Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- Bjorn’s Corner: New engine development. Part 4. Propulsive efficiency April 19, 2024
- Boeing unlikely to meet FAA’s 90-day deadline for new safety program April 18, 2024
- Focus on quality not slowing innovation, says GKN April 18, 2024
- Boeing defends 787, 777 against whistleblower charges April 17, 2024
- Dissecting Boeing CEO’s statement next new airplane will cost $50bn April 15, 2024
Pontifications: The elephant in the room
By Scott Hamilton
June 17, 2019, © Leeham News: The Paris Air Show opens today and the elephant in the room is the Boeing 737 MAX.
There is no telling when the airplane will get FAA approval to return to service. According to some news reports, Boeing will hasn’t turned 
over the MCAS revisions to the FAA for review, testing and approval.
The acting administrator of the FAA said he expects the MAX to be back in the air by the end of the year. Some leapt to the conclusion this means December—and it may, but let’s remember September, October and November are before the “end of the year,” too.
There’s no telling how other global regulators will act, and when, to conduct their own review and approvals. Airlines would like a global action. It’s tough to tell customers one country sees the airplane as safe but others don’t.
- Leeham News will be at the Paris Air Show this week, with coverage by Scott Hamilton, Bjorn Fehrm and Judson Rollins. All coverage will be open to all readers.
Safe fix, big, black eye
I’m confident the MCAS fix will make the airplane safe. LNA’s Bjorn Fehrm, an aerospace engineer and former fighter pilot, wrote he has not hesitation about flying the airplane once it’s got the MCAS fix.
My concern is, how can we be confident Boeing has told pilots everything there is to know about differences between the MAX and NG. There’s been this stead drip, drip, drip of information coming about what Boeing knew and didn’t tell pilots or the FAA.
The differences between training levels of competency across the globe, to me, mandate simulator training.
By now, there have been simulations on social media of MCAS “1.0” is virtually impossible for pilots to override. Aviation Week reported the simulation by pilots of one major US airline (there are only three that have the MAX), starting at 10,000 ft. Pilots were barely able to recover. They knew what was coming and why they were doing the simulation. The pilots of Lion Air had no clue what was happening and started at 5,000 ft. The Ethiopian pilots knew what was happening, but their event started at 850 ft and they never got higher than 1,500 ft.
Scott McCartney, the “Middle Seat” columnist for the Wall Street Journal and a private pilot, sat in the third seat of a simulator and flew the sim through MCAS 1.0 and 2.0. The 1.0 was virtually unrecoverable. The 2.0 was benign and easily recoverable.
Boeing continues to oppose sim training. Technically, there might be a valid argument to make.
To restore confidence in the MAX with the pilots and passengers, it should support sim training.
Little expected this week
Little news is expected this week about the MAX. Nothing is likely from the FAA or from Boeing. Certainly no orders are expected, though some good ones would be a real endorsement of customer confidence in the airplane if some were announced.
There won’t be any announcement of an Authority to Offer the prospective New Midmarket Airplane (NMA, or 797) from Boeing. Any decision by the Boeing Board of Directors won’t be forthcoming until the MAX position is clarified.
Any suggestion that Boeing will skip the NMA and go straight to a 737 replacement is also off the mark, in Leeham Co’s view.
There are some 4,500 MAXes in backlog, which stretches well into the next decade. There’s no new step-change engine to support a 737 replacement. There has been no market intelligence we’ve picked up—none, zilch, nada—in which Boeing has shown even a concept, let alone a design, to airlines and lessors of a 737 replacement.
Boeing isn’t about to launch a new airplane without testing market reaction.
It’s already been nearly seven years that Boeing has been talking about a Middle of the Market airplane, which has been a difficult project for which to close a business case.
A 737 replacement business case is pretty easy. But it isn’t something that will be launched on a few months’ notice.
So, no 737 replacement this week, either.
Recovery
I often get asked, will Boeing and the 737 recover? My answer is, yes, absolutely.
Within a year or 18 months after the MAX is globally returned to service, and assuming no new accident associated with MCAS or some other design flaw, all will be forgotten by all but a few of the traveling public.
There will continue to be bad stories as federal, Congressional and accident investigation unfold. Lawsuits will keep the MAX in the news. Any new crash, or serious incident, will immediately raise questions about the safety of the airplane.
Image recovery depends, I think, on having the line pilots out front in a media blitz, not some “celebrities” that Boeing apparently has been thinking about, according to a Wall Street Journal article.
To me, and to passengers, there is one thing to keep in mind above all others: the first people to any accident scene sit in the cockpit.
If the pilots are confident in the fix (and simulators will help), then this should be the driving factor in restoring confidence in the airplanes.
