FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

An open discussion of aviation safety related issues.

Moderators: FrankM, el, Dmmoore

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Sun Apr 07, 2019 4:37 pm

Yes, I know, you get an aeroplanie that likes to help with relentless pull ups...

Yes, I know, then it doesn't feel the same as other 737s (which is the major BUSINESS problem)...you can't play card that we are like Airbus where A320+/- are all the same.

But so what...just redo all the 737-MinLav training I-pads and say, "Remember, on the 'MinLav you ever royally screw up and get into a stall, this plane needs a real HARD shove over

...and maybe you can add one item to the takeoff? checklist of ALL 737s: Even though we want to never ever ever ever ever get close to stalling, you normally recover in this 737 by a:

[Legacy 737s]

deliberate-but-reserved nose over shove

[737-MinLav]

relatively vigorous shove over


(Evan can revel in type specific checklists).

Not only that, but then you can put AOA indicators and tell the pilots to look at them as part of the stall recovery...but not to focus TOO hard cuz the dang things go bonkers sometimes, so you may have to figure out that the plane is actually flying in a healthy manner.
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Mon Apr 15, 2019 1:22 pm

Gabieee: This was a fairly serious post for the purpose of a little discussion.

Given that MCAS has an arguably dark side, what would happen if it was removed?

Does A the plane simply require more nose-over input in stall situation, or B does the stall behavior become nasty and somewhat unrecoverable?

I know that situation A brings about a bunch of certification effort AND makes the plane a significantly different type vs. the other 737 line...and that means $ are involved.

But beyond that: Is there other stuff wired in- and undoing MCAS will cause a cascade of engineering and massive recertification efforts?

Or do we send the whole fleet to the scrap yard and bring back the 757?
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

User avatar
Gabriel
Posts: 2004
Joined: Sat Feb 09, 2008 2:55 am
Location: Buenos Aires, Argentina

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Gabriel » Mon Apr 15, 2019 6:11 pm

Gabieee: This was a fairly serious post for the purpose of a little discussion.

Given that MCAS has an arguably dark side, what would happen if it was removed?

Does A the plane simply require more nose-over input in stall situation, or B does the stall behavior become nasty and somewhat unrecoverable?

I know that situation A brings about a bunch of certification effort AND makes the plane a significantly different type vs. the other 737 line...and that means $ are involved.

But beyond that: Is there other stuff wired in- and undoing MCAS will cause a cascade of engineering and massive recertification efforts?

Or do we send the whole fleet to the scrap yard and bring back the 757?
Well, the problem is that I don't know if it's A or B. And, anyway, define "the stall behavior become nasty and somewhat unrecoverable". We might be already there even before the MAX.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Mon Apr 15, 2019 10:06 pm

3BSIEEE:

Gabieee: This was a fairly serious post for the purpose of a little discussion.

Given that MCAS has an arguably dark side, what would happen if it was removed?

Does A the plane simply require more nose-over input in stall situation, or B does the stall behavior become nasty and somewhat unrecoverable?

I know that situation A brings about a bunch of certification effort AND makes the plane a significantly different type vs. the other 737 line...and that means $ are involved.

But beyond that: Is there other stuff wired in- and undoing MCAS will cause a cascade of engineering and massive recertification efforts?

Or do we send the whole fleet to the scrap yard and bring back the 757?
Gabieee:

Well, the problem is that I don't know if it's A or B.
Noted and Indeed (I have the same question).
Gabieee:

And, anyway, define "the stall behavior become nasty and somewhat unrecoverable". We might be already there even before the MAX.
Are you Evan? That is not_a black and white statement question- you can list examples of "nasty and somewhat unrecoverable".

I know the exact definition may affect the aircraft certification.

For the sake of this discussion- perhaps "Nasty and somewhat recoverable" might be somewhere in the neighborhood of where the stall warning is kicking in...that maybe there's a lift component to the engine cowling that significantly compromises your ability to nose over even though you haven't stalled yet.

ALL OF this is uber ass-hat unsubstantiated babbling, and perhaps that makes it impossible to discuss.

