Combat Aircraft technology and Evolution

[gadeshi]

And MAKS videos as well:
[video]www.youtube.com/watch?v=KpLTrNoNVOM[/video]

 

[Defcon 1]

We don't know all the reasons why YF-23 was rejected. What we do know is that both YF-22 and YF-23 exceeded stealth requirements. So you can say the other qualities were deemed better on YF-22, like agility and cost of development.

Well it is generally believed that YF23 easily exceeded YF22 in both speed and stealth. If you see F22, you will find its wing design now borrow features from YF23. YF22 exceeded its counterpart in maneuverability (due to presence of TVC) and electronics. So my point was that USAF chose a fighter which was weaker in stealth and speed, and if what you said in your previous post is true, still relies on speed and stealth of the Raptor in its mission. YF23 could have done the job in a much better manner.

If you are expecting that your adversary will not have a radar lock on you and your aim is to outrun him, why go for TVC in the first place?

 

[p2prada]

Well it is generally believed that YF23 easily exceeded YF22 in both speed and stealth. If you see F22, you will find its wing design now borrow features from YF23. YF22 exceeded its counterpart in maneuverability (due to presence of TVC) and electronics. So my point was that USAF chose a fighter which was weaker in stealth and speed, and if what you said in your previous post is true, still relies on speed and stealth of the Raptor in its mission. YF23 could have done the job in a much better manner.

If you are expecting that your adversary will not have a radar lock on you and your aim is to outrun him, why go for TVC in the first place?

My point has always been the same. I used the same in the Chinook vs Mi-6 thread too and same with T-90 and Arjun. If something achieves requirements, then its other qualities are put into play.

For eg: Both YF-22 and YF-23 exceeded stealth and speed requirements. Hence it becomes moot. So other parameters come into play, one of which you mentioned, agility. Beyond that the cost of financing becomes relevant like it did with MRCA. Both EF and Rafale exceeded all requirements, hence money came into play. When it came to AH-64 and Mi-28 competition, Mi-28 could not fulfil all requirements, and fell short by 20 parameters. So, AH-64 won the tender by default and money never came into play.

In case of ATF the money factor must have pushed the deal in YF-22's favour. But this is only my opinion. There are plenty of other factors, like the kind of deals Northrop and LM had with other suppliers, or how long did either promise to complete R&D etc.

We don't know for sure why YF-22 was chosen over YF-23, but these guys follow established procedures like we did for MRCA.

YF-23 may have done a better job, but it may have come at $200 Million each instead of F-22's $150 Million each. Overall, EF may end up doing a better job in the future, after it is fully developed, but we chose Rafale, didn't we? We can't live in a "what if" world.

 

[gadeshi]

Vortex aerodynamics IRL (photos from MAKS-2013 by Marina Lystseva):
fotografersha: Почему я люблю плохую погоду

 

[Austin]

Any reason why we some times see black soot/smoke from PAK-FA engine ? Does it needs more fine tuning ?

 

[gadeshi]

Any reason why we some times see black soot/smoke from PAK-FA engine ? Does it needs more fine tuning ?

It is not only a PAK FA "feature", but the other craft (including western, yes).

It depends on several reasons from fuel chemical strucrure and flight mode to observers view angle.

 

[ersakthivel]

Re: ADA LCA Tejas - IV

A non FBW ac can be certified for FOC in about 500 flights but the biggest problem with RSS FBW ac is that every software modification has to be tested on simulator and than in actual flight which extends the number of flights and time period by many years from concept to induction. If you have a stable design, you can produce, induct and replace an ac by the time it takes to induct one RSS FBW design.

BBC News - Empty F-16 jet tested by Boeing and US Air Force

But the trade off is it is what a fly by wire fighter will do in future . it can undertake some missions even without pilots.
ADA saw the future and went for it.


BBC News - Empty F-16 jet tested by Boeing and US Air Force

Boeing has revealed that it has retrofitted retired fighter jets to turn them into drones.

It said that one of the Lockheed Martin F-16 made a first flight with an empty cockpit last week.

Two US Air Force pilots controlled the plane from the ground as it flew from a Florida base to the Gulf of Mexico.

Boeing suggested that the innovation could ultimately be used to help train pilots, providing an adversary they could practise firing on.

The jet - which had previously sat mothballed at an Arizona site for 15 years - flew at an altitude of 40,000ft (12.2km) and a speed of Mach 1.47 (1,119mph/1,800km/h).

It carried out a series of manoeuvres including a barrel roll and a "split S" - a move in which the aircraft turns upside down before making a half loop so that it flies the right-way-up in the opposite direction. This can be used in combat to evade attack.

Boeing said the unmanned F16 was followed by two chase planes to ensure it stayed in sight, and also contained equipment that would have allowed it to self-destruct if necessary.

