Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

[FrequentSLF]

Originally Posted by b1lanc

1) 737 Max is not FBW.
2) Cite your source for "FAA certifying Max in a hurry". That's utter BS. EASA ceritified it also. Were they also in a hurry?
3) It does no airline any good that flys both types. Regardless of the the certification process, an AB or B going down is not only reflective of the manufacturer but also of the airline. It impacts both manufacturers.

What a crock.

1 - Spoilers on MAX are FBW... MCAS on some extent could fall on that definition
2 - FAA delegated Boeing on certification, literally is not in a hurry, they did that because did not have sufficient workforcemto do it... which translates in a hurry, since waiting was not an option. EASA certified because of mutual agreement

[568]

Originally Posted by KRUSTY 34

Some years ago I read an interesting book on the development of the 787. Afterwards I somewhat sarcastically remarked that this aircraft will be the end of Boeing.

It appears that I was wrong!

Wait a couple of years!https://www.aljazeera.com/investigations/boeing787/

[tdracer]

I see the farcically false statements about certification process are coming back.
Repeating myself again, but go read Of modern airliner certification

[568]

Originally Posted by b1lanc

1) 737 Max is not FBW.
2) Cite your source for "FAA certifying Max in a hurry". That's utter BS. EASA ceritified it also. Were they also in a hurry?
3) It does no airline any good that flys both types. Regardless of the the certification process, an AB or B going down is not only reflective of the manufacturer but also of the airline. It impacts both manufacturers.

What a crock.

2) Widely reported that this may have been an issue from the onset.3) Commercial considerations are at play when flying "mixed" aircraft fleets.EASA also relies on the NAA (FAA in this regard) for compliance with relevant cert requirements!

[568]

[QUOTE=tdracer;10441220]I see the farcically false statements about certification process are coming back.
Repeating myself again, but go read https://www.pprune.org/tech-log/6195...685[/QUOTE]It may also be beneficial to state that any manufacturer may highlight "any possible" developments in improving flight characteristics during the cert stages.

[tdracer]

Originally Posted by 568

2) Widely reported that this may have been an issue from the onset.

Schedule pressures are hardly new on an aircraft cert - every day delay in getting Type Cert costs the airframer millions of dollars/euros, so they tend to pay attention to that stuff.
When Boeing became a delegated authority, Boeing and the FAA jointly negotiated a document the governed the process. It's huge (well over 1,000 pages and regularly updated) and governs everything from what can be delegated (and what can't be) to standard flow times for how long the FAA has to approve or reject a cert submittal. A new aircraft is a massive program, with thousands of interrelated tasks - knowing flow times is critical to putting together a schedule.
One of my biggest complaints with the FAA was that they routinely ignored the assigned flow times - reviews (approvals) that were supposed to happen in two weeks often took months. One of the things that went into our work performance review was meeting out schedule commitments - and it was hugely frustrating to bust my butt to make a cert submittal on time, only to have it sit in some FAA in basket while I missed my certification due dates.
No first hand knowledge here, but my suspicion is that much of this reported schedule pressure was simply Boeing insisting that the feds meet the flow times that they'd previously agreed to.

[GordonR_Cape]

Originally Posted by OldnGrounded

Without commenting on the merits of Nader's statement, I'll just point out that taking him seriously on matters of transportation safety is pretty much baked onto US culture. He will not be ignored or dismissed.

I am fully aware of Ralph Nader's history and reputation. My point was twofold: His comments add nothing new to the technical understanding of the causes, nor the existing media clamour. It should not matter whose relatives died in a plane crash, the numbers speak for themselves. There were multiple UN representatives from many countries on the Ethiopian flight, most arguably more well known around Africa (where I live), and others worldwide, outside the narrow scope of US media. Imagine a news headline that reads "massive plane crash in Africa, one US citizen dies". Confusing sympathy with advocacy does not make for a valid argument. All of those factors informed my gut reaction. Sorry for the rant.

[fizz57]

Originally Posted by b1lanc

1) 737 Max is not FBW..

This, I think, is the heart of the problem. Not an FBW aircraft, while being increasingly expected to behave like one.

[FlightlessParrot]

@tdracer: I respect your comments. May I ask if you have any idea why the FAA were slow? It could be that all bureaucrats are incompetent and feckless (a right-wing answer), or it could be that the FAA was under-resourced (a left-wing answer).

[Caygill]

Originally Posted by Ian W

It doesn't seem a particularly difficult task although the avionics architecture separation may make it less simple.

1. The ADIRUs receive mismatching AoA, instead of reporting 'Unreliable Airspeed' they should just disregard AoA inputs and report 'AoA Mismatch'.
2. Then as AoA is mismatched it has to be assumed that MCAS is receiving the incorrect AoA, so
3. Disable MCAS,
4. Steps 1 - 3 can only be reset by maintenance with weight on wheels
5. If MCAS is essential then AOG until AoA reporting is matched and test flown.

I also think using the input from two AoA sensors would allow an almost foolproof foundation. With any understanding of data science, voting out the faulty should not be hard - and if not possible, due to both providing sane enough data, that could lead to a different outcome.

But we need to allow killing MCAS without killing the electrical trims.

[b1lanc]

Originally Posted by CurtainTwitcher

Do you have a link for the Airbus Test Plan? I managed to find a link that looks interesting: AIRBUS FLY-BY-WIRE: A TOTAL APPROACH TO DEPENDABILITY,
Is that the one you are talking about?

Unfortunately no. They shared their FBW test strategy with the DoD (Army actually) back in the late 70's while FBW was still in development infancy. Everything was hard copy. I left those documents with the company I then worked for.

