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scbriml
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:16 pm

patrickjp93 wrote:
It was more expensive to develop MCAS and move the engines forward than it would have been to raise the landing gear, but raising the gear was made off-limits under grandfathering for the type. That's a failure of the regulation framework, simple as that. Iterative improvement has to be allowed.


How much did it cost to develop MCAS and the LEAP pylons?

All those were Boeing choices. Choices taken to try and shoehorn the MAX into the "it's just another 737" category so as to not require additional training. We have been told many times that replacing the 737's training wheels represents a very significant engineering exercise because there simply isn't the space there for longer gear. So you'd probably be looking at an entirely new winbox and associated structures. I'm struggling to believe writing some bad software was more expensive than engineering a new wing box (new pylons would have to be developed anyway).

patrickjp93 wrote:
There's plenty of room to expand the gear. Remember the 737's landing gear doesn't raise into a closed bay. It's just flush with the underside of the fuselage. It's fairly trivial to expand it.


It simply isn't "fairly trivial". We've had 737 engineers tell us before that there is no spare space for enlarged gear without a significant re-engineering of the wingbox. This topic was discussed many times during the gestation of the MAX, not least when it became clear that Boeing was using a physically smaller version of LEAP than Airbus.
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Exeiowa
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:16 pm

I remember when I thought after 3 years in my profession I knew everything.....
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:18 pm

patrickjp93 wrote:
kalvado wrote:
patrickjp93 wrote:
Changing avionics architecture would be too big, certainly. Moving from cables to FBW would be too big. Moving from Bleed Air to Bleedless would be too big. Extending landing gear and the minimal geometry changes required while not impacting the handling of the plane should be sufficiently small. The other point to consider is small enough between generations, and probably providing a sunset on common type ratings to be within one generation. In other words, if you hold training on the NG, you can move up to the MAX or down to the Classic with differences training, but if you train for the MAX and have to move to the Classic, you do the full training regimen instead of just differences training as you would for the NG, and your pilot type certificate for the MAX is revoked and replaced with the Classic.

There are easy, sensible ways to manage all of this together. Despite what many on here might consider hubris or paradigm-changing thought on my part, this is simple stuff to think through, analyze, and validate. I'm not a genius, so seriously, think through what I propose and argue on the merits/demerits. It's not like we on here are too stupid to go work at the highest levels of the FAA. The entire structure is based on seniority rather than skill anyway.

Each complex question has a great answer - simple, obvious and wrong.
Let's see how well your position holds water.
From your perspective, how floor strength rating question should be addressed? Modern rules require higer impact strength of cabin floor than what is available on 737 family, and that would be a major redesign. It is not piloting related, it is structural redesign. Cost may approach - or exceed - that of pilot retraining, though. The weaker floor is grandfathered in on MAX as it is only a small change of 737-100.

What kind of changes you think should trigger enforcing that change?

The cost would not exceed pilot retraining and the $1 billion it's now going to cost Boeing in compensating airlines for 1000+ frames at 1 million a pop. Second, this is where regulators and OEMs can work together to improve a grandfathered design without foisting undue secondary consequences from that improvement. Reinforcing the floor beams does not materially change the aerodynamic handling. It may change some rotation inertial moments to a tiny degree, but it uniformly adds weight throughout the fuselage. If that means the wing has to move back one inch to retain CoG over the wing box and thus the handling, fine, but you can still grandfather the common type just fine. It's not much more of a modification than a stretched variant.

You keep mentioning aerodynamics chages - but that is only one part of the deal.
Strength of the structure, weight, seformation/oscillation modes - things may change quite a bit. It is just one thing which may be cost critical - and your response is basically "deal with it... somehow". That makes regulator toothless.
and a billion here, a billion there - we're talking some serious money at the end of the day.
 
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scbriml
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:19 pm

patrickjp93 wrote:
Telescoping gear that retract before being stowed. Good lord they already know how to do that for the MAX 10 just for takeoff to prevent tail strikes.


That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:20 pm

zkojq wrote:
morrisond wrote:
ET though knew if they had intermittent trim issues treat it as Runaway Trim and run the appropriate checklist - there is just a lot of debate of how well or did they even get that information to their pilots.


and yet each and every single time I've pressed you on this and asked you to provide a source for your allegation you've either brushed it off and provided nothing or completely ignored me all together.


From this article - Scroll down past the damning Maintenance issues at ET to get to the Pilot Part https://www.businessinsider.com/boeing- ... er-2019-10

"Another whistleblower from Ethiopian, veteran pilot Bernd Kai von Hoesslin, told the AP in May that after Indonesia's Lion Air crash, he pleaded with Ethiopian's top executives to give pilots better training on the Max, predicting that if pilots are not sufficiently drilled on Boeing's protocols for how to disable the autopilot system in the event of a misfire, "it will be a crash for sure."


Ethiopian has said the pilots followed all the steps Boeing laid out. But the preliminary report on the crash showed they deviated from the directives and made other mistakes, notably flying the plane at an unusually high speed and inexplicably reactivating the anti-stall system shortly after manually overriding it. Six minutes into the Max flight, the plane with passengers from nearly a dozen countries cratered into the ground about 40 miles from the airport."

From AVHerald https://avherald.com/h?article=4c534c4a

"On Apr 11th 2019 The Aviation Herald received a full copy of the Flight Operations Manual (FOM), Revision 18B released on Nov 30th 2018, which is currently being used by Ethiopian Airlines (verified in April 2019 to be current). Although Boeing had issued an operator's bulletin on Nov 6th 2018, which was put into Emergency Airworthiness Directive 2018-23-51 dated Nov 7th 2018 requiring the stab trim runaway procedure to be incorporated into the FOM ahead of the sign off of this version of the FOM (the entire document is on file but not available for publishing), there is no trace of such an addition in the entire 699 pages of the FOM.

Quite the opposite, in section 2.6 of the FOM "Operational Irregularities" the last revision is provided as Revision 18 dated "Nov 1st 2017".

