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737 MAX future
Notice all 3 threads are closed , a good mod decision to merge the 3 , and indeed some of the discussions became a bit personal but these threads have seen very valuable discussions and were a very valuable source of info from the US newspapers covering the issue ( WSJ, NYT and especially Seattle times) which are not all available in many countries.
With the aircraft still grounded it would be nice to continue to have a constructive discussion both on the still coming proposed fix but basically on the future of the Max. on that point , heard in a waterhole last night that Norwegian is transferring a large parts of their Max crews for conversion training on the 787s.. not sure what it means for the long term. |
Originally Posted by ATC Watcher
(Post 10467878)
Notice all 3 thread closed , a good mod decision to merge the 3 , but why close it ? pressure from Boeing ? there threads have had very valuable discussions and a very valuable source of info from the US newspapers covering the issue ( WSJ, NYT and especially Seattle time s, not all available in many countries.
With the aircraft still grounded it would be nice to continue to have a constructive discussion both on the still coming proposed fix and basically on the future of the Max. I looked else where today and found some interesting stuff on other web pages, a really good post from a pilot (as well as other accomplishments) regarding the grounding of the 737 MAX aircraft or Grounding the MAX 737 pilots. Almost daily, new news was being presented in relation to Boeing, Max, FAA and customers not to mention some excellent feed back from 737 and MAX 737 pilots and some people that seemed "in the know" regarding engineering. |
I read every post from the first day and became fascinated by the detective work - but there was a need to bring to a halt the many circular arguments.
Since it is such a vital issue for world aviation, and this is a worldwide forum, could we not establish a thread with a set of known items that could sit at the front end? Graphs, function of relays, what would happen when we do so-and-so. Ideally, two such threads, one specifically technical. This part would be there once for perpetual reference and could be updated by the OP by installing posts by others that could then be deleted. The big problem with the original was that you could not expect the average newcomer to read it, so their bright ideas were just a yawn-inducing noise. If folk new that rambling on about something repeatedly would just met with RTFSticky, then perhaps a lot could be achieved in a 1000 posts, and not to put too larger emphasis on it, it would be a real service to aviation. I think it probable a lot of 737 pilots have read it even if not contributing. And this would be carried on by word of mouth. The problem is, one can't edit such a first post unless one is the OP, so again the workload would fall on the mods. A lot of workload. So, I'm not sure how it would be achieved, but something like that. |
Bend Alot Would you mind sharing the link? thanks |
To a great extent, Bend's post describes a lot of what was happening here. The three major publications providing a lot of Seattle information. Mentor and Peter Lemme's contributions were interesting, but then there'd be a gap and their very content would be being questioned anew.
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Originally Posted by Alchad
(Post 10467989)
Bend Alot Would you mind sharing the link? thanks |
This news article says B knew about the software problem about a year ago. https://www.foxnews.com/us/boeing-kn...g-faa-airlines |
https://www.nytimes.com/2019/05/08/b...g-737-max.html
With 737 Max, Boeing Wants to Win Back Trust. Many Are Skeptical. By Natalie Kitroeff and David Gelles May 8, 2019 A charm offensive by Boeing to persuade airlines, crews and passengers to rally behind its 737 Max plane is already running into resistance. The effort, which includes daily calls with carriers as well as meetings with pilots and flight attendants, is being hampered by a problem of the company’s own making. After a bungled response to two deadly crashes involving the jet, Boeing is facing credibility problems. When Boeing dispatched one of its top lobbyists, John Moloney, to the headquarters of the influential union representing flight attendants a couple of weeks ago, he arrived determined to win their support. He met a skeptical audience. “Reading your body language, you look cynical,” Mr. Moloney said, according to three people who were present and took notes during the discussion with the Association of Flight Attendants. “If this explanation doesn’t address your concerns, I’ll come back. I’ll bring a pilot.” Sara Nelson, the head of the union, told Mr. Moloney that she was rooting for Boeing, but wasn’t ready to tell flight attendants and travelers to fly on the Max. “I don’t know, sitting here right now, that I can tell you there’s complete confidence that everything’s been fixed at Boeing,” she told Mr. Moloney. The meeting, punctuated by contentious moments between the two sides, underscores how difficult it will be for Boeing to restore