By Bjorn Fehrm
October 28, 2019, ©. Leeham News: Tomorrow it’s one year since the crash of Lion Year JT610 into the sea in Indonesia. The aircraft which went down was a brand new Boeing 737 MAX 8 and the world was stunned how such a new aircraft could crash.
The crash triggered the deepest crisis in Boeing’s 100-year history and revealed shortcomings in Boeing’s and FAA’s airworthiness work and supervision. The Lion Air JT610 final report was issued Friday and we now know what happened.
The report is giving detailed information about what happened and also investigates the chain of events that led to the crash. Based on these investigations it points to deficiencies and makes recommendations in the following areas:
Boeing issued a press release Friday where it said it has cooperated with the investigation and have done changes to the aircraft in the areas recommended in the report and that the verification of these changes have undergone “an unprecedented level of global regulatory oversight, testing and analysis”.
The tone in the press release is very different from earlier Boeing communication regarding MAX and the crashes:
“We commend Indonesia’s National Transportation Safety Committee for its extensive efforts to determine the facts of this accident, the contributing factors to its cause and recommendations aimed toward our common goal that this never happens again. We are addressing the KNKT’s safety recommendations, and taking actions to enhance the safety of the 737 MAX to prevent the flight control conditions that occurred in this accident from ever happening again.”
No comments about Pilot proficiency or Lion Air’s questionable maintenance work around the MAX problems, even though these areas are pointed out as lacking in the report.
The changed tone is coming over as more convincing and more appropriate, a Boeing focusing on the problems in their own domain. It took a long time coming though.
We will run a series of Bjorn’s Friday Corner articles where we go in detail in all the areas listed above. The report clears a number of areas where there wasn’t enough information before. It will also analyze Boeing’s change work around MCAS in more detail.
Yeah, it appears that Mr Muilenburg had a different “approach” last November.
Not having read the report, did they mention how they came to the “conclusion” the mechanic did not perform a functional test of the pitot probe after Installation?
I just wonder if they were somehow able to verify this or are assuming that this is the case, since it did not work properly the next flight?
FAA Response is remarkable, report Comes out and they yank the license for the maintenance shop but no reaction in the direction of Boeing.
Flog the Little guy (who might have deserved it) but the big Player gets off scott free.
Sorry, but my Computer seems to be throwing in capital letters in randomly on its own and it is just too much of a PITA (pain in the …) to correct it.
Lack of documentation on the checks as well as the result (and the same from the repair shop)
It would have been beyond arrogant for Boeing to mention the faults found in other actors in this Scenario, even for them.
Sad that they need to be commended for a “fitting” reaction that should be so obviously self evident.
But I note they are still pushing their Agenda that they have corrected all of their Problems (a long time ago, it seems to imply) and are almost ready to go ASAP. Or are they really going to Change something else as a result of this report?!
Boeing did so initially despite having the preliminary report in front of them.
I wonder how we today would look at the Lion crash, if their hadn’t been a second crash.
Would thourough research and investigations have surfaced the issues we know today?
Or would it have been the “Lionair crash” (crew, maintenance, safety record) similar to TK1951, FZ981.
1. “Most likely the fault was a result of inappropriate maintenance of the sensor”
From my reading of the final report.
a. It appears the mandated response to the (report named company) pilot logged problem, an AOA error and no MCAS connection mentioned, was followed.
b. The item was checked (by a report named company) engineer and found to be unusable and hence required replacing.
c. Not having a replacement in stock one was ordered from the (report named) local supplier.
2. ” followed by a not performed functional test by the installing (by a report named company) mechanic.”
From my reading of the final report.
a. there were two acceptable methods of “certifying” the replaced item.
b. The first was to utilise a certain piece of equipment. Which the (by a report named company) did not posses.
c. The approved “alternate” method was performed and was recorded as passing the certified requirements.