According to information The Aviation Herald had received in March 2019, the Airline Management needed to be reminded to distribute the Boeing Operator's Bulletin as well as the EAD to their pilots, eventually the documents were distributed to the flight crew. However, it was never verified, whether those documents had arrived, were read or had been understood. No deeper explanation of the MCAS, mentioned but not explained in both documents, was offered.

It turned out, that only very cursory knowledge about the stab trim runaway procedure exists amongst the flight crew of Ethiopian Airlines even 5 months after the EAD was distributed. In particular, none of the conditions suggesting an MCAS related stab trim runaway was known with any degree of certainty. In that context the recommendation by the accident flight's first officer to use the TRIM CUTOUT switches suggests, that he was partially aware of the contents of the EAD and reproduced some but not all of the provisions and not all of the procedure, which may or may not explain some of the obvious omissions in following the procedure in full."

The references speak for themselves. I'll just keep posting this whenever someone else insinuates I'm a liar and making this stuff up.

As I've said I am not blaming the pilots - I am blaming the ET training system that seems to have done a terrible job of instructing there Pilots on how to deal with MCAS.
Last edited by morrisond on Tue Jan 14, 2020 3:36 pm, edited 1 time in total.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:24 pm

scbriml wrote:
patrickjp93 wrote:
It wasn't impossible or unreasonable. The rules were wrong. They should have been changed.

So we need to add "The rules were wrong" to the list of reasons why it's not Boeing's fault?

Shouldn't we be able to explore the FAA's role in the MAX tragedy without triggering the fear of Boeing absolution gag reflex?
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:28 pm

The LEAP program started in 2005 and LEAP engines were launched in 2008. Nine years is enough time to realize engines are too big.

Visually for me, C-Series engines looked disproportionately big for the frame, how is it handling CG issues?
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:29 pm

CSeries/A220 is full fly by wire and newly made for those engines.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:31 pm

Lock
TheWorm123 wrote:
Same story is carried by a tech publication The Verge as well, they’ve got some more extensive redacted emails;
https://www.theverge.com/2020/1/9/21059 ... ator-crash

Them
YouGeeElWhy wrote:
Boeing Mocked Lion Air Calls for More 737 Max Training Before Crash
https://www.bloomberg.com/news/articles ... hwarted-it

Up
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:54 pm

Checklist787 wrote:
Scbriml, are you sure to have readen D. Calhoun's email?...

https://www.boeing.com/features/2020/01 ... oyees.page


I have. Was it accompanied by emotional music and film of a soaring eagle in front of Mt Rainier?

What do you think has changed at Boeing since "Dave" started work at his new job yesterday morning? Not forgetting that he was a member of the Board that oversaw Boeing's slide to its current position, so he's not exactly untainted.
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:57 pm

scbriml wrote:
patrickjp93 wrote:
It was more expensive to develop MCAS and move the engines forward than it would have been to raise the landing gear, but raising the gear was made off-limits under grandfathering for the type. That's a failure of the regulation framework, simple as that. Iterative improvement has to be allowed.


How much did it cost to develop MCAS and the LEAP pylons?

All those were Boeing choices. Choices taken to try and shoehorn the MAX into the "it's just another 737" category so as to not require additional training. We have been told many times that replacing the 737's training wheels represents a very significant engineering exercise because there simply isn't the space there for longer gear. So you'd probably be looking at an entirely new winbox and associated structures. I'm struggling to believe writing some bad software was more expensive than engineering a new wing box (new pylons would have to be developed anyway).

patrickjp93 wrote:
There's plenty of room to expand the gear. Remember the 737's landing gear doesn't raise into a closed bay. It's just flush with the underside of the fuselage. It's fairly trivial to expand it.


It simply isn't "fairly trivial". We've had 737 engineers tell us before that there is no spare space for enlarged gear without a significant re-engineering of the wingbox. This topic was discussed many times during the gestation of the MAX, not least when it became clear that Boeing was using a physically smaller version of LEAP than Airbus.
Based on the expenditures made public about developing it for the KC-46 program, I'd say roughly 300 million for MCAS since the flight control computer architecture is different.

The space is there for longer gear if they can telescope. The MAX 10 proves this. The difference is whether they can stay extended for all ground phases rather than just takeoff & landing.

You're forgetting MCAS has a hardware implementation aspect to it too.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:57 pm

scbriml wrote:
patrickjp93 wrote:
Telescoping gear that retract before being stowed. Good lord they already know how to do that for the MAX 10 just for takeoff to prevent tail strikes.


That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 3:58 pm

dtw2hyd wrote:
Visually for me, C-Series engines looked disproportionately big for the frame, how is it handling CG issues?

The A220 has sufficient ground clearance for its engines so it does not need to have the engines in front of the wing impeding and changing the airflow. The issue the MAX has is more aerodynamic related to lift/drag than CG as CG would be very easy to fix.
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:00 pm

Exeiowa wrote:
I remember when I thought after 3 years in my profession I knew everything.....

I don't think I know everything. I think I'm perfectly capable of sitting at the adult table and reasoning through issues just as complex as they do.

Do you know what another good word for experience is? Codified bias.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:02 pm

kalvado wrote:
patrickjp93 wrote:
kalvado wrote:
Each complex question has a great answer - simple, obvious and wrong.
Let's see how well your position holds water.
From your perspective, how floor strength rating question should be addressed? Modern rules require higer impact strength of cabin floor than what is available on 737 family, and that would be a major redesign. It is not piloting related, it is structural redesign. Cost may approach - or exceed - that of pilot retraining, though. The weaker floor is grandfathered in on MAX as it is only a small change of 737-100.

What kind of changes you think should trigger enforcing that change?

The cost would not exceed pilot retraining and the $1 billion it's now going to cost Boeing in compensating airlines for 1000+ frames at 1 million a pop. Second, this is where regulators and OEMs can work together to improve a grandfathered design without foisting undue secondary consequences from that improvement. Reinforcing the floor beams does not materially change the aerodynamic handling. It may change some rotation inertial moments to a tiny degree, but it uniformly adds weight throughout the fuselage. If that means the wing has to move back one inch to retain CoG over the wing box and thus the handling, fine, but you can still grandfather the common type just fine. It's not much more of a modification than a stretched variant.

