LCA Tejas: News and Discussions

Hobbes · Post by **Hobbes** » 22 Apr 2015 06:38

brar_w wrote:In cases where you are seeking the absolute performance data you go out and use the data given in the flight manual itself. In case of the F-16C, it is public information.

https://publicintelligence.net/hellenic ... t-manuals/

Flight manual for the Mirage 2000C (in French) available at http://air.felisnox.com/view.php?dl=1&name=m2000c.pdf and the Mig-29 flight manual is right next to it at http://air.felisnox.com/view.php?dl=1&name=mig29fm.pdf.

member_20292 · Post by **member_20292** » 22 Apr 2015 06:50

nileshjr wrote:
L/D Graph

just asked for access. my email is r w n a n @g ml . com

shiv · Post by **shiv** » 22 Apr 2015 07:08

Hobbes wrote:
brar_w wrote:In cases where you are seeking the absolute performance data you go out and use the data given in the flight manual itself. In case of the F-16C, it is public information.

https://publicintelligence.net/hellenic ... t-manuals/
Flight manual for the Mirage 2000C (in French) available at http://air.felisnox.com/view.php?dl=1&name=m2000c.pdf and the Mig-29 flight manual is right next to it at http://air.felisnox.com/view.php?dl=1&name=mig29fm.pdf.

i scanned all 131 pages of the Mirage 2000 manual, which, surprise surprise, is in French.

It is a pilots manual describing systems starting from general characteristics, engine, FBW flight control going on to HUD, armament etc.

Not a single word or graph about turn rate or climb rate. There is one graph that seems to display the Alpha limit under the FBW description the graph goes flat at 29 degrees and that may be the FBW limit of Alpha

shiv · Post by **shiv** » 22 Apr 2015 07:27

brar_w wrote:In cases where you are seeking the absolute performance data you go out and use the data given in the flight manual itself. In case of the F-16C, it is public information.

https://publicintelligence.net/hellenic ... t-manuals/

Difficult to scan 500 plus pages but section V is about "limitations". Read from approx page 435 onwards. Again no information on turn rate. But what I understand suggests that the flight control software tries to limit AoA to 25 degrees.

Hobbes · Post by **Hobbes** » 22 Apr 2015 07:28

Turn performance for the Gripen

Source http://gripen4canada.blogspot.ca/2013/0 ... icism.html

Hobbes · Post by **Hobbes** » 22 Apr 2015 07:35

Mig-21 Turn Rate

shiv · Post by **shiv** » 22 Apr 2015 07:38

^^The MiG 21 and Gripen are similar - with best turn rate at about 500 knots which I believe is a fairly common combat flight speed. I suspect most fighters will have a similar performance. The real crunch is in manoeuvring where flight speeds are constantly changing and turn rate also changes.

srai · Post by **srai** » 22 Apr 2015 07:47

nileshjr wrote:...
There is easy way of sanity check. The M2K data is given along with F-16 and F-18. It should be relatively easy to get numbers for those two birds and then we can match up it with this dataset. Can someone please throw in some realistic numbers for F-16??

...

RAND: Measuring Effects of Payload and Radius Differences of Fighter Aircraft (F-16 Blk50 vs F-15E)

Code: Select all

===========================================
Air-To-Ground Weapon Delivery: High-High-High (HHH) mission profile
===========================================

                                         F-16 Blk50     F-15E
----------------------------------------------------------------------------------------

Configuration 1                                 
------------------------
2 x 370-gallon tanks (F-16)
3 (upto) x 610-gallon/conformal tanks (F-15)
2 x GBU-24 / JDAM-2000
2 x AIM-120
2 x AIM-9M
TGP & NVP pods

Straight-line radius (nmi)                    470         740    
Operational radius (nmi) (30% factor)         370         570


Configuration 2a                                  
-------------------
2 x 370-gallon tanks (F-16)
3 (upto) x 610-gallon/conformal tanks (F-15)
2 x CBU-87
2 x AIM-120
2 x AIM-9M
TGP & NVP pods

