Ethiopian airliner down in Africa

[GordonR_Cape]

Originally Posted by 737 Driver

I’m not trying to argue logic or whatever Boeing and FAA should have done. Obviously, the MCAS design was flawed. I am simply reporting what has been officially stated about how this system actually works.

For non-pilots, it may be difficult to relate to the dynamic environment of an approach to stall and recovery maneuver. The going in assumption is that the pilots would not intentionally place the aircraft close to the stall. When an approach to stall is detected, various aircraft systems kick in to both provide warning and assistance. However, it is also assumed that once alerted to the stall, the pilots will disengage the automation and hand-fly the aircraft back to a safe airspeed and altitude. This maneuver involves the same things I keep referring to - pitch, power, and trim. I can only speak for the aircraft I have flown, and not a single one of them was designed for the automation to execute the stall recovery. Assist, yes. Execute, no.

I half-understand your confusions, because to the best of our knowledge, no MCAS system has engaged and then rolled back the elevator trim. In the three cases we do know about, one was disconnected and flown entirely manually, the other two were irreversible due to stuck AOA data.

Edit: It just occurred to me that perhaps one of the reasons that Boeing has been coy about the unwinding of the trim, has been a legal one. Making a clear statement that MCAS was designed to unwind trim, when it did not do so in two crashes, could be a slam-dunk for product liability. Safer to obfuscate and clarify later, once its properly fixed!?

Part of your statement is a non-sequitur: I do not know of any situation in which an autopilot will bring an aircraft close to a stall. The whole point of MCAS is that it is for a rarely used situation in which the aircraft is already under manual control, and the pilot needs assistance to carry out maneuvers at high AOA, but below the stall condition.

My observation is that nobody has bothered to document the unwinding of the MCAS trim, because it has never happened, and if it did the effects would be relatively benign. This is implicit in the relatively low hazard classification, and the fact that no additional pilot training was needed for MCAS certification by the FAA.

I am not a pilot, but it astonishes me that some well informed members (not just you), can be so fundamentally misinformed about the specific details of MCAS operation. No wonder Boeing didn't try to explain it the first time!?

Re-posting the AOA chart first posted by LEOCh in: Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

Edit: Also refer to the detailed description by FCeng84 in: Ethiopian airliner down in Africa

[737 Driver]

Originally Posted by GordonR_Cape

I am not a pilot, but it astonishes me that some well informed members (not just you), can be so fundamentally misinformed about the specific details of MCAS operation. No wonder Boeing didn't try to explain it the first time.

When I first got into this business, our manuals used to be far more detailed. We used to say we could just about build the aircraft with the information they gave us. Nowadays, not so much. Someone decided that we pilots didn’t need all the technical details, but rather only the procedures. I’m not in that camp, but no one asked me. If not for these accidents any information that Boeing would have provided the pilots on MCAS would have been just as generic as the information they currently give us on the Speed Trim and Elevator Feel Systems (both of which are also activated in a stall).

But in regards to MCAS, I will simply repeat that Boeing has provided no information that would lead me to believe that it would ever unwind any nose down input. This behavior is entirely consistent with how the Speed Trim behaves in a stall situation, so I think you are looking for something that is not there. I am happy to stand corrected if Boeing every publishes new information to the contrary.

[hawk76]

Originally Posted by GordonR_Cape

Re-posting the AOA chart first posted by LEOCh

Remember, though, this chart was schematic in nature and speculated on what the graph might look like, to illustrate a point about what MCAS was likely doing to achieve its goal. I could be wrong, but I don't think anyone posted an actual plot for the MAX. Still, it is well-informed speculation and to me illustrates the point. And FCeng84's posts on the topic have been particularly enlightening; anyone looking to catch up should search for these.

[GordonR_Cape]

Originally Posted by hawk76

Remember, though, this chart was schematic in nature and speculated on what the graph might look like, to illustrate a point about what MCAS was likely doing to achieve its goal. I could be wrong, but I don't think anyone posted an actual plot for the MAX. Still, it is well-informed speculation and to me illustrates the point. And FCeng84's posts on the topic have been particularly enlightening; anyone looking to catch up should search for these.