3. The maintenance shop’s license was withdrawn by FAA Friday.
From information published after the report:
a. The name of the manufacturer/repair shop, who sold the item to the local supplier, has been published and been decertified by the appropriate licensing authority the FAA.
Why did you fail provide, the now published, source of the certified AOA sensor? It appears to have been an American company.
As many have previously stated, out of range AOA sensors are not a new phenomena. Many pilots have reported them historically and used their piloting skills to overcome them.
Unfortunately in the MAX that option of ignoring the faulty AOA sensor is not available, MCAS takes over control and through it’s actions, hundreds of people died.
The pilots had no knowledge, warning, training or experience even in a simulator to fall back on, the memory stick response and no quickly found page in the on-board help manual or in the electronic “training app”.
you are wrongly about your statement that the poilots couldn’t be ignored is wrong.
One option is to use the cut-ot switches, which they did on the previous flight; – they continued to the destination. As well would the use of the yoke Hstab switch ‘silence’ MCAS, and able to move the Hstab ANU (as the captain did perfectly, but the FO failed). The latter method could at least be used for a return to the departure airport, – which instructions said they should go.
What puzzles me the most is that the EA flight crew failed FIVE months later, when the same thing happened. So it’s perhaps some sense in the letter that the NTSB sent the FAA about their concerns around todays pilots skills when it comes to fly manually.
The root cause of the accidents is the flawed 737MAX MCAS system that was added to the existing 737NG avionics in order to disguise the behavior of the airplane, so that it would appear to 737 pilots that they were flying the 737NG.
Neither the 737NG and the A320ceo/neo have nowhere near the same accident rate as the 737MAX. Perhaps you should be “puzzled” as for why the 737MAX is an outlier. After the second fatal crash in less than five months, nearly every aviation regulator around the world grounded the 737 MAX — with the FAA 737MAX grounding order coming into effect later than all other major regulators. Since the point of entry into service, no other commercial aircraft has been implicated in as many fatalities so rapidly for the last 50 years.
Now, what is puzzling is how far some people are prepared to go in slandering the dead, non-American pilots of the two 737 MAX planes that crashed, with allegations/accusations of incompetence.
First; I was just commenting on a statement that in my view was incorrect. It was (is) possible to stop a runaway Hstab. A runaway Hstab can be caused by other system failures/upsets (than an MCAS going bananas).
Second; of the three AOA/MCAS incident/accidents they came in a sort of ‘wrong order’. A normal learning curve should have the flight that recovered from the situation last.
Third; I have not stated any opinion to who (solely?) caused the two accidents (persons, organizations or company). However, I may have opinions on that! I prefer to learn what happened and what can we do to avoid similar accidents. Follow the spirit of IACO annex 13, as given at the bottom of page 02 in the final report, – that’s me! (but as the saying goes: we are all different).
You say you have no opinion as to who (solely?) caused the two crashes (persons, organizations or company) — yet, you managed to flatly state in your previous comment, that what puzzles you “the most is that the EA flight crew failed five months later, when the same thing happened”.
It wasn’t the pilots who failed. Boeing designed the MCAS system so poorly that it made it extremely difficult, if not impossible, for the pilots to handle it in the available time.
Flatly stating that the “EA flight crew failed five months later” — in such circumstances — is IMJ, nothing else but slander.
What is clear, is that the crews were just overloaded with information. The NTSB’s recommendations, for example, seem to bear out that theory. It says that during simulator tests, Boeing assessed pilot responses to a generic MCAS failure. But it did not incorporate the kinds of problems that could lead up to such a failure. This meant that when the real thing happened, pilots were faced with a variety of alerts and warnings that had not occurred in the simulator — or that they were trained and prepared for — linked to the sensor failure that caused the MCAS system to be erroneously activated. As a result the pilots didn’t respond in the way Boeing had assumed they would, and did not immediately take the steps it had assumed they would take.
