DISCUSSION: THUNDER AND TEJAS

[Imtiaz_Sarwar]

Rang layay GI PAF ki faqa masti aik din. This happens when you run after commission rich F 16s and shy away from self reliance for own selfish motives. Better to wake up now and improve your bird. PAF must put a dedicated and honest person with full control to be in charge of JF 17 project. Government should ban procurement of any new fighter unless PAF rolls out JF 17 block 3. Wars are won by those nations who make and use their own weapons with pride.

I agree with you. We should use our precious resources to improve JF-17. Block 2 is in production. Block 3 is next.
We should continue with further blocks down the road in future.

 

[amardeep mishra]

Moreover, just to glaze over the balance to the Tejas... you have oversimplified the concept into low wing loading and high wing loading when infact BOTH the Tejas and JF-17 are compound wings which varying wing loading at different sections not to mention that you have NOT provided ANY news article or otherwise to show that the JF-17 is unstable in pitch or not.

@Oscar
When did i claim that only "compound deltas" have lower wing loading?That isnt entirely true.Secondly,as i have always maintained,No one from PAF,PAC to CATIC have ever claimed that JF-17 is unstable in pitch plane.I would gladly correct myself if you can feed simple statement from the manufacturer,user or literature pertaining to the same.

 

[SQ8]

GENEREALLY , I am very quick to close such discussions as neither Indians nor Pakistanis are mature enough to carry this out without their need to flame and parrot away nonsense. However, Ill be tagging all moderators here and relevant think tanks to monitor this thread closely so that any violators from either side get the boot.. that also means those parroting away.
@Horus @Irfan Baloch @waz @Dazzler @Arsalan

@Oscar
When did i claim that only "compound deltas" have lower wing loading?That isnt entirely true.Secondly,as i have always maintained,No one from PAF,PAC to CATIC have ever claimed that JF-17 is unstable in pitch plane.I would gladly correct myself if you can feed simple statement from the manufacturer,user or literature pertaining to the same.

Why does it need a statement from the manufacturer to say that it DOES not?
You have proof for neither, hence you would be biased claiming either.
Also, please read my post carefully and what the quote I put there states. ALL delta's have inherent low wing loading.

 

[amardeep mishra]

Woes of Tailless Deltas

To date, only a few tailless delta fighters have been produced besides the Mirage III/5/50. These include the F-102 Delta Dagger, F-106 Delta Dart, J-35 Draken, J-37 Viggen, Mirage 2000 and Tejas.

In a tailless delta, lift augmentation devices like trailing edge flaps cannot be installed for want of space (though in the Viggen, these are cleverly placed on the large fixed canards). Also, upgoing elevons diminish wing lift which needs to be compensated by higher take-off and landing speeds, worsening short-field performance. Many a pilot who ended up in the arrester barrier has ruefully wished for a longer runway when confronted with a take-off emergency.

@Oscar
I did not even touch the dis-advantages of tail-less deltas. I was merely using simple FBD analysis to prove two of my points and that is in- kindly pay attention- a lower wing loading results in lower turn radius and velocity required for take off.I however do not agree with the author that landing run of tejas is higher,on the contrary it is lower than JF-17.Secondly sustained turn rate is a much more comprehensive figure as compared to instantaneous turn rate figure.It depends on a lot more parameters vis-a-vis ITR.
Ok,for sustained turning capability one would have to do a lot more excercise -i.e you would have to calculate the amount of induced drag at various load factors and speeds, the amount of parasitic drag at these speeds and load factor, and thrust, and iteratively find the sustained turn capability of the jet.

 

[zebra7]

GENEREALLY , I am very quick to close such discussions as neither Indians nor Pakistanis are mature enough to carry this out without their need to flame and parrot away nonsense. However, Ill be tagging all moderators here and relevant think tanks to monitor this thread closely so that any violators from either side get the boot.. that also means those parroting away.
@Horus @Irfan Baloch @waz @Dazzler @Arsalan


Why does it need a statement from the manufacturer to say that it DOES not?
You have proof for neither, hence you would be biased claiming either.
Also, please read my post carefully and what the quote I put there states. ALL delta's have inherent low wing loading.

