LCA news and discussion

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Re: LCA news and discussion

Postby Raveen » 16 Dec 2009 01:14

Rahul M wrote:
It's not IAF or ADA but all of them (including MoD, MoF, CCS, DRDO etc) put togather needs to share the blame. It takes years to get approvals and sanctions for projects, by the time sanctions come in projects are already way behind the schedule. It is not possible to put all of the blame on anyone's door.

agree wholeheartedly. just that, the situation is looking up and now is the time for looking forward.
===============

IMO people are going overboard with this 120-130 kN business. the mig-29 will receive a 7% (i.e about 5.7 kN for each engine) increase in thrust after more than 25 years of service life.
something like 95-100 kN should do nicely even for the Mk2 unless it gains substantial weight, which seems unlikely at the moment.

inferior instantaneous turn rate due to low wing loading.

are you sure of that ? IIRC low wing loading gives superior performance both in ITR and STR. :-?



From Wiki:

"Aircraft with low wing loadings tend to have superior sustained turn performance because they can generate more lift for a given quantity of engine thrust. The immediate bank angle an aircraft can achieve before drag seriously bleeds off airspeed is known as its instantaneous turn performance. An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance: it reacts quickly to control input, but its ability to sustain a tight turn is limited. A classic example is the F-104 Starfighter, which has a very small wing and high wing loading. At the opposite end of the spectrum was the gigantic Convair B-36. Its large wings resulted in a low wing loading, and there are disputed claims that this made the bomber more agile than contemporary jet fighters "

I think the lower STR is a result of the delta wings bleeding off energy faster rather than wing loading in the LCA. Gurus pls correct me if I am mistaken

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Re: LCA news and discussion

Postby Rahul M » 16 Dec 2009 01:25

lastly, for the love of me I don't understand why HAL/ADA doesn't go the whole hog to present the 2 seat tejas as a very very viable AJT/LIFT aircraft of the T-50 mold, which apparently the IAF is interested in procuring. http://livefist.blogspot.com/2009/09/in ... ainer.html :roll:

they in fact had a proposal : http://ajaishukla.blogspot.com/2009/02/ ... r-lca.html

a no frills LCA trainer version would be perfect for the job.
===========

I think the lower STR is a result of the delta wings bleeding off energy faster rather than wing loading in the LCA.

Aircraft with low wing loadings tend to have superior sustained turn performance because they can generate more lift for a given quantity of engine thrust.

LCA has a 'low' wing loading, probably the lowest in the world among fighters.

does that answer your question ? it's always a good idea to read whatever you are posting ! :wink:

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Re: LCA news and discussion

Postby Raveen » 16 Dec 2009 01:46

Rahul M wrote:lastly, for the love of me I don't understand why HAL/ADA doesn't go the whole hog to present the 2 seat tejas as a very very viable AJT/LIFT aircraft of the T-50 mold, which apparently the IAF is interested in procuring. http://livefist.blogspot.com/2009/09/in ... ainer.html :roll:

they in fact had a proposal : http://ajaishukla.blogspot.com/2009/02/ ... r-lca.html

a no frills LCA trainer version would be perfect for the job.
===========

I think the lower STR is a result of the delta wings bleeding off energy faster rather than wing loading in the LCA.

Aircraft with low wing loadings tend to have superior sustained turn performance because they can generate more lift for a given quantity of engine thrust.

LCA has a 'low' wing loading, probably the lowest in the world among fighters.

does that answer your question ? it's always a good idea to read whatever you are posting ! :wink:


Sir, I did read what I was posting and I am aware of the low wing loading of the LCA but I am also aware that delta wings bleed off more energy and at a faster rate during sustained turns. So while the LCA's low wing loading should give it good STR characteristics, it is the relatively (relative to its overall size) large delta planform that probably/possibly negates this advantage. Here is some relevant info from Wiki :

"The disadvantages, especially marked in the older tailless delta designs, are a loss of total available lift caused by turning up the wing trailing edge or the control surfaces (as required to achieve a sufficient stability) and the high induced drag of this low-aspect ratio type of wing. This causes delta-winged aircraft to 'bleed off' energy very rapidly in turns, a disadvantage in aerial maneuver combat and dog fighting."