I think we are living in a new world. The skill and competence levels we could once expect and assume in a western setting and considered normal is perhaps no longer to be accepted. Aircraft need to be built to a new standard that reflect that they will be sold in nations struggling to emerge into a technological society. MCAS implementation was very flawed but its likely that in a US Airline the repeated sensor fault alerts that preceded Lion Air 610 for weeks would not have been ignored, some kind of 5-Why Analysis performed, the sensor replaced. The crew more likely to have reacted and recovered the aircraft. At that point Boeing would have been alerted to the flaw. MCAS flaws may never have developed in US maxes simply because of more proactive maintenance. Nevertheless I’m not exonerating MCAS as acceptable. My view is that the way that the lack of redundancy was as much a part of the MCAS problems as the lack of two sensor action. MCAS really needs 3 sensors so that these kinds of intermittent faults are much less likely to become lethal because such faults tend to be ignored or reset till they become hard faults.
William and OV-099,
may I suggest that we leave it here? Instead I highly recommend Peter Lemme’s website Satcom.Guru. Peter just published another in-depth article dealing with the JATR report and the LA accident final report. Worthwhile reading (absolutely in comparison to us continuing our exchange of views).
Imagine yourself an Airline Pilot, flying the 737 today, and tomorrow Boeing comes out with an announcement that they’ve cleared with the FAA. Because of the additional safety benefit’s of the newly enhanced MCAS II, they will be retrofitting every 737-NG in your fleet, there will be no additional training required, the change will be a simple software upload taking an hour, and a small hardware fix, that you’ll only notice the stab trim cutout name plate nomenclature changed. Would you have any questions and what would they be?
Why talk about AoA. A single sensor crashed it. Complete Boeing’s fault.
Yeah, blame the pilots with 100 lb around their necks. Ask Sullenberger.
WOW, the license of the maintenance shop. How many regulations were not respected by Boeing.
This is Boeing alone, they need to follow regulations.
Then FAA, Congress, Presidents should put safety first.
Does anyone know if the AOA sensors that Xtra Aviation (the maintenance shop that the FAA closed down), repaired in the last year will be tracked down and tested again? I would assume that is standard operating procedure in cases like these? And then to report how many other failed AOA sensors were found out there in the field.
The calibration issue was identified well before the Ethiopian crash – from WSJ Dec 2018
Is there any possibility that Lion Air and KNKT received some compensations to SUGGEST the fault is from the maintenance shop.
FAA accepted this theory and withdraw the license of the maintenance shop !!
At this stage I cannot swallow the story … for small repairs to be done in few hours it takes 5 month to get another accident of the same type and more than a year to get the MAX flying again
I am probably wrong somewere !!
Follow-up comments most welcome to put me on the right path again !!
That was the AoA sensor from the previous flight
and KNKT gave it to the US NTSB. But why …
When making accusations of gross corruption and violation of multiple civil and criminal laws in at least two nations one is generally expected to provide some evidence. Note: asserting that the accusation is “self-evident” is not considered evidence of anything other than begging the question.
Inquiring about a possibility is not the same as making an accusation.
For example: “Is it possible that John killed Jane?” is not an accusation…it’s a request for informative input.
In context and how you phrase it means volumes.
Have you stopped bearing your wife yet?
Is it possible Admiral Prune is into the Tin Foil?
Please explain me what means “into the Tin Foil”
as you will understand I am not so familiar with english slang
Known as conspiracy theorists, the tin foil shields your mind from government looking into it.
It was not intended to be an accusation … just a question to which I would like to recognize it is a stupid one !!
I take it as an accusations the way presented.
No difference between that and asking you if you have been into the Tin Foil.
Unless there is a indicator in the report then asking about their political leanings, what dogs they own, are they skimming company money is off the table.
A few questions should be asked to Boeing:
– On the evening of Day One of the Lion Air crash, with few but significant evidences, did their technical team came to conclude that MCAS could be the primary cause ? Or did they think “oh, well, another Lion Air accident, who cares..”
– On Day Two, why did not Boeing ask the FAA to issue an Emergency AD to inspect and double check the AoA sensors at frequent interval (eg. every week) and everytime a repair or replacement was done ?