Oscar, Amardeep Mishra gave his views, but your reaction is un needed and over reaction.

 

[SQ8]

@Oscar
I did not even touch the dis-advantages of tail-less deltas. I was merely using simple FBD analysis to prove two of my points and that is in- kindly pay attention- a lower wing loading results in lower turn radius and velocity required for take off.I however do not agree with the author that landing run of tejas is higher,on the contrary it is lower than JF-17.Secondly sustained turn rate is a much more comprehensive figure as compared to instantaneous turn rate figure.It depends on a lot more parameters vis-a-vis ITR.

How did you blanket an entire flight envelope based on just a basic analysis of take off performance? Again, that too based on figures that you have no provided from any published source.

Then, moving on to sustained you have decided to reverse on your supposed "rigorous mathematics" and given me the statement in red to avoid the actual discussion. Just a basic analogy can be taken in the M2K and the F-16.. and how they both compare in sustained and in ITR.

A half baked article from some unknown Indian engineer already tried to pass off this earlier. The entire article focuses on some software with very LIMITED inputs, and then goes further to show the ITR's as the main point for his claims of "superiority".

https://defence.pk/threads/lca-tejas-versus-yf-16-in-combat-part-i.405787/page-5

 

[Quwa]

@amardeep mishra - I generally try to discuss based on what I do know, and I avoid very technical subjects precisely because they aren't areas where I have done much studying. I am working to rectify that, but learning takes time. That said, everyone is welcome to add their views on the comment board of the website, I don't agree or disagree with them until I can competently discuss them.

That said, I looked at the Tejas and Thunder as broad programs. Whatever decisive advantages Tejas may have at this time, I am sure the PAF will not let them stand. With the capital investment made in the JF-17, it is a matter of time before iterative update cycles close the gap, if not for parity or superiority, then for comparability.

The days of Block-I are gone, and with Block-II, we have a modern ECM/EW suite (with subsystems sourced from numerous vendors) and BVR. Whether Block-III or earlier, HMD/S and HOBS AAM are coming.

Block-III may see other additions - e.g. composite materials, more efficient engine, etc. The JF-17 isn't going anywhere either and will remain as the PAF backbone for decades, that does open the door for additional developmental work. Adding to the developmental costs to improve an existing design will be more affordable and quicker than a clean sheet design, and there's plenty of time. It is sad that we do chide Indians for "waiting," but given Pakistan's troubles, I see no sin in time.

 

[SQ8]

Oscar, Amardeep Mishra gave his views, but your reaction is un needed and over reaction.

No it isnt. I GREATLY admire @amardeep mishra willingness to delve deep and learn and I cannot state that with more emphasis.

But when you start posting half baked analysis, it is incorrect and does not do justice to your knowledge and ability Moreover, this is a forum where both amateurs and people with years in the business roam.. but many more of the former. For that, it is always good to keep posts as public and simple as possible. There are many who will try to drown out an argument with too much obtuse information on various subjects, from aeronautics to religion.. and it is never good to just take them at face value.

Not everyone can do rigorous mathematics and for this subject it is necessary that if done so; they be done absolutely accurately to ensure that half baked attempts like those posted in the link in my previous posts are not repeated.

In fact, I can give a counter offer.

What if I was to post the exact parameters that the simulator I use takes for their flight model. Can you all come up with a general model for the Tejas and the JF-17 based on it?
It wont involve (too much) rigorous mathematics, and it will also be a much more involved activity.

Let's put it this way, I am asking for help to fix the flight models on my aircraft. Can you assist?

 

[amardeep mishra]

If low wing loading was such a miracle as you claim, every aircraft from the Su-30 to the F-22 would have chosen this path. The fact remains that only the Euro canards have chosen the delta and that too with the Canard to offset the associated woes of delta's along with offering a greater pitch movement.

