LCA News and Discussions, 22-Oct-2013

vina · Post by **vina** » 29 Dec 2014 10:30

But am also curious to know why lca doesn't have he kind of acceleration, ~~payload capacity~~ ,STR , Range of other birds with lower twr. Either that or IAF is being remarkably uncharitable towards the homegrown product bordering on treachery

Pliss to answer the kweschuns I posed to Victor babu and the answer is reveals itself , as does the remedy. The range is a red herring. It will be comparable.

Cain Marko · Post by **Cain Marko** » 29 Dec 2014 10:35

The range is not an issue, agreed; what about payload? And acceleration? Esp. When lca has better twr?

srai · Post by **srai** » 29 Dec 2014 10:45

Turn rates - Mirage-jet.Com

Turn rate

The delta wing is often criticised for it´s relatively poor sustained turn rate(STR). The Americans place great emphasis on STR and it´s importance in a turning fight is beyond dispute. However the turning fight only very rarely occurs and whilst a high STR is desirable the importance of a high instantaneous turn rate(ITR) should not be overlooked. A high ITR is more important when trying to break a missile lock or radar lock than a high STR.

Listed below are some observed turn rate parametres exhibited by the Mirage 2000 (Internal fuel).

* At 30,000 –35000 ft and 5G the ITR is 10- 12°/second.
* At 36,000 ft and Mach 2 the Mirage can maintain a 3G turn.
* At an altitude of 40,000 ft and Mach 1.05 pulling the stick nearly full-aft produces 4.5G and an angle of attack(AoA) of 25°.
* At 22,000 ft and Mach 0.9 the application of 8G produces an ITR of 20°/second. The AoA is then 27°.
The application of 9G increases the ITR to 24°/second and 28° AoA.

vina · Post by **vina** » 29 Dec 2014 10:51

Pliss to Dekho. Wiki mamu actually does a pretty good job Lift To Drag Ratio

Look at this bichhar .

Now answer kweschuns..

1) For a plane with a lower wing area , will the induced drag be less or more than for plane with a higher wing area at take off/low speeds (assuming both planes have comparable L/D ratios.. i.e., both have competent people and not baboons designing). Which plane will need MORE thrust for comparable acceleration?

2) At the right end of the envelope, which plane will have a total drag , the one with a better fineness ratio or lower fine ness ratio ?

So, with these kweschuns answered,

To improve the LCA , you will
1) Add canards or
2) Increase thrust and improve fineness (by increasing length and better form drag by more optimal shaping)

Final kweshun.

For LCA MKII , ADA are
1) Increasing thrust and improving fineness (added benefit of more internal fuel and space for more avionics)
2) Adding canards.

Final Final Kwechun.
1) ADA should listen to Khokhar and Matheswaran as quoted by Victor babu and add canards or
2) Go back to Fyzzics and listen to people like Bade Mian and folks at NAL and test models in wind tunnel and listen to scientific facts.

Must they listen to "feelings" or should they listen to scientific arguments ?

srai · Post by **srai** » 29 Dec 2014 10:56

Not sure how accurate these ITR/STR figures are ...

http://forum.keypublishing.com/archive/ ... 00552.html

kiwinopal
23rd May 2010, 22:02
What criteria are you using? Why is the Su 35 BM classified as superior to the Su 30 Mk given that the radar is not that important in your WVR only evaluation??
Where do you get info regarding the J-10's maneuverability? Please, the first two posters, cite some sources...

Most of it is guess using a few public known numbers.

The F-22 was said to have a STR of 28 deg/s by an american pilot debriefing US pilots about Red Flag.

I have read Rafale`s ITR in the range of 32-30 deg/s and STR in the order of 23.9 deg/s.

Eurofighter of 30 deg/s ITR and 23.3-22deg/s STR
the MiG-29 is ITR 28 deg/s and STR of 23.5-22.8deg/s STR.

Gripen 30deg/s ITR and 20 deg/s STR.
Su-27 it is said on the range of 27deg/s ITR and 21deg/s STR.
F-16 has an ITR of 27 deg/s and a STR of 21.5-20deg/s
Mirage 2000 has a ITR of 29deg/s and a STR of 19deg/s
F-15 has an ITR of 21deg/s and 16 deg/s STR.

The J-10 is basicly a guess since is more or less in the size and weight of the F-16 and configuration of the Gripen i would say 30-31 deg/s ITR and 21deg/s STR at the best.
The Su-30MKI can not be better without TVC than the original Su-27 due to same TRW and the drag induced by its canards
The Su-35BM has new engines.
The MiG-35 has new engines.

The Rafale is not much better than the regular MiG-29A so i guess the Su-35BM must be comparable and the MiG-35 too in performance to both Rafale and Eurofighter

Victor · Post by **Victor** » 29 Dec 2014 11:03

Khokar had "whined" about first fast-tracking the LCA Mk1 with the proven fixes that we are going to use with Mk2 before we dump all our energies and time on a new Mk2. This does make eminent sense as the Lord alone knows what dark and endless alleys we are going to travel thru with Mk2. This doesn't sound like killing the LCA to sell the Gripen but quite the opposite. (I personally don't think this is a good idea because I believe the LCA1 is irredeemable). Besides ADA had already asked SAAB for consultancy help with Mk2. So much for being a long term threat. I think SAAB knew a couple of years ago that they are an automatic writeoff by being so similar to India's strategically important home-made fighter effort. They are smart people and will take the opportunity to earn some money and goodwill from India. They know that there are other things they can sell us.

Re. my "feelings" about what would make a good fighter, I really don't think I could make you understand because some things are just too difficult to explain, like describing what pizza tastes like. However, there is loads of intellectually stimulating info out there on the internet about dog-tooth leading edges etc if that's what you're looking for.

It would be extremely stupid of us to ignore the views of senior IAF folks, including one of the LCA's top test pilots, over unproven engineers who have never flown a plane. However it seems that ADA/HAL chose to do just that. This is far from the end of the story though. Much seems to be going on beneath the surface and we may be surprised very soon.

Indranil · Post by **Indranil** » 29 Dec 2014 11:13

srai wrote:Not sure how accurate these ITR/STR figures are ...

http://forum.keypublishing.com/archive/ ... 00552.html
kiwinopal
23rd May 2010, 22:02
What criteria are you using? Why is the Su 35 BM classified as superior to the Su 30 Mk given that the radar is not that important in your WVR only evaluation??
Where do you get info regarding the J-10's maneuverability? Please, the first two posters, cite some sources...

Most of it is guess using a few public known numbers.

The F-22 was said to have a STR of 28 deg/s by an american pilot debriefing US pilots about Red Flag.

I have read Rafale`s ITR in the range of 32-30 deg/s and STR in the order of 23.9 deg/s.

Eurofighter of 30 deg/s ITR and 23.3-22deg/s STR
the MiG-29 is ITR 28 deg/s and STR of 23.5-22.8deg/s STR.

Gripen 30deg/s ITR and 20 deg/s STR.
Su-27 it is said on the range of 27deg/s ITR and 21deg/s STR.
F-16 has an ITR of 27 deg/s and a STR of 21.5-20deg/s
Mirage 2000 has a ITR of 29deg/s and a STR of 19deg/s
F-15 has an ITR of 21deg/s and 16 deg/s STR.

The J-10 is basicly a guess since is more or less in the size and weight of the F-16 and configuration of the Gripen i would say 30-31 deg/s ITR and 21deg/s STR at the best.
The Su-30MKI can not be better without TVC than the original Su-27 due to same TRW and the drag induced by its canards
The Su-35BM has new engines.
The MiG-35 has new engines.