– On Day Three, why did not Boeing directed its software team to produce an emergency patch on the MCAS logic which would have been quite simple:
a) do not trigger MCAS if input from AoA sensor is obviously out of the flight enveloppe (eg. > 30°)
b) do not trigger MCAS if input from the other AoA sensor is significantly different
c) do not trigger MCAS more than once or twice each period of eg. 10 minutes
If any of these decisions would have been taken, the Ethiopian accident would probably not have happened. And no grounding.
Failure to take these decisions, or worse, a management decision to do nothing and stay quiet, appears to be criminal in retrospect.
Aviafun, I agree whole heartily. Not just 3 days, but, 3 weeks, or 3 months, but, only an AD warning pilots to do a runaway trim memory item, if a bunch of things seem incorrect at the same time. With a stick shaker activating immediately after takeoff, pilots are focused on trying to keep the plane flying, not diagnosing if this is a false AOA problem. Ethiopian pilots did recognize the issue correctly, and went down Boeing’s checklist, and Boeing hadn’t done any of the items you have mentioned, or given then an OFF switch for MCAS, so they were in effect doomed. Boeing failed in the design of MCAS, in the immediate aftermath of the Lion Air crash, and also in the immediate aftermath of the Ethiopian air crash. And now they expect us to trust them, after not describing the problem fully? After not telling airlines about MCAS at all initially? They need to be fully open and above board with their MCAS 2 fixes, along with a full, detailed, explanation of the problem that they are fixing.
“We are addressing the KNKT’s safety recommendations, and taking actions to enhance the safety of the 737 MAX to prevent the….”
This is a partial quote, I will note they still have the “enhance the safety ” phrase in there.
It needs to be removed totally and re-stated with full up front acknowledgement or just removed.
The conclusion is the maintenance crew were incompetent and the flight crew were incompetent and many people died.
No, there are issue and contributing causes involved in this crash, but the main conclusion is if not for MCAS, the rest were routine (sadly)
most incompeten of all: Boeing
“flight crew were incompetent ”
No they were trying to fly the Max like it was a 737 NG, like they were told it was. Even if they followed every check item( and with hindsight ignoring the false warnings) the manual wheel couldnt have controlled the plane in the way it was supposed to in the time available.
The Max was certified with a new subsystem that took control from the pilot ( in a violent manner) and it relied on a single sensor from one side of the plane only. That should have never been certified . Thats what crashed TWO planes and pulled the fleet from service. And thats why all those original certification ‘lapses’ have been fixed.
That sums the whole scinario perfectly The new subsystem was not included in the FCOM and none of the pilots where instructed on the operating procedure. Hopefully this problem is fixed quickly and the Aircraft can once again fly safely. Blaming the flight Crews as incompetent is very negative and people who put this out really need to do a better background check on what happened and then make a informed statement
The “incompetent flight crew” label doesn’t convince me: LionAir has 102 737 NGs, and they take off and land every day without continuous incidents. On a similar note, Ethopian Airlines has an excellent safety record, and it has 22 737 NGs that take off and land every day without incident.
However, we know since March that even “competent” flight crews in the USA registered multiple complaints on a federal whistleblower site, including remarks such as “Flight manual is ‘inadequate and almost criminally insufficient'”, after serious in-flight activations of MCAS. Seeing as there were fewer MAXs flying in the US than outside the US, it was perhaps only a matter of time before there was a fatal incident with a US carrier.
If we go back to the 737 rudder issues in the 90’s, most of the crashes occurred on US carriers. How come nobody is labeling those flight crews as incompetent?
