Combat Aircraft technology and Evolution

Kunal Biswas

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Re: ADA LCA Tejas - IV



This is best for you level ..

It is better you keep off bumping upon the unknown ..

Yes, Tejas is a great tribute to the planes of the sixties like Mirage III or Mig-21. It is the aviation equivalent of Mini or Fiat 500. Great thinking from Indians to use nostalgy also in military aviation, not only
In consumer markets.
 

jouni

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Re: ADA LCA Tejas - IV



This is best for you level ..

It is better you keep off bumping upon the unknown ..
Those are common sight here in Europe, cant take the snowy weather...

[video]http://m.youtube.com/watch?v=9ltjyLL21mg[/video]
 

cobra commando

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Raytheon Tests AESA Radar System For F-18 Hornet Jets

Raytheon flight tested its APG- 79(V)X AESA radar system needed for F/A-18C/D Hornet jets, demonstrating extended detection ranges, simultaneous air-to-air and air-to-ground capabilities as well as production of high- resolution synthetic aperture radar (SAR) mapping. "We put our latest AESA radar capability to the test and it exceeded our expectations," said Mike "Ponch" Garcia, business development director of Tactical Airborne Systems for Raytheon's Space and Airborne Systems business, and a former F/A-18E/F Super Hornet pilot/instructor. The APG-79 system combines Raytheon's APG-63(V)3 and APG- 82(V)1 radars and also flies on the F/A-18E/F Super Hornet and EA-18G Growler jets, it added. The company has delivered more than 500 tactical AESA tactical radars from its portfolio. The portfolio includes APG-79, APG- 63(V)3 and APG-82(V)1 for F-15, F/A-18E/F, EA-18G and B-2 aircraft. The APG-79 system, a US Navy program of record, flies globally on F/A-18E/F Super Hornets and EA-18G Growlers.
Raytheon Tests AESA Radar System For F-18 Hornet Jets
 

cobra commando

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Catalyst: Aircraft Electromagnetic Interference – In extreme cases, bombs and other weapons could be unintentionally discharged due to electromagnetic interference.
Military aircraft are increasingly exposed to electromagnetic interference, whether the source is natural, like lightning strikes, or human produced, like radars. In a worst-case scenario this could result in weapons being unintentionally released. Dr Graham Phillips investigates the tests conducted to help determine the susceptibility of military aircraft to AEI.

Defending Fighter Jets From Electro-Magnetic Interference

https://m.youtube.com/watch?v=zakCbwDi0ZY
 

Victor3

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Explosive munition can be put on a gun on a aircrafts for defending against missiles? Point is that the pieces of steel eliberate by explosive munition can cover a aproximate direction in which the missile go. And can cover a lot of space by its 360 explosion
 

Victor3

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What about a dedicated missile hunter aircraft? Whit air to air intercept missiles and guns. What about subsonic aircrafts followed by helicopters?
 

Victor3

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The missile hunter would be bigger, would have poor manevraubility, would have a very big engine whit a lot of thrust and big guns and missiles. Enough to have speed and carrying weapons. If not a dedicated jet plane....
 

ersakthivel

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LREX is there to provide vortex generation not to give cranked arrow shape.

canard is also there to provide the same vortex generation job,

the lesser swept wing leading edge of tejas is also there to do the same vortex generation job.

ADA has put out a reasearch paper on the net on how that lower swept wing leading edge generates vortex at an AOA of 18 deg itself.

It is there in many forums as well.

F-16 Xl was a program whose aim was to use as much parts commonality with F-16 while getting a cranked arrow wing with low wing loading and much better RSS design.it was an evolution of f-16 design.

tejas was a clean slate design.And it is much smaller and weighs way lower. SO needs of both are very different.

Even though mirage-2000 was beaten by mig-29 in DACTs squarely in STR(very low TWR compared to Mig-29),

It was a neck and neck in ITR (mig-29 has way higher TWR and way higher loading wing, mirage2000 low on wing loading low TWR, still the difference was not as pronounced in ITR!!!)

reason mirage-2000 has only small strakes for vortex generation(which reattaches air flow in high AOA , in deltas),

It was for this flow energizing vortex generation purpose canards, and lower swept leading edge were incorporated into deltas.

if you see further the wing structure of tejas is even more complex. Near the wing root and lower swept edge , wing surface starts at a height, Then it slopes down and then flattens.

the only reason for such a complex shape should be strengthening vortex generation at high alpha.

There were many research papers put out by ADA which illustrated this vortex generation property of tejas's complex compound or cranked delta wing.

SO tejas used the vortex generation effect of f-16 XL, it did not copy it cm by cm.

Also the reason for much lower wing loading on tejas may have some thing to do with its capability to take off with meaningful loads from high altitude himalayan airfields of the future.

these aspects are often overlooked.

