LCA News and Discussions

SaiK · Post by **SaiK** » 25 Jul 2013 19:15

exactly red mull.. i want to blame the 404 for that.(but fadec and controls and the parts may be indian/or may be not) .. and we can't say that for sure cause it is not our engine. may be we can handle this issue well with 414.

viv, which twist?

Indranil · Post by **Indranil** » 25 Jul 2013 22:34

vic wrote:Does the wing twist on LCA adds to drag?

Answer: No. It reduces it. The twist is just a way to join the trailing edge of the wing to the leading edge of the tailplane. In this way, you take away the front section of the tailplane.

Explanation: I understand the dilemma you have there. From the front, it looks like it provides a larger cross-sectional area to oncoming air. This is true. But imagine level flight. You need to create lift equivalent to the weight of the aircraft. As long as you can produce laminar flow, the major form of drag at subsonic speed is induced drag where the only variable would be lift-to-drag ratio. The lift-to-drag ratio of LCA's wing is comparable to almost all other supersonic wings for fighters out there. You may ask how (Since a part of the wing is flying at a higher AoA, you can choose a much thinner aerofoil). And by removing the cross-sectional area of the trailing edge, the overall drag of the plane is actually reduced.

vic · Post by **vic** » 26 Jul 2013 20:49

Thanx for the answer

Raman · Post by **Raman** » 27 Jul 2013 07:04

vic wrote:A Question to Gurus:-
Does the wing twist on LCA adds to drag?

As with all things aero, the answer is: it depends.

(I assume you are talking about span-wise wing twist (either geometric or aerodynamic) and not the reflex camber of the wing, which is something else altogether.)

The twist can potentially increase profile drag due to increased cross-sectional area, but it can reduce induced drag. The two main ideas for wing twist are:
- Different airfoil sections of the wing operate at different angles-of-attack, so the whole wing doesn't stall all at once - it is a more degraded effect
- Tailor the span-wise distribution of lift; the more elliptical the distribution, the lower the induced drag. The wing twist helps in reducing this.

Indranil · Post by **Indranil** » 27 Jul 2013 08:14

Raman sahab,

Just checking with you. I completely agree with you on the washout. My description of the effect of reflex camber on induced drag is not wrong, is it?

SaiK · Post by **SaiK** » 27 Jul 2013 22:02

in the sense how to make the airfoil as dynamic it can be? wouldn't more multiple flaps helps rather a single large one (provided it can be controlled - well studied wing dynamics)?

Indranil · Post by **Indranil** » 28 Jul 2013 09:55

SaiK wrote:in the sense how to make the airfoil as dynamic it can be?

For what?

Raman · Post by **Raman** » 29 Jul 2013 08:13

indranilroy wrote:Raman sahab,

Just checking with you. I completely agree with you on the washout. My description of the effect of reflex camber on induced drag is not wrong, is it?

Surely you know that I don't deserve 'sahab'!

As for your explanation, honestly, I didn't quite follow your post. The reflex camber is provided so that tail-less airplanes get some "assistance" from the airfoil for trimming the airplane to level flight. As such, you can think that it reduces trim drag vs solely relying on flaperons for trim. However, since their function is to provide a moment to trim the airplane by providing a "lifting force" (in the downward direction) at the trailing edge, I'd imagine that there will be a penalty to be paid in terms of induced drag.

Lalmohan · Post by **Lalmohan** » 29 Jul 2013 11:50

SaiK wrote:in the sense how to make the airfoil as dynamic it can be? wouldn't more multiple flaps helps rather a single large one (provided it can be controlled - well studied wing dynamics)?

it depends!

trade-off between ability to achieve a more tailored wing section to your needs versus mechanical complexity of creating said shape (and weight penalties)

large aircraft often have multi-stage flaps, small aircraft not so often

RKumar · Post by **RKumar** » 29 Jul 2013 18:52

Did anyone notice that LCA flight data updates are purged? Cutoff date is 30-Mar-2011. Wonder why??

SaiK · Post by **SaiK** » 29 Jul 2013 18:56

someone is manupulating records?

red mull, i agree.. wonder what is the weight gain for each additional control system slat/moveable surface wise - assume for both electric and hydraulic.