Hi @Oscar
If you wanted to say that "higher pitch" mean pitch unstable then you're correct as canards have a destabilizing effect on the pitch stability of the aircraft for the simple reason that their AC is ahead of CG.The real reason why canard is used in these aircrafts is because it produces vortices which are very strong immediately behind canard itself, and get progressively weaker, but they also produce a downwash. Properly positioned downwash creates a low pressure region on front part of the wing upper surface which has a significant contribution to lift. Imagine bernoulli's effect and that is a wing will higher lift if the pressure differential on both the surfaces of the wing is high. Apart from creating a higher pressure differential these "euro-canards" make the aircraft dynamically unstable- mind it - it is different from static instability. Dynamic stability/instability is more concerned with the time profile of various parameters. Mathematically speaking it is closely related to the eigen values of the state matrix that we obtain after linearizing the eqn of motion.
Further,I would like to add that, vortices created by canard root, aside from improving wing lift during maneuvers by themselves, interact with vortices created by LERX (LERX itself creates vortices from both root and wing junction, helping both body and wing lift; vortices from canard tip energize outer parts of wings and do not interact with any other set of vortices but help in avoiding wing tip stall and improve response to aeliron inputs);
and lastly close coupled canards allow euro-canard fighters like rafale to maneuver in post-stall regime by increasing maximum lift coefficient (Clmax), making it supermaneuverable .

 

[MastanKhan]

Hi,

Only if it was that simple to sustain a claim for having 2 aircraft in service as compared to 66 aircraft in service---which have flown over 20000 hours by now in deployed status as compared to one with no hours---.

Let us not count the hours before deployment for the Tejas---.

Considering by the time 66 Tejas aircraft are inducted---and 66 Tejas pilots have accumulated 500 hours each on this aircraft---in that time---the paf pilots would be somewhere close to 1000--1500 hours each on the aircraft---.

It will take years for the Tejas to be integrated and operational manual ( if that is the right word for it ) written.

What the EW suite and the rets of the package for Tejas has done for the JF17----is that it has given it time to prepare accordingly. Sometimes the delay works in your favor---as is in this case.

The bottomline would be---a better trained pilot and better ew suite for the JF17 by the time the Tejas gains majority.

 

[SQ8]

Hi @Oscar
If you wanted to say that "higher pitch" mean pitch unstable then you're correct as canards have a destabilizing effect on the pitch stability of the aircraft for the simple reason that their AC is ahead of CG.The real reason why canard is used in these aircrafts is because it produces vortices which are very strong immediately behind canard itself, and get progressively weaker, but they also produce a downwash. Properly positioned downwash creates a low pressure region on front part of the wing upper surface which has a significant contribution to lift. Imagine bernoulli's effect and that is a wing will higher lift if the pressure differential on both the surfaces of the wing is high. Apart from creating a higher pressure differential these "euro-canards" make the aircraft dynamically unstable- mind it - it is different from static instability. Dynamic stability/instability is more concerned with the time profile of various parameters. Mathematically speaking it is closely related to the eigen values of the state matrix that we obtain after linearizing the eqn of motion.
Further,I would like to add that, vortices created by canard root, aside from improving wing lift during maneuvers by themselves, interact with vortices created by LERX (LERX itself creates vortices from both root and wing junction, helping both body and wing lift; vortices from canard tip energize outer parts of wings and do not interact with any other set of vortices but help in avoiding wing tip stall and improve response to aeliron inputs);
and lastly close coupled canards allow euro-canard fighters like rafale to maneuver in post-stall regime by increasing maximum lift coefficient (Clmax), making it supermaneuverable .

Dear, you are preaching to the choir. What you said, I tried to contain into one post. Again, it is great you have posted this; but for many of the audience.. my post or that from the article I quoted was enough.

Now, lets take it what I said. Why dont you help me improve the flight models and we can then see how that takes effect and try to give some semblance; and interest to your initial idea of comparing manoeuvrability.

 

[Manticore]

1 What is the wing loading in air superiority fighters?
2 Is the wing loading of ground attack fighters lesser or more?
3 How would designers adjust the wing loading of a multirole aircraft which has to do both air superiority and ground attack missions?
4 Would the mutirole aircraft be still more tilted towards either air or ground missions based on the designers preferences?
5 Do delta fighters have higher instantaneous as well as sustained turn rates?
6 Why were canards needed on a simple delta fighter?
7 Why is the location of these canards different in euro , j10 and rafale?
8 Do LERX of jf-17 generate lift? I s this lift controllable or does it have another control on the back of the aircraft?
9 Do canards generate controlled lift?
10 Has the JF-17s wing loading been published?
11 Where would a fighter having higher sustained turn rate outclass a fighter with higher Inst. TR
12 Has IAF developed specially designed bombs with reduced frontal RCS to reduce the fronal RCS of a fully loaded LCA?


