MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
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.
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.
Psychophysiological entity
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
https://www.quora.com/How-did-Boeing...chnical-giants
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.
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.
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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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.
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.
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.
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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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?
20/20 hindsight is rarely a useful thing. By the time one has it, it's too late to use it.
Many aviation regulations are built on the blood of dead passengers and crews for that very reason.
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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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.
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.
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
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
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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.....
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.....
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.
mostly harmless
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?
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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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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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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Business Insider just posted an article, here are some tidbits.
CBS News reported that Boeing said it had addressed these problems with updated software and would make these changes:
1. MCAS will now rely on readings from two sensors as opposed to just one in the original system. The new software will activate only if both sensors agree that the plane's nose is too high. Boeing had announced this updated this year.
2. Pilots will be able to override the system.
3. When they do so, MCAS will not automatically reactivate, which the original system would do multiple times.
........ Boeing also told stakeholders that it had flown 1,850 hours with the software updates and spent more than 100,000 hours engineering and test-developing them, CBS News reported.....
CBS News reported that Boeing said it had addressed these problems with updated software and would make these changes:
1. MCAS will now rely on readings from two sensors as opposed to just one in the original system. The new software will activate only if both sensors agree that the plane's nose is too high. Boeing had announced this updated this year.
2. Pilots will be able to override the system.
3. When they do so, MCAS will not automatically reactivate, which the original system would do multiple times.
........ Boeing also told stakeholders that it had flown 1,850 hours with the software updates and spent more than 100,000 hours engineering and test-developing them, CBS News reported.....