Lalmohan · Post by **Lalmohan** » 29 Jul 2013 19:58

there is also the strength of the control surface itself - and its ability to fold into the wing and maintain the right shape

SaiK · Post by **SaiK** » 29 Jul 2013 20:17

assume a single torque beam/geared and controlled separately to be interfaced with the control surface.. devicing that should not be a problem.. the only multiplicity are the embedded systems that cater to each slat that has to respond differently. i'm not considering strengthening a big issue(weight wise).

Lalmohan · Post by **Lalmohan** » 29 Jul 2013 20:24

no, multi-stage flaps follow a specific pattern - they do not go at random in different directions. they are used to make 'a flat wing curvier' so that its lift/drag curve is altered (from high speed low drag to low speed and as low a drag as possible) - if you look inside a wing (next time you are flying on a commercial liner) you'll see them follow a track and arrange in a particular order - it is quite predictable. you'll also see some airbrakes further ahead that can be put up after landing. you might see slats (at the leading edge) that come forward. i am not aware of any aircraft having multi-stage slats (but am willing to be corrected). in fact on the newer aircraft, once it has touched down and is slowing and the wing is 'all opened up' - you'll be astonished at how slender the wing really is and how much of it has been moved to make the flaps and slats and brakes work. the structure of the wing is something truly marvellous - making wing design (both aero and structural) one of the hardest things to do in engineering

SaiK · Post by **SaiK** » 29 Jul 2013 20:42

just throwing up the idea.. i may not be wrong on the possibilities, but may be on the efficient design. but, i have no idea which performs better.

the challenges are always tougher, as we get tough.. LCA as a platform should be experimented with all kinds of new designs. /jmt

Lalmohan · Post by **Lalmohan** » 29 Jul 2013 21:34

well - to be clear, you don't want multi-stage flaps all going in different directions - they must form a smooth curved shape - so sending them along a guide rail (adjustable) is the most efficient way

SaiK · Post by **SaiK** » 29 Jul 2013 21:40

would not that applies to say even controls on couple of flaps.. the directions should be controllable, else what is the point? yes on the other points.. i think such designs can go where no eagle has gone before.

Lalmohan · Post by **Lalmohan** » 29 Jul 2013 21:42

the directions are indeed controllable, but they move in concert - together - all in the same direction to form a new smooth shape - otherwise you create an excellent air brake and lift dumper and fall out of the sky faster than you can shout "musharraff!!"

and flaps and slats only ever move downwards (and retract back into their place) - they don't go against the camber of the wing

SaiK · Post by **SaiK** » 29 Jul 2013 21:49

but then, the very aspect of differential air movement and drag adjustment is what we want to have that finer controls right? why should all be in the same direction. we need to have a wind tunnel study for this.

Indranil · Post by **Indranil** » 30 Jul 2013 03:08

Raman wrote: As for your explanation, honestly, I didn't quite follow your post. The reflex camber is provided so that tail-less airplanes get some "assistance" from the airfoil for trimming the airplane to level flight. As such, you can think that it reduces trim drag vs solely relying on flaperons for trim. However, since their function is to provide a moment to trim the airplane by providing a "lifting force" (in the downward direction) at the trailing edge, I'd imagine that there will be a penalty to be paid in terms of induced drag.

I read my explanation myself. I made mistakes which I should and would correct in this post.

I agree that LCA would have to pay the trim drag penalties of a tailless config. But, it does not look like LCA's reflex camber is used for the typical usage of low moment. It is too huge for that alone. Other than the F-16XL, I haven't seen any plane with such a huge reflex camber.

The guys at ADA seemed to have fixed 2 things:
1. Air intakes by the side of the fuselage. Once this decision is made, it was desirable to have the the leading edge of wings above the and in front of the intakes to assist airflow into the air intakes at higher AoA.
2. They later on decided on having a tailless configuration to keep the plane light and simple. (ADA did study a configuration with a close coupled canard and a compound delta wing besides a conventional layout)

Part of the reason for the second choice was by having a large tailless delta, the wing loading went down. By increasing the wet area, the skin friction drag is increased, but the wave interference and trim components of drag are lower. For the F-16XL, the “clean airplane” drag is slightly lower during level flight, and forty percent lower when bombs and missiles are added (though a lot of this is related to the semi-conformal mounting of the hardpoints and making them being staggered from inboard to outboard, lowering the interference drag). Apparently, F-16 XL's wing gives it 25% greater lift to drag in supersonic flight and 11% greater lift to drag in subsonic flight (I don't know how much of this can be attributed to the active suction glove).

