F-35 JSF develops cracks.

[jhungary]

Hi,

Have a noob query here for @jhungary @Oscar @gambit @VCheng @sandy_3126@halloweene

Cannot computer simulations predict load and the potential for cracks in the system? If not, how so? If yes, why was this not detected?

cheers!

lol i am half Computer based and not aircraft based. Need to get back to you on that, may be to ask my brother.....

 

[SQ8]

USA made it, it will fix it too, to be better than ever. New technology always develops this way. No problem.

Yeah.. Yaay USA.
Perhaps its time to realize that the McNamarish idea of trying to give each service the same fighter has resulting in a handicapped performer that will leave all of them wanted for more.

 

[OrionHunter]

Who are these people? PDF members? Chinese? US Congress?

Just curious.

In July 2013, doubts were cast on the latest (long delayed) schedule, with further software delays, and sensor, display and wing buffet problems continuing. In August it was revealed that the Pentagon was weighing cancellation of the program as one possible response to the budget sequestration, and the U.S Senate Appropriations Subcommittee on Defence voted to cut advanced procurement for the fighter.

The debate continues.

 

[VCheng]

Yeah.. Yaay USA.
Perhaps its time to realize that the McNamarish idea of trying to give each service the same fighter has resulting in a handicapped performer that will leave all of them wanted for more.

Yaay? Pardon me, but your hatred is showing again.

Each service will develop the basic platform according to its own needs. It will take some time obviously but it will work quite well.

 

[DANGER-ZONE]

USA made it, it will fix it too, to be better than ever. New technology always develops this way. No problem.

 

[SQ8]

Yaay? Pardon me, but your hatred is showing again.

Each service will develop the basic platform according to its own needs. It will take some time obviously but it will work quite well.

Au Contrare.. there is no hatred here.. Rather a sarcastic look at the approach. It could have been done right the first time, the USAF and Navy could have shared the F-35 platform..and the Marines could have had a dedicated aircraft for themselves.

 

[VCheng]

Au Contrare.. there is no hatred here.. Rather a sarcastic look at the approach. It could have been done right the first time, the USAF and Navy could have shared the F-35 platform..and the Marines could have had a dedicated aircraft for themselves.

That is a fair point, but there is no "right way" at the cutting edge of technology, for there is no tried-and-true that applies in such situations. Things must be tried out and rejected if they do not work, or cannot be made to work with development. The Marine version will develop further to make it better suited to its role, just as the other versions will.

Just look at how long the V-22 spent in development for the Marines.

 

[SQ8]

That is a fair point, but there is no "right way" at the cutting edge of technology, for there is no tried-and-true that applies in such situations. Things must be tried out and rejected if they do not work, or cannot be made to work with development. The Marine version will develop further to make it better suited to its role, just as the other versions will.

Just look at how long the V-22 spent in development for the Marines.

Yet the V-22 was meant specifically for the Corps needs. It also involved the Corps backing for the tilt rotor design(as it offers the most cost-effective solution in their view) for the combination of vertical and high speed conventional flight.
There has already been an experiment in the form of the F-111 in trying to meet everyone's needs. Yet that did not play out well.. neither did the F-16 in meeting the navys needs.

The F-35 does have the potential to meet the Air force's and Navy's needs.. but its a compromise for the Marines(who are its most ardent backers) and as such does not really help in the need for allowing the Marines to fight it out alone(after all, its the Marines that move on the orders of the Oval office.. the other three require Congress approval ..is it not?)

 

[VCheng]

Yet the V-22 was meant specifically for the Corps needs. It also involved the Corps backing for the tilt rotor design(as it offers the most cost-effective solution in their view) for the combination of vertical and high speed conventional flight.
There has already been an experiment in the form of the F-111 in trying to meet everyone's needs. Yet that did not play out well.. neither did the F-16 in meeting the navys needs.

The F-35 does have the potential to meet the Air force's and Navy's needs.. but its a compromise for the Marines(who are its most ardent backers) and as such does not really help in the need for allowing the Marines to fight it out alone(after all, its the Marines that move on the orders of the Oval office.. the other three require Congress approval ..is it not?)

All forces move at the President's orders, but the funding is controlled by Congress.

The Marine version of the F-35 will serve very well too.

 

[SQ8]

All forces move at the President's orders, but the funding is controlled by Congress.

The Marine version of the F-35 will serve very well too.

thats odd.. a certain Marine I know was adamant that the Marines are the only force that only require the presidents go. i.e. First in the fight at any area regardless of what congress says.

 

[VCheng]

thats odd.. a certain Marine I know was adamant that the Marines are the only force that only require the presidents go. i.e. First in the fight at any area regardless of what congress says.