So all in all not only did I read what I posted, but my post was the result of reading some additional (relevant) stuff. I am still open to being corrected, since I didn't ask a question :wink:

Thanks,
Raveen

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Re: LCA news and discussion

Postby Jagan » 16 Dec 2009 06:05

You cant pitch the LCA-2 seater for the Hawk type of a role. MiG-21U/MOFTU, yes, but an AJT is a stretch.

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Re: LCA news and discussion

Postby Cain Marko » 16 Dec 2009 06:14

Singha wrote:other than a fairly astonishing T:W ratio I am not sure what these future high thrust engines will bring in.


Goodness! Won't bragging rights suffice? My plane got bigger ***** than yours, so there!

Although it could mean stunning acceleration and performance ala typhoon ever now and again.

CM.

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Re: LCA news and discussion

Postby negi » 16 Dec 2009 06:26

^ No there is lot more to it imho ; a high TW ratio is an indicator of good R&D in areas of material science and state of the art in terms of jet engine design (read lower stages in compressor for achieving similar compression ratio as contemporaries hence lesser parts , high reliability ,low maintenance , similarly a turbine capable of high TeT would push up the overall efficiency and help achieve those low the SFC figures for comparable Thrust by allowing for a smaller core as compared to other engines)

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Re: LCA news and discussion

Postby Gagan » 16 Dec 2009 06:35

My renderings of the LCA, from the Wikipedia LCA Tejas page

Image

Image

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Re: LCA news and discussion

Postby negi » 16 Dec 2009 06:45

Gagan nice work, fwiw in case of N-LCA the LEVCONs do not fit flush alongside the leading edge slats it is a lot more protruded

Image

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Re: LCA news and discussion

Postby Gagan » 16 Dec 2009 07:09

I thought so too, but look at the right wing above the IRST and rocket launcher pod. The slats are turned down, on both sides, and the levcons would seem to be aligned, if the slats are in a neutral position.

But have you seen an actual model and can confirm that they protrude out.

It is not clear from this pic too:
Image

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Re: LCA news and discussion

Postby suryag » 16 Dec 2009 07:18

Nice renditions Gagan ji. Btw, do we have any news on LSP-3 which was supposed to fly with the MMR. I am puzzled, as I see these on and off reports of weaponisation trials, how have we done these trials without radar ? Or is it that these trials are only being used to test free fall bombs and the the canon ?

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Re: LCA news and discussion

Postby srai » 16 Dec 2009 07:24

Gagan wrote:I thought so too, but look at the right wing above the IRST and rocket launcher pod. The slats are turned down, on both sides, and the levcons would seem to be aligned, if the slats are in a neutral position.

But have you seen an actual model and can confirm that they protrude out.

...


Since the Naval LCA is supposed to be quite similar to the twin seater version of the LCA, this picture Ajay Shukla took of the 2-seater clearly shows that the slats don't protude out.

Image

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Re: LCA news and discussion

Postby Gagan » 16 Dec 2009 07:25

They are clear here.
Image

I've changed it and am uploading the corrected one on wiki.
Image

Thanks Negi saar.
Last edited by Gagan on 16 Dec 2009 07:44, edited 1 time in total.

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Re: LCA news and discussion

Postby Cain Marko » 16 Dec 2009 07:29

The wing loading issue is interesting and one wonders if this could be some cause to worry. The LCA was originally planned as a v.light fighter with reasonable thrust and exceptionally low wingloading. Now thanks to the increase in empty weight by almost 1 ton (I assume it will be slightly less, perhaps 6300kg); will the increased wingloading cause concern in terms of lift/turn rates?

The newer, more powerful 95kN engines will offset the drop in thrust, but what about wingloading, it will surely increase to more than the original plan? Is the increased thrust enough to offset this?. Since (if I read wiki right), lift (and therefore turn rates) are a function of thrust as well. Is this another reason for the EJ-200 blokes to offer the TVC engines?

CM.