How do you produce a ‘competent’ pilot? Most flying doesn’t involve extraordinary skill. It does involve eye-hand coordination, knowledge, discipline and judgement. Most can be taught and absorbed, but, it’s tough to teach judgement and temperament. A friend of mine ran a flight school with a military contract to evaluate potential military pilots. The students were mostly graduates from the various military academies. A lot of his instructors were former military pilots. It was a good program to see who had the ‘right stuff’ before entering expensive military flight training programs. The students who passed had almost a private pilot level of training before they started into the military training program, those that washed out, saved the military money. A well trained pilot, I flew with had an always push-it-to-the-limit temperament. With not enough judgement as to safety. He had graduated from the Navy’s test pilot school and had been working with a few flight test programs. But, he’d brag about busting hard deck floors and saved the aircraft when in a spin, etc. I felt uncomfortable flying with him a few times when he’d do a maneuver at too low an altitude for safety. He finally pushed his luck too much and died in a crash at low altitude, taking a few people with him (non airline flight). So, how do you evaluate a competent pilot? I say, put them in a simulator, train them on the aircraft for a bit, so they are familiar with it, and then see how precise they can fly, and then how they deal with emergencies. They have to demonstrate the ability to recognize the event correctly, and properly deal with it. But, how do you evaluate their judgement and temperament from that? Will they take off when weather or other conditions say they shouldn’t? Will they challenge maintenance personnel when a questionable log entry is found? Will they challenge a senior pilot when they notice a possible problem? (should I have reported the push-it-to-the-limit pilot to someone? Most all knew his tendencies, as he didn’t hide it.) Is a 250 hour, well trained pilot good enough to fly the line, or does he need seasoning to instill better judgement? 500 hours of being a flight instructor? 500 hours of flying freight in a light twin? I don’t think there is any perfect answer, the best may be some sort of formula.
I completely agree with your comments.
My use of the word “(in)competent” was only with reference to what other commentators had posted above.
I find that a plane should be “flyable” by any certified pilot…and that includes Joe Average as well as Capt. Sullenberger. If a manufacturer starts bitching about inadequate pilot competence, then that points to a crappy plane rather than a crappy pilot.
“However, we know since March that even “competent” flight crews in the USA registered multiple complaints on a federal whistleblower site, including remarks such as “Flight manual is ‘inadequate and almost criminally insufficient’”, after serious in-flight activations of MCAS.”
Do you happen to have a source for this? I would be very interested to read about these incidences because I was not aware that anything like this occurred.
incidents instead of incidences
This goes for both my posts, above and below.
Apparently I’ve got angles on the brain.
Here’s a link on CNN, but there are lots of similar links on other news sites. It was a big item in March.
It’s interesting to note, I assume (I have an email in to NASA asking about this) since the 737-MAX has been grounded, there is no ability to search via 737-MAX or 737-7,8 or 9. It’s as if the plane never existed. You can select the 737-800, the 737-NG Series etc, but, no MAX. Since no one if able to fly them, there is no ability to report on them, or view part reports on them.
I did a little sleuthing and did find a mention of a 737-MAX in a report of wake turbulence. ATC was wondering if the MAX had undergone any wake turbulence testing to see if it should be classified as a ‘heavy’ aircraft. It’s only one report, that is speculative.
BTW, the 737-MAX was labeled as
“Make Model Name : B737 Undifferentiated or Other Model”
in the aircraft type search box
[EMB-145] was inbound. While level at 7,000 at 230 knots on the STAR [he] asked for an immediate descent. Once descended I asked [him] for the reason for descent request, and he reported severe turbulence. This seemed odd to have severe turbulence reported on a very active STAR with no other previous reports of any turbulence from other aircraft. I disseminated the PIREP and solicited more reports from other aircraft in the area. All other aircraft reported a smooth ride. I then realized the [EMB-145] was 5 miles in trail of a [B737-8 MAX], who was on the same STAR at the same altitude. I suspect [the EMB-145] was actually experiencing wake turbulence behind the [B737-8 MAX].