The Rafale is not much better than the regular MiG-29A so i guess the Su-35BM must be comparable and the MiG-35 too in performance to both Rafale and Eurofighter

Those figures are not accurate. If you go to the f16 forum, you will find rebuttals by pilots.

vina · Post by **vina** » 29 Dec 2014 11:17

Victor wrote:(I personally don't think this is a good idea because I believe the LCA1 is irredeemable).

Ah.. Now that the kwechuns have been answered by Uknal Googal and we have "facts" , can we stick with them and not your "feelings" . Let us leave your "thinking" and "Feeling" aside, but lets have your "inference" based on reasoning of known physics.

Re. my "feelings" about what would make a good fighter, I really don't think I could make you understand because some things are just too difficult to explain, like describing what pizza tastes like. However, there is loads of intellectually stimulating info out there on the internet about dog-tooth leading edges etc if that's what you're looking for.

I am asking you not for "feelings" , but a recipe on how to make a pizza . So, why don't you google up your "internet" sources and let us know what a "dog tooth" leading edge does and how it "boosts" performance (like Tendulkar slurping up Boost) . If that is based on scientific inference, we can have a discussion, otherwise, we will send this the way of "feelings" to some random stuff that is best ignored.

It would be extremely stupid of us to ignore the views of senior IAF folks, including one of the LCA's top test pilots, over unproven engineers who have never flown a plane. .

Ah. The best guys to design a race car are not aero dynamicsts and chassis and handling and power train engineers, but actually Jensen Button and Lewis Hamilton or Michael Schumaccher ! Have those aero dynamists and chassis engineers ever driven a formula 1 car ? Have they won any F-1 trophies ? Schumaccher has won dozens!

Hint : -- The teams have a dedicated F1 driver who gives feedback on performance and on experimental results and how they play out when implemented, and are part of the development cycle, and are not parachuted into the driver's seat just before the result and start whining. Each team has a carefully crafted strategy on where the car's weak points are, where they want to excel in the envelope, where they will focus their efforts on, what works for them etc.

member_28932 · Post by **member_28932** » 29 Dec 2014 11:30

Cain Marko wrote: Actually I have a big doubt about weight decreasing on the block 2, sounds like a fantasy. Can't think of a single fighter design in recent times where weight has reduced in the newer version - gripen, viper, fulcrum, hornet, flanker. And many of these had metal components that were replaced by composites allowing for reduction. The tejas otoh, already uses composites in a big way. Btw, all of the aforementioned birds had weight increases upon upgrade, and that is despite far more experience in such exercises. It will be a miracle if they.maintain same weight for mk1 and mk2, let alone reduction. The best candidate for weight reduction in second iteration was probably the mirage 2000 since its engine was quite heavy resulting in poor twr, a 414 would certainly have helped if the design allowed it.

Am not too sure about range / endurance being reduced based on increased power; the SFC for the 414 is better than the 404, also, it will carry more fuel, but you never know - more fuel.capacity might mean a weight and range penalty . Tech gurus can probably enlighten here

But no, the mk2 seems another candidate for overpromise and underdeliver, esp. in terms of weight reduction and ridiculously optimistic timelines.

So far as weight reduction is concern, Tejas carries about 300 KG dead weight for weight balancing in Plane. It will not be there in MK2. There are many other areas in which weight reduction is possible such as Landing gear, Radar (Since mechanical steering shall not be there), More composite components and merging of LRUS in one etc. In fact, Tejas Mk1 in itself is a very conservative and over engineered design. The challenges we face is to correct the design and ironing out the design and aerodynamic issues which Hinders the performance. They are air intake and ill designed wings, Structural problems etc and probably installation of lavcon such as navy or canard may help.

More fuel doesn't mean weight penalty but otherwise. Imagine a situation where the additional fuel is required for a mission. In MK 1 you will tie fuel tank increasing the weight of tank and drag which will not be there in MK2 since it will carry about 40% higher fuel i.e 1000 KG.

MK2 shall not be a over promise and under delivery because it does not over promise at all. It promise only to the extent which is possible with higher power engine. Infact, if they focus on aerodynamic issue such as nose cone redesign, longer fuselage (Already done), Air intake and wing redesign, Aircraft can perform much better than what they have promised.

Look at the T/W ratio and how it is going to increase in MK2. Say T/W of Tejas is X (1.07 as per wiki) . They plan 500 K G Weight reduction. It means 8% increase in T/W ratio now add to that 20% higher thrust engine. It comes to 30% higher T/W ratio. If it is 1.07 for MK1 it will be 1.40 fo MK2 which is awesome. If they do not hide the problem and focus on resolving them, than Mk2 can be a much potent plane than what it promises.

member_28932 · Post by **member_28932** » 29 Dec 2014 12:02

Krishnakg wrote:Delay in LCA FOC, is due to time taken for Cobham, in developing both IFR probe and the Quartz nose Radome, low rate of production & delivery and subsequent test flights to be done.
Interesting reads below.

http://www.cobham.com/media/917782/cob_ ... ies_fa.pdf

http://www.cobham.com/media/136971/SYST ... V10611.pdf

http://www.cobham.com/about-cobham/miss ... robes.aspx

Development of Tejas is an example of poor project management. All in charge need to ask whether they knew the Nose cone issue just before they ordered it or a long time ago? If they knew that a long time ago than why did they not ordered it in time. An ordering of Nose come and air furling probe just 6 months ago would have pushed FOC 6 months ahead since the both activity lies on critical path. (For those who have studied Project management). These all are simply eye wash. It is very much understandable that do develop some thing may take some time since it involves R & D challenges. However in-spite of knowing the problem, if you can not act in time and do a simple thing like identifying and ordering a party, yo are not a good project manager though you may be a very good technologist, engineer or designer. What we need is some good project managers to head the project.

rohitvats · Post by **rohitvats** » 29 Dec 2014 12:52

vina wrote: Madheswaran I don't know.Khokhar was a "consultant" with Saab /Gripen, who were promoting their single engine fighter and trying to kill the LCA (sure, the LCA is their closest competitor and long term threat, not just locally but globally and india has deeper pockets to support the program longer term than Sweden, hence all out efforts to kill it). I wouldn't pay too much heed to Khokhar's whining.

Vina,

The same Air Commodore Khokhar had said this in 2013 about LCA Mk-1:

Says Air Commodore (Retd) Parvez Khokhar, who was for years the chief test pilot of the Tejas programme: "The Tejas Mark I is far superior to the MiG-21 fleet that the IAF would have to operate to the end of this decade. In key respects, it is a better fighter than even the Mirage 2000. The Tejas Mark I should enter the IAF's combat fleet in larger numbers and the Tejas Mark II scaled down. This would allow the air force to retire the MiG-21 fleet sooner."

Nowhere has the late Air Commodore criticized LCA Mk-1 as a platform. His main issue was with respect to project management by ADA/DRDO.

So, let us go easy on accusing people of something basis on insinuation.

abhik · Post by **abhik** » 29 Dec 2014 13:11

Pratyush wrote:Why is the canard being discussed at this time. The ADA made the decision to go for the shape of the LCA in the early 90s. The IAF was OK with it.

It has flown over 2000 test flights and the IAF was OK with them. All of a sudden we are seeing a discussion over canards. Why??

Is it to build a consensus for the IAF to dump the LCA, In favour of the Grippen?

In favour of the Rafale.

vina · Post by **vina** » 29 Dec 2014 13:28

rohitvats wrote:
The same Air Commodore Khokhar had said this in 2013 about LCA Mk-1:
Says Air Commodore (Retd) Parvez Khokhar, who was for years the chief test pilot of the Tejas programme: "The Tejas Mark I is far superior to the MiG-21 fleet that the IAF would have to operate to the end of this decade. In key respects, it is a better fighter than even the Mirage 2000. The Tejas Mark I should enter the IAF's combat fleet in larger numbers and the Tejas Mark II scaled down. This would allow the air force to retire the MiG-21 fleet sooner."

