As I read the Nov '18 directive, it does say something sto that effect. And it does have special rules for the MAX.

For a non MAX, there is no need to cuttoff the electric control if the disengaging the auto-pilot and trim switches bring in back in balance. For the MAX, based on other listed items, the cutoff should be activated even if the initial recovery brings in into trim.

https://www.flightradar24.com/blog/w..._Emergency.pdf

It could be very difficult to manually crank back into position, so in neither case is the correct initial action to throw the cutoff.

There may well be some blame on the pilots, particularly the Ethiopean, but I still see some on Boeing here.

Knowing that the MCAS is present on your aircraft and understanding what it might do if it fails/malfunctions makes no difference in how one responds to its unintended effects? IOW the response to the aircraft bizarrely insisting on going nose down would be the same regardless of the cause?

Just trying to understand.

This characterisation of the system is not accurate. The technical accuracy of the news reporting on the 737 MAX has been dismal. Even the better reports have errors such as repeatedly calling MCAS a stall prevention system. Conclusions based on flawed reports are similarly flawed.

The DFDR data from the incident, and two accident, flights shows that the airplane can be kept in-trim indefinitely through the use of primary electric trim. The "computer" (Speed Trim System) can not override that. This matches with the expected performance of the system.

The first two steps for both the stabilizer runaway and IAS DISAGREE procedures are the same. Disengage the autopilot and autothrottles. If that doesn't stop the runaway they you continue and disconnect all electric stabilizer trim functions which includes the autopilot trim and primary electric trim. There is no situation in which you shut down parts of the electric trim systems while leaving others enabled.

The A.D. doesn't change the existing stabilizer runaway procedure nor does it create a new one for a runaway caused by unscheduled MCAS activation. It reinforced that the existing stabilizer runaway procedure must be accomplished in such a situation even though additional warnings (stick shaker, IAS DISAGREE, etc.) may also occur.

The difficult in using the manual trim, encountered by the ET302 crew, was due mainly to two factors.

1. They allowed multiple uncorrect MCAS activations to push the stab trim to a nearly full-nose-down position before they disabled the electric trim.

2. Their excessive airspeed (~390 knots indicated airspeed, about 150 knots faster than they probably should have been) both increased the nose-down moment produced by the mis-trimmed stabilizer and increased the airloads on the stabilizer jackscrew which increased the force required to turn the manual trim wheels.

The speed was that high because they did not disconnect the autothrottles, per either the IAS DISAGREE and stabilizer runaway procedures, and they maintained full climb power (91% N1) for the duration of the flight. This is why this step is at the top of the checklist.

Essentially correct. Same procedure.

I would only argue that "bizarrely insisting on going nose down" does not accurately describe a runaway stabilizer as a runaway stabilizer is something that is possible on every large airplane (and many small ones).

The airplane becomes "out of trim" many dozens, if not hundreds, of times on every flight. There's nothing bizarre about that. We respond by retrimming the airplane. During departure and arrival we are retrimming very frequently. A runaway stabilizer is a possible failure that we know can occur, have a procedure to handle, and have trained for on every transport jet that we've flown.

I can't recall ever having discussed what may cause a runaway stabilizer in any of the airplanes that I've flown because none of the reasons are under the control of the pilot. We only discussed what to do it one occurs. You could say the same for engine failures or almost any other failure.

I do defer to the technical expertise of the pilots and others on here, and I do appreciate that journalists are looking for sensational stories but there are also reputable news organizations where I think they do to try to convey the truth of issues, and I personally read news from more than one source and usually more than one country to obtain what I think is more reflective of the truth of a story. I get frustrated by the misrepresentation of financial news as I understand many of the issues and look for the journalists I know to report based on the actual situation, not sensationalism journalism.

