LCA Tejas: News and Discussions

shiv · Post by **shiv** » 12 Apr 2015 20:07

Singha wrote: Few yrs back rafale did test cft. We should get it and get rid of atleast the centerline drop tank

I think I am heading into uncharted waters here. CFTs alter the aerodynamics and even carrying empty tanks means more drag ("drag" as in weight and aerodynamically). Drop tanks are always emptied first (ie fuel transferred to internal tanks) - on the way to the target and dropping them decreases drag, increases stealth and manoeuvrability and the decreased drag may make the difference between return home or ditch in critical low fuel situations.

vivek_ahuja · Post by **vivek_ahuja** » 12 Apr 2015 20:53

pragnya wrote:the internal fuel capacity of LCA 1 is 2458 kg as has been known for long and confirmed per DRDO techfocus of FEB 2011.

Right. That is what is used for the analysis, converted to liters for consistency. 2458 kg amounts to about 1,991 Liters of fuel.

rohitvats wrote:IIRC, a ex-Navy Harrier pilot while commenting on recent LCA article by Prodyut Das put the combat radius of Tejas Mk1 at 500 kms with internal fuel.

Wonderful: a data point for the LCA! Did the pilot mention what the configuration was for the LCA for this range? Was it flying clean or had some payload attached? Also, what kind of profile did it fly: high, low or a mix of the two? If it included high altitude, what number was that?

Do you have the link to that LCA article that you could email me, perhaps? I would like to chase down whatever data points I can get to validate my analysis numbers.

-Vivek

vivek_ahuja · Post by **vivek_ahuja** » 12 Apr 2015 20:59

Karan M wrote:Vivek, can you add any comparison to the Mirage 2000 or MiG-29 or Jaguar to put the performance in context?

srai wrote:Comparison with MiG-21--the aircraft LCA is replacing-- too.

Singha wrote:I think only useful comparison is with j10 and jf17 not our own.
Tejas has to fight these two strongly to be useful.

How much its better than mig21 will not pacify iaf..threats have changed.

Um, that might take some time to get all that in there! hehe

I was going to start with the Mig-21, actually. Since that seems to be a relative low-hanging fruit in terms of computational analysis. The Mig-29 is going to be the trickiest one because of its advanced aerodynamics that will need time and data to validate against.

On a secondary note, I will reiterate my ROH (Request for Help

) from BRFites who think they can help this poor abdul with some photoshop editing for some of the graphics for his articles, such as these:

Karan M · Post by **Karan M** » 12 Apr 2015 21:06

Vivek, please include at least the Mirage 2000 (and JF-17 or Gripen if possible, basically any other LWF). MiG-21 comparison is analytically fine, but we are in a war of perception too. Every bit to accurately judge the value of teh LCA helps and Mirage 2000 is critical in that sense.

K Mehta · Post by **K Mehta** » 12 Apr 2015 21:10

vivek please make it into an article on br main site, which can be published in other msm outlet with due credit. it would
1 provide a well researched analysis that can be used on say wiki
2 be a great addition to br main site.
3 help ignite a badly needed debate on lca.

vivek_ahuja · Post by **vivek_ahuja** » 12 Apr 2015 21:21

Karan M wrote:Vivek, please include at least the Mirage 2000 (and JF-17 or Gripen if possible, basically any other LWF). MiG-21 comparison is analytically fine, but we are in a war of perception too. Every bit to accurately judge the value of teh LCA helps and Mirage 2000 is critical in that sense.

Fair enough. I think I will add that as an addendum to the existing article. That way, we have one reference which is pure for the LCA and then other articles that compare LCA with others.

K Mehta wrote:vivek please make it into an article on br main site, which can be published in other msm outlet with due credit. it would
1 provide a well researched analysis that can be used on say wiki
2 be a great addition to br main site.
3 help ignite a badly needed debate on lca.

Off topic: How do I add this LCA article on the BR main site?