Nowhere has the late Air Commodore criticized LCA Mk-1 as a platform. His main issue was with respect to project management by ADA/DRDO.

So, let us go easy on accusing people of something basis on insinuation.

Ah. But Victor Babu says Khokhar and Madheswaran want canards fitted on the LCA , is Victor babu floating a canard ? Is he just "feeling" ?

What you say might well be true. But you see , the problem is this. The Navy is going to end up with a far more capable plane with better field performance than the Airforce MK1 version! You will have to go back to the Mitsubishi A6M Zero to find a case where a carrier based fighter does far better than it's land based analogue! There would be serious blushes in the IAF and egg on their faces if that were to happen and hence the scramble to get onboard the MKII , which is all fine.

member_20317 · Post by **member_20317** » 29 Dec 2014 14:31

IAF will get the egg on their face while the omelette would be eaten by IN.

IN is one up on IAF many times. First they tagged along without needlessly pushing the scientific establishment with the clarity of when exactly they would want their specs achieved. Then despite the fact that NP-1 faced serious difficulties they allowed enough time to redo the problematic areas of NP-1 and asked for a second NP, with all the corrections implemented, so that the lesser number of PVs that they get, still get to be as nearer to production standards as humanely possible. IN has utilized the second mover advantage to the hilt, coming in fully prepared without any kind of doubts. They even indicated their interest in having 4 pieces of the F404 powered fighter version. Probably to be used for training too along with the 4 trainers that they have asked for.

This is how people should approach their projects. Put money where the mouth is, push for perfection of the delivery while allowing time (esp. if its a first time venture) to the designers about how to reach that production standard. And all this done while they themselves do not feel on the edge for having an AC ready without any aircrafts. They sounded out everybody in the world for their requirements, then settled for compromises that they had the budget for. At this rate I would not be surprised if NLCA Mk-2 ends up superior to IAF LCA Mk-2. Mind you the NLCA cone would be different and I guess they too would like to have a quartz cone. But they are probably again waiting to see how the IAF gets delivered first, to maximize their smaller resources and the second mover advantage. Already they have changed the nose cone+landing gear (planned) and environment control+fuel systems (unplanned), compared to the IAF Mk-1, tested on the SBTF, hit the highest speed in Goa and all that in two seater trainer types and all this with just one NP-1. Want to wager, the NP fuel system changes already makes things easier for the refueling probe and we will never get to hear any refueling probe difficulties with NLCA Mk-1.

All the drama associated with revised specs, revised final ver 1.zz specs, really-really final ver 1.nnn specs, was left for the IAF to deal with. IN is simply going for the basic version of what they want.

To admit the truth, I will not be surprised if IN actually does induct the JSF (subject to their budget and vision) and makes a success of it despite the fat ladies inherent shortcomings. IN will face the least bit of trouble because of stubbiness of the thing while being able to leverage the best, the sensors of the thing.

IAF should first clear up its own mind as to what they want to achieve. With what they have stated uptill now, Mk-1 is the kind it looks. Now is the time for them to spell out how they want to use the craft.

............

HAL to IAF - Mein tumhare bacche ki maa banne wali hun.
IAF (Prem Chopra) - Arri hut, jane kiska paap mere sar par madh rahi hai. Dekho Dada ji (Prithviraj Kapoor==MoD), jaane kahan-kahan se log chale aate hain.
Prithviraj Kapoor - Bites his lower lip, closes his eyes and cusses under his breath. But does not say anything.
HAL to ADA - Pita ji, mein kya karun. Ab mere bache ka kya hoga? Is nanhi jaan ne kiska kya bigada tha?
ADA - Beti mein kya bolun, Ramu Kaka (BRF), theek kahte they. Prem ki nigahen kahin aur hain aur nishana kahin aur hain.
ADA to IN - Suraj beta, badi bahen ki to kismet hi phooti hui hai, choti ka khayal jarur rakhna.
Suraj (Duttak putr of Prithviraj Kapoor) - Dada ji mujh se yeh sab dekha nahin jata. Mein choti bahen ke saath shaadi karke, kahin aur rahne jaa raha hun.
Prithviraj Kapoor - Bites his lower lip again, closes his eyes again and blesses under his breath.
Jeevan (behind the curtains) - Smiling at the success of his game-plan and thinking - Ab to mera beta Prem, hi is ghar ki Jayedad ka malik banega.

rohitvats · Post by **rohitvats** » 29 Dec 2014 14:41

vina wrote:<SNIP> Ah. But Victor Babu says Khokhar and Madheswaran want canards fitted on the LCA , is Victor babu floating a canard ? Is he just "feeling" ?

Ah! Yes, he's been 'feeling' a lot, lately.

What you say might well be true. But you see , the problem is this. The Navy is going to end up with a far more capable plane with better field performance than the Airforce MK1 version! You will have to go back to the Mitsubishi A6M Zero to find a case where a carrier based fighter does far better than it's land based analogue! There would be serious blushes in the IAF and egg on their faces if that were to happen and hence the scramble to get onboard the MKII , which is all fine.

You might well be correct.

But as Late Air Commodore mentions in his article, IN's main concern with power plant was take-off requirement from carrier deck. But all that is past. LCA Mk-2 has all the features of a world beater.

rohitvats · Post by **rohitvats** » 29 Dec 2014 14:45

Moderator Note:

1) Gentlemen, the recent discussion on LCA is meant to understand the parameters on which LCA Mk-1 requires further work and which are supposed to addressed in Mk-2. Plus, to understand additional features of LCA Mk-2.

2) Further, the short-fall in LCA Mk-1 when it comes to Air Staff Requirement (ASR) is relative – One is with respect to ASR itself and other is relative to aircraft it is supposed to replace in IAF service. This is another point which I hope will be answered in exchange of posts.

3) The objective is also to highlight short-comings with respect to Project Management on part of stakeholders - IAF, DRDO, ADA and MOD.

I'm hoping that more informed posters will provide the technical insight into the subject.

What the discussion is NOT supposed to be is a whine-fest and finger pointing. Everyone, including yours truly, has their biases, but being objective will be of great help.

Whines and rants will be summarily deleted. And if you persist, there is a warning coming your way.

rohitvats · Post by **rohitvats** » 29 Dec 2014 15:10

Post 1:

http://ibnlive.in.com/blogs/sauravjha/2 ... india.html

Here are some excerpts from recent Saurav Jha article on LCA Mk-1 and LCA Mk-2 where he and Dr. Tamilmani highlight the achievements of LCA Mk-1, short-falls and how the same are to be addressed in LCA Mk-2.

Mk-1 Achieved

1) As far as I am concerned the program really materialized in the mid-1990s and the air staff requirement (ASR) of 1995 that was agreed to by ADA at the time broadly set the ultimate performance objectives for the project. With reference to the 1995 ASR, the Mk-I has already exceeded the angle of attack (AoA) requirement of 24 degrees, by some two degrees (i.e it has achieved 26 degrees), which is highly commendable and comparable to the best that the Mirage 2000 could do. This could even be increased to 28 degrees in the future.

2) The Mk-I has also demonstrated +7G and has flown at a maximum Mach number of 1.6 at altitude.

Mk-2 Objectives

- Now while the Tejas Mk-I does boast many frontline technologies, its aerodynamic performance unfortunately cannot meet the 1995 ASR in its entirety.

- Truth be told the ASR agreed upon by ADA at the time would in any event have been difficult for the Mk-I to achieve in its current state with or without canards.

- This is perhaps a reason why only forty units of the Tejas Mk-I fighter version have been ordered till date by the IAF. An order for 16 units of the type trainer developed for the Mk-I are also expected from the IAF, with the definitive configuration for it taking to the air last month in the form of PV-6.

