.com/watch?v=cQirIH_DuAs

No, just Boeing's ego was in play - the airframe is dynamically stable, and flies perfectly well without MCAS, albeit at higher angles of attack than the older B737 fleets. For some reason, someone "up the tree" decided that MCAS should work "faster and thus better" in maintaining the same alpha for the B737Max and its older cousins. If allowed to the B737max would fly safely with about 5 degrees more nose up attitude than the older ones, due to the subtle changes in wing shape (almost getting to A32x family angles of attack!)

Are you not talking about deck angle for cruise flight as opposed to wing AoA?

Otherwise, is that not an entirely new wing for the 737 MAX requiring certifying?...

Also, MCAS is not needed for that. The purpose behind MCAS is nicely explained on:

What is the Boeing 737 Max Maneuvering Characteristics Augmentation System?

It is highly probable that the older version of MCAS could still lead into the same aggressive nose down trimming, just take a few seconds longer to get there.

My reading gives me the impression that the MCAS "v1" was implemented to counter the tendency for the new engines to pitch the aircraft nose up. Additionally, the much more aggressive MCAS "v2" was added much later after test pilots found problems for low speed flight and also for stall recovery...

Note that the large engine nacelles protruding a long way in front of the wing can be expected to add increasing aerodynamic effects as the AoA increases upon approaching a stall.

Hence, my question is whether the Boeing 737 Max can safely and quickly recover from all stall scenarios without MCAS...



All in our only world,
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

The MCAS is not a stall recovery system.
It's a system to "help" the pilots not getting their plane in to a stall situation.
Hence the word "augmentation".
But obviously the system doesn't work as designed.

The MCAS is not a stall recovery system.
It's a system to "help" the pilots not getting their plane in to a stall situation.
Hence the word "augmentation".

It is a stall prevention system as described by the legal department.

Lawyer, you can't say "prevention" unless it a stall is impossible with it.
Lawyer, you can't say "mitigation" unless it lessens it after it happens.
Lawyer you can say "augmentation" because it does something, just make sure you are neutral over it either being a good or bad change.

But obviously the system doesn't work as designed.

It likely does work as designed. However its design may not be optimal. Its inability to recognize garbage input seems to be an issue.

[...]

Lawyer[:] you can say "augmentation" because it does something, just make sure you are neutral over it either being a good or bad change.

But obviously the system doesn't work as designed.

It likely does work as designed. However its design may not be optimal. Its inability to recognize garbage input seems to be an issue.

Ring the bells, sound the klaxons, grand celebrations!!!

Is your last post a first in including not one, but TWO points of comment upon which we can agree?...


Keep searchin',
Martin

ps: Count the multiple puns! ;-)

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

FAA proposing fines
Anyone proposing that the FAA get fined for allowing an aircraft manufacturer to self-certificate?

FAA proposing fines
Anyone proposing that the FAA get fined for allowing an aircraft manufacturer to self-certificate?

I suspect that the FAA are being closely scrutinized in multiple ways by multiple official groups...

There may yet be some USA legalities lynchings to come...


All with greedy unnecessary unfortunate happenings...

All in our only one world,
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

But obviously the [MCAS] system doesn't work as designed.

It likely does work as designed. However its design may not be optimal. Its inability to recognize garbage input seems to be an issue.

That was very much a fatal 'issue'...

The sort of 'issue' that should never get through system design and the system design checks, implementation (programming) and fault checks, testing, and certification...

And certainly not fatally TWICE.

I just wonder how many warnings from pilots' experience of MCAS 'surprises' were ignored?...


All in our only one world,
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

It likely does work as designed. However its design may not be optimal. Its inability to recognize garbage input seems to be an issue.

But aren't systems supposed to recognize garbage input?
A customer would say it's a design fault.
"optimal" as you say, what it is that?
The designer says "oops" because they didn't test the system as much what is needed.

It likely does work as designed. However its design may not be optimal. Its inability to recognize garbage input seems to be an issue.

But aren't systems supposed to recognize garbage input?
A customer would say it's a design fault.
"optimal" as you say, what it is that?
The designer says "oops" because they didn't test the system as much what is needed.

Considering Boeing wanted this plane on sale asap and not be a new type. I think that the designer might say "I wasn't given enough time to test it fully"

I think that the designer might say "I wasn't given enough time to test it fully"

I think that's true as well. The final report is however not done yet.

One may, or may not, like the fact that the B737Max actually handles differently without MCAS than the older generation B737s.
Boeing wanted to get away from having to have a "new" type categorisation, so they fitted MCAS to avoid having to have the aircraft categorised as a different type. Doing so saved them a lot of time and money by not having to go through a full type approval as required for a new aircraft type, but on the lesser amount for required for a new variant.
MCAS was declared as a "handling augmentation system", not a stall prevention system. As such it was declared not a safety system (by default stall prevention systems are safety systems).
The training required was a simple "read the book" and (probably) answer a few questions - total time about an hour. Which, sadly, paraphrasing Moomin's earlir comment a "course to crash". As many have said, no mention of how the aircraft handled without MCAS, because the only way for a flight crew to turn MCAS also cut the power to the whole trim stabilisation system, and besides MCAS "couldn't affect the safety of the aircraft because it's not a safety system".

When getting "good" data MCAS worked "as designed", but as soon as garbage data came along dubious design decisions bit and the nose went down and down and down.... (I would really like to know what the "cost saving" in having a non-voting system was over having the strange non-voting system that was implemented - I doubt that it was "significant".)

One thing that many may have missed is that the B737Max actually has a higher safe angle of attack capability than its older cousins, and thus probably has a lower propensity to stall under given flight conditions. But allowing the aircraft to use this would mean it handled in a different manner to its older cousins, which of course would have changed its type characteristics, and thus rendered it liable for full type certification....

This whole saga really is evidence of profits over safety. Boeing were in danger of loosing a very large chunk of their income potential unless they got an aircraft into service that "handled the same as the old bird", and beat the latest generation offering from Airbus which was rolling across the tarmac toward them. Had they been honest, and not constrained themselves with the aforementioned desire they would have had a much better aircraft. In reality the b737MAX was only ever intended as a stop-gap until the new 100-200 seater came along in about 10 years time - or about five years had they pressed on with the new bird instead - by which time Airbus would have scooped up a large chunk of that market potential.

(I've managed to blag some time in a 737Max simulator as an observer - watch this space)

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

This whole saga really is evidence of profits over safety.

Not the fault of new engines or a software program.
Like everything in life, anything man made is NEVER 100% safe.
$$$$$$ will always be at the forefront.

(I've managed to blag some time in a 737Max simulator as an observer - watch this space)

Keep us posted.

Rob, you are describing design by lawyer not aeronautical engineer.

I just wonder how many warnings from pilots' experience of MCAS 'surprises' were ignored?...

You mean AoA failures?

No - MCAS as a systems should have been capable of riding out (in a safe manner) the failure of a single AoA.

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

Read carefully what I wrote - the whole MCAS debacle was driven by $$$ anf hours.
No doubt that lawyers were called on the come up with the right name, but that was after the project finance and planning teams had screwed engineering's budget ($$$ and hours).

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

Read carefully what I wrote - the whole MCAS debacle was driven by $$$ anf hours.
No doubt that lawyers were called on the come up with the right name, but that was after the project finance and planning teams had screwed engineering's budget ($$$ and hours).

Most likely the lawyers were the ones deciding on the $$$ and in the room from the start. Fiduciary duty to the shareholder.