You keep mentioning aerodynamics chages - but that is only one part of the deal.
Strength of the structure, weight, seformation/oscillation modes - things may change quite a bit. It is just one thing which may be cost critical - and your response is basically "deal with it... somehow". That makes regulator toothless.
and a billion here, a billion there - we're talking some serious money at the end of the day.

Resonance and oscillatory wear and tear are highly predictable these days. Architects in Singapore and Japan have been employing AI-driven solutions to testing and verifying the design requirements and conditions for nearly a decade. I did say aerospace is behind on their methods by 15 years for a reason.
 
XRAYretired
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:07 pm

patrickjp93 wrote:
PixelFlight wrote:
patrickjp93 wrote:
No, the designation drove absolutely no engineering choices on the part of the engineers.

Yes it does, per regulation requirements and as described into the relevant standards.

https://www.faa.gov/regulations_policie ... 241996.pdf
https://en.wikipedia.org/wiki/AC_25.130 ... riticality
https://en.wikipedia.org/wiki/DO-178C#Software_level
"The number of objectives to be satisfied (some with independence) is determined by the software level A-E"

Please read the JT610 final report. Start at E.1 "Functional Hazard Assessment" and see the Figure 2: "Failure Effect Categories"

Sigh, you're not listening. Separate the facts from the story. If Boeing's engineers had built the system as they wanted, the designation wouldn't have mattered. Redundancy and failover would have been built in by default. It's how their brains work for crying out loud. The only thing that the system engineers might have missed is mandating the AoA disagree light in the cockpit, but to be fair the avionics architects and designers most certainly would not have since management wouldn't have been mandating the costs of doing so away.

I've read the JT610 report. You're misinterpreting it. It's not the designation that matters. It's the end system that does. They'd have been a fault-tolerant system if allowed, and not because any designation said so, but because common sense said so as all of us prove.

Sigh, the misinterpretation is all yours. JATR, NTSB and FAA concur as do reputable commentators. Funnily enough, they concur with narrative we have from as close as we can get to the design team.

'....One of the people familiar with MCAS’s evolution said the system designers didn’t see any need to add an additional sensor or redundancy because the hazard assessment had determined that an MCAS failure in normal flight would only qualify in the “major” category for which the single sensor is the norm....'
https://www.seattletimes.com/seattle-ne ... afeguards/

As we know, the safety assessment was based upon flawed and un-validated assumptions and dodgy discounting.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:10 pm

Revelation wrote:
scbriml wrote:
patrickjp93 wrote:
It wasn't impossible or unreasonable. The rules were wrong. They should have been changed.

So we need to add "The rules were wrong" to the list of reasons why it's not Boeing's fault?

Shouldn't we be able to explore the FAA's role in the MAX tragedy without triggering the fear of Boeing absolution gag reflex?

Only if you add the necessary caveats BEFORE starting the discussion.
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:15 pm

par13del wrote:
Revelation wrote:
scbriml wrote:
So we need to add "The rules were wrong" to the list of reasons why it's not Boeing's fault?

Shouldn't we be able to explore the FAA's role in the MAX tragedy without triggering the fear of Boeing absolution gag reflex?

Only if you add the necessary caveats BEFORE starting the discussion.

Says you. The FAA should be raked over the coals six ways from sunday and the facts support that.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:18 pm

dtw2hyd wrote:
The LEAP program started in 2005 and LEAP engines were launched in 2008. Nine years is enough time to realize engines are too big.

Visually for me, C-Series engines looked disproportionately big for the frame, how is it handling CG issues?


The LEAP programme is different from the LEAP-1B which is a specific engine type. Legally it is a different engine from the LEAP-1A/C. The sizing of the LEAP-2 was done in concert with the sizing of the 737MAX.

As for the engine being too big. I am flummoxed by the idea that it is physically too big for the airframe. However, its size and the resulting installation requirements meant that the predictions of aircraft performance approaching stall were less precise than they would otherwise have been. This ultimately necessitated changes to the flight control system to ensure compliance with the certification standards. Changes to the flight control system are not unheard of between variants of aircraft. We saw it with the DC-9 series which stayed on one TC just like the 737.

The issue is that Boeing 'convinced' the regulators that these changes were transparent to the flight crews and the failure modes were sufficiently similar to those for prior 737s that no further training was necessary. Further, Boeing also convinced the regulator that the severity of failure in the new system was sufficiently low that the fail-active situation did not have to be mitigated against. In reality these were not the case. The system is somewhat different in normal operations, such that it might cause confusion when operating as intended, and its failure mode is sufficiently different so as to create catastrophic chains where they did not exist before.

The issue with the performance as the aircraft approaches stall has little to do with the CG changes from the engines being heavier, which is a function of mass distribution about the aircraft, but instead has to do with the location of the neutral point (NP) and the effective aerodynamic centre of the wing (AC), plus the lift curve slope of the wing/nacelle/body configuration approaching and through 'stall'. The stick force is a function of how close the neutral point is to the centre of gravity. The closer they are together the more elevator authority you have. This means you would need less stick force to increase the pitch angle and angle of attack. The distance between the NP and CG is known as static margin. In the first order we teach people that the AC of a wing and the resulting NP of an aircraft don't change with AoA. However, that isn't true. The AC and NP only remain fixed a few situations, and in reality we don't want it to remain fixed (for the purposes of stall ID). For Aft-swept wing aircraft the NP moves forward as the Angle of attack increases. This will reduce stick forces. When coupled with a closely coupled nacelle it will more even more radically forward, hence the need to 'artificially' increase stick force by moving the aircraft out of trim. Note you get a similar issue with increasing Mach where the neutral point moves aft as Mach increases. The result is that as you slow down, and your angle of attack increases you can get stick lightening also, hence one of the reasons for Mach trim on deceleration.