I’ve already heard some airlines plan to simply quietly slip the MAX back into service. This is a poor move. Each carrier should have a pilot-flight attendant media team hitting their hubs and focus sittings to explain to the local press why they are confident the airplane is fixed and safe.
The head-in-the-sand approach is a disservice to the passengers and to their own flight crews, who will get questions from passengers. Reservations agents and airport personnel will also get questions.
All the MAX airlines need to prepare their employees up and down the line with briefings and answers.
This is unlikely to happen, though, making the MAX recovery longer and more difficult.
“Failed to communicate crisply “= we have been lying and covering up. I strongly suspect that there are more revelations to come.
I don’t know how anybody can claim a software fix will make the airplane safe when Boeing haven’t and refuse to explain why MCAS 1.0 was written in the first place and is so overwhelming aggressive in it’s action.
Software fixes don’t all of a sudden make an airplane stable. The laws of physics define the stability of an airplane not some software algorithm. The instability will still be there. The question is whether the sofware fix can prevent the instability crashing the airplane.
I don’t have LNA (Bjorn’s) confidence and won’t have until Boeing explain the physics thereby explaining why MCAS 1.0 was developed in the first place and why it is so overwhelming aggressive in it’s action.
As I said before, I don’t think Boeing engineering exhibit collective incompetence or are collectively imbeciles. So there is a physical reason for MCAS 1.0. What is it?
If the solution to the problem could be found in a software fix and the connection to the second AOA sensor, it would long be in the hands of the FAA.
As it is not, my take is that the underlying stability problem is severe. And it’s obviously quite different at high speed and at low speed. So instead of one MCAS we may need two!
No with two additional trim systems on top of the automatic trim we have three system that work in parallel. I don’t want to be in the shoes of the programmers who try to make that faultless. And if it is possible at all, it will take a long time to develop and test. This would easily bring us to 2021 re-entry into service.
There is still a very good chance that this development will fail.
In this case we still need to address the fundamental problem, the insufficient aerodynamic stability. Gear, tail, pylons,…
Then what? Chapter 11?
Perhaps Chapter 11, but I don’t really see what the exit strategy from that is. If Boeing does go down, it’ll take a vast chain of suppliers with them. Does that go into Chapter 11 too? Where would the rot end?
It might be cheaper for Uncle Sam if they bought up Boeing.
And isn’t there a bit of a problem with a bankruptcy, regarding continuation of their role as Design Authority for all their flying aircraft? If the company ceases to exist – even if only briefly – doesn’t that mean all the aircraft have to be grounded too without adequate contingency plans for the DA role being in place? That could get very interesting, very quickly…
While I also would like to know why MCAS 1.0 was necessary and why they felt it had to be so aggressive (additionally why all of a sudden it does not need to be so aggressive?!), I wonder if any of the responsible certifying agencies will see these questions as being relevant to the issue?
Personally, I would take the view that the regulators were failing in their duty if they didn’t find out why!
The regulators need to know the envelope of an airplane, with and without moderation using software algorithms in order to establish whether an airplane is safe. The FAA, EASA and others were NOT given the information. That in itself is a crime.
So, don’t agree. The question isn’t just relevant, I don’t see how the MAX can be regarded as safe without the question being answered.
As I said software algorithms don’t change the laws of physics. The instability is there. What is it?
My take is that the center of list is changing too fast and too far depending on the angle of attack and speed.
The large nacelles in the forward position in front of the wing must have a huge impact on the airflow over the wing behind and the stabilizer/elevator further back. And this effect varies with the airspeed, which is why the MCAS was extended from a high-speed system to a low speed system. Which apparently does not work quite a smoothly as expected.
I’d call this an unstable plane that could be flown safely only with a FBW system. Besides the fact that such an unstable plane would not be legal, this FBW system is just not available for the 737. It would basically mean a new plane.
Bringing an unstable passenger plane into service is a crime, covering it up by hiding the MCAS is the second crime.
I said the same a few months ago. Specifically, the pitching moment is accelerating with AoA.
The issue is inertia. Once the pitch up speed is there it is hard to stop, remembering that if the pitch up continues the wing will stall. So slam on the brakes before inertia sets in. That’s the reason for the overwhelming aggression of MCAS 1.0. Slam on the brakes before inertia sets in, otherwise a stall can’t be prevented.
Having said all that, we must remember that the stabiliser setting changed for straight and level flight from 0.6 to 2.5 (if my memory is right). So in straight and level flight the pitch up tendency is there.
“That’s the reason for the overwhelming aggression of MCAS 1.0. ”
Overwhelming aggression – I’ll add that to my list of adjectives and adjective phrases.
from this web site http://www.b737.org.uk/winglets.htm#ATWinglets
they mention about the NG winglets..