Still, I think the questions are valid...Is the 'MinLav totally stuck with requiring some sort of MCAS?

And what are the fixes- (besides a second, third, or 13th AOA sensor)?

Thanks.
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

User avatar
Gabriel
Posts: 2004
Joined: Sat Feb 09, 2008 2:55 am
Location: Buenos Aires, Argentina

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Gabriel » Mon Apr 15, 2019 10:56 pm

Sorry, black and white was not my intent. Perhaps the correct question, rather than a definition, would be "what do you have in mind when you say nasty and somehow unrecoverable stall"? Let me explain...

There were at least 1 incident with a 737 in approach that started Turkish-style, were the throttle levers were accidentally left at idle (or the AT left them at idle), the plane was on AP so as it slowed down the AP was pulling up and at the same time it was applying nose-up trim to cancel the pull-out force. Eventually, the pilots realized of the situation and called go-around and the stickshaker started simultaneously. Full power, flaps 15, positive climb, gear up but wait, we are pitching up too much, push down... more... more What? You are already pushing to the stop? Then why does the nose keep going up? And the speed going down even with (or should I say thanks to) the full throttles... Full stall, the nose drops, down we go, we start to gain speed and the nose starts to go up again, push down, push down more... ok, with the speed gained in the fall now the elevator has enough authority to keep the nose from going uncontrollably up, stickshaker stopped shaking, but we need to keep pushing hard on the yoke to keep the plane from pitching up by itself. Time to put some nose-down trim perhaps? Duh? If we had put some nose-down trim from the beginning, we would have not lost pitch control in the first place.

Some may say that in this real incident "the stall behavior became nasty and somewhat unrecoverable". (I instead would say pilots should have it as natural and automatic that trim stabilizer is an integral part of pitch control and MUST be used, and would be used without even thinking, to control pitch, especially if elevator alone is not enough, which by the way would have applied to Lion Air and Ethiopian too).

And this incident was not in a MAX.

Is that not-black-and-white enough?

User avatar
Gabriel
Posts: 2004
Joined: Sat Feb 09, 2008 2:55 am
Location: Buenos Aires, Argentina

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Gabriel » Mon Apr 15, 2019 11:03 pm

The fixes are:
- MCAS will be based on averaging 2 AoA readings/sensors.
- Triple filter to discard spikes or transient spurious AoA values.
- There will be a triple check, any of these conditions not met will render the MCAS inhibited:
==> Difference between the 2 readings do not exceed 5 degrees or so.
==> Sanity check for the averaged value compared with other variables (like airspeed and load factor)
==> Detection of unrealistic sudden changes in the readings.
- The MCAS will not restart 5 seconds later (or ever) if nose-up trim thumb switch is actuated. during/after the operation of the MCAS.
- The FCC will compute a max nose-down MCAS input that will ensure that the pilot retain an authority of at least 1.2 Gs on the yoke.
- AoA disagree indication in the PFD will be standard (AoA indicator itself will still be optional).
- The MCAS will be described in the FCOM and AFM and specific training will be required.

User avatar
Not_Karl
Posts: 2556
Joined: Thu Nov 12, 2009 6:12 pm
Location: Buenos Aires

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Not_Karl » Tue Apr 16, 2019 12:36 am

And what are the fixes- (besides a second, third, or 13th AOA sensor)?

Thanks.
Put bigger, heavier lavs up front, to counteract the undesired nose-up tendency.

You're welcome.
Junior Janitor, Vandelay Industries, Inc., Environmental Poisoning Assurance department.

"I think, based on the types of aircraft listed, you're pretty much guaranteed a fiery death."
- Contemporary Poet flyboy2548m to a Foffie.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Tue Apr 16, 2019 1:09 am

*** specific training will be required. ***
Oh no! Curtains for Boeing (or at least curtains for minimal training).

Good idea on the lavs Not_Karlieee
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Tue Apr 16, 2019 2:07 am

Sorry, black and white was not my intent.
Cool story & appreciate the variations.

