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flyingclrs727
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 6:31 pm

Quoting packsonflight (Reply 234):
Another example is 16g seats that is requirement to day, and I am curious to know if Boeing has to go with 16g seats on the MAX or if they can grandfather in the old 9g (I think) seats from the NG.

The 9G seats were required for the 737NG. That's why WN got rid of its lounge seating near the mid-cabin emergency exit. WN didn't want to pay for the costs of certifying the seats for rear facing installation. All the 737-300's and 500's in the WN fleet were replaced with the same 9G seats as the 700's. As the new seats were retrofitted into the 300's and 500's, and the 200's were retired, lounge seating disappeared.

I would bet 16G seats would be required, just as 9G rather than 6G seats were required for the NG. Just because the NG was a derivative of the original 737-100 didn't mean Boeing wasn't required to update some of the equipment. The NG has more modern cockpit data and voice recorders than the original 737.

[Edited 2016-03-02 10:48:31]
 
roseflyer
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 6:45 pm

Quoting Amiga500 (Reply 249):

No - in what I envisage, it (the aircraft) wouldn't get certified in the first place as the "legacy" components wouldn't meet current cert requirements.

i.e., update (not PIP) your aircraft engine and you can no longer pass the wing by the requirements in place at the time of the original.


Basically, after XX years, IF you are doing a redesign/significant modification, you are no longer allowed to carry legacy assemblies that don't meet current (new-build) requirements.


You are talking about retrospective changes on frames currently flying. I am talking about doing away with the loophole of legacy assemblies avoiding current requirements when an OEM is issuing a major update to the design.

There is no reason to do this. What you essentially are suggesting is to scrap all the previous certification work because processes have changed. If you do a redesign/significant modification then yes you are required to meet the latest requirements. If the design does not meet the FARs that were current when the type certificate was created and every Airworthiness Directive issued since then, an airplane cannot receive its Certificate of Airworthiness.

Either I think you don't understand qualification based on similarity or I don't understand what your point is. It is my understanding that there are not parts on the 737 that do not meet current FAR requirements. If a part or system does not meet the FAR requirements it can't be installed based on similarity. What has changed is the testing and certification methods and requirements and even some of the requirements. Parts now are certified to different and in some cases more rigorous qualification testing. It isn't that the old design is known to fail the current criteria (if it would, then it can't be used because that would be an escapement) it is that it wasn't tested to the latest methods. Many designs have demonstrated that they are acceptable based on similarity or analytical methods.

I think you are trying to say that you don't agree with the methodology that the FAA uses. The FAA does not require that everything be redesigned every time a safety improvement is made. The FAA evaluates each and every one, goes through a lengthy NPRM process where opinions from industry experts, manufacturers and airlines are considered when new rules come out. If there is a safety benefit that is deemed to sufficiently meet the criteria, it is forced through an Airworthiness Directive. For example, if the FAA really thought that the current 737NG cannot be evacuated safely, they could force a redesign of the doors. Another example would be the magnesium control wheel. Magnesium is not commonly used in airplanes any more because current analytical techniques put in a few casting factors that reduce its strength to 12-14ksi in some very specific circumstances. While current analytical methods probably would not allow use of the same magnesium that was originally designed in the 1950s, it doesn't mean that the current design does not meet the current standards.

The current process works very well despite one poster from Iceland claiming it is BS. The 737NG safety record speaks for itself for how well the regulations work.

[Edited 2016-03-02 11:04:42]
 
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Revelation
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 6:59 pm

Quoting roseflyer (Reply 251):
It isn't that the old design is known to fail the current criteria (if it would, then it can't be used because that would be an escapement) it is that it wasn't tested to the latest methods.

That to me sounds like the "don't ask, don't tell" policy.
 
roseflyer
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:08 pm

Quoting Revelation (Reply 252):

That to me sounds like the "don't ask, don't tell" policy.

It is a little like that. We don't put components through qualification testing again because a step of the certification process changed. However if a part does not meet the certification requirements, then no it cannot be qualified on similarity. No design can be 100% safe. The regulations aren't written that way. However the regulations do require that any catastrophic failure has to have a demonstrated or analyzed probability of less than 1 in 1 Billion.