======================
“Operational Considerations
There is a small difference in rotation rate for airplanes with winglets installed and, as a result, the crew needs to be cautious of pitch rate. There is also approximately a ½ unit take-off trim change between non-winglet and winglet aircraft so the green band is slightly different for winglet aircraft.”
===============
I’m assuming the 737-MAX winglets might be even more of an effect. I assume 737-NG/MAX pilots are very aware of this caution.
Phillip,
Move along, nothing to see here.
Basically, if they can get away with the not-so-robust minimal software fix in a global scale, it becomes much easier to blame the pilots if there isn’t an MCAS to interfere and create incriminating evidence. Showing that the basic longitudinal instability caused a crash would be next to impossible if there is no obvious control system malfunction (see recent accidents involving 737NG: TAK363 and FDB981).
Real question is; will the foreign regulators, chiefly EASA, be able to block this strategy to make Boeing face the issue and provide a robust fix? I think it would take either a triple redundant AOA input or better yet, a passive aerodynamic fix (similar to a more horizontally oriented version of the ventral fins on the E-7A 737 Wedgetail).
…”next to impossible”.
NO
@ Philip,
I say “next to impossible”, because having a neutered MCAS onboard opens the door for Boeing to claim, “well, the pilots must have known how to” if a crash is caused by instability, which would be difficult to argue with. Leaning on that argument is far less cut and dried than the explanation “a system malfunctioned” to blame the pilots.
To add to my no. It is basic functionsl testing to determine the envelope of an airplane. That means were the airplane is safe and stable. So determining longitudinal stability/instability is basic. Having done that we can all then know whether the pilots can fly the airplane safely with the software algorithms turned off.
Airbus has the concept of direct law to address my words above. Direct law means the software algorithms are turned off. All Airbus airplanes exhibit natural stability and can be easily flown by qualified pilots in direct mode. The software algorithms are nice to have but not necessary.
MCAS appears to be must have. Why needs to be explained?
This thrn comes to MCAS 2.0. MCAS 2.0 is significantly less aggressive. So it will be down to the pilots to control the airplane. They need to know what they are controlling. In other words they need to know the pitch instability and how to avoid it, if it can be avoided. Anyway the pilots should always know the airplane they are flying, with and without software algorithms.
Using fins is a possible hardware fix. I said it myself a long time ago. Much better to address the stabiliser/elevators. Much, much better to raise the undercarriage to allow a pylon to be used to mount the engine. Much, much, much better to do an NSA
The only folks to have flown a MAX without MCAS are Boeing’s test pilots and the two crashes. Is that true? There is no way to ‘turn MCAS off’ from the cockpit. So as soon as you are flaps up and autopilot off, you’v armed MCAS. It does make you wonder why. And why more thought hadn’t been put into the system. A typical 737-MAX pilot has never flown a ‘naked’ 737-MAX.
Stop!
You are at best guessing.
And haven’t read Bjorn’s articles on the reason for MCAS.
(Which by the way is not ‘instability’ but control feel approaching stall, which might contribute to a pilot pitching up into a stall in an emergency.)
An alternative explanation is that Boeing is being very thorough, triple-checking, as is the FAA – who may differ on some aspects, and are looking over their shoulder at other country’s airworthiness authorities. Professional debates will occur, regulatory people sometimes get off track just as Boeing people do.
(There should be motivation to get the system right for sure, given that not being right the first time shows risk of poor work in general.)
The change probably includes not only walking back aggressiveness of the function, but logic of comparisons of AOA vanes – what threshold of difference, how much filtering (since momentary variation in vane position is possible), what speed to enable alerting to crew during takeoff roll, …. I’m guessing.
(And wasn’t there a claim that Boeing found something in an unrelated part of the control computer’s software so delayed to fix that?)
The insouciance shown by Boeing for the first 6 months after the initial crash is coming back to hurt them. Simply if they had truly ‘owned’ the problem then they would be in a far better place now. They have upset powerful stakeholders in pilots, airlines, national regulatory bodies etc to such a degree that no one is inclined to give them the benefit of the doubt.
Notice the silence of the past couple of weeks, it is almost as though Boeing is paralysed into inaction. They need someone untainted by the present issues to kick the ‘group think’ back into shape. They are going to take hits, legal, regulatory and financial but need to focus on the business at hand which is:
Re-certify plane
Recommence deliveries
Rebuild pilot confidence
Re-establish airline relationships
Regain public trust
A lot of RE..
The fact that Boeing is obviously still working on MCAS 2.0 seems to indicate, that the fix is not a simple and easy one as they keep claiming.
