DISCUSSION: THUNDER AND TEJAS

[Manticore]

Thankyou guys - It's been a nice read.

As always, this time as well the concluding remarks when members realise that the aerodynamics have taken a back seat to avionics, would be which fighter sees first/fires first? AWACS support? Capability to upgrade previous blocks quickly while tactics have been slowly polished during that time.

 

[Stephen Cohen]

@amardeep mishra

Can we say that Tejas has the Good features of BOTH F 16 and Mirage 2000

From the F 16 we have Imbibed

Relaxed Static stability ; High TWR ; Four channel Digital Fly By Wire

And from the Mirage 2000 we have got : Low Wing Loading ; High ITR ; Rapid rate of climb

HOBS missiles + HMDS is of course common to both F 16 and Mirage 2000

 

[Spectre]

It might be ancillary to the technical discussion going on - and to add I am in no way qualified to qualitatively comment on the same but few points to note

- Tejas is likely to be stationed in southern bases in interceptor role
- JF-17 has relatively short legs and is unlikely to participate in bombing runs over bases in central/south India.

In such a scenario a more important question is

1. Does Tejas's low rcs come into picture when intercepting F-16s. Meaning can it fire it's BVR missiles undetected

2. Can Tejas' current radar and AWAC coverage help get it a lock on F-16s which would be in all likelihood be employing advanced EW measures

3. How well Tejas a relatively lighter and more nimble aircraft fare against F-16s carrying drop tanks and A2G package

Similarly all comparisons with JF-17 should be made with strike aircrafts like SU-30 MKI, Mirages and Jaguars.

Other scenario is in case of Chinese - How well Tejas fare against their Flanker derivatives and J-10s.

Regards

@amardeep mishra @Oscar @Manticore

 

[Arsalan]

@GURU DUTT here is what i said.

So please keep in line or stay away!

This shows how difficult it is and how true it is that you cannot keep in line thus you omitted that part and just quoted me on "stay away". Thanks for letting us know this about yourself,
Reported the post.
Next smart *** post will be rated after repeated warnings to stop posting useless crap in the thread.

 

[Manticore]

It might be ancillary to the technical discussion going on - and to add I am in no way qualified to qualitatively comment on the same but few points to note

- Tejas is likely to be stationed in southern bases in interceptor role
- JF-17 has relatively short legs and is unlikely to participate in bombing runs over bases in central/south India.

In such a scenario a more important question is

1. Does Tejas's low rcs come into picture when intercepting F-16s. Meaning can it fire it's BVR missiles undetected

2. Can Tejas' current radar and AWAC coverage help get it a lock on F-16s which would be in all likelihood be employing advanced EW measures

3. How well Tejas a relatively lighter and more nimble aircraft fare against F-16s carrying drop tanks and A2G package

Similarly all comparisons with JF-17 should be made with strike aircrafts like SU-30 MKI, Mirages and Jaguars.

Other scenario is in case of Chinese - How well Tejas fare against their Flanker derivatives and J-10s.

Regards

@amardeep mishra @Oscar @Manticore

https://defence.pk/threads/jf-17-su-30-which-will-track-fire-first.409714/

Start a thread like this with a clear unbiased original post in the paf or general airwarfare section. Tag all the active members you see in this thread.
In the OP please lay down the expectations/parameters of discussion as I did several pages earlier.

 

[-xXx-]

I am not an aerospace engineer, but the turn performance and of TEJAS and all Mirage derived aircraft is extremely poor. As a design, TEJAS is already obsolete. Some of our boys examined it in Bahrian and they couldn't hold back their laughter. Sigh of relief for Indians to be scrapping the Rafale and going for TEJAS.

So much of hoopla on amardeep post and then we got this.

@Arsalan @Oscar

 

[Nilgiri]

Now about Tejas:
It looks to be a good light weight fighter which I think is more in tune with IAF's experience with Mirage 2k and should be a fine fighter with all the pros or cons of a tail less delta. But I am not fully sure why they chose a reverse compound alpha design. Logically they should have gone for a design more like F-16 based cranked arrow design, that would have resulted in higher turn rates. But may be their designers thought that this will result in a better performance at high altitude and super sonic ranges may be for BVR combat. But does not look to be a good design choice, you can go super sonic fast if your engine responds fast and handling may be an issue with such a design at high AOA at lower altitudes and subsonic speeds. But as they say the taste of pudding is in eating, I might be wrong.

A reverse compound "Cranked" delta offers many of the same benefits as a canard (to what exact degree I plan to find out myself by a CFD model). Greater angle of incidence in the top part of the delta enables vortex creation in the middle of the wing and permits higher AoA compared to a clean delta configuration. There is also a levcon that further assists in this process hooked up to the FBW. That is the basic rationale for the reverse compound delta (as opposed to a cranked arrow delta which is more similar to what a LERX achieves but on a somewhat larger scale - the key difference being the location of where the vortex is generated and the flow characteristics caused by this location).

