Literally no one has said that.

There’s two AOA sensors but only one feeds MCAS there will probably be a disagreement on the FDR from before the aircraft even taking off.  Some simple AOA disagree warning or some such on the ground would probably fix this

Thats why were here to learn. I know nothing about airplanes. Thats just how I understood it but really didn’t read into it. So its a training issue mostly? Can they turn off whatever reads those bad sensors?

I'm curious what they have to turn off to disable MCAS.  Can they shut the MCAS off by itself, or do they have to turn off the electric trim entirely and fall back to using the manual hand crank on the trim wheels?

IIRC, it is disabled when the AP is active or the flaps are down and the pilots can shut the electric trim off by use of a control near the engine fire cutoffs. they can then trim manually.



Great article on it from AOPA

Yep.
From the 800 FRM (flight manual).

9.2.5.5 Maneuver Characteristics Augmentation
SystemRevised: 02/01/2019

A pitch augmentation system function called Maneuver Characteristics Augmentation System (MCAS) is implemented on the B737MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack.

The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps UP flight at airspeeds approaching stall.

MCAS is activated without Pilot input and only operates in manual, flaps UP flight.
The system is designed to allow the Flight Deck Crew to use the COLUMN TRIM switch or stabilizer aisle stand CUTOUT switches to override MCAS input.

The function is commanded by the Flight Control computer using input data from sensors and other aircraft systems.  
The MCAS function becomes active when the aircraft angle of attack exceeds a threshold based on airspeed and altitude.
Stabilizer incremental commands are limited to 2.5 and are provided at a rate of 0.27 per second. The magnitude of the stabilizer input is lower at high Mach numbers and greater at low Mach numbers.

The function is reset once the angle of attack falls below the angle of attack threshold or if manual stabilizer commands are provided by the Flight Deck Crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to the current aircraft Mach number at actuation.

US Justice Department is now investigating Boeing... and theTransportation Department is investigating the FAA.

https://www.msn.com/en-us/news/us/ap-source-justice-dept-probing-development-of-boeing-jets/ar-BBUVBag?ocid=spartanntp

So if the flaps are up, and the captain wants to hand fly because he knows there is a problem, the only way to stop MCAS is for the crew to turn off the electric trim?

Assuming that MCAS is being triggered by a bad AoA indication, or some other flight instrumentation failure, wouldnt the crew already be in the middle of an emergency procedure to deal with that problem when the jet decides to start trimming the nose down?

The crew might be trained to react to a runaway trim by disabling the electric assist and using the manual hand crank, but if they are busy fighting the original instrumentation failure that caused it, I can understand why they might not diagnose the trim problem in a timely manner.

EDIT:

Also, could MCAS trimming the nose down present any significant complication to diagnosing a bad AoA indicator, thereby causing them to come to the wrong conclusions about what instruments to trust, or maybe make other mistakes?

I'm no pilot, but it seems like bad juju to have the jet start making weird trim changes when the insturments go tango uniform and the crew is struggling to make heads or tails of what the jet is actually doing.

@billofrights

Thanks for that.

That makes a lot of sense.

So, basically a Pilot typed in a 737 would have noticed the MCAS trimming down way too much and they would have just turned the MCAS off and set the trim manually ?

Correct!
I have quite a few SWA friends that fly that aircraft, and they all say the same thing - "it was poor piloting".
None of my SWA pilot friends can understand why those pilots simply didn't shut the trim system off and trim it manually.
I'm not saying the MCAS is fault free, just that a competent pilot would have shut it off when it malfunctioned.

I think it speaks volumes that the two crashes were by foreign, non-Western, pilots.

Assuming this is the case (and I'm not smart enough on things aviation to say one way or the other), then the next point of focus would appear to be what steps did Boeing take to communicate the new MCAS system to pilots/airlines and the need to understand a new checklist/fault procedure was in place for this particular 737 variant in case of MCAS problems, no?

Or asked a different way, when type rated pilots transition to the 737Max, do they need to be specifically trained on the MCAS system due to it being substantially different than older gen 737s?

It is  beginning to look like Boeing...and to some degree the FAA...really screwed up the 737 Max certification.  It will be interesting to see what comes out of the lawsuits against Boeing.