- To address the IAF's 1995 ASR fully, work is now underway on the Tejas Mk-II which will sport a new and more powerful engine in the form of General Electric's (GE's) 98 kilo newton generating F414-GE-INS6 , 99 units of which have already been ordered. The F414-GE-INS6 replaces the current MK-I engine which is the F404-GE-IN20.

- Contrary to earlier speculation, Dr Tamilmani says that the Tejas Mk-II does not require an intake re-design since the MK-I intake was in any case intended to be used with the Kaveri engine which has a greater mass flow than the current F404-GE-IN20 . Studies have shown that the existing intake can easily handle the additional mass flow from the F414-GE-INS6.

- Together with the IAF, ADA has also introduced what Dr Tamilmani terms a 'weight reduction approach' and as per him some 350 kgs have already been shaved off the Mk-II design with a reduction of 500 kgs being the ultimate goal vis a vis the baseline Mk-I design.

- The Mk-II design is also expected to achieve a 5 percent improvement in drag characteristics through 'production improvements' related to further streamlining (reduced contour variations etc) of the Mk-I airframe.

- All these changes are expected to increase the aerodynamic performance of the Tejas design sufficiently to be very close to meeting all ASR parameters according to Dr Tamilmani.

- The IAF is fully cognizant of this and is now fully integrated with the LCA program. 'The IAF has positioned 23 officers to support our program', says Dr Tamilmani. 'They also have 30 airmen on the tarmac to prepare the aircraft', he adds.

- The Mk-II design will specifically address the sustained turn rate (STR), climb rate and transonic acceleration shortfalls of the Mk-I.

- The ASR requires a STR of 18 degrees (same as the F-16's) and Mk-II will close in on that.

- The climb rate will also be more or less satisfactorily reached.

- Transonic acceleration is expected to be realized fully.

- Moreover the Mk-II airframe will certainly be able to reach and fly through Mach 1.8 in a dive.

rohitvats · Post by **rohitvats** » 29 Dec 2014 15:17

Post 2

I'm posting below excerpts from 2009 paper by someone at CEMILAC (Centre for Military Airworthiness and Certification). This paper clearly highlights that certain issues inherent with design choice were known much earlier. And in cases where possible, remedial measures had been worked out.

Source: http://drdo.gov.in/drdo/pub/dss/2009/main/2-CEMILAC.pdf

Please refer to the document for pictures mentioned in the excerpt below. The document also covers IJT-36.

Aircraft Performance Improvements-A Practical Approach - S.K. Jebakumar, Centre for Military Airworthiness and Certification

1) Reduction of Wave Drag

One of the major out-come of sea level trial of Tejas is that the drag of the aircraft is high such that the aircraft could not reach the supersonic Mach number at sea level. The components contributing for the maximum drag rise has been identified and improvement methods were worked out.

1.1) Nose cone extension using a Plug:

The major component of drag at higher speed is the wave drag. This can be minimized by following the Whitcomb’s Area rule for the aerodynamic configuration design. The cross sectional area variation of LCA along the length of fuselage is shown in Fig 12. Between station X = 5000mm & 6000mm there is a sudden increase in area. By smoothing this sudden rise, the wave drag can be minimized. A possible solution proposed is the extension of nose cone by introducing a Plug. The detailed analysis of this design and its implementation plan is being worked out.

1.2) Pylon reshaping:

Another area for improvement is identified as the pylon reshaping. The leading edge of all the pylons are blunt and it can be reshaped aerodynamically for the drag reduction. The in-board pylon before modification is shown in Fig. 13. and Fig. 14 shows the in-board pylon after the modification. The analysis shows that a drag reduction of 3.7 dm2 at M=1.2 is possible with this modification. Similar exercise for the mid-board and out-board pylons carried out and the drag reduction predicted as 0.6 dm2 and 1.54 dm2 respectively.

1.3) Trailing Edge Extension (TEC)

From the Fig. 12 it is seen that there is a sudden variation in cross sectional area at the rear end of the fuselage also. This can be minimized by the modification in the trailing edge using TEC. Fig. 15 and Fig. 16 shows the rear fuselage before and after modification. The drag reduction predicted is around 1 dm2

2) Sustained Turn Rate Improvement using Levcon

Leading Edge Controller (Levcon) is an secondary control surface located at the leading edge of the wing and the fuselage. The Levcon is initially planned in LCA Navy for the low landing speed capability and other cruise performance. An important requirement of a fighter aircraft is the Sustained Turn Rate (STR). The fighter variant of Tejas is not meeting the STR requirement of ASR. The STR is a strong function of the aerodynamic efficiency. From the wind tunnel results it was found that the Levcon produce higher L/D (Fig. 17). A detailed study to implement Levcon in fighter and identification of other design constraints is under progress.

3) Performance Improvements by Weight Reduction

3.1) Converting metal components into composite:

Weight reduction is an important activity in an aircraft program to improve the performance. Use of high performance composite material can considerably reduce the weight of the components and preserving the structural integrity. The airframe of Tejas has already undergone one cycle of weight reduction prior to Prototype Vehicle series, which resulted in a weight saving around 350 Kg. It is felt that some of the components like slat doors, casing & mounting of LRUs and rear fuselage bulkheads and pylons can be converted into composite. This will give further weight reduction.

3.2) Co-cured co-bonded wing:

LCA wing components have been manufactured separately and joined together using rivets, fastener and sealant. In the proposed co-cured cobonded wing, the bottom skin, ribs and spars are cured together. This has advantage from reduced part count as well as weight saving. The weight saving is mainly due to the elimination of sealants, fasteners and associated components. Further, the wing is expected to have improved stiffness, leak proof and better lightning protection.

4) Active/Passive fuel proportioner

The typical C.G travel (˜3%) due to the fuel consumption in Tejas is given in Fig. 18. When the aircraft in its mid weight (wing tank empty) condition, the aircraft C.G is most forward. The aircraft is more stable. The maneuvering capability is limited. Hence a passive fuel proportioner introduced in Tejas by varying the diameter of the fuel pipe. With this modification the maximum fuel travel is within ±0.5%. In future the better C.G management is planned by the Active Fuel Proportioner using the motorized valves.

A study has been carried out to find the advantage of the passive fuel control by moving the C.G aft from the earlier forward position. The C.G at 30.5% MAC and 33.5% MAC are considered for the analysis. Fig. 19 shows the amount of elevon required for trimming the aircraft. This shows the lesser down elevon required for the aft C.G configuration.

The (Lift/Drag) ratio for these two C.G configurations is shown in Fig. 20. It is very clear that moving C.G aft gives increase in L/D. This will improve the performance parameters considerably.

[I think it was mentioned on Tarmak's Blog in the beginning of this year that LCA Mk-1 does just fine with Passive Fuel Proportioning]

Karan M · Post by **Karan M** » 29 Dec 2014 16:28

I just let this discussion slide after some of the fudged up figures being posted non stop in the previous pages, to run down a program, truth and accuracy be darned but kudos to RV and vina for getting some data into the discussion.

For those looking for serious data, it might be worth looking at why the STR stuff is not really a big deal for the MK-1. That simply put has to do with the HMS + Python-V/R73E combo. These are off boresight missiles and add a HMS that allows one to cue the seeker via the Helmet LOS & it will be a rare LCA pilot indeed who engages in a turning fight! The main advantage & tactics of the delta planform, relate to its ITR. The Greek Mirage 2000s f.e. routinely tangle with the Turkish F-16s using this attribute.

Now the question comes - if both aircraft (say PAF F-16) and Indian LCA have HMS & HOBS missiles, what decides the winner? The answer there is situational awareness. In the Indo-Pak battleground, thats the key decider, both sides have radars/AEW but limited numbers of the latter. The pilot with the training edge and element of surprise (both critical to SA) will win.