Another problem with the aerodynamics that cause the NP to move is that they also reduce the ability of the aircraft to stall 'cleanly'. Ideally, you would like the wing to stall in such a way that the stick force required to maintain AoA is effectively infinite. This prevents the pilot from holding the aircraft in a stall or worse 'deepening' the stall. This problem was identified with a number of non-FBW aircraft, including the 737NG by the European airworthiness authorities. It looks as if MAX's stall performance is even less defined hence the 1g MCAS rules. While T-tail aircraft are know to have "deep stall" problems, whereby you cannot bring the nose down from some stall conditions, this problem isn't universal. 727s don't exhibit true deep stall, and it looks like the longer bodied DC-9 series doesn't either. However, both airframes have issues with stall identification, which has lead to a couple of fatal accidents where pilots held the aircraft in a stall. The A330 and A320 without envelope protection also exhibit this problem.

The solution to the stall identification problem is relatively straight-forward. You add some form of angle of attack envelope protection. This can be 'soft' or 'hard'. The softest form is to modify the elevator feel, either by nudging the stick slightly or miss-trimming the aircraft as you approach stall. This is what the Speed trim system in 737NG does. The harder methods include a stick pusher/kicker which physically forces the stick forward (making it increasingly hard to hold back) to not allowing the aircraft to be above a given angle of attack. The problem with this protection is what happens when the sensors that drive it go wrong. The softer the protection the easier it is for the pilot to counter it. If it is soft enough you don't have to ensure that the system is fail-safe. For hard protection systems fail-safe is essential. MCAS is agressive enough and the failure mode different enough from STS that fail-safe was necessary, but not included.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 4:39 pm

According to https://twitter.com/jonostrower/status/ ... 8152130560 American Airlines sees a return to service in June:

American Airlines joins United in again pushing back 737 Max service reentry date. The airline will resume schedule flights on June 4 now, another two month extension.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:01 pm

It is long due to discuss the role over regulation had in the process. Boeing could have made a better product without FAA oversight.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:12 pm

patrickjp93 wrote:
scbriml wrote:
That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.


What good is a glass dagger? What gain do you see here?

The extendable ( by way of being softer sprung in a nonlinear way) -10 gear is a Rube Goldberg solution.
It is the mech designers equivalent of a Redneck's Playboy Centerfold. .-)
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:16 pm

seahawk wrote:
It is long due to discuss the role over regulation had in the process. Boeing could have made a better product without FAA oversight.

They had the chance. There was no working FAA oversight for the MAX.
( and some of the other recent projects too? nobody dared to really look yet.)
Murphy is an optimist
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:27 pm

Exeiowa wrote:
I remember when I thought after 3 years in my profession I knew everything.....

I think one issue younger people have problems understanding is that in large teams our work has to be understood by large numbers of people, many without the kind of specialist knowledge we have, and unfortunately in a few too many cases, some without the ability to ever master some things we are able to master. It's so easy for a younger person to say I figured it out, why shouldn't you? Yet people with lesser knowledge or skills will need to work with our work so it either better be easy to understand, or be very well protected from modification by others. So many things I worked on that were carefully constructed later got wiped away by some heavy handed engineer "fixing" something, or some automated merge dumping changes into things that were already done correctly.

scbriml wrote:
What do you think has changed at Boeing since "Dave" started work at his new job yesterday morning? Not forgetting that he was a member of the Board that oversaw Boeing's slide to its current position, so he's not exactly untainted.

Or, for that matter, what has changed since McAllister walked the plank and Deal was installed many weeks ago?

IMO the Calhoun email still has a large amount of corporate doublespeak in it. Is their new transparency going to extend to examining how the "no sim training" mantra became established? It seems all the communications in the dump happened after the mantra was installed so we can't figure out exactly who in engineering signed off on accepting such a condition, which clearly happened very early in the program.

patrickjp93 wrote:
scbriml wrote:
patrickjp93 wrote:
Telescoping gear that retract before being stowed. Good lord they already know how to do that for the MAX 10 just for takeoff to prevent tail strikes.

That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.

Exactly, so it allows for a longer tail, but not a bigger engine. The extension at rotation happens because gravity pulls the gear down once the aircraft weight is removed which in turn fills a cylinder with air which allows the gear be supported once it is elongated, it is not a powered lift mechanism.

XRAYretired wrote:
As we know, the safety assessment was based upon flawed and un-validated assumptions and dodgy discounting.

https://assets.documentcloud.org/docume ... 8-MCAS.pdf is Boeing's accounting of MCAS's Development and Certification. I'd love to see a dump of the author of this document's email/texts, and/or those who wrote the documents it references. Seems if there is to be a smoking gun to be found it would be management leaning heavily on these people to turn a blind eye when preparing these analyses.

Interesting reference/background for this material: https://twitter.com/dominicgates/status ... 9655115776

It's hard to tell if the message dumps we have are mostly focused on the sim development and training issues because (a) other areas were given a good scrub and nothing was found, or (b) these were the least damaging things found and more were revealed to beat up the well known parties some more and not expand the scope to others.
Last edited by Revelation on Tue Jan 14, 2020 5:31 pm, edited 1 time in total.
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:27 pm

patrickjp93 wrote:
dtw2hyd wrote:
patrickjp93 wrote:
...
No, I can assure you it isn't any less complex. Oh, and the kernel is certified for safety-critical use just as it's certified for PCI-DSS and it's certified for use in mainframes for financial transactions. It's far more robust and fault-tolerant than Linux. IBM's Z mainframes no longer run Linux either.

JATR's conclusions can be incorrect. I can mathematically prove you don't need a single regulation to build a safe product. It's not about the process or regulatory compliance. It's about good engineering. You can do rule-compliant work without ever reading the rules. I've done it many times. And in some cases the rules can be a hindrance to safety and good engineering. In this case the strictness around grandfathering was an impediment to good design rather than an enabler of good design.


A hardened kernel helps against virus,malware,hacks or against bloated hardware interrupts unlike a general kernel.
A hardened processor protects against radiation
A reliable chip/hardware is measured in terms of mean time between failure

Here the discussion is about flight safety, and you are mixing it with kernel safety. Apples and oranges. Please don't muddle the discussion.

I'm not muddling the discussion. Most of the differences at the OS level for safety criticality come down to deterministic completion times for all operations, in addition to being able to run on fault-tolerant, hardened hardware. BSD and some flavors of Linux have been used for medical safety purposes for decades. That said, they've never been used for aerospace despite being used in satellites where the engineering constraints are even tighter.