Also long LREX s were used in high wing loading Mig-29s exactly for the same vortex generation purposes.But these high wing loading fighters are not RSS.

SO when it comes to low wing loading RSS deltas , a lesser swept wing leading edge is the obvious choice as it has been done in PAKFA or tejas, because the wings start very much near the frontal fuselage and there is no space for providing long LREX , like the one provided in Mig-29 or other high wing loading fighters.

SO high TWR canards deltas like typhoon, rafales and compound deltas like F-22 get a higher STR , much closer to mig-29 without the use of cranked arrow wing as well, .Why? canards also do the vortex gen job.

So it is not a prerequisite to have a cranked arrow high wing loading wing to get high ITR and high STR.
 

ersakthivel

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What you call elementary physics seems all Greek and Latin to you. In my response to Professor's article I had written the formula for calculating the Rate of turn and Radius of Turn which I reproduce here also.

Rate of turn T (*/sec)= 1091*tanbank/v

Radius of turn R (ft)=v^2/ 11.26 tanbank

Can you please show me where in these equations you find TWR or wing loading as a component.

Low wing loading does not result in good ITR/STR. had that been the case, gliders wud have been the best fighters in the world.

If you read these equations properly, you will find the mention of velocity and bank angle. The velocity in this case is the stall speed. F-22, Rafale and Typhoon have wings which have much lesser sweep compared to LCA. F-22 has just 42* and that gives it a very high CLmax plus it uses AMF and has negative stability unlike the RSS of LCA. So its tail plane also adds to wing lift.

LCA has a large wing, tailless design with very high sweep outwards of 62.5* which gives it extremely high stall AOA & poor CLmax and a very high power off stall speed. This is the main reason for it not having as good ITR/STR as the ac I mentioned.

Now another question for you.

How do you calculate ITR & STR and what all factors play a part in calculating them?
does the v in the equation has any thing to with engine thrust or not?

Is the value of v going to be affected by a factor called engine thrust / fighter weight or not?

Whether things like G on set rate and roll rate has any effect in close combat or not?

Does stall speed has any relations with wing area and TWR or not?

DOes wing area and thrust has anything to do with bank angle or not?

Please tell me what is the difference between neagative stability and Relaxed static stability?

just tabulate the wing loading of a combo of positive stability fighters and RSS or negative stability fighters.

Why RSS or negative stability fighters always have lower wing loading?


DO these things remotely have any association with wing area or thrust?

I am ready to learn.

If low wing loading wings have no effect on ITR,

Then why the difference between mirage-2000 and mig-29 vastly great in STR and very small in ITR?

Typhoon has a lesser swept wing. But it has canards for vortex generation and way higher TWR than tejas.
 

ersakthivel

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V in the equation is the corner velocity is affected by TWR and the STR is further affected by max G-load which pilot can sustain. The very high TWR of F-22 can give it much higher sustained G load but it gets restricted to just 6G due to pilot limitation. In the lift equation L=CL x 1/2 x density x wing area x V^2, the only factors which a pilot can vary is V & CL by way of AOA or high lift devices.

weight affects the stall speed but not the CL as CL is dependent on AOA only.

So if you want a high turn rate, you need to have a low speed, high Lift and ability to sustain that speed. as the AOA increases, the drag also increases. if you study the energy diagram/graph of any fighter you will find that their ITR is calculated for the lowest speed which allows structural G load to be reached and the STR is calculated for speeds where the thrust and Drag are equal.

The rate of onset of G and roll rate is a factor in dogfight but they too have limitations imposed by the human body. Very high rate of onset of G can result in G-LOC to the pilot. It is for this reason that most RSS and unstable platforms have a controlled rate of G onset.

As already explained, theoretically wing area is a factor but for ITR,STR & min radius turn you need low speeds and in that case its the CL max which is the determining factor.

It is for this reason that Mig-29, Su-27, SU-30MKI, SU-35 have much higher ITR and STR compared to anyother fighter in the world except F-22 and they all have sweepback of 42* and an effectively cranked arrow wing form.

LCA has tried to overcome its low CLmax by increasing the wing area which created more problems for it.

ITR is dependent more on ability to pull high G load for short duration than anything else.

M2K cud pull nearly same ITR as Mig-29 because the total lift of an aircraft Ltotal= Lwing + Lthrust. As the AOA increases, a part of thrust gets added to the total lift. In M2K, due to 58* sweep, it has very high stall AOA and when it pulls to its stall AOA, a large amount of thrust is added as lift. For a 30* AOA, up to 50% thrust forms the lift component.

So M2K is able to to turn at lower speeds for 9G turns. This is the reason for it to be able to match Mig-29. The downside is that at Higher AOA the thrust component available to over come drag also reduces which results in very poor STR.