@amardeep mishra

If you are claiming to be a more knowledgeable member in this field, then you should cover all the bases for new members.

 

[amardeep mishra]

A half baked article from some unknown Indian engineer already tried to pass off this earlier. The entire article focuses on some software with very LIMITED inputs, and then goes further to show the ITR's as the main point for his claims of "superiority".

Hi @Oscar
I am certainly not the one who did that analysis neither do I fully agree with that article.Dont you think putting me in that same bracket without even going through the details of my posts justified?Anyways,The STR of M2k was never higher than that of f-16-period! However one cant really write off ITR as it is important in evading radar and missile locks.Anyways i need to go,will write elaborately in the evening

 

[zebra7]

No it isnt. I GREATLY admire @amardeep mishra willingness to delve deep and learn and I cannot state that with more emphasis.

But when you start posting half baked analysis, it is incorrect and does not do justice to your knowledge and ability Moreover, this is a forum where both amateurs and people with years in the business roam.. but many more of the former. For that, it is always good to keep posts as public and simple as possible. There are many who will try to drown out an argument with too much obtuse information on various subjects, from aeronautics to religion.. and it is never good to just take them at face value.

Not everyone can do rigorous mathematics and for this subject it is necessary that if done so; they be done absolutely accurately to ensure that half baked attempts like those posted in the link in my previous posts are not repeated.

In fact, I can give a counter offer.

What if I was to post the exact parameters that the simulator I use takes for their flight model. Can you all come up with a general model for the Tejas and the JF-17 based on it?
It wont involve (too much) rigorous mathematics, and it will also be a much more involved activity.

Let's put it this way, I am asking for help to fix the flight models on my aircraft. Can you assist?

I remember, how my thread https://defence.pk/threads/lca-tejas-versus-yf-16-in-combat-part-i.405787/ was closed, may be by you or some other Mod, but CFT computationally evaluated performance characteristics models is the best way to evaluate the performance characteristics.

The thread, included the YF-16 to show, that how accurate the flightstream software was, since it is using simple PC, and not high power Computing power of the specialized pc to take out the graph needed. Why YF-16 analysis was done, because its graphical analysis was available in the public domain but it was taken as the attempt to create the thread for trolling.

This graph is given to prove the authenticity of the software used for the CFT analysis, not for the readers but the one who is doing analysis himself. But there are many who is simply too interested in the number, a number of substantial and ITR. When the number keep on changing with the different parameter, the graphical representation is the best.

@amardeep mishra is one of the guy, who is capable of doing it, if he has the time.
@Nilgiri -- I am sure he might give the analysis, some day

But there will be always, who will ask for the authentication, so it would be nice, if they them self plot the surface mesh themself with the software of their own choice, put them the data in the computation analysis software of their own choice and present them.

 

[amardeep mishra]

Now, lets take it what I said. Why dont you help me improve the flight models and we can then see how that takes effect and try to give some semblance; and interest to your initial idea of comparing manoeuvrability.

@Oscar
Sure,why not! Can I request you something?Please,can you kindly moderate this thread strictly so that anyone who doesnt contribute technically or using inflamatory words/trolls is not allowed to write here?In that way we can keep the thread very technical and interesting.
@Manticore
I need to meet my professor,i will reply in the evening!

With the capital investment made in the JF-17, it is a matter of time before iterative update cycles close the gap, if not for parity or superiority, then for comparability.

@Quwa
I agree,because the total combined cost of LCA program from R&D,establishing production lines,naval variant etc(as of 2015) is in the vicinity of 55000cr INR or roughly $9bn! I am sure,PAF would keep JF-17 relevent,but thats not what i am trying to allude to in my posts,i am merely comparing "certain aspects" of both these jets thats all. Of course JF-17 might have an edge in mach regime lesser than 0.8.But we will discuss that in coming posts!