While it hopefully means, Boeing this time really wants to make sure they get it right, it raises more questions for me what it is that makes it so complex. Is it a physical instability that many imply, or is Boeing suddenly just so diligent?
The information provided does not make me feel confident, and I guess I’m not the only one.
The issue I think is that they’ve found that something MCAS-esque is required to make the aircraft’s handling legal as per FAA requirements, but have come to realise that this cannot be met with a single software channel implementing the function. It needs a full, triplicate FBW system, but all they’ve got is a single compute platform; that’s 2 short. My reasoning follows.
Note that this is more than a question of how many AoA sensors are being read. One sensor feeding a single computer is not enough. That’s crashed twice now. Two sensors feeding a single computer still not enough, because you are effectively compelled (by certification requirments) to doubt that the single computer will react correctly to a failed sensor input (especially if it’d put 2.5 degrees down trim in if it got it wrong). Three sensors feeding three computers is enough, because by then you’d accept that the chance of all three computers and AoA sensors failing whilst still giving identical results (upon which the system would then act) is vanishingly small.
The alternative, i.e. to give pilots the option of power assisted manual control over the stabliser having turned off all the magic, cannot be implemented on the MAX either without wiring changes. Even if they did that, there’d then be huge pressure to train pilots in how the aircraft flew in that mode. And if Philip and Gundolf’s suspicions about the true flying characteristic are correct, the certifying bodies may not let it fly at all in that mode.
Matt, this is the best reasoning I have seen as to what might be the hold up on the software fix. Again I think FAA will sign off on anything so long as noone else is watching. In this case, they have all those other regulators to worry about – mostly EASA.
By the time it’s all said and done, it may very well turn out that a hardware/passive aerodynamic fix is cheaper than a triplex redundant FBW augmenting of the controls and/or alternate over-ride + extra training for the “direct-law”. That would be a tough sell: Boeing would have to argue ‘sorry folks, no the software fix wouldn’t work, infect, we’d like to replace the MCAS 2.0 with a solid state aerodynamic fix’. And that would beg the question, why wasn’t this done from the start? and there lies the dirty secret and the deceptive intent. In the end it will be a power struggle between the FAA and the rest of the world.
Matthew
The MAX does have two FCCs, one for thr left seat, the other for the right seat. They do talk to each other; airspeed mis-match is an example.
Not an A350. The A350 has three primary and three secondary FCCs to allow voting. The secondary FCCs only run direct law.
Sorry Matthew, you used “software channel”. The MAX has two FCCs and one software channel. A software channel looks at all sensors.
For example, on Airbus, that means each of the three FCCs looks at all three alpha vanes.
The two FCCs on the MAX look at their own sensors; for example left seat/left alpha vane and right seat/right alpha vane.
I stand to be corrected, but I don’t think there is a Level D simulator for the MAX. Level D means the software algorithms can be turned off, meaning the pilots are truely flying the airplane. In Airbus terminology, direct law.
If I’m right, it should also be understood that it takes quite a long time to develop Level D simulators. So if Level D is required, returning the MAX to service by the year end is unlikely to happen!
Still think the MAX requires hardware changes!
First it was going to be June…then that became July, which slipped to August, and then September. Now it’s “before the end of the year”. It’s hard to believe that a supposedly simple software fix is taking so long to get certified, so one starts to (strongly) suspect that there’s a rat under the carpet that we’re not being told about…
Scott, with your position that NMA will come before NSA, what sort of timeframe do you believe any NMA will force upon the earliest launch date for any NSA? Would it wait until any NMA EIS? First flight? Design complete? What year? Would it push any launch past the technologically/commercially optimal point?
Going to NMA dates, do you believe it can be launched while the current Boeing leadership is in place and the investigations into the FAA/Boeing relationship are still ongoing? My feeling is there is too significant a likelihood of enduring taint to launch until there has been seen to be some significant cleaning (preferebaly to include the replacement of Muilenberg).
Agreed. That there hasn’t yet been a housecleaning at Boeing given what’s already been reported is quite surprising.
In fact, one has to wonder if it’s “just” a matter of “fixing” the bugs/defects in the MCAS software (or other aspects of the plane’s aerodynamic’s/mechanicals, etc.) to get it recertified for reentry into scheduled service, or more realistically, a matter of “fixing” the corporate culture that prioritized profits over the 346 lives that were lost – and put at risk each and every other person (passengers and crews) that ever stepped aboard any 737 MAX but for whom vital safety information and product defects were never disclosed to until several recent news reports which allege that either critical safety related information was deliberately concealed/withheld until only after 346 lives were lost in two (2) possibly entirely preventable accidents had that information been provided to regulators, pilots, airline managers and the traveling public in a timely fashion; and for another safety feature which the company decided “could wait until 2020” to begin undertaking an effort to update/remedy.