Banked turn - Wikipedia, the free encyclopedia

When a fixed-wing aircraft is making a turn (changing its direction) the aircraft must roll to a banked position so that its wings are angled towards the desired direction of the turn. When the turn has been completed the aircraft must roll back to the wings-level position in order to resume straight flight.[4]

When any moving vehicle is making a turn, it is necessary for the forces acting on the vehicle to add up to a net inward force, to cause centripetal acceleration. In the case of an aircraft making a turn, the force causing centripetal acceleration is the horizontal component of the lift acting on the aircraft.

What this effectively means is the acceleration of any fighter in a sustained turn depends upon the "horizontal component of lift acting on the fighter".

In straight, level flight, the lift acting on the aircraft acts vertically upwards to counteract the weight of the aircraft which acts downwards. During a balanced turn where the angle of bank is θ the lift acts at an angle θ away from the vertical.

It is useful to resolve the lift into a vertical component and a horizontal component.

If the aircraft is to continue in level flight (i.e. at constant altitude), the vertical component must continue to equal the weight of the aircraft and so the pilot must pull back on the stick a little more. The total (now angled) lift is greater than the weight of the aircraft so the vertical component can equal the weight.

The horizontal component is unbalanced, and is thus the net force causing the aircraft to accelerate inward and execute the turn.

Because centripetal acceleration is:

A=v^2/R

Newton's second law in the horizontal direction can be expressed mathematically as:

L Sin θ=M*V^2/R
This formula clearly shows that fighters with higher lift(lower wing loading ) can achieve a quicker sustained turn with lesser bank angles.

Also it clearly shows that for the same speed fighters with higher lift (low wing loading) can have a smaller radius of turn.

What is the significace of the above two point in a turning fight?
where:

L is the lift acting on the aircraft
θ is the angle of bank of the aircraft
m is the mass of the aircraft
v is the true airspeed of the aircraft
r is the radius of the turn
In straight level flight, lift is equal to the aircraft weight. In turning flight the lift exceeds the aircraft weight, and is equal to the weight of the aircraft (mg) divided by the cosine of the angle of bank:

L= Mg/cosθ

where g is the gravitational field strength.

The radius of the turn can now be calculated

R=v^2/g*Tanθ

This formula shows that the radius of turn is proportional to the square of the aircraft's true airspeed. With a higher airspeed the radius of turn is larger, and with a lower airspeed the radius is smaller.


This formula also shows that the radius of turn decreases with the angle of bank. With a higher angle of bank the radius of turn is smaller, and with a lower angle of bank the radius is greater.



SO now it is clear while lift has nothing to do with radius of turn, it is the sole thing that determines the all important " net force causing the aircraft to accelerate inward and execute the turn".

SO if you have lesser lift your horizontal component of the lift force which determines your acceleration will be lower. It means the pursuing fighter with higher wing lift(low wing loading fighter) will shoot you down with his guns , because his acceleration is faster.

By giving the equation for radius of turn alone and ignoring the which gives the all crucial centrepetal acceleration in a sustained turn, you are missing the whole point of the advantage of having a lower loaded wing.
 
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ersakthivel

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F-22 wingloading is 377.05, F-35 is 526.23, Rafale is 310.72, Typhoon is 312.5 and LCA is just 242. Why do all these ac have higher ITR and STR compared to LCA and why F-22 has the highest ITR and STR among all these even though it has highest wing loading among these?
The day you find this answer. You will stop shouting about the ITR and STR values of LCA and also stop making a fool of yourself by equating ITR and STR with wing loading only.
Just FYI, F-22 has an ITR of 35*/sec and STR of 28*/sec which is the highest among all the fighters that have flown till date or are on design boards.
F-22 has thrust vectoring and high thrust to weight ratio. So there is no surprise in having high ITR and STR.

Wing loading - Wikipedia, the free encyclopedia

Effect on turning performance

To turn, an aircraft must roll in the direction of the turn, increasing the aircraft's bank angle.

Turning flight lowers the wing's lift component against gravity and hence causes a descent. To compensate, the lift force must be increased by increasing the angle of attack by use of up elevator deflection which increases drag.

Turning can be described as 'climbing around a circle' (wing lift is diverted to turning the aircraft) so the increase in wing angle of attack creates even more drag. The tighter the turn radius attempted, the more drag induced, this requires that power (thrust) be added to overcome the drag.

The maximum rate of turn possible for a given aircraft design is limited by its wing size and available engine power: the maximum turn the aircraft can achieve and hold is its sustained turn performance.

As the bank angle increases so does the g-force applied to the aircraft, this having the effect of increasing the wing loading and also the stalling speed. This effect is also experienced during level pitching maneuvers.