So, if STR is not a key decider in todays scenario, why is the IAF pushing for it? A) Because they can, since it was part of the prior ASR as ambitious as that was and

STR may matter in that one scenario where a LCA is without missiles & its guns, guns alone. As rare as this scenario is (think of a Su-30 w/10-12 AAMS f.e.), the IAF still trains for it (including Su-30 pilots).

Even so - check this out; https://www.youtube.com/watch?v=nWG2PkwKiaQ

The only solution to knocking these down is to use a DIRCM. Only the PAK-FA and JSF are to have these per reports. Flares wont work as these are IIR seekers with image discrimination capability. In short, this STR business is just a bunch of hokum.

member_20317 · Post by **member_20317** » 29 Dec 2014 17:24

Can some maths trained person calculate the difference in the 'STR of the plane' and 'STR of the neck', as adjusted by the ITR of LCA, for only the time that is needed to fire 2 WVR missiles and scoot thereafter?

TIA.

Added later - to make things really exciting you can also try 2/3 burst of cannon before the scoot.

maitya · Post by **maitya** » 29 Dec 2014 17:50

^^^^ Absolutely true!!
As KaranM has rightly pointed out above, for WVR situations off-boresight missiles with HMS is sufficient to shrugg-off a few degrees of STR deficiency here and there.

Plus in a BVR situation the slight adavantage of good STR also had got diminished with the advent of AESA equipped platforms.
(Hint:imagine 2 enemy-platforms merging at very high degree of separation angle between them - maybe even on both sides of the LoS of the defending platform - a mech scannign radar will loose time, thus on engagement range, while electronic scanners wouldn't have any such issues - the good old detection vs tracking range discussion!!).

However whilst it's true that with the advent of off-boresight missiles HMS and AESA the STR has lost a lot of it's sheen, it's still important though, as nobody would want to be outflown (aka out-turned) in a turning flight - but then again when you have such high-degree of off-boresight capability (trending to 60deg+ regimes), a couple of deg/s of STR limitation hardly matters.

ITR though still retains it's edge, as the good-old method of breaking a missile or radar or missile-radar (Active-homing soln) lock, for both BVR adn WVR situations, is still the hard-manoeuvering aspects of a flight regime.

And yes, if people are looking for excuses, such small deficiencies would be played up and amplified, with clever masking of such details like mentioned above - which is what we are seeing today.

In 1990s, F-16'sque STR figures had some relevance - copy-pasting it into LCA spec, however debatable still had more relevance then, not so much anymore. Then why is this continuous ranting of it ...

And if only people tried to look at the planform of the LCA wings, and study it little throughly, it wouldn't be too difficult to understand how "virtual" canards (aka the functionality but without the attendent addn drag and weight penalty) are hidden quite cleverly in the compound-delta plaform - plus of course the "fixed" AoA of the wing (between fore and aft) achieved at it's blending with the main body etc etc etc.
Indranil and others have written extensively on these points multiple times, but every other day you see people latching on a random quotes from here and there, and start these sort of mindless bashing.

Ofcourse, since the gulami-pasand mindset (vinaji calls it "harrruumph") can't fathom that pathbreaking ideas are also possible by a bunch of "SDRE science-project performing folks", these stuff are par ofcourse ... the same mindset which characterises "3-legged cheetah" kind of quotes.

What a sad state!!

Vishnu · Post by **Vishnu** » 29 Dec 2014 18:26

INDIGENOUS ON-BOARD OXYGEN GENERATING SYSTEM (OBOGS) BASED INTEGRATED LIFE SUPPORT SYSTEM (ILSS) FOR TEJAS LIGHT COMBAT AIRCRAFT

ILSS-OBOGS an indigenous ‘on-board oxygen generating system’ (OBOGS) based ‘integrated life support system’ (ILSS) designed and developed to provide enhanced physiological protection to aircrew of high speed and high altitude fighter aircraft -Tejas with primary objective of meeting long endurance flights was today, the 29th December 2014, symbolically handed over by Dr.VC Padaki, Outstanding Scientist and Director, DEBEL (Defence Bio-medical and Electro-medical Laboratory) to Dr P S Subramaniam, DS, Program Director - Combat Aircrafts and Director Aeronautical Development Agency, in the presence of Dr K Tamil Mani, DS and DG Aeronautical Systems and Dr Manas K Mandal, DS & DG Life Sciences, directors of Bengaluru based laboratories and DRDO officials.

Congratulating the team Dr Avinash Chander, Scientific Advisor to Raksha Mantri, Secretary Deptt. of Def. R&D & DG DRDO lauded the achievement saying “a lifesaving system involving technological challenges, development of ILSS-OBOGS is a major achievement, expressing DRDO's commitment to deliver complex technologies for armed forces ”

“Deliverability comes only if there is multi-disciplinarity”, said Dr Mandal emphasizing the role of working together towards development of multi-disciplinary systems and stated, "Individuals do not make a team - the team makes an individual." Dr Tamil Mani, emphasizing the importance of synergy and lauded the dedicated work of the young team of scientists and said, “Technology breakthrough for OBOGS for future airborne platforms is now within our capability”. Speaking on the occasion, Dr P S Subramaniam appreciated the role played by different stake-holders in the development of ILSS-OBOGS.

Designed to get integrated within the confined space available in the in the aircraft, the OBOGS replaces the Liquid Oxygen based system (LOX) by utilizing bleed air from the aircraft engine by separating oxygen from other components by a process based on Pressure Swing Adsorption (PSA) technology. Designed to provide breathing gas to aircrew continuously, the use of OBOGS technology offers advantage of unlimited endurance in the sky (unlike LOX system wherein endurance is limited by the storage capacity). In addition it also provides improved safety, reduced logistics and significantly lowered operational costs. Developed by DEBEL, a DRDO lab focused on development of bio-medical and electro-medical soldier support systems, the advanced ILSS- OBOGS addresses the need for preventing in-flight Hypoxia (during high altitude flying and emergency escape) and ‘Gravity Induced Loss of Consciousness’ (G-LOC) during high G manoeuvres.

The technology consists of On-Board Oxygen Generation System (OBOGS) that provides oxygen for breathing, a breathing regulator that supplies the breathing gas to the aircrew at desired flow and pressure, an Anti-G-Valve (AGV) that inflates the anti-G suit to apply desired counter pressure and an Electronic Controller Unit (ECU) to coordinate various functions. A dedicated solid state oxygen sensor to sense oxygen concentration in the breathing gas is an integral part of the system. In addition, many other sub-systems that provide back-up / redundancy and also impart life support during emergency escape are integral part of the ILSS-OBOGS that will now undergo ground fitment trials on Tejas, followed by flight trials. India will join the elite club of five countries who have established and mastered the technology in the field of ILSS for military flying once the trials are successfully completed. The ILSS-OBOGS has the versatility to be customized to the needs of other Indian fighter aircrafts like MIG-29, Sukhoi-30 Mk1 and Mirage-2000.

Thakur_B · Post by **Thakur_B** » 29 Dec 2014 18:44

Question, will OBOGS be part of FOC build since it can be retrofitted to any plane in the fleet ?

rohitvats · Post by **rohitvats** » 29 Dec 2014 18:49

Karan M wrote:I just let this discussion slide after some of the fudged up figures being posted non stop in the previous pages, to run down a program, truth and accuracy be darned but kudos to RV and vina for getting some data into the discussion.

Actually, most of the credit goes to Indranil's and Vipul Dave.

<SNIP>

So, if STR is not a key decider in todays scenario, why is the IAF pushing for it? A) Because they can, since it was part of the prior ASR as ambitious as that was and STR may matter in that one scenario where a LCA is without missiles & its guns, guns alone. As rare as this scenario is (think of a Su-30 w/10-12 AAMS f.e.), the IAF still trains for it (including Su-30 pilots).