I made a mistake in the previous explanation. I said, this arrangement removes the cross sectional area of the horizontal stabilizer, which helps in reducing ~~induced drag~~ wave drag.

I have learnt to learn. I will only be happy to be corrected.

Indranil · Post by **Indranil** » 30 Jul 2013 04:29

SaiK wrote:but then, the very aspect of differential air movement and drag adjustment is what we want to have that finer controls right? why should all be in the same direction. we need to have a wind tunnel study for this.

Saik sahab,

I could not follow all that you wrote.

It is fairly simple. The inboard surfaces on LCA's trailing edge are mainly for pitch control, while the out board surfaces take care of roll control. However, due to the FBW control system, when performance requires it, all four surfaces can act in either pitch or roll. Each of these control surfaces can be moved at different angles but in fixed step intervals. The intervals are chosen carefully and provide the required granularity required.

I see no use of having many control surfaces. In fact you might end up with ineffective ones if you cut them too narrow in span or length.

Manish_Sharma · Post by **Manish_Sharma** » 30 Jul 2013 04:46

Is IOC-2 going to make LCA equal to all things that Bison does?

Like switching on its radar and fire a bvr missile?

Or

We have to wait for LCA's FOC that it starts doing all the things done by bison?

srai · Post by **srai** » 30 Jul 2013 09:57

^^^
Here it is in short:

LCA Mk.1 IOC 1/2 -> +8g, AoA 26 degrees, M1.6, spin recovery, wake penetration, LGB, dumb bombs, WVR-AAM, drop tanks, ECCM

LCA Mk.1 FOC -> full flight envelope, BVR AAM w/ MMR, Guns, Rockets, plus @squadron level - support infrastructure w/ parts inventory, qualified pilots, technicians, syllabus

LCA Mk.2 -> primarily focused on flight performance improvements through higher TW ratio and slight airframe design refinements; AAR

vishvak · Post by **vishvak** » 30 Jul 2013 10:08

Thank you, sraiji.

Lalmohan · Post by **Lalmohan** » 30 Jul 2013 12:44

SaiK wrote:but then, the very aspect of differential air movement and drag adjustment is what we want to have that finer controls right? why should all be in the same direction. we need to have a wind tunnel study for this.

wind tunnell studies have been going on for the last 75 years - on exactly this

Manish_Sharma · Post by **Manish_Sharma** » 30 Jul 2013 13:30

Many thanks Srai ji !

JayS · Post by **JayS** » 30 Jul 2013 16:59

New ADA site (I liked it, much better than last one) flashes this in Latest News:

1. Tejas detachment operated successfully during the month of July 2013.

What does this refer to exactly??

rajanb · Post by **rajanb** » 30 Jul 2013 17:38

nileshjr wrote:New ADA site (I liked it, much better than last one) flashes this in Latest News:

1. Tejas detachment operated successfully during the month of July 2013.

What does this refer to exactly??

I think this has reference to point 3. in the same list:

3. Emergency jettison of all stores tested during detachment at Jamnagar.

Regards

merlin · Post by **merlin** » 30 Jul 2013 17:46

srai wrote:^^^
Here it is in short:

LCA Mk.1 IOC 1/2 -> +8g, AoA 26 degrees, M1.6, spin recovery, wake penetration, LGB, dumb bombs, WVR-AAM, drop tanks, ECCM

LCA Mk.1 FOC -> full flight envelope, BVR AAM w/ MMR, Guns, Rockets, plus @squadron level - support infrastructure w/ parts inventory, qualified pilots, technicians, syllabus

LCA Mk.2 -> primarily focused on flight performance improvements through higher TW ratio and slight airframe design refinements; AAR

LCA Mk.1 IOC-2 will not have AoA 26 degrees. Neither will it have spin recovery. ECCM looks doubtful too (judging by lack of reports on PV-3 testing).

JayS · Post by **JayS** » 30 Jul 2013 17:51

indranilroy wrote: I read my explanation myself. I made mistakes which I should and would correct in this post.