Not correct. The President can order any Federal force into an executive action as determined by him, but it is up to Congress to fund such actions, which, perhaps is equally important.

 

[FaujHistorian]

Actually, all were ready, the weight and crack things as with other problem were anticipated by the USAF and Lockheed Martin member. The aircraft itself are used in testing now as this phase is generally fish out the problem.

You cannot design something and expect nothing is going wrong with that. Especially a project this big. In computing business, this is called beta testing. Unless you are trying to tell me all Chinese Engineer and Mechanic are geniuses, China will need the Initial production testing phase too.

Plus you cannot field a squadron immediately after your plane enter production phase. You need pilot who can fly it and crew who can service it.

Isn't it the Chinese J-20 currently do not have a proper engine on it?

Well stated. If understood correctly, Chinese have to source the engine(s) from Russians

...lol, the Chinese member here actually do think like that,

J-20 enter Flight Testing, then they expect it to pass with flying colour, and then enter the Production without any hitch, and then field any squadron of the plane without any training.....lol

That's probably seperate the different in quality between American Engineering and Chinese Engineering. American care about every little detail, while these Chinese guy don't

Let me call on @gambit just for fun

You think Chinese may have a slight advantage in terms of sourcing? Besides engines they are putting everyting else together pretty much locally.

Wiki page (not the best source) says F-35 has had issues related to sourcing parts from all over the world.


Just curious

Hi,

Have a noob query here for @jhungary @Oscar @gambit @VCheng @sandy_3126@halloweene

Cannot computer simulations predict load and the potential for cracks in the system? If not, how so? If yes, why was this not detected?

cheers!

Others can give specific answers,

but simulations have a lot of limitations when compared to real world tests.

Case in point.

Every Windows release is tested via "simulations" like many inhouse tests for pretty much everything designed using CAD systems.

While CAD systems cut down a lot of basic testing, advanced real life responses come only when you take the puppy out for a run

 

[MilSpec]

Hi,

Have a noob query here for @jhungary @Oscar @gambit @VCheng @sandy_3126@halloweene

Cannot computer simulations predict load and the potential for cracks in the system? If not, how so? If yes, why was this not detected?

cheers!

Q: computer simulations predict load and the potential for cracks in the system?
A: Yes, computers can predict the load on any surface throughout the flight envelope and can also be used to predict potential cracks due to yielding, buckling, ultimate failures (ten/com) and fatigue failure.

Q: Can computer simulation predict the nature of crack propagation?
A: Yes and No

Yes: mathematical simulations can predict the fatigue failure based on known material behavior properties like flexural rigidity, Ultimate tensile stress and compression stress. for simpler materials like AL and carbon steel this is relatively simpler process... Alloys make the simulations difficult and honeycomb composites with carbon face sheets introduce large number of unknowns in the equation. Based on the direction of cyclic loading and iterative vector algorithm, relatively stable model of crack propagation can be estimated for a surface.

No: after saying the above stated, there is no guarantee that face-sheet will behave to the prediction because of the nature of the loading in a aircraft, the cyclic load pattern is non-uniform on the actual application, and to model the same set of fatigue pattern is next to impossible, and even if was done, production variations, material variations, bonding flaws, resin contamination, air contamination during transfer molding, come into the picture in case of composites. I am not sure where the crack was on this system, but it could be a result of multiple factors to varying degree. Thus modelling a crack propagation precisely is a daunting task in my humble opinion, That said the engineers working on these systems are extremely talented and they already might have a good dynamic non linear structural modelling tool tailor made for their systems. Boeing especially does a lot of research w.r.t. crack propogation for thier commercial lineup. So they might be all set with their modelling.

 

[gambit]

lol, the Chinese member here actually do think like that,

J-20 enter Flight Testing, then they expect it to pass with flying colour, and then enter the Production without any hitch, and then field any squadron of the plane without any training.....lol

That's probably seperate the different in quality between American Engineering and Chinese Engineering. American care about every little detail, while these Chinese guy don't

Let me call on @gambit just for fun

Yes, we do. And yes, they do not. Although the Chinese are learning and I experienced that first hand in the early part of my semicon career.

But to get back to aviation. The amount of attention to details -- BY ANYONE -- will be blessing and curse for development, and if the testing regime have a lot of destructive testing, particularly in weapons programs, things will get costly quick.

Here is an example of Boeing wing stress test -- to destruction...

The wings finally failed at 154% of limits. If you do not have the resources of Boeing, then you would most likely stay with tried and true wing structural designs and materials to keep development costs down. In return, your aircraft will also most likely will not be as capable as Boeing's. Likewise for the F-35.