credibility with airlines and passengers. In recent weeks, the company’s chief executive, Dennis A. Muilenburg, updated the heads of Southwest Airlines, American Airlines and United Airlines — the three carriers in the United States that fly the Max — on progress. On Tuesday, Boeing held a meeting in Amsterdam for European airlines to discuss new training for the Max, plans for a public affairs campaign and how to get idled planes ready to fly again. Similar meetings will happen in Shanghai, Singapore, Moscow, Dubai and Miami in the coming weeks. Boeing, a juggernaut with deep ties in Washington and one of the country’s largest exporters, is on the defensive. The company is facing multiple federal investigations into design flaws that contributed to the accidents, along with a spate of lawsuits from the families of victims. Company executives and board members are deeply worried about the damage that has been done to Boeing’s once-sterling reputation. “Certainly there’s concern,” David Calhoun, the lead independent director of Boeing’s board, said in an interview. “There is recognition on all of our parts that we’re going to have to get out with restoring confidence in the Boeing brand broadly for years.” But there’s a limit to how much Boeing can say. “It’s an impossible situation because we’re not allowed to comment on anything related to these accidents,” Mr. Calhoun said. “There’s only one thing to do, and that’s to get a safe airplane back up in the sky,” he said. “I can’t message my way into it. Boeing can’t message its way into it.” Boeing has been working furiously to get the Max flying again since its grounding in March. The company is preparing to submit a software fix in the coming weeks for American regulators to approve. It hosted hundreds of airline officials and pilots last month at the 737 Max factory in Renton, Wash. And it is in constant dialogue with regulators ahead of a meeting that the Federal Aviation Administration will host with global aviation authorities in Fort Worth on May 23. “Ultimately, the decision to return the Max to commercial service rests in the hands of global regulators,” Gordon Johndroe, a Boeing spokesman, said in a statement. Simultaneously, Boeing is shaping a public relations strategy to reach passengers. Although the final media plan is still in the works, Boeing will not be relying solely on its executives to win back the public’s trust — a recognition that its leadership has lost some good will. The company and airlines agree that the chief executive, Mr. Muilenburg, as the face of a company under intense scrutiny, may not be the most effective messenger. Instead, the initial plan calls for pilots to play a major role in the campaign. “We think a key voice in all of this will be the pilots for our airlines, and their voice is very important,” Mr. Muilenburg said on Boeing’s earnings call last month. “That bond between the passenger and the pilot is one that’s critical, and so we’re working with our airline customers and those pilot voices to ensure that we can build on that going forward.” Boeing has enlisted media agencies, including Edelman, to plan the strategy for reintroducing the Max, and is considering buying ads to promote the plane. Airline executives in the United States are eager for the Max to return to service and for Boeing to succeed. But many are privately frustrated with the company’s handling of the crisis, according to three people briefed on the matter. They believe that Boeing has badly mismanaged the public response to the crashes and are irked that the public relations blitz will fall to their pilots. Pilots, too, are reluctant to become brand ambassadors for Boeing, which barely interacted with them before the Lion Air crash in Indonesia last October, the first of the two deadly accidents. “Our response is, yeah, that’s cute, but we aren’t going to hop into bed with you,” said Mike Trevino, the spokesman for the Southwest Airlines Pilots Association. “We are still going to maintain an independent voice and call it as we see it.” In part, the reluctance stems from Boeing’s mixed messaging. Despite having said, “We own it,” Mr. Muilenburg has not acknowledged that anything was wrong with the design of the 737 Max, saying that the design process followed standard procedures. “We clearly have areas where we need to improve, including transparency,” Mr. Johndroe, the Boeing spokesman, said in a statement. During the meeting last month, the flight attendants pushed Mr. Moloney to explain why the company didn’t inform pilots about the software that contributed to both crashes. He acknowledged that Boeing should have told them, but kept reiterating that pilots were expected to be able to handle the conditions on both doomed flights. Passenger groups have demanded that Boeing take more responsibility for the Max debacle. “If they really wanted to fix the problem, you would think they would admit that it’s their fault,” said Paul Hudson, the president of Flyers Rights, a nonprofit group advocating for passengers. “You can’t say, ‘Oh, we own it, but we didn’t do anything wrong and it’s someone else’s fault.’” Pilots and airlines say Boeing has also struggled to