I’m unsure what kind of testing is done with these newer aircraft, but for an EMB-145 to experience severe turbulence being 5 miles in trail of a [B737-8 MAX] I’m concerned about this weight classification. I recommend further testing is done on the [B737-8 MAX] aircraft in terms of their weight class and the amount of wake they produce. If it is determined that these aircraft are creating significant wake turbulence to have an EMB-145 report severe turbulence while 5 miles in trail level flight at 230 knots, then I think reclassifying them as heavy aircraft may be necessary.
N90 TRACON Controller reported receiving reports of wake turbulence from an EMB-145 flight crew on arrival into LGA 5 miles in trail of a B737-8 MAX. Reporter expressed concern that the B737-8 MAX may have to be classified as a heavy jet for wake turbulence separation purposes.
Peter, the incidents described in the link you provided are not MCAS related. They occur when the autopilot is active, which we all now know precludes MCAS activation. So while these whistleblower complaints bring legitimate potential safety concerns to light, they clearly have nothing to do with the MCAS function.
Two comments on that:
1: Who says MCAS can’t operate on AP? Boeing? And you believe that? Boeing also told us that the AOA disagree light was connected.
2: Any other mechanism that can cause anomalous, uncommanded nose-down movements on the MAX? Does MCAS have an evil twin of which we’re (as yet) unaware?
Peter, Mike, EASA, back in July, wanted Boeing to take a look at the lagging A/P response. Of course, I don’t know if Boeing is looking at this, fixing it etc.
Peter, Mike, In the article, it seems to imply that when MCAS is active, it’s difficult to turn off the Autopilot. Which would imply that MCAS is active even when the Autopilot is on. How would you test this? Is there a way to program an A/P to stall?
Investigations have concluded that pilots who encounter a stall scenario relating to the Manoeuvring Characteristics Augmentation System (MCAS) or similar flight control emergencies have difficulty disconnecting the autopilot.
Bloomberg notes the autopilot doesn’t completely disconnect. This could mean the system is designed in a way to work with MCAS so closely it still believes it has greater authority than the pilots.
Richard, I take my hat off to you for your thoroughness 🙂
I imagine that the problems with MCAS are so convoluted that Boeing itself doesn’t understand them, yet alone anyone else. This may explain why it’s taking so long to submit a definitive MCAS 2.0 to regulators…God only knows the gremlins that have been discovered by digging around in the software/hardware. I certainly think it would be prudent to question EVERYTHING that Boeing has said about MCAS. Let’s hope that engineers at the FAA and EASA are thorough enough to expose the full extent of the rot.
One of the senators said in Muilenburg’s hearing yesterday that he’d rather walk than get in a 737MAX. I completely agree with him. I severely doubt that that plane can ever be made safe again.
In response to your two comments:
1) The KNKT enlisted the help of the NTSB to evaluate the MCAS function within the STS. Take a look at the NTSB System Safety and Certification Specialist’s Report which is reprinted in Appendix 6.2 of the KNKT Final Report starting on pg. 245. So, I believe the NTSB. Are you suggesting that the NTSB has somehow been hoodwinked by Boeing? Besides, it makes no sense for MCAS to operate within the AP. Why would the AP ever fly the aircraft close to a stall?
2) There could possibly be an issue with the AP not working correctly for whatever reason. However, this does not mean that the issue is related to MCAS in any way.
Mike, in reply to your points:
1: Yes, I believe it is quite possible that Boeing hoodwinked the NTSB. After all, they appear to have hoodwinked the FAA, so why stop there?
On the subject of whether or not it “makes no sense for MCAS to operate within the AP”, one can equally assert that there’s also no sense/logic in giving MCAS a single point of failure, or in giving it infinite authority, or in giving it repetitive authority. And yet, all those senseless aspects were present in MCAS.
2: There could indeed be an issue with the AP, as you suggest, but it’s eerily familiar that the plane made anomalous, uncommanded nose-dips, which the flight crew could not explain after reference to the documentation. I also note that there has been no discussion in the press of an AP issue…so, either this is MCAS in disguise, or we can now look forward to an unresolved AP issue in the re-certified MAX.
