My Understanding of LCA Attempt-2
To follow up to my earlier discussions on LCA, I did some more reading and also tried to understand the posts and articles of Indranil, Nilesh Rane, Surya and Maitya (courtesy lockdown).
I had always been perplexed with (aerodynamic) design choices of LCA and had no satisfactory answer. Though I hasten to add that all the articles of Indranil, Nilesh, Maitya (& posts) are correct but they are written by an expert and hence does not address, in detail, some questions which layperson like me finds perplexing. That is to say that they are dealing with Algebra while we are struggling with Sita Kaun thi?
The primary grievance against LCA is that it is inadequate and small little aircraft with short radius of action 300km-500km. Just like a Mig-21 so why did we not go with upgraded Mig-21.
Second is that LCA has not achieved what F-16 and Mirage did 40 years ago, hence why did we not adopt the design philosophies of Mirage 2000/F-16 rather than trying to re-invent the wheel?
So there goes nothing.
LCA design made 3 major choices, which have always been perplexing and rather debated, being:-
1. Delta Wingform vs Conventional Swept wing
2. Fly by Wire vs Conventional Controls
3. Use of Composites
The more I study the issue, the more I realise that these choices were forced upon DRDO-ADA and were not really a matter of free option. People offering simplistic solutions have not understood the problems/choices facing ADA.
But before we discuss the design choices, let’s have a look at the Dilemmas of the Political leadership and IAF Brass. My understanding is as follows:-
1. We did not go for upgraded Mig-21 as Soviets would not have co-operated. Further enlarging the nose of Mig-21s to put in a better radar would have given us a completely different aircraft with range even shorter than Mig-21, if we had used Mig-21 technology base.
2. We did not reverse engineer or go in for design philosophy of F-16s or Mirage 2000 as we did not have the “Engine”! No one was offering us 100kn engine.
3. Unfortunately the experts, even ex-IAF pilots look at things in compartments. It is easy to say upgrade the Mig-21 as if Soviets were their FILs with Garlands in their hands. Additionally, Soviets fighter aircraft had shit kicked out of them in 1982 Yom Kippur Israel-Syria war and we had to prepare ourselves against Pak and China acting together (perhaps using Western Equipment). We also knew that next Gen Soviet aircraft to Mig-21 being Mig23 were no match for western equipment. Even Mig-29 until recently has been very short ranged & maintenance heavy aircraft. Only when RD33/93 became powerful enough in this decade, its able to carry enough fuel using TWO Engines.
4. Rajiv Gandhi wrangled the most modern engine at the time being GE F404 (75kn) from Ronald Reagan and we set upon the task of developing a fighter equal to F-16/Mirage 2000 around that engine as we had no other choice. Rajiv Gandhi Got us:-
1. World most modern (small) Engine GE F404 75kn - USA
2. FBW – USA Martin Mareitta
3. Design – BAE, Dassault - UK, France
4. Composites and Wings construction – Italy - Alenia, Germany
5. Radar – Ericssion Sweden
And now using these building blocks we had to develop an aircraft which would be equal to F-16/Mirage 2000 and will not get its *censored* kicked like Syria in Yom Kippur 1982 and Argentina in Falklands 1982.
Intention of Indian DRDO & IAF Brass :-
We always intended to develop an aircraft way more advanced than F-16/Mirage 2000 with “more range” We went about portraying it as little toy aircraft to avoid attracting attention during Cold War Era and subsequently to avoid getting the programmed derailed by competitors. Remember our polite non-threatening Dr. Abdul Kalam working on sounding rockets. The Aim to develop long range Ballistic Missiles was always his real intent.
My understanding is that LCA was intended to be 1000-1200km range aircraft, and even now its 800-900km range aircraft (due to weight gain)
In any case, the discussion is all the more pertinent because for LCA Mk-2 we are retaining the same Wingform with Canards.
To understand the design issues facing ADA (which was to develop a aircraft equivalent to F-16/Mirage 2000 while using GE F404 – 75kn engine), we have to look at some real life examples:-
F-16 vs F-16XL
F-16xl was a delta wing variant of F-16. Most of my assertions in this article are based on 300 Page NASA Study on F-16XL which is available on Internet for public. This is the most important comparison for the purpose of present article as it indicates what would happen to range and payload (and other aerodynamic features) of LCA if Delta wing is dropped for conventional swept wing to increase STR.