communicate with them about how basic systems on the Max work. After the crash in Indonesia, pilots criticized Boeing for not informing them about the new software, which automatically pushes down the nose of the plane when the system deems it necessary. They have also been concerned by revelations that Boeing provided incomplete information about features in the cockpit. This week, Boeing said it believed a key cockpit warning light was standard on all Max jets, but learned several months after beginning deliveries in 2017 that the light worked only if airlines had bought a separate feature, known as the angle of attack indicator. Southwest bought the plane without the indicator, on the assumption that the warning light was activated. It was only after the Lion Air accident that Boeing told regulators and some pilots that the light wasn’t functional. Boeing told United something else entirely, creating even more confusion over Boeing’s understanding, according to a person who took notes at the meeting. When United Airlines ordered 100 Max jets in 2017, Boeing told United that the alert and the angle of attack indicator came as a package deal. United declined the options at the time. “Every day it seems like a new set of questions pops up,” said Dennis Tajer, a spokesman for the union representing American Airlines pilots. “I’m not here to be your arm candy. I’m here to know about the airplane.” Toward the end of the meeting with the flight attendants, Mr. Moloney made a last-ditch effort to win them over. “We want you to be able to tell your members this plane is safe to fly,” Mr. Moloney said, according to the three people in attendance. “Whatever it takes.” Ms. Nelson, the union’s leader, rattled off a list of things she needed from Boeing before agreeing. One was a letter from engineers working on the software update, saying they felt confident in the fix. Another was a full-throated apology from Boeing. Mr. Moloney promised to follow up. “We think that Boeing’s credibility directly relates to the credibility of U.S. aviation,” Ms. Nelson told him. “It’s important to us that the credibility and the leadership of U.S. aviation is maintained around the world.” A version of this article appears in print on May 9, 2019, on Page B1 of the New York edition with the headline: Boeing’s Tough Sell: Trust Us. |
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plans for a public affairs campaign As I posted early on in the initial thread ... Boeing would have been wise to let the 'chief engineer with actual signature responsibility' (so not a manager, not even the CEO, and certainly not 'slick or legal talkers') publicly and clearly explain what Boeing had done before the accidents happened. That would not have been in conflict with the running investigations. The lack of timely and trustworthy information at an early stage has eroded confidence in many quarters. Even to this day Boeing information is lagging what is available and discussed in professional circles. Openness is safety. Boeing has historically been able to be both more open and legally 'correct' at the same time. What the Boeing approach seems to forget is that after 'the public' hears something that many people check up with professionals to further explain it to them. Questions like where do I sit and who should I fly with, have changed in how do I recognize a MAX, how do I recognize a 737, and are other Boeing aircraft even safe to fly with. A new question among professionals is - did Boeing v1.0 morph into a Boeing v2.0 and when ... did it start with the 787 or is something else going on ... and what does it mean for the other designs ... for existing aircraft and future aircraft like the 777X... It appears Boeing has to act much faster and much clearer or this goes out of hand even further. One step further than this and we are talking about strategic and systemic failure, where both certainly include Boeing and the FAA and are now dragging in airlines too. |
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heard in a waterhole last night that Norwegian is transferring a large parts of their Max crews for conversion training on the 787s https://simpleflying.com/norwegian-pilot-redundancies/ |
“We think a key voice in all of this will be the pilots for our airlines, and their voice is very important,” Mr. Muilenburg said on Boeing’s earnings call last month. “That bond between the passenger and the pilot is one that’s critical, and so we’re working with our airline customers and those pilot voices to ensure that we can build on that going forward.” Per |
Originally Posted by Ancient Mariner
(Post 10468128)
Since the only interaction between pilot and pax these days seems to be a, frequently muffled, PA I'm not so sure about that.
Per Brings us quickly back to the thread on how pilots are perceived by the flying public. |
Boeing for a lot of reasons, believe that two serviceable aircraft were flown into the ground. |
An important step in the re-gaining trust process will be for pilots to think through how the Lion and Ethiopian pilots would have coped if they had been using Boeing's MCAS fix (whatever it turns out to be). Two things have to happen first.
