LCA Tejas: News and Discussions

RoyG · Post by **RoyG** » 19 Apr 2015 22:15

Gone!

Karan M · Post by **Karan M** » 19 Apr 2015 23:26

Gone!

RoyG · Post by **RoyG** » 19 Apr 2015 23:41

Gone!

Karan M · Post by **Karan M** » 19 Apr 2015 23:52

Gone!

Vayutuvan · Post by **Vayutuvan** » 19 Apr 2015 23:54

abhik wrote:The only option new entrants might have is to bring in foreign consultants or pillage HAL employee base.

Lot of HAL people have been pillaged by the US MIC in the past who actually might come back as the said foreign consultants. If, as you say, local private companies pillage talented and trained HAL personnel, at least the expertise and knowledge base (tribal or otherwise) will stay in India.

RoyG · Post by **RoyG** » 20 Apr 2015 00:01

Gone!

Karan M · Post by **Karan M** » 20 Apr 2015 00:03

chaanakya wrote:...

I think NaMo went with a straight plan in mind & that was to land the nuclear deal with Areva & L&T. Ramana has pointed this out & further confirmation is there in that other speech to the BJP guys where he is pulling them up for not being able to articulate the Govt's achievements well.
The Rafale deal was to ensure a quid pro quo, plus further develop the IndoFrance relationship beyond the US centric arms purchasing we have had for a while.
It should include 30% offsets which is a plus. This plus the SRSAM and other deals & other visits clearly indicate (at least to me) that the Govt is going to balance out our technology priorities between US, Russia, France & Israel. Its not going to be one camp alone as we seemed to be tending towards in the prior dispensation.

Karan M · Post by **Karan M** » 20 Apr 2015 00:06

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RoyG · Post by **RoyG** » 20 Apr 2015 00:10

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Karan M · Post by **Karan M** » 20 Apr 2015 00:12

Austin wrote:I too doubt if they managed to reverse engineer the GE-404 most likely what he meant probably is they disassembled studied the engine and assembled it back.

Metallurgy is very complex and unless you know the composition of metal in precise percentage and the process followed to build it along with the machinery needed you cant get it done , Even Chinese couldnt reverse engineer AL-31 having it now for more than 2 decades and they import it.

Also reverse engineer generally ends up being worse or in best case equal and you can never have an original idea or out of box thinking if all you learn is reverse engineering , it better to learn to build our own engine , fail , build it , fail again till we succeed it would take decades but that experience would be worth in gold or platinum.

We would probably end up learning much more failing to build a flight qualified Kaveri then suceeding in reverse enginieering a GE or Snemeca or some other engine.

We have tried reverse engineering with engines - it didn't really help beyond a point.

Funnily enough, exactly like ArmenT described. Vernier callipers to detailed simulations even.

But the present thing from Rajkumar was a misquote. He lays out the details in his own book.

The LCA could not proceed on its test flight program without actuators & the engine. The HAL/ADA/DRDO crew pulled out all stops in making these things happen. They certified the items on their own, made them flight worthy & did constant juggling of serviceable units between different test rigs and the flight test beds to keep the program running.

The folks abroad were certain sanctions would stop us. We didn't care, nor did we stop.

These efforts were why the messages to Fernandes went, saying the aircraft was unsafe and what not. They couldnt figure out and believe the test staff pulled all this off on their own.

Karan M · Post by **Karan M** » 20 Apr 2015 00:15

Gone!

Vayutuvan · Post by **Vayutuvan** » 20 Apr 2015 00:17

As per reverse engineering point Austin made - there is no need to reverse engineer the exact composition. What one needs is an approximation of the material which can do equal or better than the imported engine (on some important metrics of stress, heat, aerodynamic etc.) and the material is easier to work with (easier availability of raw material, an already mastered process for material and manufacturing). The geometry of the engine is known and a geometry can b recreated digitally with high precision laser scanners (which are available aplenty in India though a tad expensive), parameterized models can be created (approximations are enough for simulations). Using this as the starting point, one can optimize for Indian conditions. Mathematically speaking it is easier to explore the design space around a point (in the state space) which is already proven to work instead of starting from scratch. Moreover when everything else is already constrained, i.e. the entire platform into which the engine is going to be integrated, thn the design space itself is smaller than if one starts from scratch.