I know we had a page for ballistic missiles and their performance on BRF some time ago. I don't recall seeing one for aircraft performance, but I may be wrong.

-Vivek

arshyam · Post by **arshyam** » 12 Apr 2015 21:23

^^ Vivek sir, you could try sounding out Swarajaya mag if they can publish a summary of your findings. They are not a technical publication, but the message of your simulations can be condensed into an informed piece, and can coexist along with Saurav Jha's article, which are becoming regular there (along with many BRFites' !). Just a suggestion, since you are putting in the effort.

rohitvats · Post by **rohitvats** » 12 Apr 2015 21:46

vivek_ahuja wrote:<SNIP> Wonderful: a data point for the LCA! Did the pilot mention what the configuration was for the LCA for this range? Was it flying clean or had some payload attached? Also, what kind of profile did it fly: high, low or a mix of the two? If it included high altitude, what number was that?

Do you have the link to that LCA article that you could email me, perhaps? I would like to chase down whatever data points I can get to validate my analysis numbers.

-Vivek

Here you go:

Link to the article: http://profprodyutdas.blogspot.in/2014/ ... eview.html

Comments by the said fighter pilot - you're better judge of these things!

Professor, Your calculation regarding T/W for most aircraft are grossly wrong. you have calculated LCA on the lower side and other aircraft on the higher side. I suggest that you pls re-check your data and calculations. LCA with 6500kgs as empty weight and 9000 kgs as loaded weight has a T/W of 0.6(dry) and 1.0 (A/B). Though I do agree to just few of your points but most are bullshit to say it politely. I am a retd fighter pilot myself and very well understand what you have written here. If calculate wrong, you will arrive at wrong calculations. I do agree to your point that LCA wing shud have been reversed i.e it shud have more sweep in front and less sweep at rear and that engine shud have a bit more dry thrust. LCA does not need more of A/B thrust, it needs more of dry thrust. ADA has again gone wrong by selecting F414 engine which will give adry thrust of just 62.5KN. EJ-230 wud have done wonders to LCA with its dry thrust of 72KN.

There is a distinctive advantage of delta planforms in air combat compared to other planforms. And what matters most for ITR or STR is the CLmax and stall speed. Higher the CLmax, lower the stall speed, more is ITR & STR.

ROT=Rate of turn T (*/sec)= 1091*tanbank/v & radius of turn=Rad of turn R (ft)=v^2/ 11.26 tanbank

Many a times we go wrong in benchmarking the agility of an ac with wingloading. many ac can have higher wingloading but a very low stall speed due to a combination of many aerodynamic factors like LERX, MAW etc. One of the biggest disadvantage of low wingloading is poor gust tolerance and if we have wing like LCA, it also means extremely poor CLmax so even with low wing loading, we end up having a high stall speed which defeats the very purpose of having low wing loading. there are ac like Mig-29/Su-27 also which produce a large amount of lift from the fuselage.

If we go by efficiency of a design, A wing-tail, unstable combo is best, canard-delta RSS is second best, a wing-tail, stable design is third best and last is tailless delta RSS/Stable. All combinations of canard-delta and tailless delta suffer from high landing speeds as they can't handle double slotted flaps at TE of the wing. While canards do provide higher CLmax but use of slats-double slotted flaps provide much lower landing speeds for the same airframe. It is for this reason that I have more faith in wing-tail combo compared to canard-delta or tailless design. If we use a wing-tail combo with TVC, we can have stability and unstability on demand and such a combination emerges as the most efficient, least risky simple to operate design.

LCA as a design is inefficient and it is for this reason that they are now applying fixes to it in the form of Levcons etc. The best is to just change the wing and instead of 50*-62.5* make it 62.5*-50* and add LERX. This will reduce the wing area to a more respectable 30sqm and also take the AR to 2.25 which is the ideal AR for high speed interceptors. This will also help increase the wing fuel load.