1. Boeing (or somebody) will have to disclose a lot more detail about MCAS-as-was and MCAS-fixed. For example, what does Boeing think caused the constant mismatch between left and right AOA sensors? 2. The CVR transcript and DVR dataset will have to be made public. The bits disclosed in the preliminary reports simply aren't detailed enough to figure out what the pilots did, and why. Boeing's PR-campaign is no substitute for a hard-headed look by some independent engineers and pilots, Like those on this forum. Unfortunately, the rules governing accident investigations don't permit releasing the data at this time. Somebody (or Boeing) will have to take the bull by the horns to get the data out. The sooner it's out, the sooner the MAX can fly again. YYZjim |
Boeing is in the tank for probably $5-10 billion because no matter what it does the public believes it frigged the software to sell aircraft.
Reality is irrelevant as public opinion does not rely on reality but perception and their perception is Boeing is lying. I think Max will eventually fly again but we are a long way off from it and trust is the key issue here, there is none with Boeing and no amount of PR will win it back easily. |
Originally Posted by racedo
(Post 10468265)
I think Max will eventually fly again but we are a long way off from it and trust is the key issue here, there is none with Boeing and no amount of PR will win it back easily. |
Originally Posted by Eddie Dean
(Post 10468212)
Boeing for a lot of reasons, believe that two serviceable aircraft were flown into the ground. Assumptions made on how pilots would behave have proved unsafe - Or to put it another way there is a huge problem with training - at all levels from ab initio to continuation training both live and simulated. |
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Originally Posted by Eddie Dean
(Post 10468212)
Boeing for a lot of reasons, believe that two serviceable aircraft were flown into the ground. There is a mammoth thread on the military side about an RAF CH47 crash some 20 years ago. Suffice to say, there's a big difference between Serviceable and Airworthy. |
Originally Posted by Eddie Dean
(Post 10468212)
Boeing for a lot of reasons, believe that two serviceable aircraft were flown into the ground. As a pax I do not really care if a particular type of plane is crashing because of a technical flaw or because current pilots are not skilled enough to fly it. It is all a black box to me, with two possible outcomes; I make it home safely and on time or I do not. If there is some other type that is less likely to crash with the pilots that we have (rather than the pilots that we wish we had), I'll take it and let the enthusiasts bemoan how I selfishly ruined I find a lot of the actions taken by Boeing to be inexplicable. I'm not particularly of the "hate big companies crowd" (I did quite well at big companies and while executives are not particularly useful in my opinion neither are they particularly venial.) News stories that have come out indicate that the culture is pretty sick right now, and it does lead one to question all of their new projects. I mean really, our meetings would have gone much more easily if we had simply reorganized our test group (the test pilots in Boeing's case) away from engineering! Those testers ask so many annoying questions... My interest is in design, especially bad design and how we can avoid inflicting more of it on humans. I though that this crash would come down to what appeared to be perfectly reasonable decisions that fit prevailing standards but indicate a generic flaw in the prevailing standards. Instead it seems to be a product of FUBAR engineering which is not what I expected from Boeing or any company not based in San Jose run by three 'bros and a bunch of beer. |
Originally Posted by Ian W
(Post 10468296)
Assumptions made on how pilots would behave have proved unsafe -
The perception, at least that being portrayed by the media, is that the truth is far from out there yet and that skeletons remain in the Boeing closet around this entire MAX project. It has to get worse before it gets better. A lot of very good people stand to suffer if that does not happen |
The 'fix' includes using 2 AoA sensors. That is not a fix. The ac needs 3, so Boeing is minimizing the cost and impact of the fix.
They almost always disagree, so a 3rd is needed in the decision process. What happens if, like in the crash, one is damaged on DEP? If MCAS is inop can the ac be dispatched? How does a pilot know MCAS INOP? If the system is not active until 400 AGL, how does a pilot know the system is inop? Since the first Lion Air incident was on final, where are the parameters for that? |
Let's face it, the fix is in and nobody cares. Pilots with the right suff are going to pretend they are sure can fly this thing when it fights them, airlines are going to pretend their pilots can fly it without additional sim training, and Boeing is going to pretend they fixed it, and the FAA is going to pretend it's fixed, and the Inspector General is going to believe that the FAA certified the type correctly the first time round, and everyone is going to kick Airbus very hard under the table to make sure the Europeans accept the fix.