Even so - check this out; https://www.youtube.com/watch?v=nWG2PkwKiaQ

The only solution to knocking these down is to use a DIRCM. Only the PAK-FA and JSF are to have these per reports. Flares wont work as these are IIR seekers with image discrimination capability. In short, this STR business is just a bunch of hokum.

With respect to bold part, that is not the line of argument I'd want to take. As it is, it is a very extreme stand. Something like F-4 and AAM and no requirement for guns. We know where it all went.

The fact that IAF - and all the major air forces - train and prepare for 'Dog-Fight' scenarios is testimony to importance of parameter like STR. If memory serves me right, IAF teaches 1-vs-2 to Mig-29 pilots. The one a/c which actually holds forte in STR as well as was first to have HMCS advantage.

However, as you've pointed out with the Python example, there are solution(s) which help to compensate on this aspect. And IIRC, Python/Derby is being tried for LCA Mk-1.

rohitvats · Post by **rohitvats** » 29 Dec 2014 18:52

maitya wrote:<SNIP>Ofcourse, since the gulami-pasand mindset (vinaji calls it "harrruumph") can't fathom that pathbreaking ideas are also possible by a bunch of "SDRE science-project performing folks", these stuff are par ofcourse ... the same mindset which characterises "3-legged cheetah" kind of quotes.

What a sad state!!

MODERATOR NOTE: Which part of 'don't whine on this thread' did you not understand?

Karan M · Post by **Karan M** » 29 Dec 2014 19:22

Rohitvats wrote: Indranil and Vipul Dave.

Disagree about Dave posts have enough holes in them to sink a ship -the weight stuff in particular. Indranils cite well referenced data.

With respect to bold part, that is not the line of argument I'd want to take. As it is, it is a very extreme stand. Something like F-4 and AAM and no requirement for guns. We know where it all went.

The fact that IAF - and all the major air forces - train and prepare for 'Dog-Fight' scenarios is testimony to importance of parameter like STR. If memory serves me right, IAF teaches 1-vs-2 to Mig-29 pilots. The one a/c which actually holds forte in STR as well as was first to have HMCS advantage.

However, as you've pointed out with the Python example, there are solution(s) which help to compensate on this aspect. And IIRC, Python/Derby is being tried for LCA Mk-1.

Its not an extreme stand. That you call it so, just shows that you are prejudging the result.

Tell me, if its an extreme stand, why is the Mirage 2000 in service? Can the Mirage 2000 beat the F-16 in a turning fight? Why is the IAF continuing to invest in the Mirages A2A capability?

If not, then what does the Mirage 2000 pilot train for? Would it be automatically game over if a Mirage goes up against the F-16?

What happens when the F16 with a JMHS + Aim-9x goes up against the Mirage 2000 with a HMS + Python5/Mica? Would former win always or majority? Is it a given? Or does the Mirage pilot use his ITR to his advantage & perform a slashing attack & disengage?

Second is equally a non sequitur. The IAF trains for a 1 vs 1 scenario. Thats the guns scenario. But in the past it didnt prioritize BVR for its Mirage 2000 fleet as it realized and addressed post the first Garuda. Point is IAF training schedule is not necessarily the be-all to end a debate. The French f.e. prioritized BVR over WVR-guns.

Dog Fight is a generic term which encompasses the whole WVR issue. But question is how relevant does the guns scenario become in an era of IIR seeker equipped missile platforms w/high reliability? Please look into these missiles. They are lethal and without DIRCM, there is no stopping them, unless the opponent chooses to disengage at range. Unlike RF missiles, they cannot be jammed at present.

The fact of the matter is if the Mirage 2000, MiG-21, 27, Jaguar today get in a turning fight with the F-16, J-10, Su-27 - depending on the altitude, situation etc - they are toast, period. So it all boils down to tactics. They wont get into a turning fight.

In terms of STR, which aircraft was best in MMRCA? Was it the Gripen, Rafale or EF ? The reality is all these platforms (especially the top 3) differ in terms of STR, at different speeds, loading. Thing is though with a HMS + HOBS missile combination, the marginal differences don't really matter. Chances are that even earlier gen lightly loaded platforms can match the above 3 at specific attributes at specific parts of the flight envelope. The trick then, is to not fight to the opponents strengths.

The F/A-18 E/F f.e. has phenomenal nose pointing ability at lower speeds. The EF guys would lose constantly if they attempted to turn with the Hog. So they won't.

In a way, this comes back to the basics - no single platform is ever going to meet all the requirements. By meeting the IAF's ASR of xx deg STR or whatever, the LCA won't suddenly become better off against an aircraft with more STR, latter will have the advantage in a turning fight.

The P-47 provides a good example of the importance of tactics when a platform is used per its strengths. At typical alts where it encountered its opponents, its STR was worse off (improved at high alt).
http://en.wikipedia.org/wiki/Republic_P ... hunderbolt

Hence the importance of the LCA w/Python-V. Its a lethal combo and a well trained pilot would play to his strengths, which are first pass, acquisition, slash attacks.

The huge acquisition envelope of the Python-V/HMS combo effectively proofs the aircraft against these differences in ITR and STR versus future platforms which simply cant be forecast accurately.

Otherwise, we will have to make a fighter with ramjets (for speed/accn), TVC for high ITR, next to no weight (for STR) etc etc. Its a never ending struggle.

Which is why more than the bare platform itself, what we are adding to it becomes more and more important. That the radar stuff is being fixed is heartening. But almost important is the requirement for a high speed datalink to the IAFs IACCS - there has been little news on that.

A LCA able to "feed" off of Su-30 class radar platforms becomes far more lethal than it would otherwise be as a light fighter. It becomes a shooter in a node.

Sanjay · Post by **Sanjay** » 29 Dec 2014 19:36

Question: what are the STR and ITR of the Tejas and how do these compare to the ASR ?

Also, how do they compare to JF-17 and J-10 ?

If things are within an acceptable margin with the latter two, then there really should be no issue with more Mk.1 orders until Mk.2 comes on line.

Karan M · Post by **Karan M** » 29 Dec 2014 19:45

maitya wrote:^^^^ Absolutely true!!
As KaranM has rightly pointed out above, for WVR situations off-boresight missiles with HMS is sufficient to shrugg-off a few degrees of STR deficiency here and there.

Plus in a BVR situation the slight adavantage of good STR also had got diminished with the advent of AESA equipped platforms.
(Hint:imagine 2 enemy-platforms merging at very high degree of separation angle between them - maybe even on both sides of the LoS of the defending platform - a mech scannign radar will loose time, thus on engagement range, while electronic scanners wouldn't have any such issues - the good old detection vs tracking range discussion!!).

However whilst it's true that with the advent of off-boresight missiles HMS and AESA the STR has lost a lot of it's sheen, it's still important though, as nobody would want to be outflown (aka out-turned) in a turning flight - but then again when you have such high-degree of off-boresight capability (trending to 60deg+ regimes), a couple of deg/s of STR limitation hardly matters.

ITR though still retains it's edge, as the good-old method of breaking a missile or radar or missile-radar (Active-homing soln) lock, for both BVR adn WVR situations, is still the hard-manoeuvering aspects of a flight regime.

And yes, if people are looking for excuses, such small deficiencies would be played up and amplified, with clever masking of such details like mentioned above - which is what we are seeing today.

In 1990s, F-16'sque STR figures had some relevance - copy-pasting it into LCA spec, however debatable still had more relevance then, not so much anymore. Then why is this continuous ranting of it ...

Exactly. I suspect if the people who are cribbing about the STR stuff figure out which had the best STR per public details in the MMRCA fly off, they will suddenly start cribbing about the Rafale as well!!