In its present shape, LCA is still a capable ac and comparing it with JF-17/Mig-21 etc is wrong. this ac even today can easily take on these ac in combat. In air combat, there is a way in which you use a delta planform. today we have HMDS and agility has lost most of its meaning with missiles like R-73 but even in guns only fight which is a true dogfight, LCA will outperform the ac which you have listed but the very big question is, where will you go to fight with just 2.4tons of fuel? you will use up 200kgs in start up taxi & T/O. You will need another 200Kgs for landing circuit+400 kgs as standard reserve. That leaves you with just 1600 kgs to go to the combat zone and return. Mig-21 uses about 2000ltrs/hr and that gives it a range of 750 kms and is a turbojet engine, LCA has a turbofan, so we can assume a range of about 1000kms but than we need fuel for combat also, so we are down to a combat radius which is very easily equal to just about that of Mig-21.

LCA Mk2 will not offer much of a respite, ADA must redesign the wing and increase the length to be 14.5m atleast. that will give it more fuel and better agility.

K Mehta · Post by **K Mehta** » 12 Apr 2015 21:56

vivek i think you can post the article in lca section and i would suggest contacting sjha to post on his blog as guest as well.

sankum · Post by **sankum** » 12 Apr 2015 23:15

vivek_ahuja wrote

pragnya wrote:

the internal fuel capacity of LCA 1 is 2458 kg as has been known for long and confirmed per DRDO techfocus of FEB 2011.

Right. That is what is used for the analysis, converted to liters for consistency. 2458 kg amounts to about 1,991 Liters of fuel.

The internal fuel of LCA mk1 is 3035 litres instead of 1991 litres taken by you as ATF density is 0.81kg/ litre.

Therefore internal fuel 3035 litre* 0.81kg/litre=2458 Kg and not the other way around and range/endurance for internal fuel in your analysis will increase by (3035/1991=1.52) 52%.

Thanks for the great analysis.

The maximum fuel carried will be 6160 litres.

vivek_ahuja · Post by **vivek_ahuja** » 13 Apr 2015 00:00

sankum wrote:The maximum fuel carried will be 6160 litres.

Oh right. You scared me for a second there. I went back and checked my analysis and found that I had indeed used the mass for fuel in kg and not liters. So the plots are correct, but that conversion to liters is incorrect. I will fix the text in the writeup for it.

Thanks for pointing out the typo.

vivek_ahuja · Post by **vivek_ahuja** » 13 Apr 2015 06:00

rohitvats wrote:Here you go:

Link to the article: http://profprodyutdas.blogspot.in/2014/ ... eview.html

Geez. That article was a doozy. I couldn't read through it all despite three attempts to try and force myself to do so. I like how the professor has made far-sweeping remarks on the aerodynamics of advanced fighters as though he were designing a simple glider.

He does touch upon a few correct points, though (for example, the weight of the LCA etc.). But overall the article is far too condescending and fatally simplistic to read through without hurting your brain.

Heck, I used to teach subsonic aerodynamics and propulsion as well and while there are times when you can "get away" with simplification inside a classroom, I would shudder at the thought of comparing fighters like the way he has done for his article.

It took me many days worth of simulations to do the job I did for the LCA article. And even then its one aircraft analysis. To try and do the others to a similar level needs that much effort. You can't get away with using glider wing induced-drag computations for delta wings and blended fuselage effects!

Sigh.

-Vivek

ramana · Post by **ramana** » 13 Apr 2015 07:17

Vivek, Great job. I never could do that type of simulation. All I did was used Raymers book and gave up!!
If you have the time please do: SU 30MKI and Rafale.
So we know what is in IAF stable.

Thanks.

Indranil · Post by **Indranil** » 13 Apr 2015 07:48

Fabulous work Vivek!

pragnya · Post by **pragnya** » 13 Apr 2015 08:47

vivek_ahuja wrote:
pragnya wrote:the internal fuel capacity of LCA 1 is 2458 kg as has been known for long and confirmed per DRDO techfocus of FEB 2011.
Right. That is what is used for the analysis, converted to liters for consistency. 2458 kg amounts to about 1,991 Liters of fuel.