After reading this forum, I have come to realize that pilots are smart professionals who care bout flying planes, but do not understand that a bad design puts them in a bad place, and every pilot is convinced that *he* would find the right solution to the mechanical issue that killed his colleagues. The first pages of Tom Wolfe's book The Right Stuff come to mind. Edmund PS. I say "he" on purpose. I think the female pilots are probably less testosterone-fueled. Edmund |
We have 3 artificial horizons in order to have a tie breaker if 1 goes wrong, same with the air speed indicators and usually IRSs. I can't see how 2 AoA sensors will meet requirements if 1 starts acting up. Boeing may have to come up with a completely new stall avoidance system, even if it means recertifying the aircraft as a new type and requiring pilots to obtain a new rating.
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Let's face it, the fix is in and nobody cares. Pilots with the right suff are going to pretend they are sure can fly this thing when it fights them, airlines are going to pretend their pilots can fly it without additional sim training, and Boeing is going to pretend they fixed it, and the FAA is going to pretend it's fixed, and the Inspector General is going to believe that the FAA certified the type correctly the first time round, and everyone is going to kick Airbus very hard under the table to make sure the Europeans accept the fix.
And then it will crash again. Edmund |
Originally Posted by Smythe
(Post 10468551)
The 'fix' includes using 2 AoA sensors. That is not a fix. The ac needs 3, so Boeing is minimizing the cost and impact of the fix.
They almost always disagree, so a 3rd is needed in the decision process. What happens if, like in the crash, one is damaged on DEP? If MCAS is inop can the ac be dispatched? How does a pilot know MCAS INOP? If the system is not active until 400 AGL, how does a pilot know the system is inop? Since the first Lion Air incident was on final, where are the parameters for that? MCAS is part of the Speed Trim System (STS). There are two STS channels, and one is always required for dispatch. If one or both STS/MCAS systems became inop, we receive a warning annunciator on the flight deck. If both systems are inop, the annunciator comes on immediately - it doesn't wait until 400'. If both STS channels fail in flight, we have a non-normal procedure to address it - just like we have non-normals to address the failure of engines, hydraulics, electrics and all sorts of other things we would require for dispatch. The new Flight Control Computer (FCC) software will inhibit any STS/MCAS input if the difference between AOA's is greater than about 5 degrees. This is more stringent that the current "AOA Disagree" trigger of greater than 10 degrees. The new software also has some other tests for reasonableness. and the total nose down input is adjusted for the conditions - it will input more stab trim at low airspeeds and less at high airspeeds. Not sure what you are asking with your last question, but maybe it would be a helpful reminder that MCAS only activates with the flaps retracted. If the flight crew is operating the aircraft normally, the flaps will always be extended below 1000 feet. |
Originally Posted by edmundronald
(Post 10468558)
After reading this forum, I have come to realize that pilots are smart professionals who care bout flying planes, but do not understand that a bad design puts them in a bad place, Edmund |
Any fix is going to have to be belt and braces, bullet proof if confidence is going to be restored in the MAX. It will have to cover the lowest denominator airline flying the type not just major airlines in first world countries. A minimum standard solution might get it back in the air but cause future orders to dry up and heaven help Boeing if another one crashes.
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At the end of the day, MCAS will still be able to make inputs to a 47' flying surface. We read that these commands are to be substantially modified, fine, but still that black box has the potential to house HAL. Just how does one construct an impenetrable wall that will stop millions of junction gates from a catastrophic conspiracy - one that no one has filtered out of thousands of lines of code - one that won't show up for months or even years? My feeling is that its connection to the stabilizer should be totally removed and do nothing but warn. But then of course there's STS, MCAS's senior logic layer. That's worked okay for years but it's the sheer power of that flight surface that makes my aged sphincter-system lock up.
Even the basic premise seems bizarre to me: in certain circumstances we want to stop the elevators becoming steadily lighter, so we pitch an entire aircraft nose down? Height, flaps zero, AP off, speed within range and a complex system of relays etc., should all stop that signal going to the tail, but the potential for unwanted activation is hard wired into that aircraft for life. |
Originally Posted by 737 Driver
(Post 10468565)
I got a brief on the new software yesterday.