Sorry – NOT sorry!
But, asking the traveling public to trust the same people to oversee any “fixes” when they’re the same ones who sat on their hands already is simply unacceptable as the problem is NOT just a defective product that needs to be repaired – but also the clearly defective decisions made by people who bear responsible for NOT acting immediately to disclose defects they were aware of, and who sure do seem to have taken a very casual approach towards scheduling the implementation of a fix three (3) years AFTER the defect allegedly was known by them.
In fact, it’s not a matter of being “simply” unacceptable; but rather “wholly unacceptable” that the discussion to date seems to be confined to “just fixing” the defects of the the 737MAX, while overlooking the bigger picture of the abject immorality and moral bankruptcy of the people who made the decisions that were made, and in doing so, created, embraced, advanced and enabled a corporate culture that allowed this debacle to happen in the first place⚠️
For Boeing to regain the public’s confidence, they must do a lot more than simply “fix” a 50+ years ago designed and engineered platform for a long ago obsolete plane that probably should’ve never been built in the first place – but rather the people and the corporate culture they created must go, too, with new managers, and a more competent Board of Directors with expertise in aerospace and aviation instead of how best to make money.
And yes, agree 100% with Scott, too; pilots and crews should be the people who “sell” the plane to a public that has every right to be skeptical, including SIM time for pilots.
But, as Scott also noted, Boeing will probably blow that, too – or at least the current management and BoD will anyway – which is all the more of a reason why a thorough housecleaning is what’s DESPERATELY needed at Boeing.
Paging Gordon Bethune…please pick up the RED courtesy phone for news of an urgent matter that requires your immediate attention…Gordon Bethune…please pick up the RED courtesy phone… a very sick Boeing needs you (or someone like you…) 😉
JMHO…
Totally agree.
A house cleaning hasn’t happened yet because if they fire those managers right away, legally it can be construed as indirect admission of fault on Boeing’s part – that being said, the lists have probably been prepared for an extensive purge. They will most likely wait until the next big layoff to have a good fig leaf excuse, then “layoff” those managers in solidarity with the rank and file being let go (this is possibly coming to a Boeing site near you, and sooner than you think).
This is quote from a Reuters article, referring to things that Dennis Muilenberg said, “He said he expected the MAX to return to service this year and that 90% of customers had participated in simulator sessions with its upgraded MCAS software as the company works toward a certification flight with regulators soon. ”
Don’t Boeing usually refer to quarters to give themselves some leeway?
If he says he expects it to return to service this year, is that not the Boeingspeak of the last decade for, “It will probably be back in service around the first quarter of next year?”
Also, I wonder of Lion Air and Ethiopian are amongst that 90%?
If they were, would it not be wise for him to play that fact up?
While Boeing wants to reinforce the FAA’s position as the lead in returning the 737MAX to the air, if the FAA moves without at least european backing there is unlikely to be much confidence in the airlines or the flying public. This could lead to half empty planes and/or the need for sizeable reductions in fares. Neither will help Boeing get airlines to accept new deliveries.
The Chinese authorities are unlikely to finish recertification before the end of the trade war and given that neither Garuda nor Lion want the 737MAX, the Indonesian authorities won’t accept it either to put pressure on Boeing to cancel their orders without penalty and pay compensation. This will lead to problems for asian airlines wanting to fly into their airspace.
> Leeham News will be at the Paris Air Show this week, with coverage by Scott Hamilton, Bjorn Fehrm and Judson Rollins. All coverage will be open to all readers.
This is a really nice touch. Thank you.
In terms of physical changes to the MAX it should be R.E.M. reed that this was indeed the recommendation of Boeings first chief test pilot on this aircaft – now retired.He felt and suggested that adding some additional vortex generators would help resolve the issue.It does not make him right of course,but he was overruled and the 1st gen’ software was created.This then expanded when both high and low speed issues were uncovered.
It would be interesting to know how many times ( in the short time the aircraft has been operational) the software has felt it necessary to cut in and trim the aircraft.If the AOA is working correctly then it might be hard ( even to the pilots) to know. Whether they had ‘help’ because the software became ‘worried’ about the increasing AOA and – the consequences?
Boeing will no doubt know the answer to this question.
Did the chief test pilot say what the purpose was? Vortex generators can be used to create lift and destroy lift. Depends on where they are generated.
Either way they cause drag and therefore a fuel penalty.