I believe some of our friends from Europe do not agree with the concept that not every safety improvement is mandated. Only some meet the criteria to have an Airworthiness Directive issued. Sure we don't use girt bars in exit doors on new designs, but that doesn't make them unsafe. Some people either don't like that concept or don't agree with it. Fortunately, EASA exists and they can lobby for changes.

[Edited 2016-03-02 11:09:46]
 
mjoelnir
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:20 pm

Quoting roseflyer (Reply 251):
The current process works very well despite one poster from Iceland claiming it is BS. The 737NG safety record speaks for itself for how well the regulations work

What I am claiming is, that your argument is BS. Why than is a certain design, grandfathered for old frames, not accepted on a clean sheet design? You are twisting and turning and twisting to not go down that road. If a design would be not inferior, less safe, or simple undesirable and I do not talk about unsafe, but less safe, than it would be acceptable on a clean sheet.
It not being accepted for a clean sheet designe tells a story all by itself.
 
roseflyer
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:31 pm

Quoting mjoelnir (Reply 254):

What I am claiming is, that your argument is BS. Why than is a certain design, grandfathered for old frames, not accepted on a clean sheet design? You are twisting and turning and twisting to not go down that road. If a design would be not inferior, less safe, or simple undesirable and I do not talk about unsafe, but less safe, than it would be acceptable on a clean sheet.
It not being accepted for a clean sheet designe tells a story all by itself.

Design methodologies and strategies change over time. That doesn't mean that the old design is unacceptable or unsafe. Keeping a type certification isn't all about keeping old inferior designs around, it is about saving billions in certification costs. If there is a specific design criteria where a design does not meet the FAR requirements then it must be redesigned. There's no such thing as grandfathering designs that don't meet the FAR requirements. While the design requirements may have changed since a type certification was issued, the FAA has the ability to mandate or modify requirements by issuing airworthiness directives. If a system does not meet the requirements as described in AC 25.1309 then it must be redesigned. However that doesn't mean that designs that aren't to the latest design standards are unsafe. Safety requirements at the system level are very well described in AC 25.1309 and I think it would answer a lot of your questions for why designs that wouldn't be used in new designs are safe since they do meet the regulations and requirements. Have you read 25.1309? http://www.faa.gov/documentLibrary/m...Advisory_Circular/AC25.1309-1A.pdf

Since you seem to think that clean sheet designs are superior, do you also agree with governments like South Korea mandating that airplanes older than 20 years be retired?

[Edited 2016-03-02 11:34:51]
 
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:35 pm

Quoting mjoelnir (Reply 254):
What I am claiming is, that your argument is BS.

You should be aiming your insults at the actual policies, not roseflyer's explanation of them.

We're all supposed to be friends here, after all...

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PlanesNTrains
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:35 pm

Quoting Revelation (Reply 252):
That to me sounds like the "don't ask, don't tell" policy.

I'm still trying to figure out why we can't call it "grandfathering", even if it's somewhat of a misnomer? I think it reflects the general idea and it seems that NOT using that word is creating more problems than it's worth.

Grandfathering is a reasonable way to have change without killing development or replacement due to cost.

At my last job we added on to our single floor office building by extending it out about 80%. However, actually physically attaching it to our older structure would have required very costly upgrades and revamps on what was essentially a historical structure. It would have killed the deal or destroyed an attractive turn-of-the-century building in the name of progress. Instead, we simply put a walk-way the width of a sidewalk between the two structures and voila! We had a building that was very old on one side and a building that was brand new on the other side. It seemed like a positive outcome even though the old building was probably in some way slightly less safe or accessible or something akin to that.

I know that's not the same level of importance as an aircraft, but nobody was screaming about our structure suddenly being unsafe today when it was fine for the past 100 years.

Quoting mjoelnir (Reply 254):
It not being accepted for a clean sheet designe tells a story all by itself.

Of course. However I'm not clear on why it means that something from before is inherently "bad" or "unsafe"? If a 737 was safe yesterday, it is still safe today. It just isn't "as safe" as a clean sheet because there have been improvements in some areas. It still is a safe plane. I'll feel the same way in 30 years when there is an A320NEWneoXLR-400.