Boeing knew that they were selling to third world airlines.

Sometimes we don't know what we don't know, though.

You can only account for so much.

Here is the fault checklist - I don't know how much clearer it can get, turn the system off if it's malfunctioning and go to runaway stab checklist.

Attached File

watch the video by an AA pilot posted last page

https://www.youtube.com/watch?v=ftZ6j8onS78

the american pilots: "the system they had never heard of before called MCAS", not to mention pilots from other countries, Boeing didn't tell them the existence of MCAS, how could they know to shut it off? guess the intention is to hide the potential aerodynamic problem with software, but the software couldn't handle it properly so got the crashes. now Boeing issued "upgraded" software hope to fix the problem

No, no, no, no.

There was no general instrument failure.  Pilots should not be "diagnosing" an instrument failure, they should be flying the plane.

If the only problem is the trim wheel going nuts when it shouldn't be, then sure, figuring out the solution should be easy.  Unfortunately, it seems like MCAS may not have been the source of the original failure, but rather a fatal complication that arose as a result of instrumentation problems.  I read that both of the crews that crashed reported problems with airspeed indication, and the data from Lion Air showed that the stick shaker was going off for most of the flight, so I could understand the crew not noticing the trim wheels moving under those conditions.  Also, consider the "maneuvering characteristic" that MCAS was supposed to fix, which was the forward placement of the engines resulting in a greater pitch up moment when at high angles of attack.  Could that lovely little quirk have made it easier to induce an oscillation?

Yes, Boeing will survive. 64 on the Global fortune 500.  There are lots of loyal customers that won't just walk away.  Sure, it may drive some to change tier supply mix, but it isn't like Airbus (#105 by the way), has a spotless record,  and I don't think any western carrier is going to source Russian or Chinese planes at this point.   Boeing will take the hit in 2019 or 2020 financials and rebound nicely.

Maybe "diagnosing" is the wrong word there, but don't they need to know what instruments are giving them correct info in order to fly the plane?  If they can't trust any instruments and have to fall back to flying by "feel", could a system that keeps slowly increasing nose-down trim make that difficult?  Sure, they are supposed to notice the trim being adjusted and disconnect that system, but what are the odds that they will see that while instruments are doing strange things, bitching Betty is going nuts, the stick shaker is on continuously, and who knows what else is going on in the cockpit?

See the post below yours.

I understand that dealing with the issue is straightforward...once you KNOW what to deal with it.    It appears that even some American pilots are claiming ignorance about the system.

Again, I take no position on this as it is out of my lane.  But something appears to be amiss with the 737Max.

That procedure is in place for all 737 models, and they would have been trained on it.  The idea is that if the trim wheels move when they aren't supposed to, they go to that procedure.  It doesn't matter if the trim wheels are moved by MCAS or by something else, in an ideal world, they should have seen/heard the trim move while autopilot was disconnected, and flipped the switches to turn off electric trim assist.  My question is if it is reasonable to expect the crew to notice the trim being moved 100% of the time when other stuff is happening.  Stuff like an erroneous stall warning and stick shaker activation due to bad instrumentation; bad instrumentation that also happens to activate MCAS.  Maybe if the jet has handling characteristics that make bad piloting by third-worlders more dangerous, the automation that is supposed to "fix" it should have a bit more intelligence built into it.  Automation for flight control surfaces that is even dumber than the seat/yoke interface sounds like a bad idea to me.

On the KV-135 the Air Force added a control column activated brake to the stab trim to stop the trim wheel moving if the column is set opposite of the direction of he trim travel.  Can anyone familiar with the Max add if such a system exists on those airframes?

The 737-800 and MAX also have the column trim cutout switches.  However on the MAX, the column switch will not stop MCAS commanded trim actuation.

I have no idea why the guy in that video said that, I don't know him.
I do know half a dozen of my SWA pilot friends who fly that aircraft and all of them know exactly what and where the Trim Cut Off switches are.
Beyond that I as much in the dark as everyone else - but I'll trust my SWA pilot friends that they know what's going on in the cockpit (not all pilots are created equally).