Of course, due to a severe lack of useful information, we can only speculate at present.
If you honestly believe that Boeing successfully fooled the NTSB, arguably the world’s premier accident investigation authority, then they can fool the BEA, BFU, AAIB, and any other investigative authority. Fooling regulatory authorities, like EASA, would then be a cinch. So you believe that no authority on earth can ever get the bottom of this? This is in the realm of conspiracy theories.
If the NTSB says that MCAS and STS operate a certain way, then I believe them, of course with the exception of possible bugs. In their deep dive into original MCAS, they describe how it actually works, and how it is part of the STS that is only active during manual (AP disengaged) flight.
What do you mean there has been no discussion in the press of an AP issue? The very links that you posted revealed this issue and the Bloomberg article that Richard cites talks about how EASA is aware and has made correcting it an additional condition for MAX return to service.
So, I highly suspect your assertion that there were all these “serious in-flight activations of MCAS” (other than the 2 crashes and the previous Lion Air flight) is based on something other than known reported facts.
“Fooling regulatory authorities, like EASA, would then be a cinch.”
– Well, they fooled the FAA.
“So you believe that no authority on earth can ever get the bottom of this? This is in the realm of conspiracy theories.”
– No, I don’t believe that. But an authority can only make findings based on the information at its disposal. I can’t say that I’m convinced that Boeing has provided all relevant information/materials.
“if the NTSB says that MCAS and STS operate a certain way, then I believe them”
– That’s your prerogative.
“What do you mean there has been no discussion in the press of an AP issue?”
– The operative word here was “discussion”. There was been some summary MENTION of the issues in the press, but any meaningful DISCUSSION of the issues has been elusive. Compare that, for example, to the flood of discussion that we have on the role of AOA sensor failure, or trim wheel shortcomings.
“So, I highly suspect your assertion that there were all these “serious in-flight activations of MCAS”…”
– I’ll re-phrase my original statement to more generically indicate that pilots on US carriers have reported anomalous, uncommanded nose-down issues that they could not explain on the basis of the manuals at their disposal and that caused them to make vexed statements about the adequacy of the information with which they were provided.
There’s no real point in having a further discussion of the matter, since it’s basically a question of you believe X and I believe Y. We’ll see what time will eventually tell us.
Peter, Mike, The reason Boeing changed the Stab cutout switches on the MAX, may be related to the MCAS/auto pilot … There’s an explanation (not by Boeing), that the reason for the change is that in the past the left cutout switch cut out the manual yoke trim switch and the right cutout switch cut out the A/P (including speed trim?) on the 737-NG’s and previous versions of 737’s. On the MAX, the left cutout switch may cutout the manual yoke trim switch AND the MCAS part of the speed trim system, but, still leaving the A/P and other normal speed trim cutout’s to the right cutout switch. That’s why Boeing renamed the switch panel. Boeing is not saying this, and it’s only a working theory, but, may explain the puzzling decision to change the stab cutout switches. So the Speed Trim system has been rewired for the MAX in terms of the column cutout switches being out of the loop and the stab trim cutout’s being possibly changed. With A/P off, supposedly MCAS is not active, but, other parts of the speed trim system are?
On a typical takeoff, the speed trim comes alive at low speed helping the pilot maintain a constant speed setting until flaps up.
At that same moment, MCAS comes alive, as the speed trim shuts down. We really don’t have good documentation on the MAX changes from the NG. This is partial guesswork, because of the lac of detailed changes from Boeing. I’d love to see the speed trim /MCAS system flow charted out in detail. There are delays of about 10 seconds programmed in after a pilot issues a manual yoke trim command, to either the STS and/or MCAS and also I believe airspeed and stabilizer come into the mix as inputs for STS. We’re really trying to figure out MCAS settings, inputs and outputs using what Boeing has said and trying to black box the rest using what has been previously published about the NG, but, why the switch changes is all speculation at this point.