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Re: LCA news and discussion

Postby Raveen » 16 Dec 2009 07:45

Cain Marko wrote:The wing loading issue is interesting and one wonders if this could be some cause to worry. The LCA was originally planned as a v.light fighter with reasonable thrust and exceptionally low wingloading. Now thanks to the increase in empty weight by almost 1 ton (I assume it will be slightly less, perhaps 6300kg); will the increased wingloading cause concern in terms of lift/turn rates?

The newer, more powerful 95kN engines will offset the drop in thrust, but what about wingloading, it will surely increase to more than the original plan? Is the increased thrust enough to offset this?. Since (if I read wiki right), lift (and therefore turn rates) are a function of thrust as well. Is this another reason for the EJ-200 blokes to offer the TVC engines?

CM.


I think the built-in RSS and the FBW system compensates (at least partially) for the increased wing loading, but that is an interesting point you bring up. Maybe we should e-mail Shook-law and ask him to bring it up with HAL since they obviously love him.

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Re: LCA news and discussion

Postby Kartik » 16 Dec 2009 09:10

tsarkar wrote:>> Wing modification

Stressing a hardpoint for higher loads will add few spars and members that require exhaustive time consuming redesign and testing, however won’t add significant weight. The R-60 weighs 65 kg while the R-73 weighs 105 kg.

Point I am making here is that our baby is 6500 kg instead of 5500 kg despite some of our nation’s best minds putting their best efforts on it. That in no way makes the Tejas inferior or ADA’s overall development efforts any less worthy of praise. It is indeed a success story on every count, unlike the assistance received by the Swedes from BAe, GE and Chinese buying/stealing from everywhere.


not true, tsarkar. you cannot "add a few spars"..there is no space to add even 1 new spar. delta wing fighters may have an extra spar compared to conventional wings, but you cannot add another spar without going through VERY extensive rework, meaning changing the wing design itself. these are primary structures and you cannot say that they won't add significant weight if they need to carry more load, especially the kind of dynamic loads a fighter will experience during its entire lifetime. with the R-73 required for the wing-tip pylon, they'd have had to strengthen the spars and ribs, but that is not all- it changes a lot of things- how much loads are acting on every other structure that is connected to the spars (for instance panels) and this is considered a very significant change.

but believe me, weight reduction is quite a difficult and involved process. as more and more experience and confidence builds up with test flights carrying various stores at the full envelope of flight, the factors of safety for structures may be reduced even further, which can shave off some weight.

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Re: LCA news and discussion

Postby Kartik » 16 Dec 2009 09:15

KrishG wrote:What effect will increased wing-loading have on Mk-1 and Mk-2 ? I thought that LCA would depend on it's superior rate-of-climb in combat given it's comparitively inferior instantaneous turn rate due to low wing loading.


inferior ITR due to low wing loading ? so the Jaguar must have the most "eye-watering" ITR indeed..its the opposite. a lightly loaded wing means that the aircraft will have very good ITR (the Mirage-2000 for e.g. compared to the F-16). a large delta wing will suffer from reduced STR as energy bleeds off very rapidly. provide the pilot with excess power (like on the Rafale) and he can overcome that disadvantage of the delta wing as well.
Last edited by Kartik on 16 Dec 2009 09:16, edited 1 time in total.

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Re: LCA news and discussion

Postby Daedalus » 16 Dec 2009 09:15

Gagan wrote:They are clear here.
Image

I've changed it and am uploading the corrected one on wiki.
Image

Thanks Negi saar.


Also continuing from here.

Let me start of by saying nice work, I am just adding my 2 paisas worth and intent to leave the matter at this.
Now it looks more like Naval LCA. But what I am saying is it looks like the naval trainer and not the single seat naval variant. So please consider appending trainer to the name which the picture actually represents. Also if the picture could be at an angle where it shows the tail hook(another prominent feature for the naval variant), it will be nice at least to me.

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Re: LCA news and discussion

Postby negi » 16 Dec 2009 09:27

Gagan no saar for me don't let my post count fool you :mrgreen: .

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Re: LCA news and discussion

Postby Kartik » 16 Dec 2009 09:45

BTW, just to add to the discussion, as per 11 test pilots who've flown the Tejas, all of them rated the handling qualities of the Tejas as "very good" as per the 17th Report of the Standing Committee on Defence reporting to the Parliament. so its on record, not just word of mouth.