-Dave
 
Amiga500
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:42 pm

Quoting roseflyer (Reply 251):
There is no reason to do this. What you essentially are suggesting is to scrap all the previous certification work because processes have changed. If you do a redesign/significant modification then yes you are required to meet the latest requirements. If the design does not meet the FARs that were current when the type certificate was created and every Airworthiness Directive issued since then, an airplane cannot receive its Certificate of Airworthiness.

Yet the type cert @ time of creation + ADs =/= current FARs. Thats my problem.


I am suggesting that OEMs not be allowed to continue to compromise (and lets face it, it is compromised otherwise the new regulations would not exist) safety by only meeting ADs rather than the full regs [when significantly redesigning an airframe anyway).

Quoting roseflyer (Reply 251):

Either I think you don't understand qualification based on similarity or I don't understand what your point is.

You don't understand what my point is, or are deliberately trying to avoid what my point is. Its fairly straightforward what I'm saying.

Quoting roseflyer (Reply 251):

It is my understanding that there are not parts on the 737 that do not meet current FAR requirements.

I can assure you, there are assemblies and systems on the 737 right now that would not be allowed on a new design.

You've already brought up one of them, the FTIS (or I suppose more correctly, the flammability exposure being applicable to all tanks.)

Quoting roseflyer (Reply 251):

If a part or system does not meet the FAR requirements it can't be installed based on similarity. What has changed is the testing and certification methods and requirements and even some of the requirements. Parts now are certified to different and in some cases more rigorous qualification testing. It isn't that the old design is known to fail the current criteria (if it would, then it can't be used because that would be an escapement) it is that it wasn't tested to the latest methods. Many designs have demonstrated that they are acceptable based on similarity or analytical methods.

I have not once mentioned methods or processes for meeting requirements. You are continually bringing that up.

I am talking about a disparity between the requirements imposed on aircraft A which was built in 19XX, then significantly updated in 201X - and aircraft B which is a new design also built in 201X.

Disparity in requirements, not methods or processes to meet requirements, but the requirements themselves.



------------------------------------

While yes, ADs have their place due to evolving use, knowledge and philosophies, being allowed to continually hide behind ADs and not bringing your airframe up to full current standards while otherwise performing major design modifications is, IMO, a sham.

[Edited 2016-03-02 11:45:16]
 
Amiga500
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:43 pm

Quoting roseflyer (Reply 255):
There's no such thing as grandfathering designs that don't meet the FAR requirements.

Yes there is!

Grandfather designs meet a bastardised version of the FAR requirements, not the full current requirements.
 
WPIAeroGuy
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 7:59 pm

Quoting mjoelnir (Reply 254):
hat I am claiming is, that your argument is BS. Why than is a certain design, grandfathered for old frames, not accepted on a clean sheet design? You are twisting and turning and twisting to not go down that road. If a design would be not inferior, less safe, or simple undesirable and I do not talk about unsafe, but less safe, than it would be acceptable on a clean sheet.
It not being accepted for a clean sheet designe tells a story all by itself.

I see what you're saying. You're wondering why Boeing is allowed to make a 737-MAX, essentially a new airplane model, that may have features or may have only been certified to old amendments of regulations. You see it as a trick to get around certifying to the latest regulations. In reality however, Boeing isn't making an entirely new airplane. They're upgrading the 737. Many components will be exactly as they are on the current 737NG series. All Boeing has to show is that any new modifications 1. meet the current regulations and 2. don't affect the airworthiness of existing components (simplified explanation).

Boeing isn't creating a clean-sheet design, calling it a 737, and saying it now only needs to comply with regulations from the 70's. They are taking an existing, airworthy platform, and making upgrades. If there are aspects of that platform that are unacceptable from a safety perspective, those will be addressed via AD.
 
mjoelnir
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 8:13 pm

Quoting roseflyer (Reply 255):
Design methodologies and strategies change over time.

Designe and safety requirements change, methodology and strategy follow.