Straight-line radius (nmi)                    500         780
Operational radius (nmi) (30% factor)         390         600

Configuration 2b                                  
-------------------
2 x 610-gallon tanks (F-16)
2 x CBU-87
2 x AIM-120
2 x AIM-9M
TGP & NVP pods

Straight-line radius (nmi)                    580
Operational radius (nmi) (30% factor)         450  

Configuration 3a                                 
-------------------
2 x 370-gallon tanks (F-16)
3 (upto) x 610-gallon/conformal tanks (F-15)
2 x JDAM-1000
2 x AIM-120
2 x AIM-9M
TGP & NVP pods

Straight-line radius (nmi)                    490         770
Operational radius (nmi) (30% factor)         380         600

Configuration 3b                                 
-------------------
2 x 610-gallon tanks (F-16)
2 x JDAM-1000
2 x AIM-120
2 x AIM-9M
TGP & NVP pods

Straight-line radius (nmi)                     560
Operational radius (nmi) (30% factor)          440 


===========================================
Air-To-Air DCA CAP
===========================================


                                       F-16 Blk50       F-15E
----------------------------------------------------------------------------------------

Configuration 4a                                 
-------------------
2 x 370-gallon tanks (F-16)
3 x 610-gallon/conformal tanks (F-15)
4 x AIM-120 (F-16) / 6 x AIM-120 (F-15)
2 x AIM-9M
ECM pod

Range to loiter (nmi)                    500           500
Loiter time (minutes)                     10           100

Configuration 4b                                 
-------------------
2 x 610-gallon tanks (F-16)
3 x 610-gallon/conformal tanks (F-15)
4 x AIM-120 (F-16) / 6 x AIM-120 (F-15)
2 x AIM-9M
ECM pod

Range to loiter (nmi)                    500           500
Loiter time (minutes)                     40           100

srin · Post by **srin** » 22 Apr 2015 08:45

nileshjr wrote:
nileshjr wrote: I dont know what they do as a matter of fact but if I am designer I would choose one typical config depending upon intent of the aircraft and use that to design at one particular design point. For ex: for interceptor, aircraft with 2 WVR missles at wingtip and other pylons absent or with fairings put on them. But I would keep it simple, perhaps just a clean config as far as area rule is concerned. I wouldn't want to have an aircraft config with truckload of bombs/missiles right at the design stage.
Srin, you had asked this question some time ago. I found one fact regarding M2K. According to this link: http://www.fighter-planes.com/info/mir2000.htm

M2K is area ruled carrying four air-to-air missiles (which four, is not mentioned, perhaps 2BVR + 2 WVR)

Thanks for confirmation. Now, I'm curious about the Tejas configuration used for area ruling

Indranil · Post by **Indranil** » 22 Apr 2015 10:09

Nilesh, did you come across any paper/abstract on aeroelastic distortion under 1g flight loads for LCA?

JayS · Post by **JayS** » 22 Apr 2015 11:19

indranilroy wrote:Nilesh, did you come across any paper/abstract on aeroelastic distortion under 1g flight loads for LCA?

As a matter of fact I did come across with a paper with LCA wing loads. Can't remember exactly if its 1G or not. But it tries to optimize loading and it gives aeroelastic deflections for some loadings, something like that. Its from IITK group IIRC. Need to dig out the link. Any thing particular regarding this??

Indranil · Post by **Indranil** » 22 Apr 2015 11:25

The Concord's wings "distorted" to the profile which was more efficient for cruise.

JayS · Post by **JayS** » 22 Apr 2015 11:34

mahadevbhu wrote:
nileshjr wrote:
L/D Graph

just asked for access. my email is r w n a n @g ml . com

Oops

Sorry folks. Pasted wrong sharing link. I have updated the link with public sharing one. Won't ask for log in now. Posting again here to save you trouble to go back to the original post.

https://drive.google.com/file/d/0B9ijXl ... sp=sharing

JayS · Post by **JayS** » 22 Apr 2015 11:42

indranilroy wrote:The concord's wings "distorted" to the profile which was more efficient for cruise.