I agree that LCA would have to pay the trim drag penalties of a tailless config. But, it does not look like LCA's reflex camber is used for the typical usage of low moment. It is too huge for that alone. Other than the F-16XL, I haven't seen any plane with such a huge reflex camber.

The guys at ADA seemed to have fixed 2 things:
1. Air intakes by the side of the fuselage. Once this decision is made, it was desirable to have the the leading edge of wings above the and in front of the intakes to assist airflow into the air intakes at higher AoA.
2. They later on decided on having a tailless configuration to keep the plane light and simple. (ADA did study a configuration with a close coupled canard and a compound delta wing besides a conventional layout)

Part of the reason for the second choice was by having a large tailless delta, the wing loading went down. By increasing the wet area, the skin friction drag is increased, but the wave interference and trim components of drag are lower. For the F-16XL, the “clean airplane” drag is slightly lower during level flight, and forty percent lower when bombs and missiles are added (though a lot of this is related to the semi-conformal mounting of the hardpoints and making them being staggered from inboard to outboard, lowering the interference drag). Apparently, F-16 XL's wing gives it 25% greater lift to drag in supersonic flight and 11% greater lift to drag in subsonic flight (I don't know how much of this can be attributed to the active suction glove).

I made a mistake in the previous explanation. I said, this arrangement removes the cross sectional area of the horizontal stabilizer, which helps in reducing ~~induced drag~~ wave drag.

I have learnt to learn. I will only be happy to be corrected.

I never noticed that LCA and F16XL has reflexed camber. Are you sure??

The figure you mentioned are w.r.t. original F-16 config. The major difference came simply due to complete new wing design. Regarding the effect of suction glove, @M=2 it would not be that significant as compared to F16XL without suction glove, would it?? Skin drag is as it is a small component of total drag at that speed.

Indranil · Post by **Indranil** » 30 Jul 2013 20:14

nileshjr wrote:
I never noticed that LCA and F16XL has reflexed camber. Are you sure??

The figure you mentioned are w.r.t. original F-16 config. The major difference came simply due to complete new wing design. Regarding the effect of suction glove, @M=2 it would not be that significant as compared to F16XL without suction glove, would it?? Skin drag is as it is a small component of total drag at that speed.

F-16XL had a reflex camber the back of the wing sloped up at 3 degrees.

Of course the changes were due to a new wing design. The question is what in the wing design changed so drastically?
1. The low wing loading along with the suction glove allowed for better laminar flow reducing drag. So having a wing which morphs into the tail plane gives you a large wet area giving you a good L-D ratio. Both LCA and F-16XL also had a large washout for optimized induced drag.
2. The way the payload was carried, semi confirmal pylons in staggered fashion both reduced form drag and interference drag.

Philip · Post by **Philip** » 30 Jul 2013 22:15

Don't these two configurations go back to the Draaken and Viggen experience?

Indranil · Post by **Indranil** » 30 Jul 2013 22:33

In what way?

JayS · Post by **JayS** » 31 Jul 2013 11:22

indranilroy wrote:
nileshjr wrote:
I never noticed that LCA and F16XL has reflexed camber. Are you sure??

The figure you mentioned are w.r.t. original F-16 config. The major difference came simply due to complete new wing design. Regarding the effect of suction glove, @M=2 it would not be that significant as compared to F16XL without suction glove, would it?? Skin drag is as it is a small component of total drag at that speed.
F-16XL had a reflex camber the back of the wing sloped up at 3 degrees.

Of course the changes were due to a new wing design. The question is what in the wing design changed so drastically?
1. The low wing loading along with the suction glove allowed for better laminar flow reducing drag. So having a wing which morphs into the tail plane gives you a large wet area giving you a good L-D ratio. Both LCA and F-16XL also had a large washout for optimized induced drag.
2. The way the payload was carried, semi confirmal pylons in staggered fashion both reduced form drag and interference drag.

IIRC the 3deg you are talking about is the canting of tail section so that it wont hit the ground while taking off/landing. Tha was because the fuselage was lengthened. Pick up any report on F-16XL you will find this. One ready Ref: http://www.f-16.net/f-16_versions_article1.html

I have casually read a bunch of F-16XL reports, and never found any mention of reflexed camber, thats why asked. It may have it, but atleast I haven't seen a reference so far.

About LCA also, I never before heard/read about reflexed camber being used. Thats why was asking about it.