To add to your points - in fact, a datalinked fighter may not even switch on its radar, it will do a completely silent intercept with long range WVR missiles which now cross 10's of km!! Imagine spotting your target at ~20 odd km, well within your WVR missile envelope, locking silently & launching a Python & scooting (as the video depicts). The Israelis BTW thanks to their cost consciousness are also famous for high reliability missile rounds.

Kidhar ka STR, kidhar ka fancy degree difference??

And if only people tried to look at the planform of the LCA wings, and study it little throughly, it wouldn't be too difficult to understand how "virtual" canards (aka the functionality but without the attendent addn drag and weight penalty) are hidden quite cleverly in the compound-delta plaform - plus of course the "fixed" AoA of the wing (between fore and aft) achieved at it's blending with the main body etc etc etc.
Indranil and others have written extensively on these points multiple times, but every other day you see people latching on a random quotes from here and there, and start these sort of mindless bashing.

Ditto.

The whole LCA as a platform thing is completely missed by the junta. Suddenly they are experts versus the ADA & gosh, the fact that ADA has to rely on VR prototyping and wind tunnels is beneath the sort of conclusions we hear thrown about "200 kg weight reduction", "canards on wings".

What is being ignored - and i hinted at that in my post above - is what are the capabilities that are coming with SPs? For instance, this is what the IN has with a missile-radar + datalink combo similar to that on the LCA today.
http://www.livefistdefence.com/2009/07/ ... -test.html

Thakur_B · Post by **Thakur_B** » 29 Dec 2014 19:59

Karan M wrote: What is being ignored - and i hinted at that in my post above - is what are the capabilities that are coming with SPs? For instance, this is what the IN has with a missile-radar + datalink combo similar to that on the LCA today.
http://www.livefistdefence.com/2009/07/ ... -test.html

I believe it should be there. The same capability was displayed by MiG-29s during the early phases of IACCS implementation as a demo of capabilities.

Karan M · Post by **Karan M** » 29 Dec 2014 20:13

Can you confirm it? Thats great if confirmed. IIRC it was just an intercept. If the MiG-29s demo'ed it, that means the Rafael/CAIR/IAF datalink has gone live.

brar_w · Post by **brar_w** » 29 Dec 2014 20:20

To further add to what Sanjay, Karan and others have said about performance being relevant to what is required "today" and in to the future, as opposed to what was important in the 70's when most of the 4th gen legacy's were designed:

Beyond Boyd: A Quick Survey of the Evolution AFTER the E-M Revolution

and

http://www.dtic.mil/dtic/tr/fulltext/u2/a292573.pdf

If someone has full access to AIAA, they can read and hopefully post the links to the articles referenced in the first post. I have a friend who does have access from time to time and have contacted him to see if he can provide me with full pdf's.

vina · Post by **vina** » 29 Dec 2014 20:20

Yes,yes.. Coming back to topic , on the LCA "improvements" , yes, the Cemilac article was discussed much earlier, posted here etc. Some of those are already implemented.

Specifically with STR, the Levcons if implemented and if the predictions are close to what the wind tunnel /simulation stuff show, yes , will improve. In fact the advantage of a canard layout over a pure delta is that the canards give one additional control surface and you can use the small canard over trimming the wing itself , reducing trim drag and also induced drag. With Levcons, you close that gap. So even the put the canards on LCA dudes should be happy.

But speaking of what other technical improvements can happen, Ramana (our adminullah) already touched on that long ago. The LCA's structure as it is constructed is basically "black metal" in his words, ie carbon fiber skins riveted /screwed in place of aluminium plates as in traditional stressed monocoque construction. This is not the best way to go with carbon fiber. Ideally it should be a large single piece carbon fibre structural stuff. The wing is going to be co-cured co bonded per the article, the fuselage barrel too should be carbon fibre made , like the Boeing 787's fuselage or more relevantly for the LCA like the Hawker Beechcraft Premier I and II models with the carbon fiber honeycomb fuselage.

That is the way forward structurally and I do hope the ADA pushes towards that in the AMCA , if not in the LCA MKII for which it might not fit the timelines.

member_20317 · Post by **member_20317** » 29 Dec 2014 20:35

brar_w wrote:If someone has full access to AIAA, they can read and hopefully post the links to the articles referenced in the first post. I have a friend who does have access from time to time and have ~~contracted~~ him to see if he can provide me with full pdf's.

You mean 'contacted' right!?

Karan M · Post by **Karan M** » 29 Dec 2014 20:38

brar_w wrote:To further add to what Sanjay, Karan and others have said about performance being relevant to what is required "today" and in to the future, as opposed to what was important i the 70's when most of the 4th gen legacy's were designed:

Beyond Boyd: A Quick Survey of the Evolution AFTER the E-M Revolution

and

http://www.dtic.mil/dtic/tr/fulltext/u2/a292573.pdf

If someone has full access to AIAA, they can read and hopefully post the links to the articles referenced in the first post. I have a friend who does have access from time to time and have contracted him to see if he can provide me with full pdf's.

Excellent link!

In 1992, Cox and Downing featured Befecadu (BF) Tamrat’s 1988 metric of Combat Cycle Time in the proposed system of “functional agility metrics” they evaluated for use in measuring aircraft maneuverability: Combat Cycle Time, Dynamic Speed Turn Plots, and Aircraft Energy State. The impetus for searching for these new metrics?

During the Korean War and the Vietnam conflict, jet fighter aircraft emerged with greatly expanded altitude and Mach ranges. This era also saw the advent of the short range heat seeking missile. These missiles required maneuvering to achieve a rear-aspect firing position. The measures of merit, altered to match the increase in aircraft capability, were advanced point performances (thrust-to-weight ratio, maximum Mach number, sustained turn rate, etc.) and the energy-maneuverability performance method. In recent years, the level of fighter aircraft and weapon system technological sophistication has reached new heights; the most critical advance being the development of the all-aspect infrared missile. This missile negates the requirement of maneuvering to achieve a rear-aspect firing position and concurrently has caused the traditional point performance measures of merit to become deficient for determining the combat effectiveness of a fighter aircraft. To remedy this deficiency, new measures of merit are being investigated which examine aircraft maneuver and control capabilities not previously quantified.

We could dive deep into discussion on each metric proposed in this paper, but I would like to focus on Tamrat’s Combat Cycle Time, as it is what differs most from the pioneering but simpler Boyd-Era POV of E-M, and the authors ably describe how Tamrat builds on same:

Traditionally, the need to achieve a rear-aspect position for a gun or missile firing opportunity led fighters to engage in battles lasting several minutes. These engagements were characterized by sustained maneuvering. This type of combat made the turn rate verses Mach number diagram (doghouse plot) useful for determining one fighter's advantage over another. When maneuvering for a rear-aspect firing solution, the interior of the doghouse plot is important. This interior region is represented by the sustained turn rate line and is typically dictated by available thrust and the lift to drag ratio of the aircraft. The compressed time scales of today's air combat arena have made sustained maneuvering less critical. The desire for a first shot opportunity leads to fights dominated by transient load factor/lift limited maneuvers. The emphasis then is shifting toward more dynamic maneuvering or the exterior of the doghouse plot. .

Incidentally, the latter part is what EF/Rafale excel at. Rapid energy transitions.

Thakur_B · Post by **Thakur_B** » 29 Dec 2014 20:39

Karan M wrote:Can you confirm it? Thats great if confirmed. IIRC it was just an intercept. If the MiG-29s demo'ed it, that means the Rafael/CAIR/IAF datalink has gone live.

http://pib.nic.in/newsite/erelease.aspx?relid=65739

Ministry of Defence
14-September, 2010 16:35 IST
Antony Dedicates AFNET to the Nation

Defence Minister Shri AK Antony today inaugurated the IAF’s gigabyte digital information grid – the AFNET (Air Force Network), dedicating it to the people of the nation, for their direct or indirect participation in the communication revolution.