Non-safety critical aerospace systems use Linux though (IFE).
Stuck at age 15 thanks to the certification date of the A320-200 and my parents' decision to postpone having a kid by 3 years. At least there's Dignitas...
 
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par13del
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:28 pm

patrickjp93 wrote:
par13del wrote:
Revelation wrote:
Shouldn't we be able to explore the FAA's role in the MAX tragedy without triggering the fear of Boeing absolution gag reflex?

Only if you add the necessary caveats BEFORE starting the discussion.

Says you. The FAA should be raked over the coals six ways from sunday and the facts support that.

Yes, but we cannot discuss the FAA role in this unless we first state and restate all the Boeing errors, including share buy back, bribing congress, etc etc. etc.
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:31 pm

patrickjp93 wrote:
I gave a perfectly reasonable explanation of what is wrong with the rigid framework of grandfathering. It was more expensive to develop MCAS and move the engines forward than it would have been to raise the landing gear, but raising the gear was made off-limits under grandfathering for the type. That's a failure of the regulation framework, simple as that. Iterative improvement has to be allowed.


Seriously????

There were a lot of reaons for Boeing not to raise the landing gear, regulation framework though is very low on the list.

Regulation framework is not stopping iterative improvement. If you want a prime example of iterative improvement, look no further than A320ceo, staying more than competative from 1988 to 2015 thanks to non-stopping effort of iterative improvement . . .
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
DenverTed
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:31 pm

scbriml wrote:
patrickjp93 wrote:
It was more expensive to develop MCAS and move the engines forward than it would have been to raise the landing gear, but raising the gear was made off-limits under grandfathering for the type. That's a failure of the regulation framework, simple as that. Iterative improvement has to be allowed.


How much did it cost to develop MCAS and the LEAP pylons?

All those were Boeing choices. Choices taken to try and shoehorn the MAX into the "it's just another 737" category so as to not require additional training. We have been told many times that replacing the 737's training wheels represents a very significant engineering exercise because there simply isn't the space there for longer gear. So you'd probably be looking at an entirely new winbox and associated structures. I'm struggling to believe writing some bad software was more expensive than engineering a new wing box (new pylons would have to be developed anyway).

patrickjp93 wrote:
There's plenty of room to expand the gear. Remember the 737's landing gear doesn't raise into a closed bay. It's just flush with the underside of the fuselage. It's fairly trivial to expand it.


It simply isn't "fairly trivial". We've had 737 engineers tell us before that there is no spare space for enlarged gear without a significant re-engineering of the wingbox. This topic was discussed many times during the gestation of the MAX, not least when it became clear that Boeing was using a physically smaller version of LEAP than Airbus.

I guess the question is if Boeing had built a new wingbox and longer gear and slides, would the FAA call that a 737 in 2011? I got the sense at the time (from what I read) that they were pushing their luck as it was.
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:34 pm

WIederling wrote:
patrickjp93 wrote:
scbriml wrote:
That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.


What good is a glass dagger? What gain do you see here?

The extendable ( by way of being softer sprung in a nonlinear way) -10 gear is a Rube Goldberg solution.
It is the mech designers equivalent of a Redneck's Playboy Centerfold. .-)

So you provided an ad hominem argument with no technical analysis and expect me to bow to it as a valid argument? It's a valid, possible solution that could have fixed the issue of engine placement and removed the need for MCAS at a cost. Whether that cost would have been acceptable vs. the cost of reworking the fuselage and wing box is up for debate.
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:36 pm

1989worstyear wrote:
patrickjp93 wrote:
dtw2hyd wrote:

A hardened kernel helps against virus,malware,hacks or against bloated hardware interrupts unlike a general kernel.
A hardened processor protects against radiation
A reliable chip/hardware is measured in terms of mean time between failure

Here the discussion is about flight safety, and you are mixing it with kernel safety. Apples and oranges. Please don't muddle the discussion.

I'm not muddling the discussion. Most of the differences at the OS level for safety criticality come down to deterministic completion times for all operations, in addition to being able to run on fault-tolerant, hardened hardware. BSD and some flavors of Linux have been used for medical safety purposes for decades. That said, they've never been used for aerospace despite being used in satellites where the engineering constraints are even tighter.


Non-safety critical aerospace systems use Linux though (IFE).

Well, Android anyway. It's no longer fully compliant with the Linux kernel as of Oreo, so it's a bit of an odd duck.
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:37 pm

patrickjp93 wrote:
scbriml wrote:
patrickjp93 wrote:
Telescoping gear that retract before being stowed. Good lord they already know how to do that for the MAX 10 just for takeoff to prevent tail strikes.


That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.


How does preventing tailstrikes helps fitting larger engines??

I must be missing something, so it would be helpful if you explain that to me like I'm a nine-year old.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:38 pm

par13del wrote:
patrickjp93 wrote:
par13del wrote:
Only if you add the necessary caveats BEFORE starting the discussion.

Says you. The FAA should be raked over the coals six ways from sunday and the facts support that.

Yes, but we cannot discuss the FAA role in this unless we first state and restate all the Boeing errors, including share buy back, bribing congress, etc etc. etc.

Oh we most certainly can. All mistakes made independent of Boeing's errors are fully the FAA's fault and can be considered such without penalty to the ones discussing it. If that doesn't square with your version of reality, time to take some psychoactive corrective drugs good sir/ma'am.
 
StTim
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:39 pm

Not bigger engines - but a longer fuselage hence smaller rotation angle without the gear change!
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:39 pm

PW100 wrote:
patrickjp93 wrote:
I gave a perfectly reasonable explanation of what is wrong with the rigid framework of grandfathering. It was more expensive to develop MCAS and move the engines forward than it would have been to raise the landing gear, but raising the gear was made off-limits under grandfathering for the type. That's a failure of the regulation framework, simple as that. Iterative improvement has to be allowed.


Seriously????

There were a lot of reaons for Boeing not to raise the landing gear, regulation framework though is very low on the list.

Regulation framework is not stopping iterative improvement. If you want a prime example of iterative improvement, look no further than A320ceo, staying more than competative from 1988 to 2015 thanks to non-stopping effort of iterative improvement . . .