F-16 vs Mirage 2000
F-16 has way better engine 1 generation ahead of Mirage 2000, which is 20%-30% more powerful while being 15%-20% more fuel efficient. F-16 has more conventional swept wing vs. Mirage 2000 tailless delta wing.
(Strictly speaking F-16 is not conventional swept wing, uses leading wing root edges but we are going to keep it simple.)
Mirage III vs Mirage F1 vs Mirage 2000 vs Rafale
France developed a hugely successful tailless Delta wing Mirage III, went to conventional swept wing with Mirage F1 and then came back to Mirage 2000 again with FBW controlled tailess delta wing and moved ahead to Close coupled canard Delta Wing Rafale
Now, why the delta wing for LCA?
Did we choose a bad design and are Sticking with a bad design? Is DRDO incompetent or Lazy? Should I pick up my Phone and educate ADA-DRDO?
Answer:-LCA has Delta Wing planform controlled by FBW because it has a “longer range” than conventional swept wing inspite of the fact that Delta wing has “bigger” wing area for a “given” engine power.
Now there goes one of the biggest myths facing LCA that its wing is big & hence its draggy and “hence” LCA has a very short range of 350-500km. In fact even I thought that LCA wing with its big area was a huge draw back.
As per NASA studies on F-16XL, FBW Delta wing has 40% more range (compared to F-16, inspite of being big and (allegedly) draggy).
Refer:-
https://www.nasa.gov/sites/default/file ... flight.pdf
Fortunately the answer lies in some basic physics. Swept wing broadly acts like a normal airfoil but the lift in delta wing is generated by “vortex” generated over the wings. (Google the rest). It is counter-intuitive and is something like, Indian Ballistic Missiles with blunt noses are more accurate than pointy missiles of Pakistan (gifted by China).
Refer:-
Flight data
Due to these vortexes, Delta Wing inspite of a Bigger Area can generate lift with lesser drag and is more efficient in not only cruise but also acceleration, transonic & supersonic regimes compared to conventional swept back wing (or even advanced swept back wing of F-16). Apart from having better ITR, more storage area, better fatigue life, lower wing loading, easier to manufacture etc.
Hence Bander FC-17 with its weak *censored* thirsty engine, limited FBW, swept back wing and aluminium body may have only 40% to 60% range of LCA (not withstanding Pak fanboy posts)
But Delta Wing does have cons like longer take off & landing runs, lower STR etc.
But why waste time over FBW? Could we not have gone for conventional controls with stable aircraft? Should I call up ADA and tell them about their stupidity as I just thought about it? Even some ex-IAF pilots say so. Why did we waste 5-15 years struggling with FBW? ADA Guys are fools!! I am more intelligent!!!
But there is a catch, about adopting Delta Wing. That pesky thing called Physics again! But anyway, unfortunately the trim drag of Delta wing tends to negate the benefits unless we use, guess….., FBW.
FBW by automatic computerised movement of control surfaces can massively reduce the trim drag penalty of Delta Wing.
Therefore if we use Delta wing without FBW then it has range shorter than swept back wing, due to trim drag. For Eg, LCA range would fall by 40%-60% and it may have a range of only 300km-500km equal to Mig-21 rather than 800-1200km equal to F-16s/Mirage 2000.
So for a “GIVEN” engine size Delta wing with FBW provides (substantially) more range and better speed, acceleration, etc.
Which means that FBW is not a matter of choice and is forced upon the designers if they want good range.
Now lets test this hypothesis through empirical data:-
F-16 vs delta wing of F-16XL, using similar engine F-16XL has either double the payload or 40% more range, (says NASA)
Another Eg. French Mirage III was delta wing without FBW. So France went to Mirage F1 conventional swept wing for better range (and other benefits off course). Thereafter when it was able to develop FBW it went back to Delta wing which had even better range. Hence, France went from Mirage F1 to Delta wing of Mirage 2000 to get better range, speed and acceleration. Conclusion LCA has 40%-60% better range than Chinese Bandar FC-17
These Bloody Yinodoos, they are surreptitious scoundrels! Cheating the world media, world powers, dalal lobby; all the while developing ballistic missiles while talking about sounding rockets.