Are you referring to aero-elastic deformations related compensations such as used on B787?? The aero-elastic deformations are taken into account while designing. So you don't build the wing with optimum shape. Rather build it with the shape which when undergoes aeroelastic deformation under actual loading will take the optimum shape. I doubt LCA has too much of such deflections. It does not have thin (aero-elastically speaking) wings.

BTW, regarding the questionnaire for LCA you mentioned, would a google doc do?? I have created one. People can entre their BRF name and questions regarding LCA that they have in that sheet. We can filter the questions based on their quality later. Would be great if people put some efforts and come up with questions which are not trivial (that is can't be answered with little help from Google uncle). The more specific they are the better.

https://docs.google.com/spreadsheets/d/ ... sp=sharing

Indranil · Post by **Indranil** » 22 Apr 2015 12:25

I am aware of the aero-elastic deformations as part of the design process

. I did not expect it to be part of low aspect ratio deltas like the Concord, but it is there, and to a significant degree, which surprised me. Have grown a liking for the Concord's wings lately. Have earmarked some papers to read over the next week. It also has a twist+camber like that of the Tejas. So, I am doubly interested.

JayS · Post by **JayS** » 22 Apr 2015 13:58

indranilroy wrote:I am aware of the aero-elastic deformations as part of the design process . I did not expect it to be part of low aspect ratio deltas like the Concord, but it is there, and to a significant degree, which surprised me. Have grown a liking for the Concord's wings lately. Have earmarked some papers to read over the next week. It also has a twist+camber like that of the Tejas. So, I am doubly interested.

Expected. Its designed for high mach cruise so would have quite thin wings, so the aeroelastic effects are more pronounced, still not as much as you would see it on 787 wings precisely because its delta wing. Its an old school design where they went as thin as possible to have minimum drag at supersonic speed as CFD was not matured enough to make optimized thicker aerofoils which are reality today.

I read that the fuselage of Concorde also use to flex during flight, so much so that rear passenger could notice it while looking up the aisle!!

Indranil · Post by **Indranil** » 22 Apr 2015 14:16

Yeah, they had to account for it in every respect including wing fuel tanks etc. Also, I did not know that its fuel tanks leaked (like the SR71, but not as badly). Some great information here.

.

JayS · Post by **JayS** » 22 Apr 2015 16:33

indranilroy wrote:Yeah, they had to account for it in every respect including wing fuel tanks etc. Also, I did not know that its fuel tanks leaked (like the SR71, but not as badly). Some great information here.

Ohh, I didn't know it either. Its an incredible plane.

Coming back to topic, I went through the manuals of F16C (links given by brar_w..thanks for that!). What an incredible info those docs have. It would take me months to digest all that performance data. Difficult to get some quick numbers, too many details. But A9-1-17 has some good numbers. For Hi-lo-lo-Hi A2G role with 2 mk-84, 2 missiles, full external tanks (total fuel >11782 (1000lbs of reserve included)). That's 4000lbs bombs and 2 missiles. The manual gives combat radius of 600 nm with 88nm of combat zone radius or 810nm with zero combat zone radius.

OTOH The Dassualt data says for:

Air to Ground Mission Radius of Action
Hi-Lo-Lo-Hi with 4000 lb (1,814 kg) bomb load (8 mk-82) + Maximum tanks.
50 nm dash to and from the target @ 500 ft. (152m)and 550 knots.
Tanks dropped when empty. Missiles retained (2 missiles I pressume).

>>> Combat Range is 410nm.

This is large discrepancy, even if I consider the possibility that carrying 8 mk82 instead of 2 mk-84 would reduce number of tanks that F-16C can carry (which I don't think is the reality).

From this it looks like the combat range for A2A for F-16 will be much more than that of M2K. (710 and 780 respectively for F-16 and M2K as per Dassualt data.)

All in all I am much more confused than from where I started.