The F-35's major structures are more modular than previous designs precisely because of customer's demand to accommodate different services' requirements. Whether this is a good thing or not, vis-a-vis the F-111 debacle, is for a different debate, but modularity allows concurrent manufacturing and development. We have concurrency all the time in semicon products manufacturing, at least among the major names in the industry, anyway.

Concurrent engineering - Wikipedia, the free encyclopedia

Concurrent engineering is a work methodology based on the parallelization of tasks (i.e. performing tasks concurrently). It refers to an approach used in product development in which functions of design engineering, manufacturing engineering and other functions are integrated to reduce the elapsed time required to bring a new product to the market.

For semicon manufacturing, under concurrency, the development line will be exploratory in terms of scaling and the techniques available to achieve a certain nm goal. Techniques such as masks, temperatures, etch cleaning, gas deposition time, etc...etc..., and the manufacturing line is where it gets tricky -- how much lag do you want behind the development line?

The closer to the development line, or less lag behind the development line, the greater the financial cost will be should the development line encounters issues. How many manufacturing lines have you allocated in this venture will factor into the cost when, not if, the development line must halt to resolve issues. The allocation have already cut into the current production goals of existing designs. How much money do you want to risk to lose?

The further from the development line, or more lag behind the development line, the less the financial cost will be should the development line encounters issues. Any manufacturing lines you allocated in this venture can be quickly halted and reversed to run existing products. The problem here is that your competitors are doing the same thing and you have little clues on their levels of sophistication. You may think you achieved the best balance but that balance is for you, not for your competitors. If they have better engineers, better technology, and more financial resources, they will beat you to the market with newer technology.

The modularity in the JSF's major structures allows concurrency in development and manufacturing that the Chinese currently do not have, not just for the J-20 but probably for any future fighter projects. Modularity allows compactness of testing with no decrease in attention to details.

If issues/problems are found in one version, we can examine the other versions to see if the causes are from unique or common structures/components and we can remedy the problems with greater precision. This is what make the JSF unique in aviation in terms of development and manufacturing-- each manufacturing line also serves as development line. Simply put, for now the Chinese have nothing close. Not even halfway close.

Again -- this is because of the customer's demand that there be one common platform to accommodate three services. Any criticisms should be leveled with this perspective in mind but the main problem with the criticisms is that they are based upon the standard linear development/manufacturing process where the company spends a lot of money over many years, more like a decade, to thoroughly flesh out the design and remedy as many flaws as possible, and even then, such a rigorous testing regime does not guarantee that the deployed aircraft will not produce new defects, such as the F-16's Kapton wire or the F-18's vertical stabilators issues.

Concurrency in manufacturing is nothing new. But the scale of the JSF project is one that probably no one else in the world dare to even try in simulation, let alone actually do in real life.

 

[jhungary]

Well stated. If understood correctly, Chinese have to source the engine(s) from Russians

You think Chinese may have a slight advantage in terms of sourcing? Besides engines they are putting everyting else together pretty much locally.

Wiki page (not the best source) says F-35 has had issues related to sourcing parts from all over the world.

Just curious

Others can give specific answers,

but simulations have a lot of limitations when compared to real world tests.

Case in point.

Every Windows release is tested via "simulations" like many inhouse tests for pretty much everything designed using CAD systems.

While CAD systems cut down a lot of basic testing, advanced real life responses come only when you take the puppy out for a run

The problem with this project to say J-20 is, this is an international joint venture developement. This would make the requirement so much harder.

Simply because they need not only to think about the US Military own needs. When those coutnry who did a JV with Lockheed Martin, they all have their need in mind and when they all raise their hand and want to be a part of this, they all put forward their own request. Instead a singlar design,. the LHM people would have to write up a design for multiple nation. The brits want this while the Aussie want that and the Dutch wanted somethign else.

On the other hand, China do not have that problem, yes indeed JF-17 is a JV between China and Pakistan, but to be honest, first, China is not using JF-17, so their need on JF-17 is none, and secondly, China determine what Pakistan get in JF-17, as the project did R&D in China while Pakistan make the plane. What i am saying China dictate the term is not any thing deminishing, but rather a factual fact. Say if Pakistan wanted American Engine on JF-17, would you think China would obliged??

And J-20 is for their own use, the hull and tech need not to satisify anyone but the Chinese.....

As far as i concern, these two program cannot be even begin to compare. As J-20 is a domestic in house program, F-35 in an international developement. While the fomrer only need to satisify the need for Chinese Air Force, the latter need to satisify a whole bunch of people. And also because of that, the transperency of the program in F-35 is very high, therefore you got faults and fail news coming time after time. Because LH need to answer to not just the US government. On the other hand, the Chinese do not so, you never even hear anything abd on their program. As there are no one accountable, but themselves.