Also, computer simulation technology - hardware and more importantly software - has come a long way from the time when these engines were originally developed. Speaking for myself, I would not underestimate some of our researchers - trained in India wholly or partially.

Karan M · Post by **Karan M** » 20 Apr 2015 00:20

Vayu, that's completely right. Where we are struggling is metallurgy. Even precision manufacturing has improved by leaps and bounds over the last decade but we still tend to import a lot of stuff from Germany & Europe, precision engineered items for the most part. Part of that could be sheer lethargy on the part of the HAL-BEL-OFB combine in actually local sourcing & indigenization.

RoyG · Post by **RoyG** » 20 Apr 2015 00:21

Gone!

Karan M · Post by **Karan M** » 20 Apr 2015 00:22

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Karan M · Post by **Karan M** » 20 Apr 2015 00:28

Gone!

RoyG · Post by **RoyG** » 20 Apr 2015 01:12

Gone!

Karan M · Post by **Karan M** » 20 Apr 2015 01:29

Gone.

Anujan · Post by **Anujan** » 20 Apr 2015 01:35

Gentlemen. Lets keep the discussion civil. Please edit your posts and refrain from personal attacks. Civility is what allows frank discussion and helps informative posts and threads without banning and warning users.

I'd strongly urge everyone to clean out name calling and personal attacks from their posts.

Thanks.

Karan M · Post by **Karan M** » 20 Apr 2015 01:43

I have no issues with keeping it civil.

But asking other members to "grow a spine you joke" and similar stuff & a consistent record of baiting really gets responses in turn.

RoyG · Post by **RoyG** » 20 Apr 2015 02:01

Gone!

RoyG · Post by **RoyG** » 20 Apr 2015 02:03

Anujan wrote:Gentlemen. Lets keep the discussion civil. Please edit your posts and refrain from personal attacks. Civility is what allows frank discussion and helps informative posts and threads without banning and warning users.

I'd strongly urge everyone to clean out name calling and personal attacks from their posts.

Thanks.

Will do. Nothing against Karan. Not sure why he is acting this way.

Karan M · Post by **Karan M** » 20 Apr 2015 02:28

Gone!

Indranil · Post by **Indranil** » 20 Apr 2015 02:36

Both of you. Stop it. Your posts have been cleared. These are testing times for everybody: Tejas supporters, govt. supporters and people in between. Time for extra control.

TO ALL: THIS THREAD WILL BE ON A VERY TIGHT LEASE FOR THE NEXT FEW WEEKS. TRANSGRESS AT YOUR PERIL (IN BR). I AM VERY BUSY FOR THE NEXT FEW WEEKS. IT WILL BE SHOOT AT SIGHT.

Indranil · Post by **Indranil** » 20 Apr 2015 02:48

vasu raya wrote:Are LCA drop tanks made of composites?

Yes.

Indranil · Post by **Indranil** » 20 Apr 2015 04:23

Nilesh,

You will enjoy this. Check the references.

By the way, look at the guys who were working on the wing.

The youthful team at ADA is led by Dr T.G.Pai and Dr K.P.Singh and it consists of Biju Uthap, A.K.Ghosh, A.K.Bhattacharya, Dr Santosh Korutu
and others.

Makes me laugh on the internet ninjas who pontificate on how the wing should have been shaped. On how canards would have augmented the plane! Bla bla bla ...

Anand Kumar wrote a paper called "Accurate Development of Leading-Edge Vortex Using an Embedded Conical Grid", where he discusses how to simulate the flow at the leading edge near the apex all the way till 30 degree AoA. Unfortunately, the results for the LCA simulations are not reported in the paper. Instead the experiments depicted are for a planar delta wing with a sweep of 68.2 degrees.