That the EASA allowed and the FAA did not. They share a treaty to respect each other's certifications, but does not bind either one to follow the same process as the other.

Please list the reasons. This should be fun.
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:44 pm

PW100 wrote:
patrickjp93 wrote:
scbriml wrote:

That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.


How does preventing tailstrikes helps fitting larger engines??

I must be missing something, so it would be helpful if you explain that to me like I'm a nine-year old.

One of two ways, and no, like you're an eighteen year old whose brain isn't pickled by too many years of hitting the sauce.

And preventing the tail strike isn't important here. What the telescoping CAN ENABLE is what is important. Sure, the bays may not be expandable without significant rework. Okay, that being the case, if you make the gear telescopic, it can extend to full length for ALL ground phases and then retract for flight stowage. All of a sudden the effective height of craft off the ground--barring a crash landing--is greater than before, which increases ground clearance for the engine, allowing it to be moved further back to fix the aerodynamic characteristics back to something more akin to the 737 NG.

Now, I'm sure I'm about to get hounded over how you'd engineer such a gear, and the answer that immediately comes to mind is hydraulics for the telescoping action and more maintenance to go with it. That's the cost of getting the plane cheap up front.
 
WIederling
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:52 pm

patrickjp93 wrote:
WIederling wrote:
patrickjp93 wrote:
It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.


What good is a glass dagger? What gain do you see here?

The extendable ( by way of being softer sprung in a nonlinear way) -10 gear is a Rube Goldberg solution.
It is the mech designers equivalent of a Redneck's Playboy Centerfold. .-)

So you provided an ad hominem argument with no technical analysis and expect me to bow to it as a valid argument? It's a valid, possible solution that could have fixed the issue of engine placement and removed the need for MCAS at a cost. Whether that cost would have been acceptable vs. the cost of reworking the fuselage and wing box is up for debate.


if you see factual information as ad hominem. have your fun.

Higher gear on the ground kills the "no slides for wing exits" detail.
The MAX is really painted into a corner. no escape. checkmated.
Murphy is an optimist
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 5:55 pm

WIederling wrote:
patrickjp93 wrote:
WIederling wrote:

What good is a glass dagger? What gain do you see here?

The extendable ( by way of being softer sprung in a nonlinear way) -10 gear is a Rube Goldberg solution.
It is the mech designers equivalent of a Redneck's Playboy Centerfold. .-)

So you provided an ad hominem argument with no technical analysis and expect me to bow to it as a valid argument? It's a valid, possible solution that could have fixed the issue of engine placement and removed the need for MCAS at a cost. Whether that cost would have been acceptable vs. the cost of reworking the fuselage and wing box is up for debate.


if you see factual information as ad hominem. have your fun.

Higher gear on the ground kills the "no slides for wing exits" detail.
The MAX is really painted into a corner. no escape. checkmated.

Incorrect. During an evacuation the landing gear's telescoping can be deactivated. The engines still won't be touching the ground, but they'll be too close to it to run, taxi, and take off.
 
WIederling
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:06 pm

patrickjp93 wrote:
Incorrect. During an evacuation the landing gear's telescoping can be deactivated. The engines still won't be touching the ground, but they'll be too close to it to run, taxi, and take off.

And you are back to a convoluted Rube Goldberg machine. Fun with getting that certified.

Maybe "pyro actuated linkage separation" to be triggered in an emergency?
airlines will eat you alive :-))
Murphy is an optimist
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:10 pm

WIederling wrote:
patrickjp93 wrote:
Incorrect. During an evacuation the landing gear's telescoping can be deactivated. The engines still won't be touching the ground, but they'll be too close to it to run, taxi, and take off.

And you are back to a convoluted Rube Goldberg machine. Fun with getting that certified.

Maybe "pyro actuated linkage separation" to be triggered in an emergency?
airlines will eat you alive :-))

It can be pilot controlled and have a failsafe activation in the case where the flight control computer can no longer communicate with the gear.

See it's snarky old-guard group-thinkers like you who annoy me the most. You can't make a solid technical argument anymore and just use your experience to guide you in whichever direction feels most comfortable without thinking.
 
XRAYretired
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:11 pm

patrickjp93 wrote:
XRAYretired wrote:
patrickjp93 wrote:
Sigh, you're not listening. Separate the facts from the story. If Boeing's engineers had built the system as they wanted, the designation wouldn't have mattered. Redundancy and failover would have been built in by default. It's how their brains work for crying out loud. The only thing that the system engineers might have missed is mandating the AoA disagree light in the cockpit, but to be fair the avionics architects and designers most certainly would not have since management wouldn't have been mandating the costs of doing so away.

I've read the JT610 report. You're misinterpreting it. It's not the designation that matters. It's the end system that does. They'd have been a fault-tolerant system if allowed, and not because any designation said so, but because common sense said so as all of us prove.

Sigh, the misinterpretation is all yours. JATR, NTSB and FAA concur as do reputable commentators. Funnily enough, they concur with narrative we have from as close as we can get to the design team.

'....One of the people familiar with MCAS’s evolution said the system designers didn’t see any need to add an additional sensor or redundancy because the hazard assessment had determined that an MCAS failure in normal flight would only qualify in the “major” category for which the single sensor is the norm....'
https://www.seattletimes.com/seattle-ne ... afeguards/

As we know, the safety assessment was based upon flawed and un-validated assumptions and dodgy discounting.
Someone familiar with the evolution? BS. You've got plenty of senior engineers or the equivalent of software architects who oversea the macro design's interactions and thus have responsibility to ensure proposals for solutions at the individual component level are sufficient to handle inter-system requirements. Get me an actual name and position title. And reputable posters? Ethos, or authority by confidence, is a crutch used by people who can't properly interrogate or construct arguments themselves.

Touched another nerve have I? I find JATR, NTSB, FAA, and Boeing narrative far more compelling than unsupported rhetoric accompanied by tales of slapping regulators (idiots were they?, Jedi mind tricks involved?), egotistical tales of bravado and achievement and personal insults. Not clever at all mate.