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Re: LCA news and discussion

Postby vina » 16 Dec 2009 10:26

Rahul M wrote:going by ajai shukla's definition of 'loaded', those 3000 kg corresponds to

Foggedabout Shook Laws and In Laws and Out Laws.

http://www.flickr.com/photos/20125521@N02/2366848903/sizes/l/


Grand Mullah Enqyoob-ud-din-e-Gas-Turbine ( Hakeem-o-Hafeez-e-Aerospace Yin Jin Earring), himself cannot pass more powerful Fatwas than what is written in the picture above.

It says .
Empty Weight --> 6500 Kg.
Take off weight - Clean --> 9500Kg
Definition - Clean take off weight is weight of aircraft with No Weapons, but includes Fuel, Fluids (consumables like Lubes, coolants etc), and Pilot. Sort of like Airshow configuration


So if you take a very very big fat pilot of 85 Kg and a large amount of lubes , coolants etc of around 115 kg and work backwards, fuel weight should be 9500-6500-85-115 , roughly around 2800 kg internal fuel at least.

That is what I wrote about earlier. Internal fuel of approx 3000kg. Mark my words, that bird ain't no short ranged point defense fighter with a 'Bingo' as soon as you barely take off from Bangalore and fly to just Chennai kind. This one will have F-16 kind of range and persistence because it has very very similar fuel fraction of 30% or so.


if so, then by the same calculation above, loaded wt should be 9500 kg.


That 9500 is the clean take off weight

but, ajai shukla says loaded wt is 10500 kg, 1000 kg more than even the revised estimates !
http://ajaishukla.blogspot.com/2008/07/ ... es-on.html


Yes.. This is not the weight in the story board. This has pylons and two missiles and probably the rounds for guns in place !. So you can load up the rest of the pylons upto the MTOW limit of the plane!. So even if you are carrying max payload of 4+ tons (whatever that limit is) and you take off with less than full fuel, a quick tank up from an IL-78 Midas will take care of that.

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Re: LCA news and discussion

Postby SanjibGhosh » 16 Dec 2009 10:36

Nod to Rs 8,000cr for production of Tejas
http://203.197.197.71/presentation/left ... tejas.aspx


Folks very good news here ....

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Re: LCA news and discussion

Postby karan_mc » 16 Dec 2009 10:39

SanjibGhosh wrote:Nod to Rs 8,000cr for production of Tejas
http://203.197.197.71/presentation/left ... tejas.aspx


Folks very good news here ....


i am getting error

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Re: LCA news and discussion

Postby krishnan » 16 Dec 2009 10:39

SanjibGhosh wrote:Nod to Rs 8,000cr for production of Tejas
http://203.197.197.71/presentation/left ... tejas.aspx


Folks very good news here ....


Gives run time error.

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Re: LCA news and discussion

Postby marimuthu » 16 Dec 2009 10:40

vina wrote:Ah Philip -- Relax.,

Just got the latest issue of Vayu by mail today and it had a piece about the LCA. In fact the "Good News" is already here, but DDM didnt know how to report it.

The Vayu said that by the "middle december" a test team of 4 aircraft PV1, PV2, PV3 and LSP2 would be based out of Dabolim and in an intensive exercise open out the full envelope as per the IOC standard .



Can we expect the scans to be uploaded here?

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Re: LCA news and discussion

Postby SanjibGhosh » 16 Dec 2009 10:57

krishnan wrote:
SanjibGhosh wrote:Nod to Rs 8,000cr for production of Tejas
http://203.197.197.71/presentation/left ... tejas.aspx


Folks very good news here ....


Gives run time error.



Here is the full text ...

Nod to Rs 8,000cr for production of Tejas

B.R. Srikanth

Bengaluru

Dec. 15: In a major leg-up for one of the country’s most crucial indigenous defence initiatives, the Centre has sanctioned a massive Rs 8,000 crores to begin production of the fighter jet Tejas for the IAF and Indian Navy.