Point taken, partly speculation about how it should work! However if you were designing a system that could apply MCAS repeatedly, then unwinding trim would be the first step. Otherwise there would be a high probability of ending up in an irreversible nose-down trim situation, following a series of repeated nose up elevator inputs (even with a functioning AOA sensor). Even the greenest system engineer or programmer would have picked up that issue, though not the more subtle case of stuck AOA data (which everyone focuses on).

It seems likely that most of these documents are under legal lock-down, so we may not know the truth for some time. Equally likely is that when the revised MCAS is certified, the details will be better documented. Either way, there will probably be some degree of training implications.

[SamYeager]

Originally Posted by Icarus2001

I completely agree with your post. The fact that the day before the Lionair crash another crew flew on safely and landed, to be able to write up the defect, speaks volumes.

Supposedly this first crew might well have been amongst the first victims if they hadn't been lucky enough to have a jump seater to point them into the right direction if the rumours are true. Your logic may be suspect.....

[PerPurumTonantes]

Originally Posted by edmundronald

Interestingly, on this forum, pilots seem to blame the Max pilots for not flying their planes, while engineers blame the design and the process. Quite possibly both are correct.

I'm an engineer and a pilot. The responsibility is with Boeing/FAA, no question. Yes the ET302 crew could have done a few things different. But they had 6 minutes. In a little box in the sky, where the wrong answer meant death, with alarms going off, and not just useful alarms but alarms telling them to do the opposite of what they needed.

You train pilots to trust in safety systems, trust in automation, follow the checklists, follow the SOPs. They do this every day successfully for years. Then you expect them to instantly drop this and distrust all the safety systems and automation, work out which one is faulty and what to do about it, while simultaneously hand flying an aircraft that's behaving like they have never experienced before in any of the hand flying they've done.

Boeing had plenty of time, in nice safe offices that weren't about to crash into the ground, to get this right.

[OldnGrounded]

Originally Posted by olster

I think the point (presumably) he is trying to make is that he would not have crashed due to superior flying skill. Basically rubbish of course.

Yes. We have some pilots here who are quite certain that, "It wouldn't have happened to me." This, in the face of what are now mountains of evidence suggesting that it could easily have happened to anyone. Confidence is a good thing for professionals to have. Arrogant over-confidence is scary and dangerous.

[alf5071h]

Perception of risk

Icarus2000 Ethiopian airliner down in Africa
‘The fact that the day before … another crew flew on safely and landed …’

#4287 ‘Your logic may be suspect.....’
The outcome of an event does not alter the risk that existed before the event, nor without mitigation, the future risk.
Just because flights land safely every day does not remove the risk from flying; if thought otherwise then aviation is best be avoided.

[ATC Watcher]

Originally Posted by HundredPercentPlease

They have not considered how HF will affect their operation, in the event of a serious problem.
They are therefore not prepared.

If we just blame the pilots for being a bit crap, then nothing in the industry will improve.
Can we please focus on how we contribute to make the industry better (safer)?

Very well said ! Glad to see some common sense coming back and shifting the discussion to at least half the problem in both these accidents : human factors.
Training on a simulator for abnormal situations to create automatism works well, but not everybody will react the same way when confronted with the REAL emergency.

For instance how do you explain how a 55 years old captain with 16.000h assisted with an FE with 19.500h can reject a take off after V1 (and even VR ) contrary to all SOPs and maybe dozens and dozens of SIM sessions ?
This happened in 1982 with a DC10 , and in that era , incident investigations reports had 20+ pages on human factors . The aim was to understand what went in the head of the captain in order to make the system better not blaming individuals .
PPRuNe did not exist in 1982, but I am sure it it had, there would have been thousands of posts blaming the crew. but the reports says differently..

The report of that accident is on line if you have time to spare, the HF part is very good. : Malaga DC10 1982

[hec7or]

Originally Posted by GordonR_Cape

I do not know of any situation in which an autopilot will bring an aircraft close to a stall.

Try mountain wave at high altitude

I am not a pilot

quite

[Water pilot]

Originally Posted by 737 Driver

When I first got into this business, our manuals used to be far more detailed. We used to say we could just about build the aircraft with the information they gave us. Nowadays, not so much. Someone decided that we pilots didn’t need all the technical details, but rather only the procedures. I’m not in that camp, but no one asked me. If not for these accidents any information that Boeing would have provided the pilots on MCAS would have been just as generic as the information they currently give us on the Speed Trim and Elevator Feel Systems (both of which are also activated in a stall).