Equally, care must be taken with the stabilise. Another commentator has suggested that the flow over the stabiliser ie bring disrupted causing elevator inoperability. A theory, but worth consideration
What new FAR’s should be put in place from lessons learned on the 737-MAX?
One, that I’d like to see, is that any input control system affecting the major control surfaces, of the aircraft be fully described in the flight manual of the aircraft.
It’s operational details, normal known fault limits and required override procedures and backup systems and procedures described. How Boeing was able to add an
additional control function (stall protection) to the (STS) speed trim system, without any explanation of it, to even its own test pilots, amazes me.
One that operated and depended on a single AOA sensor. With limitless (to the physical limit bounds of the trim system), activation ability. And with no ability to
switch it off. Are there any other changes on the 737-MAX, not fully described in the flight manuals?
Boeing has made references to their MCAS 2.0 change being limited, so as to not allow loss of elevator authority over the stabilizer. Still no OFF switch for MCAS,
in an emergency. So, ultimately, with the control column in one pilots lap, the other is still working with a hard to operate, manual trim wheel in certain instances.
No backup trim motor, no electric / hydraulic backup. Just a cable and pulley system to work with. At least a geared low/med/high manual shifting system would seem
to be in order. As in a bicycle, when you’re going up a steep hill, vs when you’re on level ground. So as to give the pilots a last fighting chance. Rather than some
dipsy-doodle flying technique that eats up thousands of feet of valuable altitude.
In the past, Boeing had large, design review meetings, with multiple groups involved. Your piece of the project was presented, and questions answered, from various groups.
By the end of the meetings you had a much better understanding of how everything worked together. I wonder how the MCAS change would have fared in that environment? Would
the only one AOA sensor be divulged and challenged? The reason for MCAS be looked at from different angles? It sounds like the MCAS change was reviewed and put into production
by just a few peoples knowledge. A small software change, ultimately controlling the pitch of the aircraft. Nothing for the FAA to review here.
One thing I don’t understand. Is the root ‘pitch up’ at close to stall condition, (the reason for the MCAS change) caused entirely by the new engine placement? Is it just
the pitching force from the pivot point? Are there any other parameters such as the speed of the change? The acceleration of the engine being more powerful than previous
engine versions? I’m not that well versed in aerodynamics, but, a slow change of speed seems to me, to be less of an issue, than a sudden acceleration causing a pitch change.
Is MCAS software the best alternative? The Ercoupe, a stall proof aircraft, simply limits the ability of the control column. Could a similar system be employed to avoid
high AOA situation in the 737? A stiff spring is engaged on the control column over “X” degrees of movement? If a mountain appears on takeoff, then the pilot would still
have the ability to pull hard into the high AOA region, to try and avoid the mountain, being aware he needs to be more alert to a stall.
As regards to simulators. From what I understand (and that is not much), full motion, level D simulators are just that, simulations of the real thing. They are very good for
training devices, but, they weren’t designed for hardware/software flight testing. The Flight control computer for the 737, is not built into the simulator. (I could be 100% on this, I don’t have direct access to a simulator to find out). Any MCAS 2.0 software fix, can’t be downloaded directly into a simulator. It would have to be described from the
FCC vendor, to Boeing, to the Simulator vendor, and then incorporated into the simulators own software. (Anyone that knows better, please chime in) So, if and when airlines have the OK to load new MCAS 2.0 software into their grounded aircraft, I hope they have some testing, verification of their own to see that it’s installed correctly. Pilots
will then have a new control system installed into their aircraft, with no real ability to ‘fly’ with it, unless all of the changes had already been built into an updated simulator. Obviously, Boeing is flight testing the MCAS 2.0 changes, and hopefully an official Boeing test pilot report written for airline pilots, will be available. I don’t
trust the FAA, looking over Boeing’s shoulder at this point. I want a Chuck Yeager type to come out and say, I’ve flown this aircraft, under these conditions and here’s what I found. To put his personal reputation on the line. The same with the engineering and software. I’d like to see the engineers on the firing line, not some manager. I want to hear from the Morton Thiokol engineer, not the manager that signed off, but, the engineer who wouldn’t.
Richard, I get upset too. A great list of questions. All need to be answered!
Just a few more questions:
Why didn’t MCAS 1.0 look at height and airspeed sensor data. Why didn’t MCAS 1.0 look at inertial reference data, given they contain accelerometers.
Why the questions? MCAS 2.0 will now look at both alpha vanes but still ignore other data. Why? It takes a long time to write software algorithms that moderates numerious data inputs. So no, limit the inputs. The software algorithms becomes simple. But it doesn’t work, as proven by two crashes.
Boeing is still mickey mouse relative to Airbus. If Boeing want to use software algorithms to control their airplanes they need to do a lot more thinking!