However, there are so many journalists working the MAX story, and I must admit I am not reading technical aviation articles, and am not reading anything that gives me comfort about Boeing or the FAA in relation to the MAX. Boeing has the arrogance of a Fortune 50 company that can do no wrong and I have said it before there is something rotten about the MAX program. I like Boeing products well enough but not the MAX. I think Boeing took shortcuts in developing a product to be competitive with Airbus instead of taking the time to actually design a new plane. I think the FAA just went along with what Boeing was doing, because it was Boeing and Boeing were the "experts", so they deferred to the experts. Part of my struggle, which I think is the struggle for many non-technical folks (although the AA pilots sounded like they felt pretty upset with Boeing) is that they say the MAX is the same as the other 737s (non MAX) and yet to my layman's brain they appear to he different and I am not booking away from 737s and would book away from a MAX.

What Boeing needs to do is not have celebrity endorsements for the MAX (but then I am not part of a generation or a person that buys because a celebrity endorses a product as I know enough about marketing and advertising to know most of that is worthless "information:) ), but have an honest sit down to explain the technical issues in layman's terms to a reputable journalist who the public trusts (say a Norah O'Donnell with an aviation expert to maybe be the go between) and clean house at the top.

Not sure what you do to reinstall confidence in the FAA but perhaps hire some aviation experts who are not aligned with Boeing.

I watch this thread with the same back and forth and understand the frustrations on both sides. I think the airlines, such as United, are caught in the middle of very bad public perception of the MAX which Boeing is not helping to change (at this stage) and the public that is reading and seeing reports that provide no comfort about the safety of the MAX.

Then why are so many pilots angry that Boeing didn't inform them of the presence of MCAS if its potential effects in a malfunction would elicit a standard response regardless of the cause?

This reads as an abundance-of-caution directive to me: the MCAS is not enabled when in autopilot anyway. On an NG, if it were to continue to show a runaway stabilizer after the autopilot were disabled, you'd cut it off. What they're saying here is that, after the LionAir incident, if you find yourself in this situation, go ahead and turn the system off entirely just in case. I see what you're saying, and I grant the point that they've tweaked the procedure, but I still don't see this as evidence of negligence on Boeing's part in not pointing out the MCAS in advance.

I agree entirely -- the procedure is to trim the stabilizer electronically into place and then cut it off and fly manually. And, yes, initial indications are that the ET pilots may not have followed this procedure: but, again, that's preliminary.

The biggest issue I have with Boeing is that they built the MCAS with a single point of failure, thus leading to what appears to be a higher rate of runaway stabilizer failure than the NG. This was a poor design, appears to have been a direct contributor to both crashes, and is being fixed. The fact that pilots are trained to deal with this situation does not excuse Boeing for having it happen more frequently.

That's bad enough -- and, if we can leave it there, without sensationalizing it further, then it becomes possible for people to understand what happened, how it could have happened, and whether or not the plane is safe to fly in the future. But if we keep saying incendiary things like "the plane flies itself into the ground" or implying that there are all of these massive conspiracies, then all we're doing is stoking fear. I fail to see the point of that.

That is my understanding, yes -- if the plane's attitude changes unexpectedly, after getting the nose back into position (if possible*), disengage the automatic stabilizer (throw the switch marked STAB TRIM CUTOUT) and fly manually.

* In the event of a total system failure, where the automatic stabilizer doesn't respond at all, you may have to disengage the stabilizer even though the nose is still out of position. This appears to have been what was done in the simulator that was referenced a few days ago, and accounts for the difficulty reported in getting the plane to level out.

Thank you! That is precisely what I have been trying to say, but you did it much more succinctly. ^

Because people died and pilots are human.

[MENTION=8598]jsloan[/MENTION] your post #1446 is the first one I have read where I finally have a better understanding of the issue - it is in terms I finally understand. Thank you.

Ummmm...this seems a tad too sanguine a response. Could it be that the angry pilots realize now that there was an unknown (to them) system on board, and that knowing that it was there (i.e., knowing the ultimate cause of the plane's erratic behavior) might change the way they respond to its unintended effects?

I don't believe so, no. The procedure remains the same: disable the automatic stabilizer.

First of all, an aircraft does not need to be fly-by-wire to fly itself into the ground. Secondly, this aircraft did in fact basically do that. An ambiguous system, unknown to many flight crews and controlled by the data from a single sensor automatically trimmed the nose towards the ground for no reason multiple times giving the flight crew only seconds of control of their own aircraft.