The lion’s share of this outlay, Rs 5,000 crores, will be for the manufacture of the jets for the IAF, while the rest will be for the development of a variant for the Navy, P.S. Subramanyam, director of the Aeronautical Development Agency which coordinates the Light Combat Aircraft programme, told this newspaper. "This is very good encouragement for a homegrown programme, but the challenge ahead is that we must deliver the jets on time. The first of these fighters will join the IAF’s fleet early 2011. The Air Force has ordered one squadron (20 fighters), and is in the process of ordering another squadron," he said.

Official sources said the IAF has committed to the purchase of 140 more jets, for seven squadrons, with more powerful engines. Next year, the LCA programme will cross another milestone with the maiden flight of the naval version.

This variant will be designed to operate from aircraft carriers INS Vikramaditya and the Air Defence Ship.

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Re: LCA news and discussion

Postby Shubham » 16 Dec 2009 11:21

SanjibGhosh wrote:Here is the full text ...

Nod to Rs 8,000cr for production of Tejas

B.R. Srikanth

Bengaluru

Dec. 15: In a major leg-up for one of the country’s most crucial indigenous defence initiatives, the Centre has sanctioned a massive Rs 8,000 crores to begin production of the fighter jet Tejas for the IAF and Indian Navy.

The lion’s share of this outlay, Rs 5,000 crores, will be for the manufacture of the jets for the IAF, while the rest will be for the development of a variant for the Navy, P.S. Subramanyam, director of the Aeronautical Development Agency which coordinates the Light Combat Aircraft programme, told this newspaper. "This is very good encouragement for a homegrown programme, but the challenge ahead is that we must deliver the jets on time. The first of these fighters will join the IAF’s fleet early 2011. The Air Force has ordered one squadron (20 fighters), and is in the process of ordering another squadron," he said.

Official sources said the IAF has committed to the purchase of 140 more jets, for seven squadrons, with more powerful engines. Next year, the LCA programme will cross another milestone with the maiden flight of the naval version.

This variant will be designed to operate from aircraft carriers INS Vikramaditya and the Air Defence Ship.


Since Gov is the buyer and Gov is the producer , how does this kind of deal works out ?

I hope the part of this fund infusion ie 5K crore is meant for HAL to establish production line and other facilities to produce LCA.

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Re: LCA news and discussion

Postby Rahul M » 16 Dec 2009 11:33

Jagan wrote:You cant pitch the LCA-2 seater for the Hawk type of a role. MiG-21U/MOFTU, yes, but an AJT is a stretch.

Jag, I said a modified no-frills version. how different is it from the korean T-50 ?

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Re: LCA news and discussion

Postby Philip » 16 Dec 2009 12:19

In the light of the last few posts,it is amply clear that there is a maximum weight and thrust ratio that rules the LCA.Therefore,regarding weight,the payload/fuel factor has to be juggled with respect to the role the IAF wants the aircraft to perform.There is little point in trying to make the LCA peform a medium sized combat aircraft's role.From the tortured history of the aircraft,its requiremements kept on increasing and this mission "creep" has in major part been responsible for some of the delays.It was meant to replace the MIG-21,with more bang for the buck and that would be the best way to go.The MIG-21 Bisons one must remember are old aircraft upgraded and will not have more than another decade of life left in them and will have to be replaced in turn by the LCA,which we hope has a better all round capability than the Bison.

Rahul's aide of an AJT out of the LCA project is an excellent one and I think several experts have commented on that score,many moons ago,that we should've first developed an AJT which then would mature with upgrades into an LCA.The reverse can certainly be done and we can save a lot of forex by doing this instead of buying more Hawks which the GOI is examining.In fact,a supersonic trainer,with limited air defence and GA capability is what many nations are looking for and the LCA in a basic mode,without BVR,AESA,some bells and whistles like ECM,etc.,would fit the bill perfectly,as it would also be very cost-effective.The LCA MK-1 would fit the bill for the IAF,which will induct hopefully about 140+ of the aircraft.An LCA AJT which would also be used for pilots moving onto the MMRCA and heavier aircraft like the MIG-29s and Sukhois.I don't see why this line of thought is not being articulated in aviation circles,as the various prototypes are already flying and orders for the first sqd. confirmed.The only stumbling block would tne production rates,especially if exports are to be a primary focus and the GE engine,which the US would try and prevent from being sold to certain friends of ours with whom it has issues.