But in regards to MCAS, I will simply repeat that Boeing has provided no information that would lead me to believe that it would ever unwind any nose down input. This behavior is entirely consistent with how the Speed Trim behaves in a stall situation, so I think you are looking for something that is not there. I am happy to stand corrected if Boeing every publishes new information to the contrary.

Well, given that they didn't even tell you about the system in the first place, I would be a little reluctant to conclude that they have told you everything about it now. However, I certainly hope that by the time the plane is certified again pilots will know more about MCAS than the project managers at Boeing knew during design.

This really has the feel of the sort of thing I have been unfortunately involved in (not aviation), the "we aren't exactly going to lie about this but it raises uncomfortable questions so let's hide it under the rug" patch to save the project once the company is committed to a course that in retrospect was not the best solution to the problem. Engineers realize that if they talk about it too much they are going to be tasked with updating the copyright notices on 10,000,000 lines of code and baby-sitting the 3a.m. builds. The cynical ones accept it because the project is so %#@!! already that it doesn't stand a chance of working anyway.

That sort of mentality takes a long time to get over and I still feel some of that energy coming from Chicago. What exactly "minor control surface" issues were also fixed in this latest patch?

The good news to a Boeing supporter on the horizon is that they are writing off $1 billion for the repair (supposedly not liability) which to me sounds as if it is more than a 1/2 hour software upgrade. That sort of money sounds like a hardware fix, which is what I think they need.

[hawk76]

Originally Posted by HundredPercentPlease

If we just blame the pilots for being a bit crap, then nothing in the industry will improve. We need to understand why these pilots, despite all of their efforts, could not keep the aircraft from the ground. Only when we understand, can we make the correct changes to stop it happening again.

If we just blame Boeing for being a bit crap, and ignore pilots, then nothing will improve, either.

Can we please focus on how we contribute to make the industry better (safer)?

I think that is what we're trying to do. It's not clear to me why the fault has to be all Boeing or all pilot. Why some say that as soon as the AOA vane went, the plane was doomed. To me both pilot and plane have some fault, and to be fair, part of that fault on the pilots may be due to insufficient training. But let's consider all possibilities without making offensive ad hominem arguments seen in a lot of posts on this thread. Then we may have the better understanding you mention.

[737 Driver]

Originally Posted by GordonR_Cape
I do not know of any situation in which an autopilot will bring an aircraft close to a stall.​​​​​​

Also any flight with the autothrottles on placard.

[PerPurumTonantes]

Originally Posted by 737 Driver

The notable exception was AF447 - loss of airspeed, confusing alerts, systems reacting in ways the pilot flying wasn’t expecting, improper crew response, followed by a hull loss and major loss of life. This was another clear example of the pilots’ failure to revert to basics and fly the aircraft. Their ethnicity or employment at a major European carrier granted them no special protection from a failure of airmanship.

AF447 is not really comparable. The aircraft did not actively try to kill them. The AF447 crew's actions were less competent than the ET302 crew. Continuous back pressure stalling the a/c all the way down?

AF447 crew crashed the aircraft (with a bit of help from Airbus' sidestick design). Whereas ET302 the aircraft crashed itself despite the crew's efforts.

[michaelbinary]

All the armchair pilots giving it large, they should have done this or that or the other are talking crap.
This whole thing was about money and how to spend as little as possible.
Boeing producing an aircraft not fit or safe to fly without extra added systems to correct the inherent pitch instability.
Boeing for not telling about or training the pilots what MCAS was or did and how to defeat it.
Boeing for not designing any redundancy into the system or cross checking with other systems.
Boeing for not testing the system and/or the software that controlled it properly or extensively enough to cover all eventualities
Boeing for not having a bloody OFF switch that allowed the pilots to fly the plane when all else fails.
FAA for being complicit in allowing Boeing to self certify an aircraft (WTF ?)
US Government for being complicit in allowing FAA and Boeing to act that way.

All these organisations should be completely ashamed of themselves, there was nothing wrong with the aircraft at all, but the computers didn't allow the pilots to fly it.
I hope Boeing, gets the arse sued out of it, by everybody, they deserve it.

