JF-17 Thunder Multirole Fighter [Thread 7]

[CriticalThought]

Chak Bamu is a respected poster. Being junior please learn to disagree with respect. Opening mouth without engaging brain leads to fights and unsightly arguments. So please bear that in mind.
Secondly may I know the source of the Mach 2 revelation that you have just posted. The reason I ask is that to my knowledge which indeed is very limited there is no fighter in existence that approaches mach 2 while utilizing DSI as a feature. Perhaps I might have missed something.
I do not know much about aerodynamics or aeronautical engineering but to support what Chak said, a small but well publicized change in block 3 is replacement of all the small antennas which jut out of the body. This was considered to be both and aerodynamic as well as( a sign of old age the right word escapes me totally- but your visibility on a radar----- Ahhhh!! Radar cross sectional area) blemish. It may also be pointed out that all efforts are made to remove the seems and rivets from Stealth fighters to reduce their radar signatures. I remember the holding bay doors of the J31s being shown extensively as an example.
Regards
A

The reason I lashed out is that the suggestion that rivets are used to create a vortex that provides additional lift is so ridiculous, it needs to be called out for what it is. And coming from a senior poster, it is even more crass. As you have seen already, he only has personal intuition to back up his claims. And I lashed out only because he himself became confrontational about it. If he had just accepted at the very beginning that this is based only on personal intuition, things wouldn't have proceeded any further. But at my polite request to ask for the source of his information, he became snobbish.

Secondly, I have made no 'revelation' about Mach 2, I am only saying there is a theoretical possibility that max speed will be increased so it is something interesting to look forward to. Why?

1. The possibility of RD-93 MA with increased thrust, while increased composites reduce the weight of the airframe itself.

2. The B Version has a higher sweep angle to the tail and there is a potential for this to be carried over to Block 3. Higher sweep angle leads to better management of supersonic shock waves.

3. Try to search for DSI under @Jungibaaz he has dispelled the myth that DSI cannot work for Mach 2. In fact, DSI can work all the way up to Mach 2. Interestingly, I have seen CATIC information saying Thunder can go up to Mach 1.8, but PAF keeps the limit at Mach 1.6.

Anyway, the original discussion wasn't about rivets, it was about generating lift through vortex creation. Rivets play no role in that, and to suggest the same is akin to twisting the very face of aerodynamics.

Now, interestingly, even the F-35 has a lot of rivets.

The rivets are covered with special surface paint

Now talking about protruding antennas, the Thunder has a better nose cone design than the F-16. The protruding pitot tube on any aircraft's nose has been found to be extremely finicky and it is almost impossible to control the airflow. Which is why modern nose cone designs have no protrusions at the front.

And finally, even the viper has those protruding antennas you like:

I can post a picture of Tejas as well if you like. Embedding the antennas in Block 3 just shows how far on the technological curve they are taking it.

So what's the point you are trying to make?

 

[araz]

The reason I lashed out is that the suggestion that rivets are used to create a vortex that provides additional lift is so ridiculous, it needs to be called out for what it is. And coming from a senior poster, it is even more crass. As you have seen already, he only has personal intuition to back up his claims. And I lashed out only because he himself became confrontational about it. If he had just accepted at the very beginning that this is based only on personal intuition, things wouldn't have proceeded any further. But at my polite request to ask for the source of his information, he became snobbish.

Secondly, I have made no 'revelation' about Mach 2, I am only saying there is a theoretical possibility that max speed will be increased so it is something interesting to look forward to. Why?

1. The possibility of RD-93 MA with increased thrust, while increased composites reduce the weight of the airframe itself.

2. The B Version has a higher sweep angle to the tail and there is a potential for this to be carried over to Block 3. Higher sweep angle leads to better management of supersonic shock waves.

3. Try to search for DSI under @Jungibaaz he has dispelled the myth that DSI cannot work for Mach 2. In fact, DSI can work all the way up to Mach 2. Interestingly, I have seen CATIC information saying Thunder can go up to Mach 1.8, but PAF keeps the limit at Mach 1.6.

Anyway, the original discussion wasn't about rivets, it was about generating lift through vortex creation. Rivets play no role in that, and to suggest the same is akin to twisting the very face of aerodynamics.

Now, interestingly, even the F-35 has a lot of rivets.