In another paper called "Burst vortex flow-field on a delta wing - A numerical simulation using Euler equations", he studies the vortex breakdown over a wing. Again, the model wing is not the Tejas wing.

One thing is for sure, they knew vortex flow around a delta wing really well.

Between, in 1997, they were planning to have 2 wet pylons per wing.

Indranil · Post by **Indranil** » 20 Apr 2015 04:31

Nilesh,

I am being a little lazy. Will you please remind me of your vortex theory that you presented with the following PIV diagram? The shorter the better. The vortex axes of the inward and the outward wing intersect. Do you also suspect that the secondary vortices energize each other and pulls the primary vortices inward and delays vortex breakdown?

It might well be, because look at the reattachment point of the primary vortex. That is close to the wing root!

vivek_ahuja · Post by **vivek_ahuja** » 20 Apr 2015 07:15

Geez. I come back bearing goodies and see that this thread has imploded in the meantime!

Sigh.

Allrighty, then. Let's see if we can focus this thread back to the LCA analysis.

This weekend I finally pulled up my code and uploaded the Mirage-2000C in there to see how it compared with the LCA. I was able to get a decent quality geometry file for the aircraft online and cleaned it up in FlightStream to yield the following:

And I ran it through the solver to get the surface vorticity distribution, which is then integrated for the aerodynamic loads.

I then ran the performance module with the data obtained and saw that I got good comparison with the Dassault flight-data:

Mach 0.8, 30,000 ft ASL
Mirage-2000C carrying center-line drop tank (1,300 L), two external drop tanks (1,700 L each), 4 MICA and 2 Magic missiles

Dassault Range: 2,886 km
FlightStram Range: 2,756 km

So that sounds reasonable. I also compared the simulation data with Polhamus results and they also look reasonable.

I then ran similar numbers for the LCA and the Mirage-2000C at 20,000 ft ASL and got the following (note: aerodynamic coefficients corrected for the LCA reference areas and lengths):

The bottom line is that the LCA has a better engine and fuel efficiency and so it gets close to the Mirage-2000C in range and endurance.

I cannot reconcile how the lift-to-drag ratio for the Mirage-2000C is so much better than that of the LCA. I guess I need to do some more analysis and verification of my algorithms to see if I haven't made a mistake anywhere. But I would bet against it. There is a possibility that my code is overpredicting the Mirage performance and the Dassault guys are simultaneously lying (

). That's the problem with having just isolated data points to verify against: you can't tell if you are wrong, they are wrong or both are wrong!

The LCA data, on the other hand, is based on the ADA wind-tunnel data, so that isn't expected to be wrong. Unless again, the ADA guys are also lying in their technical papers!

Anyway...

I just thought you guys will like to see what I am up to. Perhaps you all can suggest some validation data sources or thoughts on why the aerodynamic performance of the two aircraft is so different.

I will dig more into this in the coming days.

-Vivek

Indranil · Post by **Indranil** » 20 Apr 2015 07:31

Excellent, I was about to ask you for this analysis.

~~One way to verify would be to make a geometry file for LCA and run it through FlightStream simulations. If everything is fine, the L/D curve should match the wind-tunnel results.~~

Just checked your last blog entry. You seemed to have done it and got a good match. Hmmm.

sohamn · Post by **sohamn** » 20 Apr 2015 08:10

vivek_ahuja wrote:

The bottom line is that the LCA has a better engine and fuel efficiency and so it gets close to the Mirage-2000C in range and endurance.

I cannot reconcile how the lift-to-drag ratio for the Mirage-2000C is so much better than that of the LCA. I guess I need to do some more analysis and verification of my algorithms to see if I haven't made a mistake anywhere. But I would bet against it. There is a possibility that my code is overpredicting the Mirage performance and the Dassault guys are simultaneously lying ( ). That's the problem with having just isolated data points to verify against: you can't tell if you are wrong, they are wrong or both are wrong!