Singha · Post by **Singha** » 22 Apr 2015 17:22

well the F-16 has progressively got better engines while the M2K engine never changed from the P53 on day1(bill gunston book calls it leaky turbojet than a true turbofan).
f-16 got massive orders both domestic and foreign hence could get a lot of money for block upgrades. the M2K only got 1 block upg which was M2k-5.

secondly I think the f-16C is lighter, really slim fuselage. however one weak point is its small radar aperture (small nose) vs comparable ones like m2k and mig29.

ramana · Post by **ramana** » 22 Apr 2015 18:30

GD, The Mirage 2K and the F-16 were competitors for the NATO fighter in mid 1970s. The F-16 won that. After that it got into strike role.

Rakesh · Post by **Rakesh** » 22 Apr 2015 20:51

Apologies if this has been posted before. Unsure where else to post this, but it seems apt here in light of the Mirage 2000 discussions going on above.

President Confers Vayu Sena Medal to Squadron Leader Kapil Kareem
http://www.business-standard.com/articl ... 473_1.html

deejay · Post by **deejay** » 22 Apr 2015 21:44

^^^ Thank You for getting this to attention. This is a super display of calm professionalism under extreme duress. Well done Sqn Ldr Kapil Kareem, VM . Salute.

JayS · Post by **JayS** » 22 Apr 2015 22:28

^^ Amazing how the Sq Leader kept his cool. Hope he is well and flying high again. We are proud of such heroes.

BTW Indranil, this is the paper I was talking about.

Optimal trends in Manoeuvre Load Control at subsonic and supersonic flight points for tailless delta wing aircraft, P.S. Suresh, G. Radhakrishnan, K. Shankar

Two are ADA guy and 3rd one from IITM. But there is nothing much interesting in that paper.

member_20292 · Post by **member_20292** » 22 Apr 2015 23:20

Singha wrote:well the F-16 has progressively got better engines while the M2K engine never changed from the P53 on day1(bill gunston book calls it leaky turbojet than a true turbofan).
f-16 got massive orders both domestic and foreign hence could get a lot of money for block upgrades. the M2K only got 1 block upg which was M2k-5.

secondly I think the f-16C is lighter, really slim fuselage. however one weak point is its small radar aperture (small nose) vs comparable ones like m2k and mig29.

I wish the defense ministry sees yours and Ramana's post below this and buys the f 35s already.

m2k:f 16 = rafale : f 35 ...again.

time for defmin and iaf to aggressively become friends with the US mil-ind complex

sankum · Post by **sankum** » 23 Apr 2015 00:24

The specifications of JF 17 from internet gives endurance of 3.5hr and ferry range of 3000km to 3700km and combat radius of 1350km for a maximum fuel fraction of 37%.

I don't think LCA mk1 performance should be far different as it also carries 37% maximum fuel fraction and why would IAF,IN or ADA choose such an aerodynamic design which doesn't match contemporary fighters.

I just did some back of the envelope calculations. Correct me if I am wrong. Max L/D ratio from ADA is 9 which will be maintained to get max endurance.

That means approx. 1.5T (15kN) thrust for a 13.3T aircraft.

The non afterburning specific fuel consumption of GE 404 is 82.6 kg/(kN·h) That means 1239Kg/hour fuel consumption and for 5000Kg total fuel it comes to 4 Hours endurance and thus matches JF 17 performance.

The average weight of the aircraft will be 10.8 T for the flight time as fuel is consumed which means 23% more endurance but I am not factoring in as best efficiency of jet engine comes at full power.

member_20292 · Post by **member_20292** » 23 Apr 2015 09:37

? have you warned me before ? sure , in retrospect the post is OT...but the censure is unnecessarily severe in language. and, again....there has to be a mistake since I dont think ive been warned before.

Indranil · Post by **Indranil** » 23 Apr 2015 10:09

Sorry, case of mistaken identity. Checked user notes. It was not you. On the other hand, just two pages back.

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

pragnya · Post by **pragnya** » 23 Apr 2015 10:14

sankum wrote:LCA mk1 with full external payload of 3500kg with max external fuel tanks+2*250kg PGM and 200kg LDP weight estimate is as follows.