Could the flight crew have saved the aircraft? Maybe, but that seems highly unlikely based on what we know about the way the system functions and the characteristics of the flight at the time.

The aircraft should never have been certified to fly based on the way this system was designed and the way it operates. That's why 100% of them currently sit on the ground.

You would have to ask them. I hope I've done a good job in explaining the reasoning behind my conclusions. Ask them for theirs, then compare them to mine.

To me, the A.D. was a reminder of the correct procedure and that the accompanying warnings should not distract you from accomplishing it.

The procedure is the same on the NG and MAX. There never has been any difference. The procedure has not changed.

It is not. Trimming electronically is not mentioned in the procedure. It's something you do like keeping the wings level, pitch attitude set, maintaining airspeed, etc. Unless the failure prevents the primary electric trim from working, you would be expected to keep the airplane (close to) in-trim with primary trim as the stabilizer runaway procedure is accomplished.

That isn't unusual and not limited to Boeing.

During most operations (except autoland), the autopilot that is flying the airplane is doing so based on a single set of inputs. One pitot/static system, one AoA, one inertial reference system, one flight control computer, etc. The flight instruments that I look at are also driven by single sources. The other pilot's instruments are driven by a different set of single sources. The redundancy comes from having the separate systems so discrepancies can be identified and the faulty inputs isolated.

During the certification process a failure analysis is conducted and each failure mode is categorized based on the severity of the failure. Failure modes categorized with higher severity categories require more comprehensive backups.

In the case of the autopilot example, when conducting autoland operations the consequences of a failure is quite severe so a dual-channel, or triple-channel, system is required. (The dual-channel is categorized as fail-passive, triple-channel as fail-active). During those operations, all of the autopilots work together, each using its independent data inputs and power sources, to control the airplane. (Fail-active allows the airplane to land without the pilots seeing the runway prior to touchdown. Fail-passive requires the runway to be in sight by 50' above touchdown)

Unscheduled MCAS activation was not categorized as severe enough to require a fail-passive backup which is why it was certified to work based on a single input. This categorization was based on the expectation that the existing stabilizer runaway procedure would be used to stop runaway and prevent a loss of control. After the first accident, Boeing began work on a software update to upgrade the system so that it would meet the higher standard by using dual AoA inputs and inhibiting activation when a disagreement was detected. The second accident occurred before that update was completed.

The pitch attitude shouldn't change. When the airplane goes out-of-trim the pilot (or autopilot) holds pressure on the control column to maintain the desired pitch attitude while retrimming the stabilizer. The pilot will recognize the stabilizer runaway condition when the airplane repeatedly trims itself out of trim despite multiple pilot corrections. If flown properly, the pitch attitude will not change during this process.

Some want to make this out as a US Pilots vs. 3rd World Pilots issue. It is not. This is an issue for all pilots and is why our safety focus has been on human factors, threat/error management, and similar programs. At the top of our Quick Reference Checklist, the first place we go for a non-normal or emergency checklists, are the words, "FLY THE AIRCRAFT -- SILENCE THE WARNING -- CONFIRM THE EMERGENCY". That is to remind us of our priorities for working through the situation and making sure that we are accomplishing the correct procedures all while always keeping our first priority; flying the airplane.

Yes, it does, because only a FBW aircraft has automated flight systems that can't be turned off.

By that logic, any failure that causes a crash consists of the aircraft flying itself into the ground, except for intentional pilot action (e.g., the GermanWings disaster).

Both crews almost certainly could have saved the aircrafts if they'd diagnosed the problem correctly at first and followed the proper procedure. That doesn't mean that it can't still be improved. I base this on the fact that the previous LionAir flight was saved, and there were immediate reports after the ET crash about similar experiences by other pilots, none of which led to a fatal crash.

The key here is why didn't the pilots cut back on the throttle? The excessive air speed clearly made the aircraft unable to be manually trimmed. The only thing I can think of is that the pilots believed that by cutting speed, the airplane would increase the nose down input as it would during a normal, properly trimmed phase of flight.