There is no argument. We have the formal reports.
 
Carlitos471
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:15 pm

seahawk wrote:
It is long due to discuss the role over regulation had in the process. Boeing could have made a better product without FAA oversight.


The FAA didn't prevent Boeing from doing a clean sheet or to design the MAX properly.
Boeing chose not to do it properly. They knew the regulations before they started the development, regulations did't change half way thru.
 
WillyEckers
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:21 pm

Revelation wrote:
It's hard to tell if the message dumps we have are mostly focused on the sim development and training issues because (a) other areas were given a good scrub and nothing was found, or (b) these were the least damaging things found and more were revealed to beat up the well known parties some more and not expand the scope to others.


It would be terrible if it were option 2...

Like you, I'd love to see the decisions taken when MCAS was designed!
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:27 pm

Carlitos471 wrote:
seahawk wrote:
It is long due to discuss the role over regulation had in the process. Boeing could have made a better product without FAA oversight.


The FAA didn't prevent Boeing from doing a clean sheet or to design the MAX properly.
Boeing chose not to do it properly. They knew the regulations before they started the development, regulations did't change half way thru.

They did not prevent a clean sheet, but they were directly an impediment to "designing the MAX properly" as I've discussed upthread. If grandfathering frameworks were more flexible in iterative improvement Boeing would have just raised the landing gear and not spend $300 million USD on building MCAS v1.0 and risked this nightmare.
 
morrisond
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:33 pm

WillyEckers wrote:
morrisond wrote:
Unless of course you don't think Pilot's can be trained to counter a runaway trim and run a Runaway Trim NNC? That is a required Pilot skill of many type ratings.


I should not feed the troll but...

These quotes exist in various places but the AVweb article is asy to access https://www.avweb.com/insider/two-tragi ... -sim-time/

Boeing assumed that in the unlikely event that the system failed, pilots would be the last backstop to keep things from spinning out of control. But consider what the pilots of Ethiopian Airlines Flight 302 that crashed in March faced. The list included an active stick shaker inaccurately warning of an impending stall, an overspeed clacker, an aural “don’t sink” warning and several other disagree and warning lights. Sullenberger said he struggled to regain control in a simulator run mimicking the accident flight.

It's not a Runaway Trim NNC

In delivering his testimony, APA President Daniel Carey was blunt in brushing back a budding movement to blame the pilots. “I can tell you that the members of APA are offended by remarks made by those who seem to blame the pilots killed in those two crashes,” he said. “I am here to tell you that I worked in Africa and trained African pilots to fly large aircraft. I am very familiar with Ethiopian Air’s pilot training program and facilities, and I can tell you that they are world-class,” he added.

I think it's sad that you, who seems to have little experience (C172 but you don't say if that's XPlane or FSX...), needs to be so critical of the pilots who are firstly - not here to defend themselves and secondly, pretty much everybody of any stature has understood that it is not a pilot problem, it's an aircraft problem.

Anyway, I'm out of here :-)


Yes it a Runaway Trim NNC as per ET's own procedures as seen in the ET302 Preliminary report - if these symptoms happen - run this checklist - See pages 28-33 https://leehamnews.com/wp-content/uploa ... ET-AVJ.pdf

And when have I ever said there wasn't a problem with the aircraft? Or are you one of those who deny that there was anything wrong with Lionair maintenance or at the FAA as well and there is only issues at Boeing?

Please stop accusing me of blaming the Pilot's I am blaming ET's training system as my post from this morning demonstrates.

"From this article - Scroll down past the damning Maintenance issues at ET to get to the training Part https://www.businessinsider.com/boeing- ... er-2019-10

"Another whistleblower from Ethiopian, veteran pilot Bernd Kai von Hoesslin, told the AP in May that after Indonesia's Lion Air crash, he pleaded with Ethiopian's top executives to give pilots better training on the Max, predicting that if pilots are not sufficiently drilled on Boeing's protocols for how to disable the autopilot system in the event of a misfire, "it will be a crash for sure."


Ethiopian has said the pilots followed all the steps Boeing laid out. But the preliminary report on the crash showed they deviated from the directives and made other mistakes, notably flying the plane at an unusually high speed and inexplicably reactivating the anti-stall system shortly after manually overriding it. Six minutes into the Max flight, the plane with passengers from nearly a dozen countries cratered into the ground about 40 miles from the airport."

From AVHerald https://avherald.com/h?article=4c534c4a

"On Apr 11th 2019 The Aviation Herald received a full copy of the Flight Operations Manual (FOM), Revision 18B released on Nov 30th 2018, which is currently being used by Ethiopian Airlines (verified in April 2019 to be current). Although Boeing had issued an operator's bulletin on Nov 6th 2018, which was put into Emergency Airworthiness Directive 2018-23-51 dated Nov 7th 2018 requiring the stab trim runaway procedure to be incorporated into the FOM ahead of the sign off of this version of the FOM (the entire document is on file but not available for publishing), there is no trace of such an addition in the entire 699 pages of the FOM.

Quite the opposite, in section 2.6 of the FOM "Operational Irregularities" the last revision is provided as Revision 18 dated "Nov 1st 2017".

According to information The Aviation Herald had received in March 2019, the Airline Management needed to be reminded to distribute the Boeing Operator's Bulletin as well as the EAD to their pilots, eventually the documents were distributed to the flight crew. However, it was never verified, whether those documents had arrived, were read or had been understood. No deeper explanation of the MCAS, mentioned but not explained in both documents, was offered.

It turned out, that only very cursory knowledge about the stab trim runaway procedure exists amongst the flight crew of Ethiopian Airlines even 5 months after the EAD was distributed. In particular, none of the conditions suggesting an MCAS related stab trim runaway was known with any degree of certainty. In that context the recommendation by the accident flight's first officer to use the TRIM CUTOUT switches suggests, that he was partially aware of the contents of the EAD and reproduced some but not all of the provisions and not all of the procedure, which may or may not explain some of the obvious omissions in following the procedure in full."

The references speak for themselves. I'll just keep posting this whenever someone else insinuates I'm a liar and making this stuff up.