And what i meant is the wing shape itself gives most of the achieved improvement in L/D without suction glove. I will try to find out exact data on this.

Philip · Post by **Philip** » 31 Jul 2013 19:26

The cranked delta wing planform.Quote from Wik.

In another variant known variously as compound delta, double delta or cranked arrow, the inner part of the wing has a very high sweepback, while the outer part has less sweepback, to create the high-lift vortex in a more controlled fashion, reduce the drag and thereby allow for landing the delta at acceptably slow speed. This design can be seen on the Saab Draken fighter, the prototype F-16XL "Cranked Arrow" and in the High Speed Civil Transport study. The ogee delta (or ogival delta) used on the Anglo-French Concorde Mach 2 airliner is similar, but with a smooth 'ogee' curve joining the two parts rather than an angle.

Here is a feature on the bird and its revolutionary wing.
http://fly.historicwings.com/2012/10/ri ... he-draken/

Today in aviation history, on October 25, 1955, marks the first flight of the SAAB J 35 Draken, a revolutionary fighter interceptor that established the Swedish military aviation industry as a global competitor with the United States, Russia, France, and England. This achievement is all the more remarkable given that Sweden’s entire population is less than that of New York City and its suburbs. Moreover, Sweden, a neutral power like Switzerland (though heavily leaning to the West during the Cold War), pioneered a number of innovations that were beyond anything the others had yet achieved though, on first glance, those innovations are not readily apparent. So just what had the Swedes accomplished that was so special?

Early SAAB J 35A in testing. Photo Credit: SAAB

Key Design Features

The SAAB J 35 Draken was originally conceived as a replacement for the Swedish Air Force’s venerable J 29 Tunnan, an aircraft that was the equivalent of the F-86 Sabre and MiG-15 in its capabilities, range, performance and load. The Tunnan looked every bit like a fat barrel with sweptback wings bolted on, yet those looks belied the extraordinary maneuverability of the little plane — as one pilot joked, “On the ground, it is an ugly duck, but once aloft, it is a swift” (referring to the beautiful flight of the swift, a type of bird common in Europe and noted for its speed and agility). Yet where the Tunnan had been ugly and fat, the Draken was anything but — it was a needle-nosed aerodynamic masterpiece.

SAAB 29 Tunnan (J 29) “Gul Rudolf” in flight at the Swedish Armed Forces’ Airshow 2010. Photo Credit: Gnolam

The chief innovation was its unique double-delta wing. The plane’s fuselage was a predictable tube with the engine mounted inside and the cockpit at the front and a vertical stabilizer attached to the tail. The pointed nose cone contained a radar system and the air intakes for the engine were on either side of the cockpit at the forward point of the wing root. The double-delta began at the air intakes — for roughly two thirds of way toward the tips, the sweep back measured an incredibly sharp 80 degrees. This allowed the plane to achieve design speeds that were in excess of Mach 2.0. However, with such a sharp sweep, it was recognized that the plane would be seriously lacking in maneuverability. Thus, the last one third of the wings toward the tips carried a completely different sweep angle, much shallower at 60 degrees. This brought excellent maneuverability and enhanced control at low speeds.

First Flight of the Prototypes

On October 25, 1955, the first prototype aircraft took off for initial tests. The performance of the double-delta had been aerodynamically predicted and even proven in a small scale flying mock-up, the SAAB 210 “Lilldraken”. Once those tests were successful in 1952, Saab proceeded with the full-scale prototypes. Exactly as predicted, the J 35 Draken proved to be fast and agile once aloft. In fact, the second prototype, which was fitted with an afterburner, accidentally broke the sound barrier on its very first flight — while in the initial climb out!

One of the most famous photos of the J 35 Draken, showing a pair of fighters aloft over Sweden, giving an excellent view of the key design features of the aircraft. Photo Credit: Flygvapnet

The plane was a dream to fly. Later variants could accelerate rapidly with afterburner to Mach 2.0 (the first model topped out at around 1,200 mph, still extraordinarily fast), making it an ideal point interceptor to combat the potential threat from incoming high altitude Soviet bombers. The plane could be started, scrambled and get to high altitudes and speeds in just a few minutes. This gave the Swedish nation the confidence that even with a close proximity of Russian and Warsaw Pact bases across the Baltic, they defend their country in war.