On our jet it’s a physical brake that stops stab trim movement if for example the stab is going nose up while the column is pressed down.  I’d be a little surprised if such a thing was prevalent in the real word, but the SPO got the idea from somewhere.

Isn't there electric trim stabilization on previous 737 models???  If so, how to deal with it on the MAX doesn't seem much different than on previous models.

There was no general instrument failure.  One sensor failed, and that sensor had a functioning back-up.

One of the posts someone said you could simply grab the trim wheel and hold it on a runaway trim?

Mooney I owned was somewhat unusual in the it had no elevator trim.
You trimmed by moving the entire tail assembly. I always usually trimmed by the yoke button but with the right hand felt the trim wheel
move that was between the seats on the floor.

Also had altitude hold that mainly used the trim to maintain altitude.
Most times the AP was constantly moving the trim wheel.

I know a Mooney is no MAX but the systems were vaguely the same.
In IMC I always monitored the AP operations like a hawk.

On the 73, it's just a switch that cuts out the stab trim if you apply opposite yoke force far enough.  Sounds like it essentially does the same thing you described, except by cutting the power to the stab trim, instead of a physical brake.

That is correct, grabbing either trim wheel and holding it will stop the trim.  It's been a long standing Boeing joke (on the airplanes with the spinning trim wheels) that if it ran away, the ca would grab the fo's knee, and pull in into the trim wheel to stop the trim runaway.

it says right in the checklist posted above, step 5
Attached File

to do exactly that.

The MCAS doesn’t use both sensors? Even fly by wire steering on tractors uses redundant steering sensors. Seems pretty stupid to run a system like that off a single sensor. All sensors fail eventually.

The reason I pointed out that it was designed under the 737 type rating, is because the whole thing was caused by the manufacturer trying to make the FAA believe that it handled similar enough to be certified under that 737 type rating.    That’s a big deal, because training pilots for a new type rating costs anywhere between $20,000 to $60,000 per pilot.
An average Western trained pilot Probably would have automatically hit the electric thumb operated trim several times to undo the MCAS commanded nose down trim.  Then, would have said, “WTF, I’ve got a weird trim issue going on here, turn off the electric trim and let’s get it sorted out”.

Probably.

But that initial point where you retract the flaps, is a busy and critical time.   So, they’re wondering why is the Nose suddenly heavy?   Trying to figure it out, and after a few seconds the airspeed rises, and when it does, that nose down trim becomes more effective, until you literally don’t have the strength to hold the nose up.    Most American pilots use the electric trim a lot, so they would automatically counter it effectively.   However, pilots that aren’t used to using electric trim, might not automatically go to it.

And, it wasn’t reasonable for Boeing to assume a pilot could diagnose the issue and turn off the electric trim within a few seconds.    Especially, when they didn’t even tell anyone about the system or the potential failure mode.

In short, the first accident was all Boeing.

After Lion Air, pilots were aware of it and were ready to turn off the trim within about a second or two, which is no big deal at all.

The worst part of the tragedy, is that the system was un needed to begin with.

It was just a silly attempt to make the Max handle a little more like the original 737 at very high angles of attack.

Probably, an FAA pilot or Boeing test pilot said, “Oh, this doesn’t have enough nose down feel in a high power, high pitched turn...we have to make it feel just like the original...”.
-And then some egg head said, yeah, we can fix that, no problem.”
And then a bunch of people died.

It really isn’t a big deal, now that we know about it.
I’m interested to see exactly how the scenarios played out.

The AOA vane is like a tiny wing that sticks out from the nose, if it’s taped, or otherwise jammed, it can’t rise and start measuring AOA, so yeah, it’s going to be telling the pilots they’re in a stall.  Pilots would respond by going nose level and full power.

It should have been easy for them verify by other instruments they are not in a stall, But, with the MCAS pushing the nose down harder and harder, you don’t have time for a checklist.

You would either do the right thing immediately (stop the trim).
Or die.

That simple.

