JF-17 Thunder Multirole Fighter [Thread 7]

[Sinnerman108]

I have an issue with pdf think tank...news to me. Care to name the think tank?
No I am not mad at you? Why would I be?
I just think you should understand the basics of design b4 going off on assumptions.
People have zero understanding of how over designed structures really are. For example someone said jf17nis stressed to +8g and -3g. That's the envelope but stressing is done way beyond the envelope taking i account of critical and unlikely events

Good Sir, My apologizes for asking a question that caused you to go into a tirade, here to hoping that you didn't pop a vane or two due to that. As you are so knowledgeable per you posts that I do nod my head in your admiration, however I also do hope that you are not in academia at this time or at any time as I would feel real sorry for the students.

Please read your posts # 13,417 & 13,428, seek some medical help, too much anger is not good for health. Learn to ignore people you deem not worth of your time or worth explaining or providing correct answer(s) even if it pi$$e$ the daylight out of you, online forum phew phew is not worth popping a vane or two over.

PS: I asked a question, never assumed anything or didn't mean it to come as such. Sorry if it caused you to pop a vane or two as such was not my attention. It seems you anger got the best of you and took it out on 'we,' I would love to buy you a 'Cold One, soft drink' so you could chill a bit, perhaps some day we may cross path IRL and I will or best yet to hoping 'never.'

On a side note, not relevant to topic here. Richard Sherman to Tom Brady. 'You Mad Bro' ? after victory in 2012 SB, a classic in NFL.

Specifications are a wish list
Design is when you come up with constraints
Engineering is discovering and knowing which compromises to make.

Everything machine that you see, be that some thing as simple as internal combustion engine, to a jet has many compromises in it.

 

[denel]

Hi,

You don't deserve to know and neither is anyone else when it comes to weapons and weapons systems and you know it as well. What were you thinking when you wrote that comment?

Bilal's note is about overall malaise. The mere fact they fumbled shows that there is a huge gap in basic materials testing. If you recall when Indian media started to note that many jf17s were grounded due to structural challenges; it is not without any merit.

Materials testing and structural stress tests are very standard norm; albiet it is very possible and fair to say PAC did not know how to do it plus given this was not a priority from Chinese, there was not any importance or priority given. Is this the same issue in Blk3 - hard to say but it still begs the question why did this even occur in the first place.

THis is an example of how the JS1 wings are tested at my former university where JS gliders are built. If a small university like ours can do it and produce world class gliders.

 

[MastanKhan]

@denel,

When I was going to school in utah in the early mid 80's there was not a quarter that went by when an F16 did not crash into the great salt lake.

Hill AFB was the largest afb in the US at that time and there were modifications and performance tests done to the F16's that only the need to know people would know what happened.

And after a couple of crashes---all the F16's would be grounded, upgrades and modifications suggested and made and the aircraft put back into service.

And I don't see anything different in the JF17's case over here.

You and I both know that when we develop a product---after testing and becoming operational, we start to push the limits the machine would go before breaking apart just to see how far we can take it.

Now for the JF17 going supersonic to launch a missile---it is good if it happens---.

But if it don't, then no sleep needs to be lost if it doesn't.

There are many an aircraft that won't go into mach1 +++ territory to launch a missile.

JF17 is an able, capable & a stable platform.

It has taken many a years for the Paf to create this level of secrecy about its equipment and that is not bad.

 

[Sinnerman108]

Bilal's note is about overall malaise. The mere fact they fumbled shows that there is a huge gap in basic materials testing. If you recall when Indian media started to note that many jf17s were grounded due to structural challenges; it is not without any merit.

Materials testing and structural stress tests are very standard norm; albiet it is very possible and fair to say PAC did not know how to do it plus given this was not a priority from Chinese, there was not any importance or priority given. Is this the same issue in Blk3 - hard to say but it still begs the question why did this even occur in the first place.

THis is an example of how the JS1 wings are tested at my former university where JS gliders are built. If a small university like ours can do it and produce world class gliders.

It is not reasonable to assume that such testing was not done,
all load bearing structures are tested beyond limits. NO argument there.

Metal fatigue is a bitch to figure out, and it changes with age.
I can test a structure today, and after usage of one year the characteristics will change.

I am not associated with the program, and my connections are long broken; so I am only going to make guesses as educated as I can and base my opinion on science that I know.

However the above premise holds true ONLY when you assume that structural problems
were the cause, I am leaning towards the other theory of tran-sonic flight properties.

Regards.

 

[ghazi52]

.,.,.,

 

[Mrc]

Btw the question that started above discussion that why is there no video of jf going super Sonic


I want to ask is there any video of pakistani f 16 going super Sonic ?

Or f 16 has the same fatigue problem?