As @Taygibay has already mentioned, doctrine can be evolved specifically to design around the advantages and disadvantages of any specific platform. This is covered well in the extensive flying done by the F-16 XL and comparing it to the F-16 in flight characteristics. The doctrine migrated from using superior STR to taking advantage of the superior ITR (of a delta by more responsive pointing and locking). Unfortunately the XL program was cancelled and much data and effect on doctrine is thus unavailable....the Tejas may be charting its own territory to some degree here....given it has hedged its AoA performance (to some degree) at low speed with the reverse compound delta design.

Thus, if the deficiencies are properly mitigated at the relevant scenarios (i.e the AoA capability mentioned before) and the doctrine designed to focus on the strengths of the Tejas (ITR for WVR engagements, and superior supersonic performance of a delta for BVR engagements esp with the proposed AESA radar)...there is no fundamental "design" reason stopping the Tejas from achieving its personalized niche in air combat.

Hopefully my future CFD analysis will shed some light on the degree of function correlation between a canard, LERX and reverse compound delta through their vortex generation characteristics. The Levcons will add another degree of complexity to modelling this as well.....heres where a wind tunnel and real life prototypes are so much better

 

[amardeep mishra]

And don't even get me started on what should have been revealed or not. That's a whole different can of worms.

Hi @JamD
Well,I am not talking about some super secret weapons technology that pakistan might have incorporated into this jet.I am afraid you did not get my point,which was,had this feature been present in JF-17,I am sure the chinese designers would have definitely advertised it in various air shows- I am sure you know JF-17 has taken part in a lot more air shows than tejas. And they have advertized a lot of things in these airshows to be precise,in fact if i recall correctly,itz ability to integrate CM-400 missile was revealed in one of the airshows.So,when they can reveal these,i dont have a reason to believe they wouldnt do in case of RSS(had it been really present!)
So,Since they have NOT advertised it or declared it,we have no reason to believe it is there! I hope you get my point!

 

[GURU DUTT]

@GURU DUTT here is what i said.


This shows how difficult it is and how true it is that you cannot keep in line thus you omitted that part and just quoted me on "stay away". Thanks for letting us know this about yourself,
Reported the post.
Next smart *** post will be rated after repeated warnings to stop posting useless crap in the thread.

with due respect TT sir i was not trolling but giving answer to a poster making fun of by trying to say everything about Tejas is "WILL HAVE" i simply showed what does Tejas "has as of NOW"

secondly all such tejas Vs JFT threads are nothing but troll fest where almost all pakistani members want to beleve that Tejas is obsolete and JFT is the best fighter jte out there but the hard fact remains they both are very diffrent air crafts in every aspect as JFT was the choice PAF made to get away from american sanctions and hegemony while Tejas was made to replace 1960s era Mig21s and later Mig27s

thirdly since tejas was concived as a low cost quick reaction light fighter for internal air policing and point defence role which would never be able to be a frontline fighter and always have to fight in shadows of big boys of the IAF while JFT was made as a multi role air superiorty frontline fighter

finally im no engineer or a fighter pilot to know minute details all i was saying since many make fun of tejas by saying it wont be good in low speed low altitude high manuvoring-turning dog fights my post was that tejas was made with HMDS and HOBS and BVR combat in mind for which it dint needed that kind of manuvering capbility (lessons india learned after studying gulf wars )

so @Arsalan sir im not here for trolling but when someone makes fun of your hard work you tend to reply back thats human nature and i did the same cause no matter what pakistani patriots think tejas will never fight any PAF fighter jet its to fill up numbers and cabaple enof to hold back enemy fighters if ever they defete all frontline of IAF and enter indian airspace with offensive designs ... THANK YOU SIR consider it my last post on this thread

 

[amardeep mishra]

Not all canards work the same. You are right about the vortices and other effects when closed-coupled!
The canards placement on the Typhoon so far from the wing is exactly chosen to minimize wing interaction
while instilling maximal moment on the nose authority. The Rafale placement does the exact opposite.
Just because of the control of airflows over the wing, a Raffy can land at lower speeds than traditional delta
designs. It was a design objective so the plane would be able to land on carriers since omnirole, Dassault dixit.

Hi dear @Taygibay
I should have made it clear in my post that i was in fact writing on rafale and NOT EFT.In fact I did mention towards the end of my post you've quoted above.Yes i was emphasizing close coupled canards as opposed to canards far away from wing!

Why? Why would a design team avoid a technology but then decide to use a bit of it?
Simple answer for good design teams : when necessary / required / can't be avoided.
So pitch change rate was deemed too fast for a traditional interface and pilot inputs ...
at the very least. If more control over it is required, it has to be difficult to control in the
first place if not impossible. As Oscar and even yourself explained, instability is exactly
that, the threshold past which the human piloting is overwhelmed and FBW required.

@Taygibay
I am sure you know that presence of FBW doesnt guarantee the existence of RSS-for if it were true then all the modern airliners(particularly those from airbus) would have been unstable. What FBW does is,it infact removes all mechanical linkages and gauges and replaces them with wires connecting pilot interface with sensors and actuators. IN F-16,pilot doesnt directly control the "de" elevator deflection(stabilators to be precise),he/she merely decides the AoA ,the rest everything else is taken care by the computer. Computer then actively controls the stabilators to trim the aircraft at a particular alpha-without pilot intervention.
PS- i forgot to add this bit in my previous comment and that is- the aerodyanmics of rafale is perhaps the most complex I have had the chance to study recently. I have never heard of any canard apart from maybe rafale and grippen that use downwash to their advantage- they turn one of the dis-advantages in terms of stability into a great adavntage!