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Re: LCA news and discussion

Postby vina » 16 Dec 2009 12:29

In the light of the last few posts,it is amply clear that there is a maximum weight and thrust ratio that rules the LCA.Therefore,regarding weight,the payload/fuel factor has to be juggled with respect to the role the IAF wants the aircraft to perform


Ah Philip, but that is true with EVERY AIRCRAFT , including the ones from the beloved Rodina like the Mig 29 and Su 30! .You have to do the exact same juggling.

For eg, if you want the Mig 29 or 35 or whatever the aircraft entered in the MRCA is called to do ground strike with all the pylons loaded up with A2G weapons. It will have terrible range on internal fuel, even if it sports the unseemly bulges and the big fat back that the Mig 29 S versions seem to have grown to take care of the terribly low fuel fraction that it was designed with.

Yeah. One point of yours is true. Bigger Aircraft --> More Payload . But in many ways, efficiency can trump size. A smaller more efficient aircraft might end up carrying similar payload and having similar range! That is another thing to consider.

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Re: LCA news and discussion

Postby Singha » 16 Dec 2009 12:40

the expenses and timeframe of MRCA, and PLAAFs increasing number of J-10 seem to have convinced IAF that we need huge nos too, not just qualitative superiority.

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Re: LCA news and discussion

Postby sumshyam » 16 Dec 2009 13:26

The news is that Indian Govt has sectioned some 8000 Cr rupees for the production if LCA TEJAS and further development of neval tejas.
Nod to Rs 8,000cr for production of Tejas

The lion’s share of this outlay, Rs 5,000 crores, will be for the manufacture of the jets for the IAF, while the rest will be for the development of a variant for the Navy, P.S. Subramanyam, director of the Aeronautical Development Agency which coordinates the Light Combat Aircraft programme, told this newspaper.


well... I think this much amount would be enough for some 40 birds...!

Considering well discussed price of 25 million $$ each...Correct me...if I am wrong...Please....!

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Re: LCA news and discussion

Postby Kailash » 16 Dec 2009 13:44

Singha wrote:the expenses and timeframe of MRCA, and PLAAFs increasing number of J-10 seem to have convinced IAF that we need huge nos too, not just qualitative superiority.


Couldn't agree more. The LCA outperform any pakistani bird currently in service. Number of cheap and light LCAs deployed on the western front, at the least, will free up the heavier birds to be deployed against the eastern neighbour. Pilot shortage ramping up production of LCA might be the only true issues at hand.

About an ATJ role for the LCA, should we still depend GE engines or will Kaveri suffice?

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Re: LCA news and discussion

Postby vasu_ray » 16 Dec 2009 14:05

while I haven't heard about indo-israeli air exercises, when will the Tejas be ready for any such action? after FOC?

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Re: LCA news and discussion

Postby tsarkar » 16 Dec 2009 14:22

Kartik – I am not doubting the amount of redesign and testing work you mentioned; what I want to understand is how much weight will we add if we stress a hard point to carry a 105 kg missile at 9 g instead of a 65 kg missile at 9g? I guess not more than 100 kg at a stretch? Same goes for the intake hardpoint for the Litening.

Vina – isn’t the 2300 kg fuel published data? I concur with your 30% fuel fraction as a worthwhile design consideration.

Rahul – I agree on the intake hardpoint and outer wing hardpoint, however disagree on the EW suite (that isn’t there on the PVs & LSPs), wiring won’t take 100 kg (come on, this ain’t Gorshkov ) and the heavy radar isn’t IAF’s fault. So I will guess 200-300 kg empty weight increase due to ASR revisions.

I believe the 5500 -> 6500 kg has been a development issue, most probably due to building more tolerances in individual components since this was done for the first time and designers wanted to play safe. As written earlier, overall effort has been commendable by any yardstick.

Jagan – If we do an assessment of peacetime flight hours during a year, we’ll find most sorties are operational training, like air combat and weapons delivery training, that don’t require state of the art performance. We don’t need a top of the line fighter for these roles and certainly induct more numbers for this role.