 

[Sinnerman108]

Btw the question that started above discussion that why is there no video of jf going super Sonic


I want to ask is there any video of pakistani f 16 going super Sonic ?

Or f 16 has the same fatigue problem?

Yes F-16, and all metal structures have the same problems.
that is how metals behave.

 

[lightning F57]

Am I right in saying block 3 has more composites in its airframe

 

[Abramar]

Btw the question that started above discussion that why is there no video of jf going super Sonic


I want to ask is there any video of pakistani f 16 going super Sonic ?

Or f 16 has the same fatigue problem?

F-16 going supersonic.

Also make no mistake, JF-17 can easily go supersonic. The absence of evidence, is not the evidence of absence.

 

[alimobin memon]

Why are you guys even arguing. Jf17 doesnt go supersonic. Why are our neighbours so worried then

 

[Mrc]

F-16 going supersonic.

Also make no mistake, JF-17 can easily go supersonic. The absence of evidence, is not the evidence of absence.

Well good idea to look on YouTube

 

[denel]

It is not reasonable to assume that such testing was not done,
all load bearing structures are tested beyond limits. NO argument there.

Metal fatigue is a bitch to figure out, and it changes with age.
I can test a structure today, and after usage of one year the characteristics will change.

I am not associated with the program, and my connections are long broken; so I am only going to make guesses as educated as I can and base my opinion on science that I know.

However the above premise holds true ONLY when you assume that structural problems
were the cause, I am leaning towards the other theory of tran-sonic flight properties.

Regards.

Most definitely agreed. But i know the chinese too well; they can cut corners on alloys as well. Problem is who is to validate the alloys or even the stress tests?

The classical case of good enough in such machines is defnitely not good enough.

 

[SQ8]

I have an issue with pdf think tank...news to me. Care to name the think tank?
No I am not mad at you? Why would I be?
I just think you should understand the basics of design b4 going off on assumptions.
People have zero understanding of how over designed structures really are. For example someone said jf17nis stressed to +8g and -3g. That's the envelope but stressing is done way beyond the envelope taking i account of critical and unlikely events

They do take into account critical and unlikely events. A 747 overspeed incident put enough G’s on the airframe that most of its rivets were bent but the aircraft made it back.. only to be written off because it was unflyable.

However, as a structural engineer you are also aware of why aircraft have “no step” on them. Everything from a F-16 to a A380 - that is because aerodynamic loads are spread out over the wing, but point loads like say a person’s foot.

Max take of weight ofAirbus A320 is 78,000 kg. Wing area is 122 m2. It makes specific pressure of 640 kg per m2 or 6 kg per dm2 .

Typical human has 80 kg , one sole of foot area is cca 2.5 dm2. It makes spec pressure of 32 kg per dm2 !!! Five times more!

Now replace that human foot with equipment attached to a point on the aircraft, likely drilled in or otherwise in an area marked no step or not to be used per oem. Normal load bearing areas like hard points are connected to the structure of the spars and included in the stress tests by OEM. However, any connection outside of those areas means you are stressing a weak point and could potentially cause a cascade failure as this seems to be.

I do have an alternative theory to this well, they did put the measurement equipment on the right points but somehow didn’t attach it correctly to where it came off midflight during a maneuver and might have gone through the aircraft tearing it apart. But its a very weak theory.

 

[Trango Towers]

They do take into account critical and unlikely events. A 747 overspeed incident put enough G’s on the airframe that most of its rivets were bent but the aircraft made it back.. only to be written off because it was unflyable.

However, as a structural engineer you are also aware of why aircraft have “no step” on them. Everything from a F-16 to a A380 - that is because aerodynamic loads are spread out over the wing, but point loads like say a person’s foot.

Max take of weight ofAirbus A320 is 78,000 kg. Wing area is 122 m2. It makes specific pressure of 640 kg per m2 or 6 kg per dm2 .

Typical human has 80 kg , one sole of foot area is cca 2.5 dm2. It makes spec pressure of 32 kg per dm2 !!! Five times more!

Now replace that human foot with equipment attached to a point on the aircraft, likely drilled in or otherwise in an area marked no step or not to be used per oem. Normal load bearing areas like hard points are connected to the structure of the spars and included in the stress tests by OEM. However, any connection outside of those areas means you are stressing a weak point and could potentially cause a cascade failure as this seems to be.

I do have an alternative theory to this well, they did put the measurement equipment on the right points but somehow didn’t attach it correctly to where it came off midflight during a maneuver and might have gone through the aircraft tearing it apart. But its a very weak theory.

Simple equation
Pressure = force / area
Yes you are quite right. Thats why people don't walk on wings other than the allocated ares often clearly marked.

 

[Kingslayerr]

Well good idea to look on YouTube

Those are clearly mirages.