We can test this hypothesis further. Mig-21, Mig-23Mig-29s, (earlier versions) all are very short ranged. USA had to use two engine heavies like F-15s and Soviets Su-27s with 300%-400% more power than LCA to get range and STR. Even present versions of Mig-29s which are really replacements of Mig-21s are giant beasts.
Hence, without FBW, without Delta wing, without composite body, the penalties are very heavy,. The only alternative is 2 “bigger engines” and as aforesaid we DID NOT have a Bigger engine.
We had a underpowered Marut and now underpowered Jaguar. Wonder why Jaguar was not used in Srilanka, Kargill and Balakot Revenge Strike??? It has everything the Desk Jockeys want. No FBW, No Delta and No Composites, not even a Radar, so did we want LCA to be like that?
Even though USAF rejected F-16XL because they did not want to give up sustained turn rate (among other reasons, like they may have wanted twin engines) but Note:- they did not use F-16 but had to go in for much bigger aircraft ie F-15 with almost 3x the engine power of F-16 (relative to the weight of aircraft)
Similarly (as aforesaid) Soviets had to use Mig-29 which is again is twin engine and still short ranged (compared to Mirage 2000) as it has neither FBW or Delta (nor any composites). Their Mig-23 was a dead end.
Coming back to LCA. LCA has a very advanced engine GE F404 and FBW with excellent fuel efficiency, FBW and Delta wing.
Hence, My guess is that the narrative about its/LCA short range is incorrect. Some (old) discussions on BRF which gave Relative Range of Mig-21 as 400km, LCA-500km, Mirage 2000 as 700km and F-16 as 900km are also incorrect. Perhaps they estimated the range using conventional comparison of frontal area & surface area. As aforesaid, the lift and drag on Delta plan forms is completely different and not directly comparable to swept back wing on linear basis.
My best guess is that range of Mirage 2000 & LCA MK1 is better or more than F-16 A-D, (without conformal wing tanks). Or to put it differently Israel carried out the famous Iraqi Osirak Raid at 1100km range in lo-lo-hi mode using F-16s. Both Mirage 2000 and LCA would be able to do that with weapon payload similar to F-16.
Arguing the issue from another angle:-
India did not have much choice. One suggestion was to simply develop Mig-21 further. It would not have led to much benefit and would have faced Soviet Resistance. We must remember that upgraded Mig-21s, Mig-23s, Mig-29s all, are no match to overall capabilities of Mirge 2000 and F-16s. Not to forget that we were already manufacturing Mig-21s and intended to license Manufacture Mirage 2000.
We tried to upgrade the design of Marut & did other sort of paper designs but were running into all sort of difficulties.
We were developing Kaveri engine (which was at initial stages) and with great difficulty Rajiv Gandhi wrangled GE F404. Was anyone offering bigger or better engine? Soviets were NOT offering RD-33 or Al-31!
Therefore DRDO had to design an aircraft around GE F404 (& potential Kaveri) which would successfully compete against Mirage 2000 and F-16s of the world. Hence there was no option but to adopt Delta Wing and FBW.
Off course there was a follow on two engined aircraft planned (MCA) but that’s another story.
What about the penalties of using Delta wing ? After all USA does not use it “nowdays” and neither does Russia.
Yes, there are penalties of using Delta Wing. Lets again look at F-16 vs Mirage 2000 for this.
USA retained F-16 wingform but inspite of being an aircraft in similar category of Mirage 2000, it uses 20% to 40% more powerful engine which is 15%-20% more fuel efficient ie basically a generation ahead of M53 of Mirage 2000.
Hence if we do not intend to use FBW controlled Delta wing we need a bigger engine and preferably two bigger engines which are also more fuel efficient because………..? they are bigger! Get it? (Which as aforesaid we don’t have, even today.)
Now, Inspite of F-16 bigger and more powerful and more efficient engine, still in lots of scenarios Mirage 2000 is better due to its Delta wing, like tau, response time, bank, roll rate, ITR, acceleration to supersonic regime etc.