View attachment 449199

View attachment 449200

The rivets are covered with special surface paint

View attachment 449202

Now talking about protruding antennas, the Thunder has a better nose cone design than the F-16. The protruding pitot tube on any aircraft's nose has been found to be extremely finicky and it is almost impossible to control the airflow. Which is why modern nose cone designs have no protrusions at the front.

And finally, even the viper has those protruding antennas you like:

View attachment 449203

I can post a picture of Tejas as well if you like. Embedding the antennas in Block 3 just shows how far on the technological curve they are taking it.

So what's the point you are trying to make?

I asked a few pertinent questions. My assertions are and remain.
A. Senior posters need to be treated with respect. Disagree and again ask repeatedly but dont use words like BS, which you might not care to use in front of your elder brother. There are other ways of dispelling a notion but not in the way that you did.
You have pointed to the rivets of F35 and then said that they are covered by a special paint. Doing what? As you have shown they end up with a surface which is smooth! Again why?
You have pointed me to Jungibaz post but my actual assertion remains unanswered, ie are there any planes in existence with DSI who achieve Mach 2 or 2 plus. Secondly what is the utility of mach 2 in our air theatre where FOBS are within a couple of hundred miles. RD93MA when it comes on board will mean more plwer and thrust but is it only to achieve mach 2? Why has PAF and indeed the F35 been limited to mach 1.6?
Lastly you ignored the bit about the J31 and its seemless design. Again supporting what I was saying.
You have picked up on the antennas of the block 3 being merged into the body but omitted to read the fact that they help in reducing the RCS as well as drag. If I am wrong in my assumptions please feel free to disagree but for the purposes of this debate try and avoid bringing other examples to mire the debate into diverse direction and make it more convoluted.
I could have given you a couple of negative rating for disrespecting a senior poster or asked one of the mods to give you a cooling period. I like your posts therefore have very gently reminded you of forum rules. By all means disagree and challange. If you feel aggrieved by someone's blunt style do report it or nicely point it out to the person. But anger in response to disdain is perhaps not the right way to go on a brotherly forum. We are all a family here lets keep it that way.
Kind regards
A

 

[MastanKhan]

Hi,

The MIG25 had all rivetted joints----

" In order to reduce the effect of skin friction drag, aircraft designers utilize flush mount rivets and remove any irregularities which may protrude above the wing surface. In addition, a smooth and glossy finish aids in transition of air across the surface of the wing. Since dirt on an aircraft disrupts the free flow of air and increases drag, keep the surfaces of an aircraft clean and waxed. "

http://learntoflyblog.com/2016/04/11/aerodynamics-drag/


RE:---Mach2 debate---

It is better to spend the money on a better EW suite and better missiles than gaining that extra .4 of a mach speed---which won't get you anywhere---.

 

[khanasifm]

I asked a fea pertinent questions. My assertions are and remain.
A. Senior posters need to be treated with respect. Disagree and again ask repeatedly but dont use words like BS, which you might not care to use in front of your elder brother. There are other ways of dispelling a notion but not in the way that you did.
You have pointed to the rivets of F35 and then said that they are covered by a special paint. Doing what? As you have shown they end up with a surface which is smooth! Again why?
You have pointed me to Jungibaz post but my actual assertion remains unanswered, ie are there any planes in existence with DSI who achieve Mach 2 or 2 plus. Secondly what is the utility of mach 2 in our air theatre where FOBS are within a couple of hundred miles. RD93MA when it comes on board will mean more plwer and thrust but is it only to achieve mach 2? Why has PAF and indeed the F35 been limited to mach 1.6?
Lastly you ignored the bit about the J31 and its seemless design. Again supporting what I was saying.
You have picked up on the antennas of the block 3 being merged into the body but omitted to read the fact that they help in reducing the RCS as well as drag. If I am wrong in my assumptions please feel free to disagree but for the purposes of this debate try and avoid bringing other examples to mire the debate into diverse direction and make it more convoluted.
I could have given you a couple of negative rating for disrespecting a senior poster or asked one of the mods to give you a cooling period. I like your posts therefore have very gently reminded you of forum rules. By all means disagree and challange. If you feel aggrieved by someone's blunt style do report it or nicely point it out to the person. But anger in response to disdain is perhaps not the right way to go on a brotherly forum. We are all a family here lets keep it that way.
Kind regards
A

What the fu() is senior poster ? Who gives two ($&&( everyone need to be respected

End of story

 

