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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 8th Dec 2019, 21:59
  #4341 (permalink)  
 
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Originally Posted by Big Pistons Forever View Post
Because for the first time ever 20 + yrs worth of klufges and work arounds dating back to the first 737NG, got a good looking at.......and the results were not pretty. The 737 is certified under the regulations that existed in 1967, those regulations ignored/allowed stuff that is now considered completely unacceptable. Getting the existing mish mash of technology to be compliant is, I would suggest, a lot harder than starting from scratch.

Tome the ultimate irony is a complete upgrade of the cockpit and flight control technology was going to add 1 year to the Max development schedule and cost up to 10 Billion extra dollars. It was rejected out of hand at the project kick off yet here we are, grounded for at lest a year and the bill to Boeing is 8.3 Billion and rising.......
This is true. It would also result in a plane that Boeing's customers did not want as it would not fit into their existing 737 operations.

20/20 hindsight is rarely a useful thing. By the time one has it, it's too late to use it.
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Old 9th Dec 2019, 01:54
  #4342 (permalink)  
 
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Originally Posted by Big Pistons Forever View Post
Because for the first time ever 20 + yrs worth of klufges and work arounds dating back to the first 737NG, got a good looking at.......and the results were not pretty. The 737 is certified under the regulations that existed in 1967, those regulations ignored/allowed stuff that is now considered completely unacceptable. Getting the existing mish mash of technology to be compliant is, I would suggest, a lot harder than starting from scratch.
Nice post, too bad it's almost entirely wrong.
There is something called the "Changed Product Rule" or CPR (and before you get on about the FAA, CPR has been completely harmonized with EASA).
CPR basically says that when you make a major change to an aircraft (and new engines qualify), anything that is changed has to step up to the latest regulations.
If you bother to check the MAX TCDS, you'd find precious few regulations date back to the original 737 TCDS (mainly having to do with structures).
For all the problems with the MAX, the regulations it was certified to are not one of them.

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Old 9th Dec 2019, 02:09
  #4343 (permalink)  
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Virtually every night I read in here and then go to Quora. Tonight, I come back with this, because I wonder how Frank Borman would have altered his career path if he'd known he might one day be responsible for Boeing's demise. The sheer power of the Butterfly effect.

https://www.quora.com/How-did-Boeing...chnical-giants
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Old 9th Dec 2019, 02:58
  #4344 (permalink)  
 
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Originally Posted by tdracer View Post
Nice post, too bad it's almost entirely wrong.
There is something called the "Changed Product Rule" or CPR (and before you get on about the FAA, CPR has been completely harmonized with EASA).
CPR basically says that when you make a major change to an aircraft (and new engines qualify), anything that is changed has to step up to the latest regulations.
If you bother to check the MAX TCDS, you'd find precious few regulations date back to the original 737 TCDS (mainly having to do with structures).
For all the problems with the MAX, the regulations it was certified to are not one of them.
But the interpretation (selection) of classification/s have been somewhat bias in the design process, lots of lets call dark grey areas white!

So while the MAX was indeed compliant whit the latest regulation/s that Being deemed was the classifications to be meet - they fudged the numbers and the result ended catastrophic TWICE because that classification was two rungs lower than what it should have been.

I would love to see the paper trail of the reduction of manual trim wheel size that happened from the NG - no doubt it was not classed as a major change (hard to believe when the roller coaster manoeuvre was documented for the larger wheel).

Lots of smoke and mirrors seem to have been used over the last few models.
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Old 9th Dec 2019, 03:40
  #4345 (permalink)  
 
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The "changed product rule," or 14 CFR 21.101, does require changed areas and areas affected by the change to step up to the latest rules as of the date of application for the change as a supposed default, but it has HUGE loopholes in it that are regularly exercised to allow reversion to earlier versions of the rule based on impracticality or an argument that little benefit is provided by stepping up because the unchanged area still doesn't comply. (An example of this would be that it doesn't make much sense to put in three rows of 16 g seats if the rest of the seats are 9 g seats.) The negotiation paper regarding the certification basis for a major derivative transport airplane program ends up being dozens of pages long with all the arguments for reversion to earlier rule versions. Some of these reversions make sense, others are questionable compromises.
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Old 9th Dec 2019, 03:40
  #4346 (permalink)  
 
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Originally Posted by Bend alot View Post
But the interpretation (selection) of classification/s have been somewhat bias in the design process, lots of lets call dark grey areas white!