LCA mk1 clean weight 9800kg with full internal fuel of 2458Kg, pylons, pilot, cannon ammo etc. and 2 SR R73 AAM.

Clean weight 9800 Kg+ 2*1075 kg( 2*1200lt external underwing tanks)+ 650Kg(725lt centerline tank)+200kg LDP+ 2*250Kg laser guided bombs=13300Kg(MTOW)

From Vivek's plots 6.5t empty weight+5 t fuel weight we get ranges for 1800Kg payload.

sea level 1100Km range i.e, 550Km radius range.

20000ft 1300Km range i.e, 650Km radius range

30000ft 1200Km range i.e, 600Km radius range

couple of nitpicks but i could be wrong.

on the bolded, IIRC LCA can carry 2*800litre takes on weapon stations 1 and 2 and 1*1200litre on the centreline station? also for the 1200litre it comes to 972kg. you write 1075. does it mean the weight of the tank itself which would be 103kg? isn't it the 800 litre instead of 725lit?

TIA for clarification.

sankum · Post by **sankum** » 23 Apr 2015 10:24

The weight of empty tank is taken as roughly 10% of 1075 kg and the net fuel is 972kg. It is based on Hawk fuel tank with gross weight of 500kg and net fuel of 453.5Kg.

Lca carries composite fuel tanks, so total weight can be less than 1075 Kg.

The inner wing stations on LCA mk1 can carry 2*1200 lt tanks or 2*800 lt tanks while centre line can carry only 725lt tank. Initially it was told that centerline can also carry 1200 lt tank but only news so far is that 725lt tank will be carried.

720 lt supersonic external fuel tanks are also planned.

Singha · Post by **Singha** » 23 Apr 2015 10:29

I recall a old mag from mid 80s where the F-16 the PAF block15-20 was given a radius 750km and M2K was given as radius around 600km. I had no idea of all these load/altitude/speed stuff then.

Philip · Post by **Philip** » 23 Apr 2015 10:59

The latest IMR has a feature on the specs/eqpt.,etc., of the upgraded MIG-29s,with radar range,range,weaponry,etc., about double that of the basic aircraft.There is a considerable hump behind the cockpit for additional fuel. It would be interesting to compare the performance of the upgraded M2Ks and MIG-29UGs along with that of the Rafale,as these will be the medium sized force of the IAF's inventory,around 140+ aircraft altogether.

pragnya · Post by **pragnya** » 23 Apr 2015 11:03

sankum wrote:The weight of empty tank is taken as roughly 10% of 1075 kg and the net fuel is 972kg. It is based on Hawk fuel tank with gross weight of 500kg and net fuel of 453.5Kg.

Lca carries composite fuel tanks, so total weight can be less than 1075 Kg.

The inner wing stations on LCA mk1 can carry 2*1200 lt tanks or 2*800 lt tanks while centre line can carry only 725lt tank. Initially it was told that centerline can also carry 1200 lt tank but only news so far is that 725lt tank will be carried.

720 lt supersonic external fuel tanks are also planned.

thanks sankum. appreciate that. i did not know that stations 1/2 can carry 1200lit tank. also since the under fusalage is much stronger stucturally, felt it can take 1200lit tank.

also if you do not mind please clarify the methodology for this -

The non afterburning specific fuel consumption of GE 404 is 82.6 kg/(kN·h) That means 1239Kg/hour fuel consumption and for 5000Kg total fuel it comes to 4 Hours endurance and thus matches JF 17 performance.

that is from your previous post. actually i need to know a lot from you and others about these calculations.

sankum · Post by **sankum** » 23 Apr 2015 11:11

The non afterburning specific fuel consumption of GE 404 is 82.6 kg/(kN·h) data is from wiki.

15kN*82.6 kg/(kN.h)=1239Kg/hour.

Just ball park approx. figures Total fuel 5000kg/(1239Kg/hour)= roughly 4 hours.