The launch, a significant milestone in the IAF’s quest towards achieving a capability for Network Centric (NCW) operations was held in the presence of Union Minister of Communication & IT, Shri A Raja, Raksha Rajya Mantri, Shri MM Pallam Raju, Minister of State for Communication, Shri Sachin Pilot, Marshal of the Air Force Arjan Singh, Chief of the Air Staff, Chief of the Army Staff and other officials from the three services and members of the Industry.

Outlining the two-fold aim of ‘Network for Spectrum’ approach of the government – to facilitate the growth of national tele-density on the one hand, and ensuring modernization of defence communications with the state-of-the-art communication infrastructure, the network will have the potential to support net-centric operations, Shri Antony said.

A practice interception of simulated enemy targets by a pair of Mig-29 fighter aircraft airborne from an advanced airbase in the Punjab sector neutralizing intruding targets in the western sector was played out live on the giant screens at the Air Force auditorium offering a glimpse of the harnessed AFNET potential.

Further, various other functionalities contributing towards NCW were also showcased. These comprised of facilitating video from Unmanned Aerial Vehicle (UAV), pictures from an AWACS aircraft to the decision-makers on ground sitting hundreds of kilometers away, providing intelligence inputs from far-flung areas at central locations seamlessly. This was possible mainly with the robust networking platform provided by AFNET.

Raveen · Post by **Raveen** » 29 Dec 2014 20:59

Cain Marko wrote:Victor,

The problem here is that you are comparing incorrect versions. The most reasonable comparison is between the Gripen C and the LCA; you will notice that the C is actually heavier by 300kg (6800 vs 6500kg for the LCA). End result is that the range values are similar, but the Gripen does a better job on payload and probably tturn rates.

Hard to figure out why exactly the LCA suffers in terms of Payload, acceleration and turn rates when it has a better TWR than both the Gripen and the Mirage 2000.

Gurus, any thoughts?

Still, be as it may , it does.outperform the fishbed/flogger/jaguar in all these criteria.

TWR does account for drag. TWR is a hp/ton power/wt ratio. Drag is an aero number, a billboard with a jet engine behind it would have amazing TWR ratio but the drag would ensure it doesn't fly.

brar_w · Post by **brar_w** » 29 Dec 2014 21:20

ravi_g wrote:
brar_w wrote:If someone has full access to AIAA, they can read and hopefully post the links to the articles referenced in the first post. I have a friend who does have access from time to time and have ~~contracted~~ him to see if he can provide me with full pdf's.
You mean 'contacted' right!?

Yeah, sorry about that. Corrected it in the original.

Incidentally, the latter part is what EF/Rafale excel at. Rapid energy transitions.

Most modern designs have been emphasizing that aspect among others. Furthermore, you have to add detection advantages, stealth and sensor fusion to the mix when you figure out advanced versions of the LCA and eventually the AMCA. With stealth you do not need to have the "jousting" requirements beyond visual range that you once had. Even in a stealth on stealth engagement your detection ranges for both fighters are much smaller and as such you do not have to worry about doing a lot of hard maneuvering at say 40 miles out in order to get into a favorable kinematic position for a BVR shot (based on your platform-weapon-sensor setup). For example, in BVR F-22 v F15, the Raptors go high and up the speed upon detecting and really do not need to do much hard maneuvering as they have the freedom to position/reposition as they are not inside the detection range. This saves a lot of fuel, and allows them to get into the best "tactical" position for the Apg77/AIm-120C combination. They also have the option to choose to use the AMRAAM much closer then and trade off range for a higher PK. Stealth allows for this. Another dimension is setups like EODAS of the F-35, a technology that is bound to proliferate eventually into the global fighters currently in the workup. This allows you to mix up your MRAAM shots and spread them out in the RF and IR domains thanks to the fact that modern IR missiles (some) are also being delivered with data links. You can choose to launch say an AMRAAM or an IR missile at 20 nautical miles for example complicating the response. In a way, sensor fusion, HMD/EODAS integration also frees you up from the hard POINTING required to fully utilize an opportunity if it presents itself. You may just want to retain energy and use your DAS to feed your IR setup. This would obviously give you more "life" if the fight gets uglier compared to a peer that lacks some or all of this. It allows you to plan a few stages ahead in the engagement rather than focusing your entire offensive enterprise on getting the missile to the target, i.e slowing down, doing a hard high G high AOA point and shoot. I expect the AMCA to exploit this, in addition to the PAKFA and other 5th generation efforts. This would have a considerable affect on how not only how aircraft are designed but how missions are planned.

rohitvats · Post by **rohitvats** » 29 Dec 2014 22:46

Karan M wrote:<SNIP>Its not an extreme stand. That you call it so, just shows that you are prejudging the result.

Karan - I'm not prejudging anything here.Please allow me to clarify my stand.

As rest of your post demonstrates, various factors (aerodynamics, performance of AAM missiles, sensors, pilot training, tactics) determine the performance of a fighter in A2A role, especially the WVR variety. My only submission is that STR is an important component of that whole dynamic which determines the final output.

When it comes to LCA Mk-1 and STR (or other issues) - my objective here is to flesh out the issues and their counter-point in detail, so that we don't end up in same debate a later stage. Because unless you do so, we'll have the same cycle again.

Hopefully, we can put together these points and counter-points together as a resource center for reference of others.

Courtesy last couple of posts, we have an answer to the STR issue - what remains unanswered is the number/range within which it falls and

(a) Number/range they're trying to achieve.
(b) comparison with adversaries in the neighborhood
(b) existing a/c in the inventory.

maitya · Post by **maitya** » 29 Dec 2014 22:49

vina wrote:...ie carbon fiber skins riveted /screwed in place of aluminium plates as in traditional stressed monocoque construction. This is not the best way to go with carbon fiber. Ideally it should be a large single piece carbon fibre structural stuff. The wing is going to be co-cured co bonded per the article, the fuselage barrel too should be carbon fibre made ...

Vinaji, that in itself is a quite good example of the type of challenges that we face while executing an ab-initio program like this. Of course, ADA (and HAL) folks would have been compleely aware of the need of cocured cobonded wings - problem is how to manufacture them.
The largest autoclave that HAL has/had-in-2005-or-so is a 8mx4m one (I think the one in NAL is even smaller) - good enough for a cocured-cobonded fin and rudder manufacturing but how does one go about manufacturing a wing with a 8m span.
And large autoclaves like these are not easily available from a 3rd country that easily.

So if HAL is getting confident about en-masse manufacturing of co-cured/cobonded 8m-span-wings, then such autoclave manufacturing ability has either been mastered inhouse or some other country may have agreed to give us (which I doubt).

But the important point is that is how gradually manufacturing infra/capability is built ...

Karan M · Post by **Karan M** » 29 Dec 2014 23:37

rohitvats wrote:
Karan M wrote:<SNIP>Its not an extreme stand. That you call it so, just shows that you are prejudging the result.
Karan - I'm not prejudging anything here.Please allow me to clarify my stand.

As rest of your post demonstrates, various factors (aerodynamics, performance of AAM missiles, sensors, pilot training, tactics) determine the performance of a fighter in A2A role, especially the WVR variety. My only submission is that STR is an important component of that whole dynamic which determines the final output.

When it comes to LCA Mk-1 and STR (or other issues) - my objective here is to flesh out the issues and their counter-point in detail, so that we don't end up in same debate a later stage. Because unless you do so, we'll have the same cycle again.

Hopefully, we can put together these points and counter-points together as a resource center for reference of others.

Courtesy last couple of posts, we have an answer to the STR issue - what remains unanswered is the number/range within which it falls and

(a) Number/range they're trying to achieve.
(b) comparison with adversaries in the neighborhood
(b) existing a/c in the inventory.

Ah, get your point.