Quoting roseflyer (Reply 255):
That doesn't mean that the old design is unacceptable or unsafe

The old design is unacceptable for the clean sheet, so it has to be inferior or less safe.

Quoting roseflyer (Reply 255):
Keeping a type certification isn't all about keeping old inferior designs around, it is about saving billions in certification costs

Now we hit the main point.

Quoting roseflyer (Reply 255):
Since you seem to think that clean sheet designs are superior, do you also agree with governments like South Korea mandating that airplanes older than 20 years be retired?

Why should it be unreasonable? It is a common practice all over the transportation industries. There have been accidents because the age of an airplane, but yes only very few. Yes, I know Icelandair would than have to renew its fleet.

At the end one very simple question, what is the reason to disallow certain old designs on clean sheet new frames?
 
PlanesNTrains
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 8:18 pm

Quoting mjoelnir (Reply 261):
less safe

The existing design is not less safe or unacceptably unsafe. The new design is simply safer. That comes at a tremendous price. Yes, price (cost) matters. If updating designs would require a full re-certification, it might lead to not updating designs and therefore having (in your view perhaps) unsafe aircraft for much longer.

Quoting mjoelnir (Reply 261):
Why should it be unreasonable?

Because it's simply an arbitrary number that isn't necessarily grounded in fact. Why 20 years? Why not 15 or 19 or 30? Because 20 sounds nice.

-Dave
 
WPIAeroGuy
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 8:31 pm

Quoting planesntrains (Reply 262):
The existing design is not less safe or unacceptably unsafe. The new design is simply safer. That comes at a tremendous price. Yes, price (cost) matters. If updating designs would require a full re-certification, it might lead to not updating designs and therefore having (in your view perhaps) unsafe aircraft for much longer.

  
 
roseflyer
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 9:04 pm

Quoting mjoelnir (Reply 261):
The old design is unacceptable for the clean sheet, so it has to be inferior or less safe.

Safety is determined at a systems level through probability. That's the essence of FAR 25.1309. The requirement is still there. There are many ways to meet the requirements. More maintenance inspections can make up for a design that has lower reliability or less life. It isn't black and white one is less safe than the other. There are different ways of meeting the requirements and an old design that might not be used, isn't necessarily less safe.

Quoting Amiga500 (Reply 259):

Grandfather designs meet a bastardised version of the FAR requirements, not the full current requirements.

Well, good luck getting the FAA to change their process. This is the way it works and it works really well. The really important changes are mandated. The updates that aren't critical are not.

Quoting Amiga500 (Reply 258):

I am talking about a disparity between the requirements imposed on aircraft A which was built in 19XX, then significantly updated in 201X - and aircraft B which is a new design also built in 201X.

Disparity in requirements, not methods or processes to meet requirements, but the requirements themselves.

Do you then also think the A320neo, A330neo and all other derivatives need to be brought up to the 201x standards? Do you believe that we should essentially get rid of qualification based on similarity and make every change a major change and require a certification plan that demonstrates compliance to every FAR? What type of change to an airplane forces the requirement to upgrade to the latest standard? Does changing the thickness of primer count or length of a fastener? Does new engines affect an entire airframe?

You are correct that the requirements for an amended type certificate are different than a new type certificate. That difference is billions of dollars in certification testing. What value does eliminating amended type certificates do?

[Edited 2016-03-02 13:06:31]
 
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SQ22
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 9:18 pm

Quoting Amiga500 (Reply 235):

Boarded an A321 the other day in Dublin (hmm, maybe it was Frankfurt on the way back) using Door 2.

It is possible and LH for example uses it frequently at their hubs. I am not an expert here, but not so long ago someone in another thread mentioned that it is more an issue with the jetbridges being used. So they need to be modified or maybe another design is required.

Can someone with more insight.
 
Amiga500
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 10:14 pm

Quoting roseflyer (Reply 264):

Do you then also think the A320neo, A330neo and all other derivatives need to be brought up to the 201x standards?

Yep.

Quoting roseflyer (Reply 264):
Do you believe that we should essentially get rid of qualification based on similarity and make every change a major change and require a certification plan that demonstrates compliance to every FAR?