So it is crystal clear now that high wing loading fighters have to have more AOA (to stop the descent) in a Sustained turn. This can be achieved only by using the up elevator which increases drag. This increased drag will lead to lower acceleration.

But fighters with low wing loading don't have to increase the AOA by that much, (to get a higher lift component to stop the descent). So they dont have to use up elevator that much, which results in lower drag and increased acceleration in turns.


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[who?] that this made the bomber more agile than contemporary jet fighters (the slightly later Hawker Hunter had a similar wing loading of 250 kg/m2) at high altitude. Whatever the truth in that, the delta winged Avro Vulcan bomber, with a wing loading of 260 kg/m2 could certainly be rolled at low altitudes.[10]

Like any body in circular motion, an aircraft that is fast and strong enough to maintain level flight at speed v in a circle of radius R accelerates towards the centre at v^2/R. That acceleration is caused by the inward horizontal component of the lift, L * sin θ , where [θ is the banking angle. Then from Newton's second law,

Mv^2/R= L *sin θ=1/2 * v^2 *P * A* Sin θ (P- atmospheric pressure)

SOlving for this R is

R= 2* Ws/ p* Cl * Sin θ
 

ersakthivel

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I will chose a wing which gives me highest lift and that may not be just low wing loading alone. To have high ITR & STR you need good TWR and a as low as possible speed. So you must have a wing which gives very high lift at lowest possible AOA and speed.

A very low wing loading like LCA with very high sweep resulting in poor CLmax, is a sure shot recipe for disaster as that will force the aircraft to have exceptionally high TWR to overcome the huge drag of its airfoil.

If we go by your logic, than Russians, Americans, French and British are fools who designed aircraft with wings which had higher wing loading compared to LCA. But their ac somehow have far superior ITR & STR.
Then how can you explain the difference between wing loading of PAKFA and SU-30

and

the difference between wing loading of F-16 and F-22?

their aircrafts have thrust vectoring and superior thrust to weight ratio, which is going to be solved in tejas mk2 which will have better TWR if not thrust vectoring.

What is the ITR , STR of these fighters in hot indian conditions?

It is prof das in his article which went into the causes of Mig-21 crases in IAf who has said that indian hot temp saps ten percent of engine thrust besides 12 percent of wing lift for any given fighter.

thats why I am asking what is the ITR and STR of foreign fighters in indian hot conditions ?

As explained in my posts if you want a wing which gives very high lift at lowest possible AOA and speed, then go for low wing loading wing like tejas.

you dont know what is the Cl max of tejas, neither do I.

rest assured ADA would have got the right sweep angles for lesser and higher swept part of the wing leading edge and would have got the right Clmax for tejas wing.
 

ersakthivel

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"Lift is dependent on many factors which I enumerated in my posts"

What are these factor?


But first you try to understand the Newtons's Second law of motion.

Then you will know why lift is the deciding factor in Sustained turn rates and low wing loading design is the best way to get a higer horizontal component of lift which gives higher acceleration in a sustained turn due to the lower AOA required(which reduces drag) and avoids the loss of altitude compared to high wing loading fighter!!!!!
 

ersakthivel

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F-16 does not have very high ITR & STR and nor do F-15 & F-18. mig-29 and Su-27 series have higher wing loading but better ITR & STR than them, You may have heard that briefing by the USAF col after red Flag 2008 regarding IAF. He agreed that Su-30MKI has far superior ITR & STR compared to any teen series fighter of USAF.

Hot conditions effect the engine performance if the tempratures are beyond the flat rating limits of the engine. within the flat rating limits temperature has no effect on thrust.

If I have to chose a wing, I will chose a wing which gives me a high CLmax, ability to increase lift by use of high lift devices which includes use of vortices and gives me a nice balance of wing loading and drag. Too big a wing which gives very low wing loading will also result in high drag and so I will need more powerful engine which may further create problems of weight and fuel.

So a good fighter ac is one which has finest balance of wing loading, CL and Drag.
Do the Migs , Su-30s , F-16s , F-15 s, gripens, rafales, typhoons and Gripens have flat rated engines?

Su-30 MKI in those exercises had thrust vectoring engine. None of the US fighters had it.

f-22 has a combo of thrust vectoring engine and high TWR so it has best ITR and STR.

you are at liberty to chose any wing.

I have already told you that the lower swept front leading edge of the tejas wing exactly does the same vortex generation job, without the usual penalties involved in the canards design like, force coupling, high weight penalty and forcing the wing to stall to before canards thewre by depriving the wing from reaching its peak Cl max.

Even in aeroindia 2015 tejas was flying with restricted flight envelope.

And its AOA was limited to 20 deg AOA in aeroindia 2013, Now it is crossing 26 deg.

SO we will see what comes out after FOC.
 

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