Again, now that we know about it, it’s not a big deal at all.    I would fly a Max tomorrow with my entire extended family on board.  It’s a damned good airplane, except for that one simple design flaw.

i think it's way more complicated than that, Boeing engineers/managements are not stupid nor so irresponsible, only when put under huge pressure of money saving vs proper re/design, they tried the best compromise, but obviously now proven not good enough. there's just no easy way out unless spend huge amount of money for rework. i don't trust this new software "upgrade" to fix this problem either, i'd stay away from 737max unless they do it right

Two sensors isn't an elegant solution. If their readings disagree, and aren't nailed at the highest or lowest extreme, which one is correct?

Triple redundancy is the usual answer. With three sensors, you use the two that are closest in value (called a 2 of 3 voting system). For some applications, quadruple redundancy is used (4 systems, if one fails you still have two of three voting, in the case of inputs).

Most sensors exhibit what is called a bathtub reliability curve. There are early failures (aka infant mortality), a long region of low failures, then end of life failures as things wear out.



Tech article on failure and how to analyze and reduce it

Note that the useful life portion of the bathtub curve does not guarantee zero failures, just a lower probability of failure than when brand new or old and worn out.

Because failures can occur at anytime, any single point of failure in a critical part of a system gets enormous amounts of testing and what is called "burn in", or use under accelerated life conditions, to get past the initial steep part of the bathtub curve.

That being said, we could be looking at a sensor problem, a non-intuitive design of the MCAS software kludge, a little of both or some black swan.

I've personally worked on systems that had intermittent, catastrophic faults, that were eventually traced to improper storage of a single component before assembly. A temporary software patch was issued to mask the problem. Instead of doing some things I recommended, the company made the temporary patch permanent. Companies don't typically care about making the best product they can. MBA's are trained to make the cheapest product that just meets specifications. Anything more is considered wasteful. Most of the time it works. Most of the time.

There is an "integrated standby flight display", it incorporates all standby instruments into one stand alone electronic display.  It provides attitude, altitude, airspeed, heading and localizer/glide slope information.  It has it's own attitude data source, and uses the alternate pitot and static sources.

It's in-between the inboard two displays, at the top of the main panel.

The pilots of a doomed Lion Air Boeing 737 MAX scoured a handbook as they struggled to understand why the jet was lurching downwards, but ran out of time before it hit the water, three people with knowledge of the cockpit voice recorder contents said.
https://finance.yahoo.com/news/exclusive-cockpit-voice-recorder-doomed-lion-air-jet-061922280--finance.html

The people who designed the MCAS system, the people who authorized it to be added to the 737, and the people who decided not to tell the Pilots about it - All of them, are the very definition of “stupid and Irresponsible”.

The original designer may well have been an aspie genius who simply couldn’t foresee what would happen - In the Real World, when you give unlimited nose down trim movement to a single point failure of the AOA indicator.    But somewhere, somebody, should have asked that question.    It takes a huge amount of institutional arrogance at Boeing for this to have happened.   Nobody stopped to ask: “Hey guys, do we have this exact system on any other airplanes?   If not, Why not?

This will be studied in aviation as an example of what happens when stupid irresponsible engineering meets stupid irresponsible Corporate/Government leadership/Oversight.

Relevant this discussion:  Lion air jumpseater saved the aircraft the day before the accident from the same malfunction

The so-called ‘dead-head pilot’ on the earlier flight from Bali to Jakarta instructed the crew to cut power to the motor driving the nose down.

Just the next day, under command of a different crew in what officials said was an identical situation, the plane crashed, killing all on board.

https://www.9news.com.au/2019/03/20/12/49/boeing-crisis-pilot-who-hitched-a-lift-saved-lion-air-max-day-before-disaster?fbclid=IwAR1zMSKhsRYINo8D6UqZN8jzKwU0ZMV271QiqhwUOLXbjPRO8pChEd5aMak

i agree using software to "cover up" and "smooth out" the potential aerodynamic problem is irresponsible decision (money saving won), but the unlimited nose down trim that eventually leads to crash is a software bug that nobody had foreseen, otherwise i don't think anybody would dare using that for production, try to save money for profit yes, but crazy they are not

Can't speak for Boeing, but I've seen "temporary patches" become permanent.

I wrote the algorithm for one issue (the software guys implemented it). I specified and told everyone that it was an emergency patch to alleviate a hardware problem. I then found the hardware problem, designed a subsystem to replace it (at roughly equal cost), and watched the proper fix project canned by management, and the permanent adoption of the emergency patch.