Lots more questions!
As an illustration of Boeing’s Mickey Mouse-ness, look no further than their recent announcement that they were adopting a “model based systems engineering approach”. Terrific. That’s decades after everyone else, and I’m pretty sure NASA had a model based systems engineering approach back in the 1960s, i.e. back in the time the 737 was being developed.
Boeing feels like the sort of company that has got away with not doing systems engineering for a long time because there was no effective competition, and then it’s run into a competitor that does do systems engineering properly (Airbus) and has not paid sufficient attention to that. And so they’ve got into trouble almost without realising it. How else does one explain why Airbus made the A350 6″ wider than the 787?
I strongly suspect that the current delays to returning the MAX to the skies are because the truth of what is actually required is slowly sinking into the minds of Boeing’s management. However they’re probably still asking questions like “are you sure?” and “can you have another go?”. The fact that US politicians seemingly are now queueing up behind Boeing (and insulting pilots all over the world in doing so) is another bad indication that they’ve not fully accepted the situation they’re in.
“Model based…”. I noticed that too. Emperical science defines safety not theoretical science. If true, Boeing have lost it, big time.
Too true, Boeing seems to be affected by a paralysis of inaction. No one seems to believe in the MAX and they are going through the motions as if on strong tranquillisers. To think that we are looking at something close to 700 aircraft either grounded or not delivered by the back end of the year and still no design fix.
If, “Boeing (still) hasn’t turned over the MCAS revisions to the FAA for review, testing and approval.”
But on April 3, two and half months ago this read:
“(Reuters) – Boeing Co said on Wednesday its chief executive, Dennis Muilenburg, had joined a test flight on a 737 MAX 7 jetliner for a demonstration of updated MCAS anti-stall software.
During Wednesday’s test flight, the flight crew performed different scenarios to test failure conditions, Boeing said.
“The software update worked as designed, and the pilots landed safely at Boeing Field (near Seattle),” it said in a statement.
“Boeing will conduct additional test and demo flights as we continue to work to demonstrate that we have identified and appropriately addressed all certification requirements. We will submit the update for FAA (Federal Aviation Administration) review once that work has been completed in the coming weeks.”
Wonder what the hold up is on submitting MCAS 2.0?
No final accident reports have been issued yet. MCAS softwre has problems. That we know. But, the Lion Air aircraft had issues that seem to be more than just a bad AOA sensor. Multiple previous flights had airspeed issues. The installed a different AOA sensor and still had problems. Maybe there’s other software issues in the air data computer software? The Ethiopean accident working therory is that a bird hit the AOA sensor causing a sudden large change. I don’t know if anyone yet knows for sure. Again, a problem with the air data unit, or some other component might prove the problem, not the AOA sensor. If Boeing comes out with a fix for MCAS and then the final accident reports show that the cause is in another part of the software, or another part of the air data computer.. What then? Boeing probably has folks trying to help decipher the accident data, sifting out the true cause. They have to get it right this time, or go back to square one.
Philip
Not that I read.I think it was the New York Times article a few weeks back but not 100% certain.But I am 100% sure it was the previous chief test pilot who has now retired.And as I recall it was the ‘mark 1” problem which was the AOA at higher speeds as I recall.The article definitely states that he suggested the application of vortex generators.I guess to kill some lift at a particular AOA.But as you say they do create drag.Also the common theme running through all of this is that it had to be ‘just like the NG’ so they probably didn’t want to deviate too far and use a software correction.
“I’m confident the MCAS fix will make the airplane safe. LNA’s Bjorn Fehrm, an aerospace engineer and former fighter pilot, wrote he has not hesitation about flying the airplane once it’s got the MCAS fix.”
This confidence is based on something other than actual facts; it’s important to acknowledge that. Let’s call it a “feeling” that attention is now being paid. Fair enough. As far as we know, erroneous activation of MCAS will still be possible with <5.5 degrees of discrepancy between the 2 AoA sensors. This means that STAB TRIM would need to be cutout. That leaves the pilots with only manual HS trim for the remainder of the flight. This, as we now know from a lot of anecdotal feedback from pilots, is a potential problem at some level of probability for a second event X, unrelated to MCAS (I am assuming that the pilots would fairly easily have re-trimmed the airplane first).
Boeing could restore the STAB TRIM switch and circuit architecture of the NG to the Max, thus providing an off switch for MCAS but maintaining pilot access to the HS electric motor. Such a step would cut through a lot of nonsense. Peter Lemme has gone into this in detail.