My context was the 737-MinLav...and just how much nose over help it needs...does it really need the DCAS (Dive Causing Augmentation System) to ‘assure’ recovery, or is it ‘only’ “nice to have” and ‘only’ to make it FEEL like the 737-TraditionalLav?
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

User avatar
Gabriel
Posts: 2004
Joined: Sat Feb 09, 2008 2:55 am
Location: Buenos Aires, Argentina

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Gabriel » Tue Apr 16, 2019 8:53 am

My context was the 737-MinLav...and just how much nose over help it needs...does it really need the DCAS (Dive Causing Augmentation System) to ‘assure’ recovery, or is it ‘only’ “nice to have” and ‘only’ to make it FEEL like the 737-TraditionalLav?
The example that I gave shows how, at very low speeds and high nose-up trim setting and high AoA, changing from very low power setting to very high power setting may render the elevator (alone) unable to control pitch and prevent an uncontrollable pitch-up that can end in a full stall crash burn did died. In the MAX this effect is likely stronger due to the more more forward location of the engines. Likely, too, in both cases using trim thumb switch to trim down and hence augment the effect of the nose down elevator would be enough to control the situation, as also would pulling back a but on the thrust. But how much more violent would the effect be in the MAX? It's just a handling feel difference or it makes the condition not compatible with airworthiness?

So, again, the answer is I don't know if the MAX would be certifiable without the MCAS or if it is just a matter of having both airplanes feel more similar so you can have pilots flying both types alternatively and under the same type rating. Educated gossip in youtube and forums seem to point to the later.

elaw
Posts: 531
Joined: Thu Jul 24, 2014 7:01 pm
Location: Massachusetts, USA

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby elaw » Tue Apr 16, 2019 12:25 pm

I wonder if a partial solution to this sort of thing would be a revamp of how type ratings work.

It appears now it's "all or nothing"... if you're rated on the old-school 737 and they decide you need a new one for the 737-CrashMatic, you have to go through an entire new training program. This of course involves time and expense which nobody wants because training people doesn't generate income and thus is to be avoided at all cost.

But how about some sort of "endorsement" system where to fly the new damn-similar-to-the-old plane, you spend maybe 2 hours in a classroom and 1/2 hour in a sim, being instructed on what's different about this plane vs. the one you were previously rated on?

Image
HR consultant, Yoyodyne Propulsion Systems, Inc.

User avatar
flyboy2548m
Posts: 3973
Joined: Sat Feb 02, 2008 12:32 am
Location: Ormond Beach, FL

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby flyboy2548m » Tue Apr 16, 2019 1:34 pm


But how about some sort of "endorsement" system where to fly the new damn-similar-to-the-old plane, you spend maybe 2 hours in a classroom and 1/2 hour in a sim, being instructed on what's different about this plane vs. the one you were previously rated on?
"We" do that already, but thanks for the suggestion.
"Lav sinks on 737 Max are too small"

-TeeVee, one of America's finest legal minds.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Tue Apr 16, 2019 1:57 pm

Gabieee:

So, again, the answer is I don't know if the MAX would be certifiable without the MCAS or if it is just a matter of having both airplanes feel more similar so you can have pilots flying both types alternatively and under the same type rating. Educated gossip in youtube and forums seem to point to the later.
Yes, I don't think any of us will every know the TOTAL answer- that's probably somewhere inside of Boeing and they won't be saying one way or the other.

If DCAS really is 'only' a "nice to have", I'd say unplug the dang thing...the old version is just so darn creepy that I can't bring myself to like the new one...

...and yes, do whatever certification / training you need to do (as Elaw describes and Flyboy confirms is currently done).

However, I am guessing that unplugging/deactivating/removing/whatever is an over simplification.

And then the issue of "nice to have" vs. "need to have"...a gray area.