L/D of 9 .

Then 1.5 T thrust(drag) will generate 13.5T lift.

1.5T*9.8m/sec square= roughly 15 kN thrust requirement

pragnya · Post by **pragnya** » 23 Apr 2015 11:58

sankum wrote:The non afterburning specific fuel consumption of GE 404 is 82.6 kg/(kN·h) data is from wiki.

15kN*82.6 kg/(kN.h)=1239Kg/hour.

Just ball park approx. figures Total fuel 5000kg/(1239Kg/hour)= roughly 4 hours.

L/D of 9 .

Then 1.5 T thrust(drag) will generate 13.5T lift.

1.5T*9.8m/sec square= roughly 15 kN thrust requirement

thanks again but while i could understand fair bit but some i could not. i would be happy if you can point me to a site for calculating fuel fraction, range - taking into account the L/D ratio, thrust, weight etc.. or if you have a methodology worked in some sort of excel sheet, i would be happy to jump on it.

i end this here as this could be OT and mods may take note.

JayS · Post by **JayS** » 23 Apr 2015 14:15

nileshjr wrote:
Looks like there is only one dataset, that too given by Dassault and everyone uses those values only.

Disclaimer: I am doing this Range calculation for the first time for any jet. Doing some very crude back-of-the envelop calculations. So take it FWIW. They might be totally off.

According to the dataset @max power, M0.8 and 15000ft fuel consumption is 275 kg/min (assuming that is with A/B.for combat manoeuvre).
Max fuel capacity is 8000lit. Assuming 1000lit for reserve/taxiing/TO/Landing etc. Usable fuel in air is 7000lit. With 5 min combat as mentioned earlier about 275*5~1400kg ~ 1800lit fuel is spent. This leaves 5200 lit fuel. Now if the jet has 1444 km of combat radius, even with economical cruise of ~M0.8 at high altitude it would take around ~2885/850 ~ 3.4hrs to and fro. That gives fuel consumption rate of ~5200/205 ~ 25lit/min ~ 20kg/min. That's ridiculously less as compared to 275kg/min at max thrust. It should be of the order of 100+kg/min and then the combat radius would be <1450/2.5 ~ 580 km. Now that looks more realistic.

There is easy way of sanity check. The M2K data is given along with F-16 and F-18. It should be relatively easy to get numbers for those two birds and then we can match up it with this dataset. Can someone please throw in some realistic numbers for F-16??

EDIT: Checked sfc values of M53 from wikipedia. And that gives us:
64 kN (14,300 lbf) military thrust
95 kN (21,384 lbf) with afterburner
Overall pressure ratio: 9.8:1
Bypass ratio: 0.36:1
Specific fuel consumption:
0.90(kg/daN.h) Dry engine thrust >>> 96kg/min (my guess of 100kg/min is sensible then)
2.10(kg/daN.h) military thrust >>> 332kg/min

I think i did at least two mistakes here. First, I should have done

That gives fuel consumption rate of ~5200/205 ~ 25lit/min ~ 20kg/min. That's ridiculously less as compared to 275kg/min at max thrust. It should be of the order of 100+kg/min and then the combat radius would be ~290km. (combat range<2885/5 ~ 580 km).

Thats 290 number should have told me there was a mistake in assumption of 100kg/min.

But I realised it from above calculations by Sankum.

I considered cruise thrust of 100% of dry thrust whereas it should be only 30-40% of it. With 40% of dry thrust the Combat Cruise Range for above configuration would be around ~ 2885/2 ~ 1450km and thus Combat Radius of ~1450/2 ~ 725 km. Considering that the drag will be reducing as the plane's weight goes down, the required thrust will also go down and so is the fuel consumption, the Combat radius could ~800km. Still a far cry from 1444km given by Dassualt.

Gyan · Post by **Gyan** » 23 Apr 2015 17:41

Lot of details are available about Operation Opera of Israel. I wonder whether it would be possible to plug in these empirical details in the alogarithms to test the charts?

http://forum.keypublishing.com/archive/ ... 35637.html

sankum · Post by **sankum** » 23 Apr 2015 21:38

Thanks gyan, good data of a practical mission.