The LCA data, on the other hand, is based on the ADA wind-tunnel data, so that isn't expected to be wrong. Unless again, the ADA guys are also lying in their technical papers!

-Vivek

LCA has better fuel efficiency mainly because of the engine, which is a generation or 2 advanced than the mirage engine. However, it is expected to have a very poor lift to drag ratio. With wartime payload most ADA documents mention a range of 500kms. Also, since LCA has a far less overall lift generating surface area than mirage, a full weapons load will consume most of the surface area and hence will degrade the lift significantly. May be a conformal tank on LCA will help significantly.

Can you do a similar simulation with Gripen vs LCA ? It might be a better comparative analysis.

Singha · Post by **Singha** » 20 Apr 2015 08:18

The m2k pylons seem taller than most,holding the weapon far from the wing or fuselage..does that help lift in any way?

Sanjay · Post by **Sanjay** » 20 Apr 2015 08:36

A question: after reading all the analysis, can it still said Tejas Mk.1 is underpowered ? Isn't that too simplistic ? Would ITR and STR be about par with M2K ?

Singha · Post by **Singha** » 20 Apr 2015 09:05

it is not underpowered in the absolute sense but power is only one factor in the equation - its more draggy fuselage and less lifting surface in real world use cases brings it to the level of m2k (I think) when in reality it should have sharper specs due to larger wing area (less wing loading) , albeit mirage has more powerful engine also.

secondly the M2k has moving shock cones in the inlets that are necessary to boost speed above mach1.8 and it can sprint at mach2.2 vs mach1.8 of tejas. it routinely does mach2 for sure (I recall a m2k pilot in a DD interview long back...he said it was "top of world feeling" above the clouds and mach2).

Sanjay · Post by **Sanjay** » 20 Apr 2015 09:07

Thanks Singha. Any idea on how they compare ITR/STR ?

Singha · Post by **Singha** » 20 Apr 2015 09:11

A member named Shalav had done a analysis XLS once. note those are clean theoritical numbers and might not have all data on the drag problem of fuselage as thats not in public domain.

I think qualification of the more streamlined supersonic drop tanks is another pending activity. have not seen the kind of sharp nose fuel tanks seen on Mig21

Sanjay · Post by **Sanjay** » 20 Apr 2015 09:13

I haven't seen Shalav's analysis - what did it indicate in this regard ?

Indranil · Post by **Indranil** » 20 Apr 2015 09:14

The supersonic drop tanks will be added post FOC. That is the answer I had got from the Tejas-LCA FB page handler.

RoyG · Post by **RoyG** » 20 Apr 2015 09:24

Did the LCA designers incorporate anything from the Mirage 2000 into the design besides maybe the delta type wing? On what parameters does LCA score over Mirage 2000? Someone mentioned once that a canard design was once considered. Why wasn't it ever pursued?

Singha · Post by **Singha** » 20 Apr 2015 09:25

Sanjay wrote:I haven't seen Shalav's analysis - what did it indicate in this regard ?

afair the tejas figures were superior to m2k but inferior STR to f-16. people have speculated since the bundar also uses similar wings and tail as f-16 the same holds true for bundar as well wrt STR.

Singha · Post by **Singha** » 20 Apr 2015 09:27

RoyG wrote:Did the LCA designers incorporate anything from the Mirage 2000 into the design besides maybe the delta type wing? On what parameters does LCA score over Mirage 2000? Someone mentioned once that a canard design was once considered. Why wasn't it ever pursued?

I think complexity and weight. the LCA designers did not have the size and weight budget given to the M2k. they were told to make it small and they did.
another big decision was not to have the moveable shock cones and settled for m1.8 max....lot of eminent a/c like F-solah, rafale and gripen also accepted that.

but air superiority oriented birds like F-15, EF, Su27 family and m2k have shock cones or moveable constricting surfaces in inlet tunnel to ramp it up to mach2+
for some reason even the tornado has it though designed as a all-weather dpsa..and it can do mach2 at high level apart from being very speedy and very slippery at low level.