So while the MAX was indeed compliant whit the latest regulation/s that Being deemed was the classifications to be meet - they fudged the numbers and the result ended catastrophic TWICE because that classification was two rungs lower than what it should have been.

I would love to see the paper trail of the reduction of manual trim wheel size that happened from the NG - no doubt it was not classed as a major change (hard to believe when the roller coaster manoeuvre was documented for the larger wheel).

Lots of smoke and mirrors seem to have been used over the last few models.
Mistakes were obviously made during the MAX cert. Perhaps mistakes where made during the NG cert (although apparently not very serious mistakes, since the NG is statistically slightly safer than the A320 series). I hazard to guess that, since humans are involved, mistakes have been made during the cert of every aircraft flying (obviously some more serious than others)
But a common theme of this thread has blamed the MAX problems on a 1967 cert basis. Which is quite simply wrong. Cert basis had nothing to do with it.

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Old 9th Dec 2019, 04:20
  #4347 (permalink)  
 
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Would the flight testing of the MAX have been any different from what was required for a clean sheet design? I still have a hard time believing that MCAS wouldn't have been corrected if anybody had actually flown the failure scenario. I assume that a clean sheets design would require flight testing lots of combinations of sensor failures, right?
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Old 9th Dec 2019, 06:56
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20/20 hindsight is rarely a useful thing. By the time one has it, it's too late to use it.
It may be too late to USE IT in that instance but it can sure guide future decisions.

Many aviation regulations are built on the blood of dead passengers and crews for that very reason.
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Old 9th Dec 2019, 11:34
  #4349 (permalink)  
 
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But a common theme of this thread has blamed the MAX problems on a 1967 cert basis. Which is quite simply wrong. Cert basis had nothing to do with it.
Can you expand on your position on that a little? This whole saga came about because of grandfathering certificates and the inability to change anything substantial. The issue of MCAS can be aerodynamically solved if there were no certificate restrictions in the first instance. MCAS was installed because they weren't allowed to aerodynamically change the aircraft, as far as I understand it.
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Old 9th Dec 2019, 12:27
  #4350 (permalink)  
 
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Originally Posted by tdracer View Post
Nice post, too bad it's almost entirely wrong.
There is something called the "Changed Product Rule" or CPR (and before you get on about the FAA, CPR has been completely harmonized with EASA).
CPR basically says that when you make a major change to an aircraft (and new engines qualify), anything that is changed has to step up to the latest regulations.
If you bother to check the MAX TCDS, you'd find precious few regulations date back to the original 737 TCDS (mainly having to do with structures).
For all the problems with the MAX, the regulations it was certified to are not one of them.
Based on the JATR report it could be argued there is a problem with the changed product rule. Recommendation R1.

The changed system was not required to be tested with a top down approach. Testing on how it integrates with the rest of the systems. Leaving it open the issues we see.

Recommendation R1
Based on the JATR team’s observations and findings related to the application of the Changed Product Rule to the certification of the flight control system of the B737 MAX, JATR team members recommend that the FAA work with other civil aviation authorities to revise the harmonized approach to the certification of changed products. Changed Product Rules (e.g., 14 CFR §§ 21.19 & 21.101) and associated guidance (e.g., Advisory Circular 21.101-1B and FAA Orders 8110.4C and 8110.48A) should be revised to require a top-down approach whereby every change is evaluated from an integrated whole aircraft system perspective. These revisions should include criteria for determining when core attributes of an existing transport category aircraft design make it incapable of supporting the safety advancements introduced by the latest regulations and should drive a design change or a need for a new type certificate. The aircraft system includes the aircraft itself with all its subsystems, the flight crew, and the maintenance crew.
These Changed Product Rule revisions should take into consideration the following key principles:
• A comprehensive integrated system-level analysis recognizing that in this complex interactive system, every change could interact with other parts of the system.
• The assessment of proposed design changes on existing systems at the aircraft level includes using development assurance principles, system safety principles, and
systemsthe
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Old 9th Dec 2019, 14:26
  #4351 (permalink)  
 
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Originally Posted by neville_nobody View Post
MCAS was installed because they weren't allowed to aerodynamically change the aircraft, as far as I understand it.
Who didn't allow them to change it?