MCAS is part of the Speed Trim System (STS). There are two STS channels, and one is always required for dispatch. If one or both STS/MCAS systems became inop, we receive a warning annunciator on the flight deck. If both systems are inop, the annunciator comes on immediately - it doesn't wait until 400'. If both STS channels fail in flight, we have a non-normal procedure to address it - just like we have non-normals to address the failure of engines, hydraulics, electrics and all sorts of other things we would require for dispatch. The new Flight Control Computer (FCC) software will inhibit any STS/MCAS input if the difference between AOA's is greater than about 5 degrees. This is more stringent that the current "AOA Disagree" trigger of greater than 10 degrees. The new software also has some other tests for reasonableness. and the total nose down input is adjusted for the conditions - it will input more stab trim at low airspeeds and less at high airspeeds. Not sure what you are asking with your last question, but maybe it would be a helpful reminder that MCAS only activates with the flaps retracted. If the flight crew is operating the aircraft normally, the flaps will always be extended below 1000 feet. So if that is true, then how can the MCAS part of the STS be tested before flight? Lion Air seems faulty AoA fitted - would the annunciation illuminate in this case? The current MCAS AoA had no limit of disagree, and there was no problem withe the STS operation previously - MCAS really looks more than just a sub-sytem of STS. Now the that is worrying - variable amounts of input! So if you are going slow with a high angle of attack - how long do you watch that trim wheel spin for? From the previous thread Mr Driver your instinct would be to trim have you then disabled MCAS and stopped it from its certification requirement? Would your current practice still stand? - keep flap out, or Autopilot on to bypass MCAS from being able to activate? |
Originally Posted by Loose rivets
(Post 10468585)
At the end of the day, MCAS will still be able to make inputs to a 47' flying surface. We read that these commands are to be substantially modified, fine, but still that black box has the potential to house HAL. Just how does one construct an impenetrable wall that will stop millions of junction gates from a catastrophic conspiracy - one that no one has filtered out of thousands of lines of code - one that won't show up for months or even years? My feeling is that its connection to the stabilizer should be totally removed and do nothing but warn. But then of course there's STS, MCAS's senior logic layer. That's worked okay for years but it's the sheer power of that flight surface that makes my aged sphincter-system lock up.
Even the basic premise seems bizarre to me: in certain circumstances we want to stop the elevators becoming steadily lighter, so we pitch an entire aircraft nose down? Height, flaps zero, AP off, speed within range and a complex system of relays etc., should all stop that signal going to the tail, but the potential for unwanted activation is hard wired into that aircraft for life. |
Originally Posted by Alchad
(Post 10467989)
Bend Alot Would you mind sharing the link? thanks https://www.theatlantic.com/notes/20...HKWMiGTRbWIC3c |
Re 737 Driver's post.
Yes, but it's the initial unwanted command to the H-Stabilizer that I take issue with. Should all the protection fail again, and that jack-screw run its full distance, then those braided steel cables seemingly still won't save the day. I've thought long and hard about fly by wire since 'flying' a model in a box at Farnborough in the 70's Given the sophistication of the electronics, I concede the probabilities make my worries all but groundless, but then there's a hefty lighting strike into the electrics bay scenario which would indeed put Boeing way ahead. . |
737, Sorry, but I am not in agreement here. I understand you are a pilot, and so are many of us. The parameters and the if/then scenario have never been properly detailed. We would not have 3 incidents and 2 crashes if it had been.
While MCAS is part of the Speed Trim System (STS), the parameters appear completely different. I know the Boeing ac, but are not current like I am on Airbus ac.. From what I have seen on the STS system, STS Mach gain is fully enabled between 100 KIAS and Mach 0.60 with a fadeout to zero by Mach 0.68. 10 seconds after takeoff, 5 seconds following release of trim switches, and Autopilot not engaged. IF STS utilizes AoA , then why was MCAS required? What are the parameters that engage MCAS? I really do not agree with 2 AoA sensors, and the pilot is not the 3rd sensor, especially if there is only one left for whatever reason (as in the Ethiopian crash). As I have stated before, the AoA's are always in disagreement in many conditions, such as climbout and short final ,and while you claim the pilot has a decision, well, where or what is that decision based? Lose 1 out of 2 sensors, and what is your decision based on? Those AoA vanes always have issues and you know it. |
Originally Posted by Bend alot
(Post 10468591)
There was the Boeing spokesman that said the AoA disagree only worked above 400ft after they found it actually was not active all all.