Vivek sir, i am no good in these conversion tables (kg to litre etc..) but i distinctly remember when i had to help out a kid for one of these (he had no access to internet) conversions when per kg ATF showed more litres. since it was the opposite in the article you wrote, i flagged it. but hey, since you clarified and corrected it, that settles it.

sankum, thanks for making me recollect that conversion i had long forgotten.

ArmenT · Post by **ArmenT** » 13 Apr 2015 09:09

vivek_ahuja wrote:
pragnya wrote:the internal fuel capacity of LCA 1 is 2458 kg as has been known for long and confirmed per DRDO techfocus of FEB 2011.
Right. That is what is used for the analysis, converted to liters for consistency. 2458 kg amounts to about 1,991 Liters of fuel.
-Vivek

Are you sure about this number? Reason I ask is because I remember water is nearly one-for-one (i.e.) 1 kg. of water is approximately 1 liter in volume. Therefore 2458 kg. of water should be approximately 2458 liters in volume. Given that jet fuel has less density than water, this means that 2458 kg. of jet fuel ought to occupy more than 2458 liters in volume. I remember from school days that specific gravity of kerosene is around 0.8, therefore, my back of envelope calculations show that the volume should be 2458/0.8 = 3072.5 liters approximately. I figure that jet fuel is similar enough to kerosene that its specific gravity should be close to the same value (0.8 ) as well.

[edit]I see someone else has pointed that out as well.

[/edit]

vivek_ahuja · Post by **vivek_ahuja** » 13 Apr 2015 09:12

ArmenT wrote:I see someone else has pointed that out as well.

Pointed out and corrected as well. Please see the blog article again. All plots corrected.

Always trust yours truly to do a full fledged computational simulation and then mess up the unit conversions.

-Vivek

pragnya · Post by **pragnya** » 13 Apr 2015 09:52

relevant to LCA wrt Composites -

NAL's Indigenous Autoclave Technology

Kemrock - NAL Carbon fibre tech commercialised

Zynda · Post by **Zynda** » 13 Apr 2015 14:48

Vivek,
I am not an aerodynamics engineer by any stretch and I may be using words without understanding them.

Have you had a chance to use a free wing analysis simulation software called XFLR5? From my limited understanding, it is a popular software used for prelim design of primarily RC controlled planes. Also apparently it may be inaccurate at high Reynolds Number, which I assume is the domain of high subsonic and beyond (?).

In any case, one can model the wing along with the relevant airfoils along the span and get relevant polar plots as well as basic wing aerodynamic analysis. The learning curve for me wasn't very steep but then again I need to use the software to obtain just the lift load distribution. The other data was irrelevant.

I am not sure if a wing analysis software is of help to your efforts and also you may have access to much more sophisticated aerodynamic packages but nevertheless thought of giving the suggestion.

Singha · Post by **Singha** » 13 Apr 2015 20:10

my spider feel says 60 Tejas mk1 are going to be ordered

Vamsee · Post by **Vamsee** » 13 Apr 2015 20:18

Centre scraps $20 billion MMRCA deal for 126 Rafale jets for IAF, LCA Tejas to replace MiG-21

Singha · Post by **Singha** » 13 Apr 2015 20:20

"replacing Mig21" is a loaded word. we have around 110 Bisons left, of the original 120 or so upgraded to Bison std (few have crashed over the years).

with 40 Tejas Mk1 on order there is still a gaping hole of 70 airframes just to reach parity in numbers, not to speak of reaching the famed 45 squadron level.