[The Accountant]

I asked a fea pertinent questions. My assertions are and remain.
A. Senior posters need to be treated with respect. Disagree and again ask repeatedly but dont use words like BS, which you might not care to use in front of your elder brother. There are other ways of dispelling a notion but not in the way that you did.
You have pointed to the rivets of F35 and then said that they are covered by a special paint. Doing what? As you have shown they end up with a surface which is smooth! Again why?
You have pointed me to Jungibaz post but my actual assertion remains unanswered, ie are there any planes in existence with DSI who achieve Mach 2 or 2 plus. Secondly what is the utility of mach 2 in our air theatre where FOBS are within a couple of hundred miles. RD93MA when it comes on board will mean more plwer and thrust but is it only to achieve mach 2? Why has PAF and indeed the F35 been limited to mach 1.6?
Lastly you ignored the bit about the J31 and its seemless design. Again supporting what I was saying.
You have picked up on the antennas of the block 3 being merged into the body but omitted to read the fact that they help in reducing the RCS as well as drag. If I am wrong in my assumptions please feel free to disagree but for the purposes of this debate try and avoid bringing other examples to mire the debate into diverse direction and make it more convoluted.
I could have given you a couple of negative rating for disrespecting a senior poster or asked one of the mods to give you a cooling period. I like your posts therefore have very gently reminded you of forum rules. By all means disagree and challange. If you feel aggrieved by someone's blunt style do report it or nicely point it out to the person. But anger in response to disdain is perhaps not the right way to go on a brotherly forum. We are all a family here lets keep it that way.
Kind regards
A

I agree with @khanasifm... To have respect we need to give respect... Even you are bashing critical thought but he never responded to you like that as you never cross the line and never tried disrespecting others

 

[CriticalThought]

I asked a fea pertinent questions. My assertions are and remain.
A. Senior posters need to be treated with respect. Disagree and again ask repeatedly but dont use words like BS, which you might not care to use in front of your elder brother. There are other ways of dispelling a notion but not in the way that you did.
You have pointed to the rivets of F35 and then said that they are covered by a special paint. Doing what? As you have shown they end up with a surface which is smooth! Again why?
You have pointed me to Jungibaz post but my actual assertion remains unanswered, ie are there any planes in existence with DSI who achieve Mach 2 or 2 plus. Secondly what is the utility of mach 2 in our air theatre where FOBS are within a couple of hundred miles. RD93MA when it comes on board will mean more plwer and thrust but is it only to achieve mach 2? Why has PAF and indeed the F35 been limited to mach 1.6?
Lastly you ignored the bit about the J31 and its seemless design. Again supporting what I was saying.
You have picked up on the antennas of the block 3 being merged into the body but omitted to read the fact that they help in reducing the RCS as well as drag. If I am wrong in my assumptions please feel free to disagree but for the purposes of this debate try and avoid bringing other examples to mire the debate into diverse direction and make it more convoluted.
I could have given you a couple of negative rating for disrespecting a senior poster or asked one of the mods to give you a cooling period. I like your posts therefore have very gently reminded you of forum rules. By all means disagree and challange. If you feel aggrieved by someone's blunt style do report it or nicely point it out to the person. But anger in response to disdain is perhaps not the right way to go on a brotherly forum. We are all a family here lets keep it that way.
Kind regards
A

OK. We need to step back a bit, because I have lost track of what we are debating vs what we are merely discussing.

For me: saying rivets lead to vortex generation that provides additional lift is a huge point of debate.

For me: I am keenly watching out WHETHER Block 3 will or won't increase the max speed. What is the point we are debating here?

The rest of the points are just a friendly discussion. Can you please confirm?

 

[Chak Bamu]

OK. We need to step back a bit, because I have lost track of what we are debating vs what we are merely discussing.

For me: saying rivets lead to vortex generation that provides additional lift is a huge point of debate.

For me: I am keenly watching out WHETHER Block 3 will or won't increase the max speed. What is the point we are debating here?

The rest of the points are just a friendly discussion. Can you please confirm?

So, I did waste my time on google just so I could substantiate my observation and prior study (25 years ago!) that you call 'intuition'.

" In case of compressible flow, analysis results showed that increase in roughness height causes a significant increment in drag along with some increase in lift force. "
Aerodynamic Performance Analysis of Rough Rectangular Aircraft Wing for Subsonic Flow (PDF Download Available). Available from: https://www.researchgate.net/public...h_Rectangular_Aircraft_Wing_for_Subsonic_Flow [accessed Jan 22 2018].