I seriously doubt I'm the only design engineer ever to have experienced that.

yes it's a never ending battle between engineers and business/management, engineers want properly done bullet proof product, management worry about cost/sales/profit. in this Boeing case business/management won, but ended with disasters, both in terms of lives lost, reputation damaged, and money cost. so lesson learned is listen to the engineers, don't try to cut corners, especially for critical issues like plane safety

'Allahu Akbar' were last words of first officer on board Indonesian Lion Air jet that crashed, as cockpit recording reveals pilot desperately scoured instruction manual as it went into fatal dive.

A short Islamic prayer were the final words of one of the pilots on the doomed Lion Air Boeing jet, as it nosedived into the sea off Indonesia last year, a cockpit recording has revealed.

The Indonesian first officer can be heard saying 'Allahu Akbar' - meaning 'God is greatest' in Arabic - as he and his colleagues ran out of time while desperately looking through the instruction manual trying to save the aircraft.

Pilots scoured the handbook as they struggled to understand why the Max 8 aircraft was lurching downwards - but ran out of time before it hit the water, according to people with knowledge of the recording.

The investigation into the crash, which killed all 189 people on board in October, has taken on new relevance as the U.S. Federal Aviation Administration (FAA) and other regulators grounded the model last week after a second deadly accident in Ethiopia.



The pilots of a doomed Lion Air Boeing 737 MAX (stock photo) scoured a handbook as they struggled to understand why the jet was lurching downwards - but ran out of time before it hit the water, three people with knowledge of the cockpit voice recorder contents said.

More

The other battle is that as soon as you idiot-proof anything, they built a better idiot.

In the railroad business, a locomotive was a $2M asset. It cost the railroad roughly $1000/day.

Presumably this scales.

MAX 7: US$99.7 million
MAX 8: US$121.6M
MAX 200: US$124.8M
MAX 9: US$128.9M
MAX 10: US$134.9M as of 2019[7]

Say an average of $120M, so $60K/day would be a ballpark cost to the airline.

There are 376 built, according to Wiki

376 x $60K = $22.56M / day

Just to get an idea of the dollars involved in the problem (excluding potential lost / cancelled orders from Boeing, if things get ugly). Tack on the inevitable lawsuits.

No idea how airline finance works, do banks own the planes and airlines lease or ?

In any case, someone is going to want reimbursed for their investment being parked. To what degree is unknown.

Right now, at Boeing, they're in a "fix this now" mode. Are they pursuing a fix that requires new type certification for pilots? That would be disatrous. Are they dialing back the trim or coming up with different algorithms? Maybe limiting the number of times MCAS can kick in over a short interval? Surely. Are there managers whto were promoted on something other than merit fouling things up? Probably. Who will get the attaboy for finally fixing the problem? Not the low man on the totem pole who actually does it. His bosses will get credit and add it to their resumes.

Gotta be a chinese fire drill there now. The people working the problem have their managers asking twice a day (or more often) for updates.

And they'll probably still have to fill out timesheets and write weekly reports.

Meanwhile, the management during the original patch cluster have taken their bonuses and moved on. Top 3 from that era are gone. McNerney was making $27M a year. So typical. Sacrifice everything for those quarterly numbers and bail before it all blows up. Rinse and repeat.

If we didn't have merger mania from the 80's onward, we'd still have viable US competition for commercial planes. Now we've got too big to fail Boeing.

ETA: I've lived this, although not in the airplane business. The worst was some manager demanding to know how long it will take to find a problem and fix it.

How the hell do I know? I might find the problem in the next 10 minutes or it might take 10 days. Until we find it, we have no idea what the fix is, or how long it will take.

"Need a number" was always the reply, so you tell em anything to make them go away so you can get back to working the problem. They inevitably come back with "1 week is too long, we need it in 3 days"

This really happens. Management then takes your best number, leans it out, then passes it up to his boss and on and on. By the time it reaches top manglement, it's "probably tomorrow". Then everyone shits on low man because they don't think he's working hard enough (staying at the office past 11 pm, back in 8 hours later).

SNAFU / TARFU / FUBAR