Scott wrote:
“Scott McCartney, the “Middle Seat” columnist for the Wall Street Journal and a private pilot, sat in the third seat of a simulator and flew the sim through MCAS 1.0 and 2.0. The 1.0 was virtually unrecoverable. The 2.0 was benign and easily recoverable.”
That’s fine, but it rather assumes that an MCAS 2.0 system that is supposed to be limited in how much down trim it can generate is in fact genuinely limited, and that there are no fault conditions / failure paths leading to it acting inappropriately. Given that (AFAIK) there are only one FCS in circuit at any time on the 737, and that safety critical certification requirements demand 3, it’s difficult to see where that guarantee comes from.
So yes, it may well have behaved nicely whilst a WSJ chappie was in the cockpit, but that’s not the same as “safe to fly” under all reasonable circumstances. However it does indicate what behaviour an appropriate implementation should exhibit.
I wonder if Scott McCartney will get called as a witness against Boeing in the coming court cases?
There was a Wall St. Journal Article 6/20/2019 .. discussing the effort involved in moving the manual trim wheel in certain situations. Unnamed FAA and Boeing were reviewing the manual trim wheel procedures in terms of physical strength.
https://www.wsj.com/articles/physical-strength-of-pilots-emerges-as-issue-in-returning-737-max-to-flight-11560937879?mod=hp_lead_pos2&ns=prod/accounts-wsj
or the non-paywalled version The FAA today refuted some of the discussion
https://www.cnbc.com/2019/06/19/faa-says-pilot-strength-isnt-delaying-boeing-737-max-recertification.html
I have a simple solution. Change the two Stab Trim Cutout switches to work as they did on the original 737. That will give pilots something to do, when they see the AOA disagree light come on. Emergency Procedure step 1) flip Stab Trim Cutout switch #2 to OFF position, disabling the autopilot and MCAS. Step 2) fly the plane using manual electric trim. This would involve changing the switch wiring, repainting the switch panel and another page in the quick reference guide. No hand cranking of the trim wheel required. I wonder why they haven’t thought of this yet? (and why Peter Lemme’s doesn’t have an answer from Boeing on why they changed the switch settings in the first place).
There’s seems to be more focus on the trim system of the 737-MAX because of the inability of the ET 302 flight to move the trim manually at high speed.
https://www.chicagotribune.com/business/ct-biz-wp-boeing-737-max-cockpit-controls-20190620-2du2u45m7bdvnmvqhv3dqfxa6a-story.html
MCAS is part of the STS (Speed Trim System). Could the FAA / Boeing be thinking about limiting the amount of trim ability at high speeds on the 737’s? It would have to be a fully FBW certified system, but, would limit the ability of the Stabilizer at high speeds. I can’t think of any need for high trim settings at high speeds? If a pilot notices a mountain on go around, he’ll be pulling up on the elevator, just long enough to clear the obstacles. This would help keep the aircraft in the safe zone of the flight envelope, from the trim point of view, still allowing elevator authority. The only bad thing I can think of would be working against a jammed elevator. You’d want all the trim ability you could muster then.
As for someone’s claim that Boeing would not keep producing 737s if there were to be hardware changes, not just software changes, note that rework after rollout is often done. Yes, it is costly, but so is stopping and restarting a production line. Think it through as if you were in the shoes of Boeing’s bureaucrats.
(Of course changes to computer and display hardware are easily done since those are in LRUs easily changed, though needing some testing after reinstallation.)
(Boeing may have a workforce problem – if they slash production rate people who get laid off may bail to other jobs to feed their families, etc. and not return soon if at all. Perhaps Boeing can convince more production employees to take vacation in this summer.
Technicians will be very busy once the software change is approved, depending in part on how much testing after installation is needed in this situation where some people may be concerned about the possibility of existing wiring errors. (Yes, I’m guessing, perhaps wiring checks can be done before then.)
We keep referring to Boeing’s MCAS and Boeing’s software changes, but, I’m guessing Boeing is really just directing, helping manage, and testing the software. The actual software being written and produced by a 3rd or 4th party. Actually, Boeing has outsourced for years, a lot of the avionics. As referred to in this article.
https://www.seattletimes.com/business/boeing-aerospace/boeing-setting-up-new-in-house-unit-to-build-avionics-controls/
And…. I don’t think people commenting on ‘model-based’ know what they are talking about.
It isn’t a panacea, and its usefulness depends on what the aspect being coded is – logic or user interface for example. And what is meant by ‘model’ – a display layout for example can be made graphically but the logic behind what to display when may be trickier.
Yeah, even Nancy A. Levenson misled in a trashy article someone published, her remarks did not cover practices in high integrity work like aircraft.
(And certainly we don’t want ‘model’ to mean a theory that have not been checked against reality – the case with climate alarmists.)