 

[dadeechi]

@Quwa

Most important points

Astute readers (especially those familiar with the JF-17) will notice that while the Tejas – inducted in 2016 – is fully equipped, the JF-17 – inducted in 2011 – is being improved via relatively frequent iterative cycles.

Tejas followed Waterfall while JF-17 followed Agile project management

The implication of this for some countries, such as Nigeria and potentially others, could be immense. Just consider Nigeria, which is one of Sub Saharan Africa’s top economies. That country does not have many foreign vendors willing to sell it sensitive equipment, and its funding constraints limit its ability to readily pursue the few existing avenues.

Tejas is akin to Eurofighter Typhoon while JF-17 is akin to RAFALE

Customers prefer to deal with limited vendors hence today RAFALE & JF-17 have better sale prospects.

India needs to really work on expanding the options on the subsystems to make it more attractive to a wide variety of prospects.

 

[amardeep mishra]

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.

@Manticore
I will begin my explanation,
1)There is no hard and fast rule,Wing Loading depends on the design and weight carried by the aircraft,however for air superiority fighters it is generally in that range- 60-100 lb/ft^2(in american literature).In certain designs even fuselage contributes to lift-ex- F-16 and Mig-29 etc,hence their wing loading will be inherently lower than the aircraft which doesnt have blended fuselage.
2)Again It depends on design,I would suspect wing loading of ground attack fighters or bombers to be much higher than that of normal fighters.
3)You must understand that wing loading is not a static number,as has been explained by @JamD ,it depends on area and the weight.The aerodynamicist selects the wing loading based on the task desired from the aircraft.The only way to actively change wing loading "in-flight" is to have a variable geometry design- of course keeping weight constant!
4)Well,dont you think it depends on what the designers envisages?
5)Higher ITRs but lower STRs
6)Well,it is not simple to explain,but i will try,first and foremost one must understand that canards provide a de-stabilizing pitch moment.What it means is that in the expression for Cee-em-alpha,the contribution from canards is de-stabilizing.Next,position of canards determine if the interact with airflow over wings or not.In simple designs,it is normally a practice to keep canards far away from the wing as you find in EFT,however in more complex aerodynamic systems,canards interfere with the flow over the wing.The downwash created by the canards are used to generate more lift.in fact in rafale it actively increases CLmax.
7)I have answered it in my comment above- In certain designs like "close coupled canards" the canards not only provide a instability but also interact with the flow field over wing.
8)i dont think the purpose of LERX is to provide additional lift(although it does generate it because at the end of the day it is part of the wing).LERX basically control the flow over wing at high AoA.They basically delay the onset of stall,hence their presence increases the max AoA possible. LERX basically helps in delaying the flow separation by creating a strong vortex over the wing.Now as you'd know,we can delay the separation by increasing the energy level of the boundary layer,what that vortex does,is,it transfers some of the energy from high moving free stream to the boundary layer thus forcing the boundary layer to remain attached. Thats the simplest explaination i could come up with,I must confess that I am not an aerodynamicist.I mostly work with controls. I am sure other members who have majors in aerodynamics can explain better!
9)I think you wanted to ask about nose strakes?
10)I dont think they've designed bombs just for LCA. Frontal RCS of LCA is already very low.

 

[LOGICAL BOSSS]

No one mentioned this, due to low wing loading LCA can carry far higher payloads at much ease with little drop in performance at high altitudes like leh and kargil comparatively to JF and J 10 (* J10 had already withdrawn from Indian front due to this lack of capability ).
It is built for true mountain warfare environment.
Also LCA cleared same trials at high altitude in Leh which majority of MMRCA participants failed to clear.
Combination of both LCA and LCH would be a yam raj for enemy.
Could be Delta design is not the best design of the world BUT it is the best design for India looking our own requirement, we have nothing to do with Island countries defense needs.

 

[Mssniper966]

I'll try to keep my contrevesial statement short -
" Tejas is currently much better on paper and future prospects, but JF-17 is already flying with comparable to less capabilities. That makes JF-17 more successful as of now. If Tejas deliver what MK1 promises truly(i.e fullfils mission requirements) till 2019 and MK1A is inducted by then, Tejas will be a greater success.

Ur statement is true but why compare tejas mk1A...a 2019 year aircraft with an old JF-17 Block 1....
Compare it with Jf-17 Block 3...which if delivered according to the promises would be still superior to Tejas mk1A

 

[Quibbler]

Ur statement is true but why compare tejas mk1A...a 2019 year aircraft with an old JF-17 Block 1....
Compare it with Jf-17 Block 3...which if delivered according to the promises would be still superior to Tejas mk1A

Thats what i did . I find JF17 blk3 comparable to less of MK1A