Please note that the point being debated (from my side at least) was the difference in the effects of drag from circular seam welds and rivets. I asserted (based on observation & study, not intuition) that the rivets on wing surface would provide an asymmetrical effect, with some positive difference in lift. Thus drag from circular seam welds and rivets is not one and the same thing.

Now that I have established that I was in fact right in my statement (any engineer worth his name should be able to at least guess that wing asymmetry would give rise to difference in forces), can we please shut this derailment down?

Thanks @araz sb for making a point for decency's sake.

I apologize if I seemed brusque, but debating such a minor point to hijack the thread into derailment seemed so very pointless.

 

[CriticalThought]

So, I did waste my time on google just so I could substantiate my observation and prior study (25 years ago!) that you call 'intuition'.

" In case of compressible flow, analysis results showed that increase in roughness height causes a significant increment in drag along with some increase in lift force. "
Aerodynamic Performance Analysis of Rough Rectangular Aircraft Wing for Subsonic Flow (PDF Download Available). Available from: https://www.researchgate.net/public...h_Rectangular_Aircraft_Wing_for_Subsonic_Flow [accessed Jan 22 2018].

Please note that the point being debated (from my side at least) was the difference in the effects of drag from circular seam welds and rivets. I asserted (based on observation & study, not intuition) that the rivets on wing surface would provide an asymmetrical effect, with some positive difference in lift. Thus drag from circular seam welds and rivets is not one and the same thing.

Now that I have established that I was in fact right in my statement (any engineer worth his name should be able to at least guess that wing asymmetry would give rise to difference in forces), can we please shut this derailment down?

Thanks @araz sb for making a point for decency's sake.

I apologize if I seemed brusque, but debating such a minor point to hijack the thread into derailment seemed so very pointless.

This discussion is not irrelevant. We pride ourselves in the quality of information posted by title holders whom people respect and look up to. But in all cases, we are honest, straightforward, and unapologetic in refuting false knowledge.

Now, what you have presented above has serious flaws.

1. The publication is from a journal of no academic merit.
2. The study looks specifically at sand grain roughness. This has no relation to the imperfections caused by rivets or seam welds.
3. The study is limited to 73048 Pa and 283.24 K. From here:

https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

that turns out to be approx. 2.5 km (8200 ft) (and 10 degrees Celsius. I have skydived from 12K+ ft on a cold June evening on the outskirts of Sydney where the temperature can fall to below 0 degrees Celsius. This is a non-representative parameterization that does not reflect the real world.
4. Most glaringly, the study is based on output from a software and does not provide any wind tunnel tests or indeed any real world tests.

Which means we cannot take this as proof that rivets would cause increased lift on a fighter jet.

Not only this, but all textbooks on aerodynamics teach 'Lift induced drag'. No one has ever heard about a 'Drag induced lift'. This just doesn't exist in respectable academic material today.

 

[araz]

What the fu() is senior poster ? Who gives two ($&&( everyone need to be respected

End of story

Read the forum rules. Even if you dont agree abide by the rules .I dont particularly care for the language used in your post. Kindly refrain from using profanities which are not necessary for emphasising a point.
A

 

[Bratva]

thanks to SDF @ Hendrik_2000

Type KLJ-7A airborne fire control radar installed on the Y-7 testbed tests the ability to detect multiple targets.

The event belongs to same series of test that was previously disclosed in CCTV documentary couple months back

https://www.youtube.com/watch?v=4Z8x1e3PNJo (Timestamp 13:00)

 

[araz]

I agree with @khanasifm... To have respect we need to give respect... Even you are bashing critical thought but he never responded to you like that as you never cross the line and never tried disrespecting others

I am not in the habit of bashing anyone unnecessarily. Read my posts again and if you find anything that is remotely like bashing then feel free to point it out and I will apologize. Your point about respect works both ways. The debate need not have gone down the route it did but for the fact that posters lost their cool. This is undesired and the gist of my post has been to point it out. Disagree but do so with respect of one another. Banter has its own place, but foul language has no place on this forum and needs to be discouraged.
A

 

[CriticalThought]

I am not in the habit of bashing anyone unnecessarily. Read my posts again and if you find anything that is remotely like bashing then feel free to point it out and I will apologize. Your point about respect works both ways. The debate need not have gone down the route it did but for the fact that posters lost their cool. This is undesired and the gist of my post has been to point it out. Disagree but do so with respect of one another. Banter has its own place, but foul language has no place on this forum and needs to be discouraged.
A

Agreed.