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Re: LCA news and discussion

Postby rakall » 16 Dec 2009 15:36

tsarkar wrote:
Vina – isn’t the 2300 kg fuel published data? I concur with your 30% fuel fraction as a worthwhile design consideration.

.



From the designer's mouth at AI09 --

LCA has precisely 2350kgs internal fuel.. 100kg used during normal take-off.. has 2250kgs once airborne..
Accounting for reserve fuel - has about 1800kg fuel that can be spent on mission..

One LCA TP said "".. "Its endurance or range is slightly better than Mirage with lesser fuel".. Mirage2000 has about 3150kgs internal fuel..

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Re: LCA news and discussion

Postby vina » 16 Dec 2009 16:07

tsarkar wrote: what I want to understand is how much weight will we add if we stress a hard point to carry a 105 kg missile at 9 g instead of a 65 kg missile at 9g? I guess not more than 100 kg at a stretch? Same goes for the intake hardpoint for the Litening.


Before the wing redesign became public, I had speculated right here in this thread that the reason why they were not able to do the carriage and separations trials were not being done was because the IAF had given an outdated weapons requirement and that once they woke up and changed the requirements, a redesign would be required.

Siva , a former structures designer at ADA ,and had gone for his Master's in US, who used to post here (he doesn't do so anymore, maybe he has been told to shut up by the powers that be) fessed up and said, yes a redesign was done and that the wing was strengthened for torsion for the new weapons load out.

DDM picked up that bit of news from this thread here and I think it became an "issue" once it was picked up.

So I asked him how much mass was added , and he replied negligible, since all it required was a couple of layers of carbon fiber in the right places!

I guess, I have a pretty good record in speculation. I also speculated that GTRE have a working engine finally and it looks like they do . I did this when there was D&G all around about the Kaveri and there was dead silence from GTRE. This was before all the Shook Laws and In Laws of the world actually started getting into the act and doing the actual ground work and visiting places.

from the designer's mouth at AI09 --

LCA has precisely 2350kgs internal fuel


So let me speculate here as well. I might be third time lucky , who knows.

Yes that 2350 is for the "old" air frame with the targeted weight of 5500kg (Gripen has same 2250 kg internal fuel for a 6500kg airframe). I am absolutely willing to bet that the Air Force will not sacrifice range and persistence under any circumstance. Think of it , what is the point in being able to carry ordnance, if you cant reach the place where you need to drop it!.

I am willing to bet that when the MKII version rolls out, you will see the internal fuel at close to 2800 kg / 3000 kg. How can that be done ?

Let me think.. All air craft and ships and submarines and stuff are designed with some 3 % to 5% ballast (usually concrete blocks or lead weight) to allow for weight growth as equipment gets added and also to balance out the CG etc as the final version of the plane gets designed in (you cant redo the entire General Arrangement on the fly each time some equipment is changed /added/removed, you tend to add weights/remove weights as appropriate).

Now the most optimized airframe will be the one with Zero Ballast and all components at their most optimal with factors of safety that are just right. I am willing to bet that the current version has ballast and "unoptimized" components.

I doubt the current LCA is there yet in terms of optimal layout. It makes no sense to do it, because this is just an interim level with an interim engine and weapons and radar fit!. No point in doing it.

Once the final engine choice is made (EJ200 or GE 414), and the absolute final weapon fit is chosen , including the radar ,then you can have the "final" config in place , you can get the weight down to it's bare minimum..

And oh.. you will need to "fine tune" the control laws and FBW again for this final version and do the flight tests I think, since the weight , CG etc will be different and the dynamic response of the plane as well... But I guess the idea will be to "teach" the flight control system to fly with a different weight layout than the current one.

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Re: LCA news and discussion

Postby rakall » 16 Dec 2009 16:34

vina wrote:
from the designer's mouth at AI09 --

LCA has precisely 2350kgs internal fuel


So let me speculate here as well. I might be third time lucky , who knows.

Yes that 2350 is for the "old" air frame with the targeted weight of 5500kg (Gripen has same 2250 kg internal fuel for a 6500kg airframe). I am absolutely willing to bet that the Air Force will not sacrifice range and persistence under any circumstance. Think of it , what is the point in being able to carry ordnance, if you cant reach the place where you need to drop it!.