As I've said I am not blaming the pilots - I am blaming the ET training system that seems to have done a terrible job of instructing there Pilots on how to deal with MCAS."
Last edited by morrisond on Tue Jan 14, 2020 6:36 pm, edited 1 time in total.
 
hivue
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:33 pm

PW100 wrote:
patrickjp93 wrote:
scbriml wrote:

That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.


How does preventing tailstrikes helps fitting larger engines??

I must be missing something, so it would be helpful if you explain that to me like I'm a nine-year old.


Forget the engines. The MAX 10's fuselage is long. The (1960s design) 737 sits very low to the ground. The tail is thus low to the ground. It extends far back because it is long. Thus when the airplane rotates there is an increased likelihood of a tail strike. Thus the main gear are designed to push the fuselage higher from the ground at rotation.

BTW, this sounds a little too kludgey for me. The MAX itself is sounding more like a kludge all the time.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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SheikhDjibouti
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:44 pm

patrickjp93 wrote:
scbriml wrote:
That gear doesn't raise the height of the 737-10 by a single mm. It only helps at rotation. Next idea?

It DOES raise the MAX 10 off the ground an additional 4 inches during rotation to avoid tail strike.
It can be pilot controlled and have a failsafe activation in the case where the flight control computer can no longer communicate with the gear.
Not. Good. Enough.

Revelation wrote:
...so it allows for a longer tail, but not a bigger engine. The extension at rotation happens because gravity pulls the gear down once the aircraft weight is removed which in turn fills a cylinder with air which allows the gear be supported once it is elongated, it is not a powered lift mechanism.
Rev; I first got a handle on this several months ago, but your description of the system takes it further, and leaves me with some questions.
(Hopefully answering them will assist Patrick too.)
What happens to this "air suspension" following take-off (when there is even less weight on the undercarriage)? I'm guessing that whilst still on the runway, as ground speed increases, the wings generate lift and take some of the load, allowing the gear to extend naturally via it's own spring mechanism. But it surely needs to be "locked" at that height, else at rotation when the weight firstly comes off the nosewheel, there will be a momentary transfer to the main u/c causing it to collapse again. I'm a bit fuzzy on this part, so pretend you are explaining it to a complete idiot. :wave:

Apart from that, my understanding is....
The gear extension at rotation is purely to (help) avoid a tail strike.
It can only happen at rotation because at all other times the gear must NOT raise the height of any 737, otherwise it would invalidate the (grandfathered) overwing emergency exits.
Finally, it must exhibit a failsafe default whereby when all other systems fail (electric, hydraulic, whatever) the gear allows the aircraft to sit low enough that pax can use the overwing emergency exits. This is just about do-able for the MAX10.

But if you are relying on this extending undercarriage to re-position the LEAP engines underneath the wing, it simply cannot be there for you, and you will find that even whilst taxying towards the runway, anything more than a crisp packet on the pavement, will bring the MAX to a halt.
(At this point I have an absurd mental image of a re-engined 737 MAXv2 stranded somewhere on a taxiway, balanced on a combination of it's nosewheel and the undersides of the two engine nacelles, whilst the main undercarriage itself is "airborne". Kinda like a wheels up landing, but in a more gentle way)

Summary; designing an extending undercarriage that is both totally failsafe, and yet also fits within the existing wheel wells is only part of the answer. You need to factor in new emergency exits, with new doors that are easier to open than the existing 1967 design. And suddenly grandfathering becomes impossible. Add several more $$$billion to the cost.

Have I missed anything?
Nothing to see here; move along please.
 
mwananchi
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:51 pm

patrickjp93 wrote:
And you don't need the AoA to get your air speed. Using triangulation from the radar sensors or Boeing's upcoming Lidar implementation, you can derive craft speed based on the bounce time of reflected beams at a given distance ahead since Special Relativity is a well-understood scheme at this point.


Take the case of over-water flights: whether radar would provide actual craft speed readings is probably a question for the forum experts to chew over.

Lidar at high altitude over water for speed measurement purposes sounds like quite an advanced application too.
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:53 pm

SheikhDjibouti wrote:
Summary; designing an extending undercarriage that is both totally failsafe, and yet also fits within the existing wheel wells is only part of the answer. You need to factor in new emergency exits, with new doors that are easier to open than the existing 1967 design. And suddenly grandfathering becomes impossible. Add several more $$$billion to the cost.

Have I missed anything?

Add fitting evacuation slides since wing goes above 6', and that is no longer jumping range
 
XRAYretired
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 14, 2020 6:58 pm

patrickjp93 wrote:
WIederling wrote:
patrickjp93 wrote:
So you provided an ad hominem argument with no technical analysis and expect me to bow to it as a valid argument? It's a valid, possible solution that could have fixed the issue of engine placement and removed the need for MCAS at a cost. Whether that cost would have been acceptable vs. the cost of reworking the fuselage and wing box is up for debate.


if you see factual information as ad hominem. have your fun.

Higher gear on the ground kills the "no slides for wing exits" detail.
The MAX is really painted into a corner. no escape. checkmated.

Incorrect. During an evacuation the landing gear's telescoping can be deactivated. The engines still won't be touching the ground, but they'll be too close to it to run, taxi, and take off.

And land. You've just added a whole bunch of complexity and catastrophic failure modes. It would require a multiyear expensive programme to develop proof of concept before it could be considered for use on a commercial transport aircraft. Not commercially viable, might as well go for a new frame with appropriately designed gear length.
 
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Polot
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Re: Boeing 737MAX Grounding News and Reference Thread 2020

Tue Jan 14, 2020 7:27 pm

SRQLOT wrote:
ShamrockBoi330 wrote:
AA pushes RTS out to June

MAX taken off American Air schedules through June 3

https://seekingalpha.com/news/3531747?source=ansh


While Ryanair now says April? When just recently it was October.

https://www.yahoo.com/finance/news/ryan ... 08241.html

Airlines don’t know when RTS is, because it is depends on the regulators and know one is sure how long they are going to take. Most airlines are erring on the side of caution now (better to ‘uncancel’ flights or have fleet slack if RTS is before end of schedule than have to cancel flights in the near future).

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