The text you post are the words of Sam Chui, “one of the world’s most followed aviation bloggers” and “also a world renowned content creator (vlogger)”. So he’s a guy who blogs about traveling the world and probably has some familiarity with various aviation issues but, as far as I can tell, has no real technical experience. I’m surprised you would consider his opinion on par with that of the NTSB experts when it comes to explaining or interpreting incidents involving aircraft flight control systems. If there was some sort of convolution between MCAS and the AP then don’t you think the NTSB would be all over it by now?
Here is the only quote in the Bloomberg article cited by Sam Cui that talks about EASA’s finding regarding the AP:
There is no mention of MCAS. Stall is mentioned but I find that confusing in the context of an AP. Perhaps EASA is concerned about a disruption emergency occurring while the AP is engaged that then requires the AP to be disengaged before the crew can recover.
Anyhow, the NTSB says that MCAS is part of the STS and that the STS is only active when the AP is not engaged. This makes perfect sense because the these flight control laws are only needed to help the pilot. These laws aren’t needed to “help” the AP because the AP has it’s own independent control laws that don’t need to cater to a pilot.
This post on Satcom Guru by Peter Lemme gives a pretty good description of the stabilizer trim systems on both the NG and the MAX. It has diagrams if you’re interested in slogging through them all. I made it through all the NG related ones and Half the Max related ones before I had to start skimming.
Left console stabilizer cutout switch is labeled MAIN ELECT and cuts off all electrical power and control signals to the stabilizer motor.
Right console stabilizer cutout switch is labeled AUTO PILOT and cuts off the control signals from the FCC to the stabilizer motor.
The distinction between autopilot and speed trim happens in the software on the FCC. Speed trim is only active when autopilot is not in command mode. Both functions control the stabilizer through the AUTO PILOT cutout switch. So, switching AUTO PILOT to CUTOUT will block both the autopilot and speed trim, like you suspected.
Left console stabilizer cutout switch is labeled PRI (for primary) and cuts off all electrical power and control signals to the stabilizer motor.
Right console stabilizer cutout switch is labeled B/U (for backup) and does exactly the same thing as PRI (they are wired in series).
The distinction between autopilot and speed trim again happens in software on the FCC just like for the NG and speed trim is only active if autopilot is not in command mode. Since the MCAS function is implemented in speed trim, it also will only activate if autopilot is not in command mode.
Mike, So, with the A/P on, the speed trim system (including MCAS is off). Does that mean that the A/P uses a separate system to run the horizontal stabilizer from? Or does it completely ignore speed as it’s controlled by the auto-throttle then?
As far as Peter Lemme writes, no. Both the A/P and STS with MCAS reside as software in the FCC. They use the same signal path to control the stabilizer.
I don’t know any specifics on how the auto-throttle is controlled.
After searching for sources to support your claim “…after serious in-flight activations of MCAS” I couldn’t find anything. I did find several references to a handful of whistle-blower complaints on a Federal site that talk about the inadequate flight manual and some AND incidences when the autopilot engaged but were resolved after disengaging. We know now that MCAS never activates when the autopilot is engaged, so not MCAS related. Are you sure you have your facts right?
incidents instead of incidences
I did it again.
In the right hand corner (picture); is that you shooting a handgun?
In today’s climate that is a loaded question.😀
Yes. It was at night while a colleague took the picture with an open shutter and an acoustically triggered flash.
Here are alternative links:
Again, neither of these links describe incidents related to MCAS. They are describing the same two incidents involving the autopilot.
I guess my perception is still correct, that there were no significant MCAS related incidents reported in the media other than the 2 instances with Lion Air and the one with Ethiopian.
It reminds me 737 crash in the nineties
It was in Indonesia
The pilot was said responsible
Numerous AD’s and modifications were triggered by inadequate rudder’s design
just from memory !!
Where did they learn to “pilot” an aircraft?
BELIEVE … the same word to express doubt and certainty
I believe it’s going to rain … I believe in God
not so usefull word in LNA