The J 35 Draken passed all flight testing. Quickly, it was deployed in large numbers to squadrons at various bases around Sweden. First deliveries of the J 35A models began in 1959. The first fully equipped operational squadron was F13 at Norrköping, which was joined in 1961 by F16 at Uppsala. Of all models that followed, approximately 600 were delivered to the Swedish Air Force alone. Despite its extraordinary capabilities and despite Sweden’s tradition in supporting UN peacekeeping operations, the Saab J 35 Draken was never used in war and never fired a shot (or missile) in anger, even if its predecessor, the J 29 Tunnan, had flown combat missions in the Congo as part of the UN force deployed there 50 years ago.

Overhead view of an early J 35A Draken. Photo Credit: SAAB

Other Innovations

So what were the other innovations that made the SAAB J35 Draken so extraordinary? Beyond the extraordinary maneuverability attained with the unique double-delta wing, there were three major innovations that are not apparent on first look: low maintenance; rapid refueling and rearming; and take-off and landing capabilities. These seemingly hidden features turned out to be the J 35′s key advantages.

First is the innovation of very low maintenance. Performance was a given once aloft, but most modern air forces are seriously challenged with aircraft readiness. The number of hours of maintenance required for each hour of flight time (yes, you read that right, hours of maintenance per hour of flight time) are typically very high. However, the SAAB J 35 was simple and robust, despite being a competitive platform when compared against its contemporaries. Saab had achieved what amounts to a masterwork of reliability in a highly engineered, high performance combat fighter. For the J 35 Draken, as little 15 minutes of maintenance work was required for each hour of flight — a dramatic reversal of the usual equation. This meant that the Drakens had very high availability rates. Typically, Swedish fighter squadrons kept nearly all of their aircraft ready to fly on short notice. For comparison, other aircraft of that era might have had a 50 to 60 percent availability at best. This meant that a single squadron of J 35 Drakens had the equivalent combat power of two USAF or RAF squadrons due to higher readiness.

Satellite image of the Håle-Täng Highway Strip that served J 35 Draken interceptors based at Såtenäs Airbase, 4 miles to the northwest; the strip is just 1,100 meters long; revetments are visible at each end of the strip. Photo Credit: Hitta.se

Second was the rapid refueling and rearming capabilities. This was essential to the mission requirements of the Flygvapnet, which had originally required just 10 to 15 minutes of ground time to turn the aircraft back into the air during combat. Thus, the J 35 Drakens enjoyed yet another “mission multiplier” that added to their capabilities — they could launch, climb, shoot and recover in very short times and then quickly refuel and rearm and return to the air battle. Even more impressive was that the refueling and rearming as well as all typical between mission maintenance requirements were developed so that they could be accomplished by untrained citizen-soldier reservists who would likely be called up in times of war. Essentially, whereas most Western aircraft require years of training to support, the Drakens were “out of the box” ready to go. They could be kept in service by regular conscripts who were drawn from the ranks of those required to serve just a few years as part of their basic citizenship requirement (at that time in Sweden).

Finally, the aircraft’s take off and landing capabilities were perfect for the nation’s air defense requirements. The plan was that if a war began, the Draken squadrons would disperse to multiple sites, including outlying airfields as well as many small, improvised strips that were little more than highways that had been built so as to run straight for the required lengths. These highways were widened and had reinforcement for the increased weight of the aircraft. At the ends of each of these temporary highway strips were reinforced shelters built into hillsides and forests so as to protect the planes while they were deployed or during landings to refuel and rearm between missions. The Draken could take off and land on these relatively short strips, where most other aircraft of today’s air forces could never have done that.

Final Thoughts

Few other aircraft in aviation history have achieved the unique advantages of the SAAB J 35 Draken (in its time). Whereas most modern fighter designs require significant maintenance depots, hangars, special equipment and support, the Draken enabled an entire generation of pilots in the very small Flygvapnet to provide credible, highly capable air defense for Sweden, even though it was on the front line of the Cold War. One can only wish that other aircraft manufacturers could master the engineering of Saab and build planes that had such low maintenance requirements and high availabilities — and if they could, the cost of today’s air supremacy aircraft would be a little more palatable to decision-makers.