PS: Flyboy, your rare, somewhat biting and harshly realistic, yet light and humourous input to our all-important discussions is always appreciated.
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

elaw
Posts: 531
Joined: Thu Jul 24, 2014 7:01 pm
Location: Massachusetts, USA

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby elaw » Tue Apr 16, 2019 2:10 pm


But how about some sort of "endorsement" system where to fly the new damn-similar-to-the-old plane, you spend maybe 2 hours in a classroom and 1/2 hour in a sim, being instructed on what's different about this plane vs. the one you were previously rated on?
"We" do that already, but thanks for the suggestion.
Then why go to such great lengths to make planes flyable by people with the same type ratings as others?
HR consultant, Yoyodyne Propulsion Systems, Inc.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Tue Apr 16, 2019 2:56 pm


But how about some sort of "endorsement" system where to fly the new damn-similar-to-the-old plane, you spend maybe 2 hours in a classroom and 1/2 hour in a sim, being instructed on what's different about this plane vs. the one you were previously rated on?
"We" do that already, but thanks for the suggestion.
Then why go to such great lengths to make planes flyable by people with the same type ratings as others?
I think you are debating a no-win-purely-gray concept...You wanted to not_do type ratings, but instead a fuzzy, gray, in-between-but- short compare contrast...

To which Flyboy said, ""We" already do that".

How different a plane is ideally determines how much compare/contrast training you need.

At some point, when the differences become great (and perhaps conflicting) you draw a line...different type and the "cross-certified" thing doesn't really work.

Ironingly- I guess I can claim that I am rated in BOTH the 172M AND the 172XP (The XP required a logbook endorsement). To be honest, I never felt comfortable in the XP, it was very nose heavy and required rather relentless pull ups just to flare the thing. I should ask Bobby if he knows what it's like to turn final with three hundred and sixty injected cubic inches of power, constant-speed prop and 2300 lbs and a 2500 ft airstrip?
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

User avatar
Gabriel
Posts: 2004
Joined: Sat Feb 09, 2008 2:55 am
Location: Buenos Aires, Argentina

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Gabriel » Tue Apr 16, 2019 3:55 pm


But how about some sort of "endorsement" system where to fly the new damn-similar-to-the-old plane, you spend maybe 2 hours in a classroom and 1/2 hour in a sim, being instructed on what's different about this plane vs. the one you were previously rated on?
"We" do that already, but thanks for the suggestion.
Then why go to such great lengths to make planes flyable by people with the same type ratings as others?
Because 2 hours of classroom and 1/2 hour of simulator is way much more expensive and time-consuming than 45 minutes of self home training in an iPad. Pus, you need to have simulators available, of which there were somewhere between very few to none when the MAX was introduced.

User avatar
Gabriel
Posts: 2004
Joined: Sat Feb 09, 2008 2:55 am
Location: Buenos Aires, Argentina

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby Gabriel » Tue Apr 16, 2019 4:09 pm

I should ask Bobby if he knows what it's like to turn final with three hundred and sixty injected cubic inches of power, constant-speed prop and 2300 lbs and a 2500 ft airstrip?
He owns and flies a J3, so... I think we will laugh at you at both ends of the spectrum.

User avatar
3WE
Posts: 5090
Joined: Wed Feb 06, 2008 2:37 pm
Location: Flyover, America

Re: FAO: Gabriel; Why don't [i]we[/i] just unplug MCAS?

Postby 3WE » Tue Apr 16, 2019 4:34 pm

I should ask Bobby if he knows what it's like to turn final with three hundred and sixty injected cubic inches of power, constant-speed prop and 2300 lbs and a 2500 ft airstrip?
He owns and flies a J3, so... I think we will laugh at you at both ends of the spectrum.
IMMATERIAL....wimpy ass 75 horse carbureted fixed pitch stick-controlled tail dragger, 1700 lbs and much lower stall speed and ridiculous short-field performance.

Cub vs. Hawk XP are very different types...type rating not_required, but there better be a couple hours of classroom, a good I-Pad class and "simulator" time before you hope from one to the other. (Yes, there is a tail-dragger set of requirements and endorsements).

(Please read all of this with a little bit of blue shading AND a little bit of technical accuracy, and trim your sense of humor control significantly up).
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.


Return to “Aviation Safety Discussion Forum”

Who is online

Users browsing this forum: No registered users and 2 guests