So if that is true, then how can the MCAS part of the STS be tested before flight? Lion Air seems faulty AoA fitted - would the annunciation illuminate in this case? The current MCAS AoA had no limit of disagree, and there was no problem withe the STS operation previously - MCAS really looks more than just a sub-sytem of STS. Now the that is worrying - variable amounts of input! So if you are going slow with a high angle of attack - how long do you watch that trim wheel spin for? From the previous thread Mr Driver your instinct would be to trim have you then disabled MCAS and stopped it from its certification requirement? Would your current practice still stand? - keep flap out, or Autopilot on to bypass MCAS from being able to activate? I'm not sure about what you mean about testing STS/MCAS before flight. There are various logic tests going on in the background for many of our onboard systems, and we will get warning annunciators if one of those self-tests fails. Otherwise, most of our systems are assumed to be working until proven otherwise. I don't see what is worrying about variable amounts of input. If the system is working and you really are approaching a stall, then that is what you want. If the system somehow got past the new software checks, then MCAS would be making an input when there was no stall while the pilot was hand-flying. As discussed in other threads, the pilot should notice such an anomalous input and take corrective action. At some point, you have to assume that someone is minding the store. If not, there are other systems on the plane that you should be far more worried about. To your question of what I would do with an unwanted MCAS input, it would be the exact same thing I would do with any unwanted stab trim input. By my count, there are six different sources of input into the electrically-driven trim system on the MAX (five on the 737NG). Our runaway stab procedures are completely agnostic to the source of the undesired trim. Step 2 of that procedure is to oppose and counter the unwanted trim with the yoke trim switch. It is not until Step 5 that the cutout switches are used. This was one of the errors the ET302 crew made - they went right to Step 5. Once MCAS is disabled, yes, the aircraft no longer meets its certification dispatch requirement. That statement also applies when we lose engines, hydraulic systems, generators, and so forth. That is why we have non-normal procedures to get the aircraft back on the ground where it can be fixed. The technique I spoke of before about engaging the autopilot before flap retraction was an interim approach until Boeing rolled out a long term fix. That will no longer be necessary with the new software. |
Originally Posted by Loose rivets
(Post 10468596)
Re 737 Driver's post.
Yes, but it's the initial unwanted command to the H-Stabilizer that I take issue with. Should all the protection fail again, and that jack-screw run its full distance, then those braided steel cables seemingly still won't save the day. . |
Originally Posted by Smythe
(Post 10468597)
737, Sorry, but I am not in agreement here. I understand you are a pilot, and so are many of us. The parameters and the if/then scenario have never been properly detailed. We would not have 3 incidents and 2 crashes if it had been.
While MCAS is part of the Speed Trim System (STS), the parameters appear completely different. I know the Boeing ac, but are not current like I am on Airbus ac.. From what I have seen on the STS system, STS Mach gain is fully enabled between 100 KIAS and Mach 0.60 with a fadeout to zero by Mach 0.68. 10 seconds after takeoff, 5 seconds following release of trim switches, and Autopilot not engaged. What are the parameters that engage MCAS? I really do not agree with 2 AoA sensors, and the pilot is not the 3rd sensor, especially if there is only one left for whatever reason (as in the Ethiopian crash). As I have stated before, the AoA's are always in disagreement in many conditions, such as climbout and short final ,and while you claim the pilot has a decision, well, where or what is that decision based? Lose 1 out of 2 sensors, and what is your decision based on? Those AoA vanes always have issues and you know it. Yes, it would be great if we had triple-redundancy on everything on the 737. However, I must point out that it has relied on double-redundancy with a pilot as tiebreaker for, well, ever since the plane has been flying. It is pretty much a fact of life on the 737, and it really hasn't been an issue. If I lose one of anything, there is always a way to figure out which one is working and which one isn't. |
My sad prediction: The next Max crash will involve a 3rd world airline without mature Western Airline training and experience with a crew so hyper vigilant about a MCAS runway that they will misdiagnose something else as a MCAS failure go to the stab cut out switches and now have to manually trim an out of trim aircraft, which is basically never done, get behind the airplane and fly it into the ground...... |
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