Now for all those clever dicks on here who think the pilots should have done this or that or the other. I reckon from reports, the plane was around 9000 ft AMSL which is about 1342 ft AGL. In that time an object in free fall will take about 9 seconds to hit the ground. So before you finished reading the third line of this post you would be dead. Good luck in fixing a problem in a system you were not trained on or even told about.

[MurphyWasRight]

Originally Posted by michaelbinary

All the armchair pilots giving it large, they should have done this or that or the other are talking crap.
This whole thing was about money and how to spend as little as possible.
Boeing producing an aircraft not fit or safe to fly without extra added systems to correct the inherent pitch instability.
Boeing for not telling about or training the pilots what MCAS was or did and how to defeat it.
Boeing for not designing any redundancy into the system or cross checking with other systems.
Boeing for not testing the system and/or the software that controlled it properly or extensively enough to cover all eventualities
Boeing for not having a bloody OFF switch that allowed the pilots to fly the plane when all else fails.
FAA for being complicit in allowing Boeing to self certify an aircraft (WTF ?)
US Government for being complicit in allowing FAA and Boeing to act that way.

.

A few more for the mix:
Boeing for minimizing the changes in the emergency AD to keep the "covered by existing procedures" and 'just like NG" myths alive..
Boeing for REMOVING the OFF switch, 737 NG right hand trim cutout of automation only, MAX either switches cut all electric trim.
Boeing/others? for removing training on unloading to allow manual trim when severely out of trim. (roller coaster)
Boeing for providing an emergency backup manual trim system that could not be operated under some out of trim conditions.

Penultimate Lion Air pilots for the as yet unexplained minimal write up that led to AoA sensor not diagnosed/corrected.

Unknown at this point cause of Lion Air sensor reading 20 degrees offset not detect during post instal testing.

As some have suggested it is possible that ET crew awareness of MCAS may have been a factor, impossible to say of course what would have happened had they been the first to experience this.

[Bend alot]

Also MCAS was documented at 0.6 for certification, but in reality is it was 2.5.

[Water pilot]

Originally Posted by MurphyWasRight

Penultimate Lion Air pilots for the as yet unexplained minimal write up that led to AoA sensor not diagnosed/corrected.
.

I thought that the sensor had been replaced before the fatal flight, or am I mistaken? My understanding is that there are three failed sensors, not necessarily for the same reason.

[Water pilot]

Boeing still does not get it.

Boeing CEO denies any 'technical slip' in 737 MAX crashes

Boeing chief Dennis Muilenburg denied Wednesday that the two recent crashes of the 737 MAX were due to any “technical slip” by Boeing during the jet’s design or certification.

Muilenburg conceded that erroneous information was fed to the airplanes on both flights by a faulty sensor on the fuselage, and that this false signal activated a new flight-control system on the MAX that repeatedly pushed the jet’s nose down.

Still, he adamantly denied that any fault in the design led to the deaths of the 346 people aboard the two planes.

“There is no technical slip or gap here,” Muilenburg said on an early morning conference call with Wall Street analysts following release of Boeing’s first-quarter earnings. “We understand our airplane. We understand how the design was accomplished, how the certification was accomplished, and remain fully confident in the product.”

So they understood that a single failure of a sensor would cause the plane to pitch nose down shortly after takeoff and they did not feel that it was necessary to inform pilots of this quirk? The words "reckless disregard" come to mind.

I understand that the CEO is trying to walk the line between what he wants to say for the lawyers (" not our fault, just a coincidence that two horrible pilots crashed our new design plane") and what he wants to say for customers ("we are on it, figured out the problem and now we have it fixed") but in my opinion he is failing as badly as the engineers. Liability for the two crashes is the least of Boeing's concerns at this point. Statements like this do not give me confidence that they are really interested in finding and fixing the fault, since they do not want to admit that there is one.

[Icarus2001]

Yes the ET302 crew could have done a few things different. But they had 6 minutes

No, the six minutes was the result. Had the PF used electric trim ANU they could have had as much time as they wanted to try a memory item, like turning off the trim system.
Some aircraft do not have a manual trim wheel, this one does. Get the trim somewhere near correct with the electric trim switch and then turn off the trim. As 737 Driver keeps saying, this is not test pilot territory. It is basic flying skills, trim away the pressure.