I really do not think the Mig21 and Mig27 fleet can be used beyond 2020...already they are well past the age at which RuAF would use and throw things in their system...even 2020 is a bit iffy. and the kopyo radar is not exactly a stalwart in the skies ...

so bottomline we cannot wait for the mythical Mk2 of Tejas.

call it Mark1.5 or something and throw in whatever is ready for the mk2 on the same mk1 airframe.......thats the onlee way out of the Chakravyuh

member_23370 · Post by **member_23370** » 13 Apr 2015 20:50

I sincerely hope by 2020 we have atleast 3-4 squadrons of Tejas. Mig-21 and 27 are too old and flogged beyond their expiry date. Good thing the MMRCA was scrapped. As and when the Mirage and Mig-29 retire (2025-2030) we can order additional Rafales.

arshyam · Post by **arshyam** » 13 Apr 2015 21:14

At least he has stated his intentions w.r.t. the LCA publicly, something the previous RM was loathe to do. But we need some concrete orders, and soon.

chaanakya · Post by **chaanakya** » 13 Apr 2015 21:18

ADA will get G2G order of 172 Tejas in different tranche after IAF gives FOC. DM is now on record that LCA is replacement of MIG21 . IAF can not say much. Line of succession will have to be invoked.

arshyam · Post by **arshyam** » 13 Apr 2015 21:39

x-post from Rafale thread:

arshyam wrote:Btw, did Parrikkar say anything about LCA mk2 specifically, or just that LCAs will replace the MiG-21s? Maybe he is telling the IAF to get ready to accept the Mk-1 itself in more numbers?

Austin · Post by **Austin** » 13 Apr 2015 22:17

Saurav Jha @SJha1618 · 2h 2 hours ago

HAL Tejas MK-2 with 5-10 % reduction in drag, higher TWR, more stealth, kickass integrated EW suite, better cockpit can sure be a winner.

HAL Tejas MK-2 will carry formidable weapons, will be difficult to find and get a fix on and will be able to pull numerous routine patrols.

rohitvats · Post by **rohitvats** » 13 Apr 2015 23:28

BTW, what happened to March 31 deadline for hand over of SP-2 to IAF?

Raveen · Post by **Raveen** » 13 Apr 2015 23:53

rohitvats wrote:BTW, what happened to March 31 deadline for hand over of SP-2 to IAF?

Like most HAL deadlines - when it came down to the line, it was dead

Prasad · Post by **Prasad** » 14 Apr 2015 00:24

Why is HAL having a tough time getting sp2 out? Can anyone she'd any light? Also, have we got the radome from chobam?

pankajs · Post by **pankajs** » 14 Apr 2015 01:10

Don't know if this was a sham handover but here is one line on sp2

http://timesofindia.indiatimes.com/city ... 204973.cms
LCA is poster plane of Modi's Make-in-India campaign (Feb 12, 2015)

Bengaluru: It's delayed and incomplete, but light combat aircraft (LCA) Tejas is still the most popular indigenous defence product after the Agni missile series. It will lead the Indian defence fraternity's 'Make-in-India' campaign at the five-day Aero India, entering its 10th edition.

For the first time, its makers will be able to boast that their customer, Indian Air Force, has accepted it. LCA will fly in formation during the customary flypast, presided over by PM Modi, defence minister Manohar Parrikar and others. The series production-2 (SP2) version of Tejas, which was handed over to IAF, will not be flying.

Dennis · Post by **Dennis** » 14 Apr 2015 02:08

As an additional point of reference, HAL has just 1 pilot (Air Cmde Muthanna (Retd)) qualified to fly the LCA SP aircraft.

Cosmo_R · Post by **Cosmo_R** » 14 Apr 2015 02:43

Raveen wrote:
rohitvats wrote:BTW, what happened to March 31 deadline for hand over of SP-2 to IAF?
Like most HAL deadlines - when it came down to the line, it was dead

Epic

Cosmo_R · Post by **Cosmo_R** » 14 Apr 2015 02:47

Singha wrote:my spider feel says 60 Tejas mk1 are going to be ordered

My spidey sense says the same. Namo's directive to Parrikar is to get HAL/IAF to walk the talk.