PS:It would be most interesting to see what turn around time our current aircraft have in comparison,as well as the logistic support scenario planned for the LCA.It is a great pity that the Viggen was sabotaged by the US for the DPSA contest,because of its yanqui engine.Had we acquired that bird instead of the Jaguar,perhaps Indian combat aviation history would've been more successful,as the Swedes were very geneorous in offers of TOT.

Indranil · Post by **Indranil** » 31 Jul 2013 20:01

nileshjr wrote: IIRC the 3deg you are talking about is the canting of tail section so that it wont hit the ground while taking off/landing. Tha was because the fuselage was lengthened. Pick up any report on F-16XL you will find this. One ready Ref: http://www.f-16.net/f-16_versions_article1.html

I have casually read a bunch of F-16XL reports, and never found any mention of reflexed camber, thats why asked. It may have it, but atleast I haven't seen a reference so far.

About LCA also, I never before heard/read about reflexed camber being used. Thats why was asking about it.

And what i meant is the wing shape itself gives most of the achieved improvement in L/D without suction glove. I will try to find out exact data on this.

I think you did not get what I have been arguing. I did not say that great reflex camber gives lower LD. In my first reply to Raman sir, I started by saying that the "reflex" camber on LCA was not for just 0 moment around the AC. It is to allow morphing of the wing into the tail plane. This morphing allows many advantages and then I have described the advantages.

I know why the trailing edge of the F-16XL was curved up. But this curve will certainly not go away while in flight. What will you call such an aerofoil? In fact they were worries if it would increase drag. But nothing significant was observed due to the curve.

Indranil · Post by **Indranil** » 31 Jul 2013 22:03

Philip sir, I would not attribute the F-16XL's wing design to the Draken. SAAB was not the pioneer in the aerodynamics of compound delta wings. The aerodynamics of compound deltas were known before. The question always remains as to what is the best planform to choose for the plane you want to build. SAAB was building a plane for its requirements and the compound delta was a good choice for their development.

I really love the F-16XL. There are very few more optimized flying machines in the history of combat flying.

suryag · Post by **suryag** » 01 Aug 2013 00:21

LCA flight update from 2271->2273->2276 - no bird specific details from the website.

rajanb · Post by **rajanb** » 01 Aug 2013 12:31

suryag wrote:LCA flight update from 2271->2273->2276 - no bird specific details from the website.

I would think there is a reason for that because different birds were concentrated to test out different tasks. So the covers will come on. I would not also believe the performance characteristics in the public domain, even those given out by those who drink chai at ADA, HAL, IAF or MoD.

Sometimes, even misinformation will be circulated.
Cheers

JayS · Post by **JayS** » 01 Aug 2013 16:39

indranilroy wrote:
nileshjr wrote: IIRC the 3deg you are talking about is the canting of tail section so that it wont hit the ground while taking off/landing. Tha was because the fuselage was lengthened. Pick up any report on F-16XL you will find this. One ready Ref: http://www.f-16.net/f-16_versions_article1.html

I have casually read a bunch of F-16XL reports, and never found any mention of reflexed camber, thats why asked. It may have it, but atleast I haven't seen a reference so far.

About LCA also, I never before heard/read about reflexed camber being used. Thats why was asking about it.

And what i meant is the wing shape itself gives most of the achieved improvement in L/D without suction glove. I will try to find out exact data on this.
I think you did not get what I have been arguing. I did not say that great reflex camber gives lower LD. In my first reply to Raman sir, I started by saying that the "reflex" camber on LCA was not for just 0 moment around the AC. It is to allow morphing of the wing into the tail plane. This morphing allows many advantages and then I have described the advantages.

I know why the trailing edge of the F-16XL was curved up. But this curve will certainly not go away while in flight. What will you call such an aerofoil? In fact they were worries if it would increase drag. But nothing significant was observed due to the curve.

I didn't say trailing edge. I said tail section (of fuselage).
As I understand, the canting up of 3deg is to the tail part of fuselage (i.e. the part which contains engine) This one would create problem when the fuselage was lengthened. It should not affect the trailing edge of wing at all.

I have been trying to find any reference which says, F-16XL uses reflex camber airfoil. So far no luck. All i could find is, it uses NACA 64A003.2 airfoil for root part and NACA 64A005 for tip part. All I was asking you is, are you sure F-16XL (and LCA) has used reflex camber and you have a reference to which you can point? Just want to be sure, you know.