.



The "current flying airframe" has 2350kgs internal fuel.. That is what the designers had told me at ADA pavilion..

There is no sacrificing range or persistence there because the aerodynamics turned out to be better than expected (as per KPrasad's post from AI conference) & also fuel efficiency of GE engine.. And also as i mentioned in my previous post, an LCA TP quoted "it has slightly better endurance or range when compared to Mirage". So no range/endurance shortfall..

GE F404-IN20 has a SFC of 82.5Kg/KN.hr and a dry thrust of 49KN... Snecma M53-P2 has a SFC of 90Kg/KN.hr and a dry thrust of 64KN (obviously higher thrust required for Mirage bcoz the MTOW is higher.. and hence the engine is also heavier than GE engine)...

As an assumption -- if one operates both engines at 75% thrust continously (though one has to actually account for cruise L/D ratios of individual fighter a/c.., this is the best approx I can make now) then for one hour of operation the GE engine will burn 3032kgs of fuel.. where as the Snecma engine will burn 4320kgs of fuel.. the ratio is same as that of the the useful fuel that both fighters hold.. 3032/4320 = 0.70 & 1850/2550 = 0.70. So in current config, LCA has nearly same range/endurance as the mirage -- which is quite good..

If LCA MkII can be bumped up to have 3000kgs of internal fuel -- good.. But before ADA accomplishes that, they will have to reduce weight from the current version by carefully shaving off weight from wherever they have used "extra conservative safety margins"; which in the first place has been a "partial contributor" to the extra 1000kgs..

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Re: LCA news and discussion

Postby SaiK » 16 Dec 2009 17:38

rf-mems should further cut down RCS for those al-li slats.

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Re: LCA news and discussion

Postby tsarkar » 16 Dec 2009 17:52

So I infer while IAF carelessness added a lot of work of ADA, it didnt really add weight.

Rakall, extra conservative safety margins was a partial contributor. What are the other contributors?

Secondly, intakes - IAF says there’s air starvation (and I assume they say so based on their engineers and test pilot’s assessment). It is apparent that the shutters are a temporary solution. I believe the situation will be worse for Mk2 engines that will need more airflow.

So what can be done to rectify the situation? Will simply increasing the inlet cross section suffice? By doing so can we increase the performance of Mk1?

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Re: LCA news and discussion

Postby Rahul M » 16 Dec 2009 17:59

Raveen wrote:"The disadvantages, especially marked in the older tailless delta designs, are a loss of total available lift caused by turning up the wing trailing edge or the control surfaces (as required to achieve a sufficient stability) and the high induced drag of this low-aspect ratio type of wing. This causes delta-winged aircraft to 'bleed off' energy very rapidly in turns, a disadvantage in aerial maneuver combat and dog fighting."

So all in all not only did I read what I posted, but my post was the result of reading some additional (relevant) stuff. I am still open to being corrected, since I didn't ask a question :wink:

Thanks,
Raveen

Raveen, no sir please. your questions have their answers in the
> bolded part above,
> the very next line from the paragraph that you have omitted ! :wink:
This can be solved with relaxed stability, strakes and canards.

> and the fact a large number of fighters being made today are deltas and all of them are claimed to be very maneuverable. the M2k for example is said to trump the F-16 quite regularly in dogfights.

so, does this datapoint about old generation delta's still hold ? :wink:

in fact the very next paragraph has the indications.
http://en.wikipedia.org/wiki/Delta_wing ... variations

http://www.centennialofflight.gov/essay ... Tech10.htm
Sometimes, a technology persists despite its problems and eventually is rescued by other technologies. The delta wing story provides an excellent example.

____________________________

Secondly, intakes - IAF says there’s air starvation (and I assume they say so based on their engineers and test pilot’s assessment). It is apparent that the shutters are a temporary solution. I believe the situation will be worse for Mk2 engines that will need more airflow.

So what can be done to rectify the situation? Will simply increasing the inlet cross section suffice? By doing so can we increase the performance of Mk1?

air intakes will be enlarged in Mk2. according to knowledgeable folk that should do the trick.


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