Cain Marko · Post by **Cain Marko** » 14 Apr 2015 03:55

Prasad wrote:Why is HAL having a tough time getting sp2 out? Can anyone she'd any light? Also, have we got the radome from chobam?

My guess is they will all come out at FOC standard....IFR, new radome, BVR integrated. at least I hope this is the case.

vina · Post by **vina** » 14 Apr 2015 05:15

The LCA is all set to go and ready to be rolled out in numbers. There are no big issues left. How do I know ? I don't of course. But just connect the dots and follow the golden role .."See how the guys actions , not hear his talk" , you can infer it.

No responsible govt will have been able to stare down the IAF flyboys and their shopping for the best toys in the global a toy market fixation without having an alternative that is ready. If the govt has finally done that, it can mean only one thing and that is that we have good news with the Tejas.

Remember the old adage as far as GOI concerns go. No news is good news. If there is bad news, it will be all over the media with the competitors /dalals/presstitutes pushing their spin. Like I said, the DPSUs are boxing against pirates armed with cutlasses and pistols with one arm tied behind their backs and bound by the Marquess of Queensberry rules (govt rules/codes/ whatever). You need the "Bhais" who will enter the industry now and make no mistake they will take on all of competitors/dalals and just grind them to pulp.

srai · Post by **srai** » 14 Apr 2015 05:25

Cain Marko wrote:
Prasad wrote:Why is HAL having a tough time getting sp2 out? Can anyone she'd any light? Also, have we got the radome from chobam?
My guess is they will all come out at FOC standard....IFR, new radome, BVR integrated. at least I hope this is the case.

The IAF prefers to get all of them in FOC standard. Most nations with a history of aircraft development would have started induction of the LCA at IOC-1 in 2010 itself. But this is an uncharted territory for the IAF. They are far from being a "builders" air force.

sivab · Post by **sivab** » 14 Apr 2015 07:49

Here is the full interview, must see. MP has good grasp of things, including DRDO, Make in India, Private sector participation, OROP, CDS etc.

Kashi · Post by **Kashi** » 14 Apr 2015 08:14

vina wrote:The LCA is all set to go and ready to be rolled out in numbers. There are no big issues left. How do I know ? I don't of course. But just connect the dots and follow the golden role .."See how the guys actions , not hear his talk" , you can infer it.

No responsible govt will have been able to stare down the IAF flyboys and their shopping for the best toys in the global a toy market fixation without having an alternative that is ready. If the govt has finally done that, it can mean only one thing and that is that we have good news with the Tejas.

I agree with you there, do you think we'll see more MK1s than those already geared for and MK2s to be inducted as and when they are available? Or are we going to see a freeze on MK1 numbers and a solid commitment to include unspecificed numbers of MK2 as they become available?

Of course that will need HAL to ramp up both MK1 and MK2 production.

pragnya · Post by **pragnya** » 14 Apr 2015 08:27

pankajs wrote:Don't know if this was a sham handover but here is one line on sp2

http://timesofindia.indiatimes.com/city ... 204973.cms
LCA is poster plane of Modi's Make-in-India campaign (Feb 12, 2015)
Bengaluru: It's delayed and incomplete, but light combat aircraft (LCA) Tejas is still the most popular indigenous defence product after the Agni missile series. It will lead the Indian defence fraternity's 'Make-in-India' campaign at the five-day Aero India, entering its 10th edition.

For the first time, its makers will be able to boast that their customer, Indian Air Force, has accepted it. LCA will fly in formation during the customary flypast, presided over by PM Modi, defence minister Manohar Parrikar and others. The series production-2 (SP2) version of Tejas, which was handed over to IAF, will not be flying.

the highlighted part read with your 'sham handover' comment gives a meaning completely out of context. to put it in perspective - per the article, the the handed over SP 2 will not be flying at AI 2015. that is all.