[b1lanc]

Originally Posted by tdracer

I see the farcically false statements about certification process are coming back.
Repeating myself again, but go read Of modern airliner certification

My perspective having dedicated FAA reps on site at two prior locations - FAA has always been top loaded and under-funded and under-resourced at the technical level. USAF adds to the FAA workload. It isn't only certifications that suffer, but ATC upgrades take generations.

[lomapaseo]

Originally Posted by FlightlessParrot

@tdracer: I respect your comments. May I ask if you have any idea why the FAA were slow? It could be that all bureaucrats are incompetent and feckless (a right-wing answer), or it could be that the FAA was under-resourced (a left-wing answer).

May I ask what this question refers?

Does it have something to do with the initial certification or does it refer to the recent action against the type cert?

[JPcont]

Originally Posted by FlightlessParrot

May I ask if you have any idea why the FAA were slow? It could be that all bureaucrats are incompetent and feckless (a right-wing answer), or it could be that the FAA was under-resourced (a left-wing answer).

One problem could be that regulators have taken closer look the actual implementation rather than definitions in the paper work. MCAS is clearly more AoA (stall prevention ) related feature than maneuvering characteristics related feature. It might be that the regulator expects that it is certified as such.

The MCAS measures the AoA and so it tries to control AoA due the feedback measurement it uses. As far as I have understand, the stall depends mostly on AoA and less on Reynolds and even less other factors (in a specific plane). The “stick force augmentation” is only a side effect of MCAS control law. The system dynamics and fluid mechanics are not interested in the political naming convictions and they don't care economical consequences. They follow their own laws and don't care of our opinions. So, also we should care of the namings.If the aim really have been to emulate the “grandfather feeling”, the main feedback would have been the stick force (not AoA). The set point to the sick force would been calculated from AoA and other factors.

That kind of control law (with stick force limits) should have not force (with reasonable force limits) the plane ground even if the actuator were the stabilizer. I hope, the shortcuts are not allowed this time.

[Fonsini]

Regardless of the technical intricacies of fixing one of the worst single point failures in any modern aircraft one thing remains certain, as and when the Max goes back into service any subsequent crash resulting from any type of control issue will end this aircraft. Pax will simply not fly on the things.

[Arydberg]

He wrote a book about a car called " unsafe at any speed" about the corvair. The car was discontinued

[GlobalNav]

Originally Posted by JPcont

One problem could be that regulators have taken closer look the actual implementation rather than definitions in the paper work. MCAS is clearly more AoA (stall prevention ) related feature than maneuvering characteristics related feature. It might be that the regulator expects that it is certified as such.

The MCAS measures the AoA and so it tries to control AoA due the feedback measurement it uses. As far as I have understand, the stall depends mostly on AoA and less on Reynolds and even less other factors (in a specific plane). The “stick force augmentation” is only a side effect of MCAS control law. The system dynamics and fluid mechanics are not interested in the political naming convictions and they don't care economical consequences. They follow their own laws and don't care of our opinions. So, also we should care of the namings.If the aim really have been to emulate the “grandfather feeling”, the main feedback would have been the stick force (not AoA). The set point to the sick force would been calculated from AoA and other factors.

That kind of control law (with stick force limits) should have not force (with reasonable force limits) the plane ground even if the actuator were the stabilizer. I hope, the shortcuts are not allowed this time.

Is it accurate to say that MCAS is AoA stall prevention at all? How would it prevent a stall at all, in normal, non-malfunctioning conditions? It adds nose down trim, yes, while the A/P is off, but it doesn't really prevent stall, at best it gives the pilot a better trim condition for high AoA, which might enable the pilot to prevent a stall. Just asking. MCAS does not make the 737 impossible to stall.

[42...]

MCAS, again, is not a stall prevention device, it is a handling modifier. It makes the nose feel heavier to the pilot. Catastrophically so if activated improperly.

It is or claimed to be needed by Boeing flight engineers to prevent a lighter than desired stick force at higher AOA's.

The jet is designed to feel nose heavy at high AOA, the MAX engines being further forward in CG, act to increase nose up moments at higher AOA, not because of thrust, because of the aerodynamics of the motors being further forward. This lighter nose feel was not desired by the engineers, so MCAS was developed, or so I have read. Of note I believe in the two years the MAX has flown, the MCAS has never activated. Except for two accidents, erroneously.

[A0283]

Originally Posted by b1lanc 1) 737 Max is not FBW.

Certainly not saying you are right or wrong here (that would depend on how you define "FBW" and how you define a "FBW AIRCRAFT"). But we have to note that Boeing uses the term "FBW" in its own documentation for the MAX. And, in his Senate hearing testimony the acting Administrator of the US FAA uses the term "FBW" for the MAX.

There are at least 2 functions and solutions in the MAX that, depending on how you define it, could be ranked under FBW.

If you accept them as such, then we would have to make a distinction between aircraft with one or more 'FBW functions' and 'FBW aircraft'. For some this distinction might not be big, but for others this is big.

For the last group of people, definitions are extremely meaningful and therefore important. If you use another definition then you may be talking about very different 'things'.

For example - one way to look at it is - that the A320 came with a "FBW unless philosophy" (which implies a certain level of "automation", but also added a "glass cockpit" and "sidesticks", and embedded this in the philosophy of "how and where Airbus puts pilots in the loop" (which implies a certain level of "automation").

Between the 'iron' 737 and the 'fbw' 320 there is a large grey area. The 737MAX is somewhere in that grey area. The 2 accidents discussed here indicate to me that we all need clearer definitions. We need them first to understand eachother, and second to get to better solutions.

[fizz57]

Originally Posted by 42...

It is or claimed to be needed by Boeing flight engineers to prevent a lighter than desired stick force at higher AOA's.

The stick force gradient is a certification requirement.