Though the sustained turn rate is slightly poor to way more powerful F-16. Take off and landing distance is also more than F-16. Same problems are there in LCA also. As per some/lots of experts this minor difference in STR is not material compared to other benefits. Look at F-18 being used by USN, it is supposed to a pig.
Flight data
Further in any case, LCA was always intended to be followed up by 2 engine aircraft. The preliminary designs started circulating since 1990s as MCA. This would have been the follow up aircraft intended to address any deficiency in LCA.
Now coming to composites, Its incorrect to say that we had no exposure to composites.
We were already started absorbing composite technology with ALH, Dornier aircraft etc. The use of composites was essential as we had a punny engine with a big wing area, and an undeveloped aviation sector. It was an insurance against excessive weight gain, while maintaining competitive performance aganst F-16s, Mirage 2000, Mig-29s of the world.
I am not saying that LCA programme is perfect or that delay is justified but that the design choices were forced upto DRDO ADA and there was no easy way out. It was not a simple to say:-
Drop FBW, which would have led to 25%-50% range fall
Use aluminium body, which would have led to weight gain and 20% range fall
Using conventional swept wing, with aluminium body and conventional controls would have led to Mig-21 type range with bigger nose radar i.e. 20%-40% range fall
People tend to forget that the only low tech equivalent aircraft is FC-17 of China and we have no real world knowledge of its performance. But based on discussion above it will have less than half the range of LCA and very poor performance.
We (including myself) have always found LCA inadequate primarily due to short range. Seems like a punny aircraft. But based on my reading of NASA reports on F-16XL, I would like to say that LCA has range better or equal to Mirage 2000, F-16 (without conformal fuel tanks) and better than Gripen, Jaguar, early version of Mig-29 and double or triple the range of FC-17. Import dalals have been trying to create doubts in our minds by negative leaks and articles.
LCA with ferry range of 2100km in itself indicates a combat radius of 700-900km and these are early days when everything is done safely.
Compound Delta Wing
Now another minor (?) Gripe is that we use an over-complicated compound delta wing. Why did we not a simple pure delta like Mirage 2000. The answer is equally simple we were trying to decrease the limitations of Mirage 2000 and achieve a better performance.
Low swept Angle of wing (adjoining the fuselage) is intended improve low speed handling, angle of attack and to improve STR. Perhaps that is why LCA has a better STR than Mirage 2000. LCA also has a very small turning radius.
Compound Delta is well studied wing form used in Viggen and F-16XL.
Maitya & Indranil Excellent discussion is at :-
viewtopic.php?f=3&t=6663&start=3200#p1774291
viewtopic.php?f=16&t=6663&start=3240#p1775430
http://delhidefencereview.com/2019/02/2 ... er-part-i/
LCA MK-2 and why does it use Canards
Now if all of above is right and correct, and everyone lived happily thereafter, then what about LCA Mark-2. Why does it use Canards and why did we not use canards earlier?
LCA Mk-2 can use Canards to get better STR, shorter take off and landing distance because it has access to bigger engine GE F414, which generates almost 25% more power than GE F404
So the Canards will add some penalty of weight & drag but with bigger engine, more fuel we end up getting everything like better STR, shorter take off and landing distance alongwith more fuel, hence more range, more payload as LCA MK-2 is a bigger aircraft Rafale, Eurofighter also used Canards as they have 2 engines while Gripen is a short ranged pig
LCA Mk2 will be equal to or better than F-16/21 even with conformal fuel tanks and way ahead of upgraded Mig-29s, Gripen E/NG.
Naval LCA MKI, MK-2 will not be better than Mig-29Ks as NLCA is still evolving design which is heavy and underpowered compared to Mig-29Ks. Though there is serious doubt about the availability of Mig-29Ks on Naval deck.
http://delhidefencereview.com/2019/02/2 ... t-fighter/
http://www.indiandefencereview.com/news ... d-options/
Future
In AMCA we have gone for a different wingform as we wanted a stealthy aircraft but we are using two engines more powerful than Single Engine of LCA MK1.
Navy which wanted to longer range has (for now) stuck with LCA MK-2 wing form and Canards. Navy may want TDEF/ORCA to match or better Mig-29k reported 1200 km combat range with 6000 kg payload
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