Do you understand that qualification based on similarity is very, very, very different to what I am saying?

Qualification to rule19XX based on similarity is very different to qualification to rule201X based on similarity!

Quote:
Does changing the thickness of primer count or length of a fastener? Does new engines affect an entire airframe?

I would draw the line at changes to primary structure (PSEs).

Quote:
You are correct that the requirements for an amended type certificate are different than a new type certificate. That difference is billions of dollars in certification testing. What value does eliminating amended type certificates do?

Can you not see the way the industry is going?

I can see an A320neo2 happening. Maybe even a neo3.
I can see the A330 going up to a neo2 as well.

Do we really want designs that are based on 19XX regulations + ADs coming off assembly lines post 2050? [They aren't inherently unsafe, but the longer they are left to fly around, the larger the safety gap will be between them and state-of-art.]

It is something that will be addressed eventually I suppose, it's just going to take some time before the issue is large enough that it can no longer be ignored.
 
roseflyer
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 11:00 pm

Quoting Amiga500 (Reply 266):


It is something that will be addressed eventually I suppose, it's just going to take some time before the issue is large enough that it can no longer be ignored.

Will I am not convinced it is an issue. If an incident happens because an airplane is using outdated FARs then maybe but I have not heard of that happening
 
DfwRevolution
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RE: New 757 Replacement NMA Information - Part 4

Wed Mar 02, 2016 11:10 pm

Quoting Amiga500 (Reply 266):
Do we really want designs that are based on 19XX regulations + ADs coming off assembly lines post 2050? [They aren't inherently unsafe, but the longer they are left to fly around, the larger the safety gap will be between them and state-of-art.]

I would answer with a resounding: Y-E-S

The mechanical safety record of present generation aircraft is damn near perfect. The A330, 777, and 737NG all made it a decade into their service life before a write-off accident could be attributed to their design. That should speak to the fact that "19xx regulations" are, in fact, spectacularly good.

Amending type certificates with ADs from lessons learned is a great way to prevent regulatory creep from over-designing aircraft past the point of the social welfare. Said another way, it is possible to over-engineer systems to the detriment of the people they are supposed to serve and amended type certificates are a good counterweight to overactive bureaucrats.
 
JHwk
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RE: New 757 Replacement NMA Information - Part 4

Thu Mar 03, 2016 12:26 am

Quoting Amiga500 (Reply 258):
I am suggesting that OEMs not be allowed to continue to compromise (and lets face it, it is compromised otherwise the new regulations would not exist) safety by only meeting ADs rather than the full regs [when significantly redesigning an airframe anyway).

Ultimately, you get to a point of what is an acceptable change without fully recertifying the airplane to current standards? Can we add a winglet? Can we change a Xeon strobe for an LED one? Is it "oh, sorry, you can't do that without upgrading the exit doors!"

There needs to be some reasonable balance. (Personally I would say the Max exceeds that rational balance, but it isn't what the FAA says, which is what matters.)
 
atlflyer
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RE: New 757 Replacement NMA Information - Part 4

Thu Mar 03, 2016 12:52 am

 
PlanesNTrains
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RE: New 757 Replacement NMA Information - Part 4

Thu Mar 03, 2016 5:06 am

Quoting Amiga500 (Reply 266):
Do we really want designs that are based on 19XX regulations + ADs coming off assembly lines post 2050? [They aren't inherently unsafe, but the longer they are left to fly around, the larger the safety gap will be between them and state-of-art.]

Considering how safe this generation of aircraft are, I have to wonder if the cost to completely clean-sheet designs right now would be worth it? Certainly if the MAX couldn't happen without re-certification, we'd be looking at Boeing either moving forward with a $10B-$12B clean sheet that likely wouldn't be measurably that much better than the neo, OR we'd have them continue to produce the dreaded, old, less safe 737NG's. Are either of those outcomes demonstrably better than the MAX?

-Dave
 
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KarelXWB
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RE: New 757 Replacement NMA Information - Part 4

Thu Mar 03, 2016 8:40 am

New 757 Replacement NMA Information - Part 5 (by KarelXWB Mar 3 2016 in Civil Aviation)

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