The optimum low-level cruise speed was 360 knots/667 km/h, but decreased to ~340 knots/635 km/h, when the F-16s become lighter.
"Charlie" was the code, when the 38 th longitude was passed, intercepted by an Boeing-707 flying over Mitspe Ramon as relay. The mission was monitored by IAF HQ.
Fuel burn 2270 kg/h. 370 gal wing fuel tanks jettisoned near Sakakah AF to the north.
Al Jouf vortac navigational aid was tuned in. (11 o'clock) Fuel burn drops to 2043 kh/h.
From Bahr al Milh Lake the reducing weight was used to pic up speed to 390 knots/722 km/h. 1725 local-time (1625 Israel-time) TOT 1735 local-time. Small city to the south
Al Mardh and to the north Ar Rahhaliyah. (INS update). 480 knots/890 km/h for attack and pop-up to ~5500 feet.

The overall distance was around 1134 nm or 2100 km. Flight time ~ 3 h and 8 min, which gives an average of 362 knots or 670 km/h.

I used to do mathematical numerical analysis with primitive aerodynamic knowledge 25 years back when I was a electronic engineering student with no computer and I have moved on and can,t tax my brain with limited knowledge.

I am sure experts can analyze the above.

My 2 bits LCA mk1 with full fuel load can do a above similar mission up to 700 Km radius and flying high at 40000Ft where air density is 4 times lighter the range will double minimum to 1400 Km combat radius as velocity will double though several factors come in play and I may be wrong and my apologies for it but it is logical.

Sanjay · Post by **Sanjay** » 24 Apr 2015 02:09

Just to ask a straightforward question, is the new analysis pointing to a Tejas Mk.1 that is inferior to its potential rival the JF-17 in STR and ITR by such a margin that it is at a severe disadvantage in WVR A2A combat ?

The technical debate is one which I can only look on in admiration as to the quality of the contributions.

ramana · Post by **ramana** » 24 Apr 2015 02:11

+Sankum.

Vivek, Is the issue the weight gain for the aero profile of LCA?

Its not credible that the performance is lacking when they had the Mirage 2K for so many years.
Only thing I can surmise is the weight is the issue.

Suppose for kicks you reduce the weight of the LCA and keep the aero profile what does your solver say?

Shalav · Post by **Shalav** » 24 Apr 2015 05:24

nileshjr wrote:... I considered cruise thrust of 100% of dry thrust whereas it should be only 30-40% of it. With 40% of dry thrust the Combat Cruise Range for above configuration would be around ~ 2885/2 ~ 1450km and thus Combat Radius of ~1450/2 ~ 725 km. ...

TIFWIW - IIRC; rough rule of thumb for throttle positions-

idle - 20-30% of full throttle
climb - 90-100% of full throttle
cruise - 60-80% of full throttle. (depends on altitude too)

Thrust is by and large, linear with above throttle positions.

I have a pooch - I am assuming the variables for STD atmosphere are changing appropriately based on altitude in these calculations?

Sanjay,

WRT ITR the LCA has a lower wing loading than the FC1. In calculations AND practical real-world conditions, a lower wing loading means a lower V(corner), which means faster ITR.

V(corner) = corner velocity = the lowest velocity at which the airframe can achieve the highest bank angle (which means tighter turn)

WRT SRT - IIRC and generally speaking Sustained Turn Rate is greatest at C(Lmax) of the airframe. All airframes have different C(Lmax), and these vary with air density and pressure which in-turn change with altitude and temperature along with velocity. Most brochure STR are quoted at the C(Lmax) of the airframe at its most advantageous altitude, velocity, pressure and air density . So the C(Lmax) for airframe A may be best at 2,000m and that of airframe B at 2,500 m. In combat it is up to the individual pilot to make the merge happen at the velocity and altitude most advantageous to them.

C(Lmax) = maximum co-efficient of lift