 

[araz]

This discussion is not irrelevant. We pride ourselves in the quality of information posted by title holders whom people respect and look up to. But in all cases, we are honest, straightforward, and unapologetic in refuting false knowledge.

Now, what you have presented above has serious flaws.

1. The publication is from a journal of no academic merit.
2. The study looks specifically at sand grain roughness. This has no relation to the imperfections caused by rivets or seam welds.
3. The study is limited to 73048 Pa and 283.24 K. From here:

https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

that turns out to be approx. 2.5 km (8200 ft) (and 10 degrees Celsius. I have skydived from 12K+ ft on a cold June evening on the outskirts of Sydney where the temperature can fall to below 0 degrees Celsius. This is a non-representative parameterization that does not reflect the real world.
4. Most glaringly, the study is based on output from a software and does not provide any wind tunnel tests or indeed any real world tests.

Which means we cannot take this as proof that rivets would cause increased lift on a fighter jet.

Not only this, but all textbooks on aerodynamics teach 'Lift induced drag'. No one has ever heard about a 'Drag induced lift'. This just doesn't exist in respectable academic material today.

Great way of refuting a post.
Regards
A

 

[The Accountant]

I am not in the habit of bashing anyone unnecessarily. Read my posts again and if you find anything that is remotely like bashing then feel free to point it out and I will apologize. Your point about respect works both ways. The debate need not have gone down the route it did but for the fact that posters lost their cool. This is undesired and the gist of my post has been to point it out. Disagree but do so with respect of one another. Banter has its own place, but foul language has no place on this forum and needs to be discouraged.
A

I agree you never bash and that's why we all respect you without question.. You have earned it but same cannot be said about other senior poster... I agree that discussion was lost but this has to be taken by both senior and junior member... Let's close it here as thread is getting derailed...

 

[Chak Bamu]

This discussion is not irrelevant. We pride ourselves in the quality of information posted by title holders whom people respect and look up to. But in all cases, we are honest, straightforward, and unapologetic in refuting false knowledge.

Now, what you have presented above has serious flaws.

1. The publication is from a journal of no academic merit.
2. The study looks specifically at sand grain roughness. This has no relation to the imperfections caused by rivets or seam welds.
3. The study is limited to 73048 Pa and 283.24 K. From here:

https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

that turns out to be approx. 2.5 km (8200 ft) (and 10 degrees Celsius. I have skydived from 12K+ ft on a cold June evening on the outskirts of Sydney where the temperature can fall to below 0 degrees Celsius. This is a non-representative parameterization that does not reflect the real world.
4. Most glaringly, the study is based on output from a software and does not provide any wind tunnel tests or indeed any real world tests.

Which means we cannot take this as proof that rivets would cause increased lift on a fighter jet.

Not only this, but all textbooks on aerodynamics teach 'Lift induced drag'. No one has ever heard about a 'Drag induced lift'. This just doesn't exist in respectable academic material today.

If you really did pride yourself for accuracy of information, then you would not be putting words in my mouth. I never spoke about Drag-induced lift. I said that Seam welds are different from rivets and that their effects would be different. It is not an important point to debate and that is the reason why you would not find much research on this topic. The paper that I provided is not about sand etc... it is about circular surface irregularities that approximate rivets. If you had read the paper and checked the references, you would have found the material. I did read about surface irregularities resulting from abrasion, oil slicks, & research conducted where corrundum of various sizes are used to approximate various scales of irregularities. This research was done in 1930s & 1940s.

Your finding fault with research is just you trying to clutch at straws. Go find research about rivets and effects on drag and lift. Then come back and open another thread somewhere else.

Just the fact that you can not give up this diversion is because you love to argue and can not resist the temptation to have the last word. Using words such as 'honest, straightforward, unapologetic' is just a screen. PDF is known for trolling, thread derailments, & sheer number of thread launched by multiple posters who wish to discuss one thing. If you want quality of information, debate, & technical knowledge, you either go elsewhere or improve the level of debate here.

If you continue this derailment, then you would have the unique honor of being the first one on my ignore list.