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Old 9th Dec 2019, 14:29
  #4352 (permalink)  
 
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Originally Posted by Sallyann1234 View Post
Who didn't allow them to change it?
The certification rules about what you can or can't change while still getting away with a grandfathered Type Certificate from 1967.
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Old 9th Dec 2019, 16:56
  #4353 (permalink)  
 
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Originally Posted by Sallyann1234 View Post
Who didn't allow them to change it?
The airlines. They requested a modern airliner on a 737-typerating with minimum training costs...

It's not all on Boeing...😉
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Old 9th Dec 2019, 17:02
  #4354 (permalink)  
 
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The Type Certicate Data Sheet for the Boeing 737 is A16WE. It covers every model of 737 made and was issued in 1967. The FAA also only issues one type rating that covers every model ever made. Every possible effort was made to avoid the requirement to recertify changes. This combined with a corporate culture of “do it cheap and fast” instead of “do it right”, made this debacle inevitable.

Speaking of 2020 hindsight, how about the 747 program. The CEO bet the company on what was a transformational engineering aspiration. 777 and the 787 permanently changed the airliner landscape, and yes I am fully aware of the 787 problems but it was not a lack of vision that screwed up this program it was a failure of execution when the bean counters started to displace the engineers.

Sadly the 737 program was a failure of both imagination and execution. A clean sheet design was off the table almost immediately because the only decision criteria was what would goose the stock price this quarter.

The true irony is if they had gone with a clean sheet design the entry into service engine woes would have significantly blunted Airbus first mover advantage and going forward they would be offering a brand new airframe against an almost 30 year old Airbus 320 competitor, but that would have required the kind of vision in the C suite you do not see much of these days.....
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Old 9th Dec 2019, 17:05
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Originally Posted by Icarus2001 View Post
It may be too late to USE IT in that instance but it can sure guide future decisions.

Many aviation regulations are built on the blood of dead passengers and crews for that very reason.
In this instance I was pointing out that comparing the cost to Boeing to make changes that made no business sense vs the cost of the current delay cannot be a basis of criticizing the decision. The alternative is to spend $10 Billion on every engineering design point on the off chance that a failure there could generate a similar cost in the future.

What failed in this case is imagination - that pilots would not re-trim the plane to lower the control forces to a point they could manage.

A similar failure of imagination occurred within the FAA over allowing passenger access to the cockpit that led to four hijacked planes setting off two major wars and probably dozens of smaller ones, and likely leading to the ultimate killing of a million civilians before it's all over. The FAA had 20/20 hindsight over planes that had been crashed under similar circumstances. It did no good.

People do learn from certain mistakes and regulations are written in blood - but they rarely avoid new mistakes.
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Old 9th Dec 2019, 17:08
  #4356 (permalink)  

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Just an SLF here with a question.

The first MAX-10 just rolled out a few days ago and will now undergo the testing and certification process. It has, I understand, a taller undercarriage to prevent tailscrapes. It does not require MCAS but (I suppose due to the changed centre of gravity) apparently has the same pylon and engine position as the MAX-8 etc.

My question. As a last resort, would it be possible to produce (even rework) MAX-8s etc with the MAX-10 undercarriage and a revised pylon and engine position to avoid the flying characteristics that require MCAS?
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Old 9th Dec 2019, 17:14
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Originally Posted by The Bartender View Post
The airlines. They requested a modern airliner on a 737-typerating with minimum training costs...

It's not all on Boeing...😉
Perhaps they should have remembered the parable about new wine in old bottles.
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Old 9th Dec 2019, 17:25
  #4358 (permalink)  
 
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The Money men ? They went for the option that would save them a lot of bucks and enable them to bring the aircraft into service quickly. Interesting comments that the Max 10 does not need the kludge called MCAS.
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Old 9th Dec 2019, 17:48
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and now, with more searching, I'm less sure that the MAX-10 does not have MCAS.
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Old 9th Dec 2019, 19:52
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Originally Posted by answer=42 View Post
and now, with more searching, I'm less sure that the MAX-10 does not have MCAS.
I haven't done the research on the MAX-10, so this is a guess: Stretching the fuselage doesn't usually change the COG in relation to the wing chord very much (because it's important not to do that if you're not designing new wings), but it might well increase the authority of the H-stab and the elevators, so . . . more info needed.
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