The firm added that the flight attained 7Gs of acceleration but was capable of carrying out manoeuvres at 9Gs - something that might cause physical problems for a pilot.

"It flew great, everything worked great, [it] made a beautiful landing - probably one of the best landings I've ever seen," said Paul Cejas, the project's chief engineer.

Lt Col Ryan Inman, Commander of the US Air Force's 82nd Aerial Targets Squadron, also had praise for how the test had gone.


The jet flew over the Gulf of Mexico on the test carried out on 19 September
"It was a little different to see it without anyone in it, but it was a great flight all the way around," he said.

Boeing said that it had a total of six modified F-16s, which have been renamed QF-16s, and that the US military now planned to use some of them in live fire tests.

However, a spokesman for the Campaign to Stop Killer Robots warned of the temptation to use them in warfare.

"I'm very concerned these could be used to target people on the ground," said Prof Noel Sharkey.

"I'm particularly worried about the high speed at which they can travel because they might not be able to distinguish their targets very clearly.

"There is every reason to believe that these so-called 'targets' could become a test bed for drone warfare, moving us closer and closer to automated killing."

This is not the first time a jet has been retrofitted to fly without a pilot inside. The US Air Force has previously used adapted F4- Phantoms for target practice.

A digital Fly by wire fighter like tejas can be programmed to fly even without pilots and if the software is advanced it can take off do it's mission and land all with pilot out side the fighter safely in a base station or it it is a pre programmed mission it does not even need the external pilot.

I hate it whenever these officials come out saying they will achieve IOC or FOC in this and this time when they should have done that 10 years ago with a more basic design with analog FBW + hydraulic controls, what it should have been.

IOC/FOC dates changed from 1999/2001 to 2006/2008 and every one year after 2008 right up to 2014/20XX and even then there is ridiculous support for this aircraft.

you can keep on hating it for decades to come.

basic design with analog FBW + hydraulic controls-'"is obsolete scheme of thing that is being implemented on only one new fighter in the world. Guess what the fighter is. No prize for guessing it is the,"Junk fighter JF-17 of PAF.. IAF won't touch such a fighter even with a barge pole in these days. For a fighter force which asked the Russians to develop a specific IAF SU-30 MKI version as early as 1990, a fighter with ---basic design with analog FBW + hydraulic controls scheme of things is fit only for training for purpose".

When funding was expected in late 1980s with contracted Fly By Wire software help from US they may have projected-- IOC / FOC dates in 199/2000.

But when funding was given only in 1993 for building two TDs and complete withdrawal of US from Tejas project after Nuclear tests there is no possibility of IOC and FOC even in 2008.

But the above unmanned flight capacity was achieved by ADA in its first combat fighter program. The entire fly by wire development was fully indigenous without even an iota of external help.

According to Kota Harinarayana the control laws based on which the fly by wire software developed for Tejas was so good, When a US test pilot used in to fly a USAF F-16 , It flew better with the Tejas control laws.

http://tejas.gov.in/featured_articles/dr_kota_harinarayana/page02.html

My fascination for aviation began in 1965 when I passed out from BHU and that was the year we had a war. It was the first time that India used aircraft in a war. There was a beautiful aircraft called Gnat.


It was a small aircraft. And Gnat did extremely well in dog fights with F-86 'Sabre' aircrafts which were much bigger in size. I found that very fascinating. I always believed that the agility and the maneuverability which is a very important quality for a fighter aircraft could be achieved when you have a small aircraft.



Wing Commander Kothiyal was our test pilot. He was a very professionally competent person. I know that he had never flown a prototype in his life. That too an unstable aircraft. So, I thought about how to give confidence to him. We did two or three things. One was to work on the control laws.

We tested on a modified F16 aircraft in USA. One of the comments of the test pilot from the Pentagon was that the F16 flies better with LCA control laws. Even the aerodynamics of the aircraft was excellent. It gave a lot of confidence to our pilot.

 

[ersakthivel]

Re: ADA LCA Tejas - IV

A non FBW ac can be certified for FOC in about 500 flights but the biggest problem with RSS FBW ac is that every software modification has to be tested on simulator and than in actual flight which extends the number of flights and time period by many years from concept to induction. If you have a stable design, you can produce, induct and replace an ac by the time it takes to induct one RSS FBW design.

please give me one example of a stable design fighter being introduced in any country.

Other than passenger planes and civilian cargo planes the stable aerodynamic configuration has no use in these days.

 

[Decklander]

Re: ADA LCA Tejas - IV

Have you heard of F-4 phantoms being used as target drones? They are non FBW. Any ac can be configured for remote piloting. Long back NASA flew a B707 for crash testing in similar manner.

 

[p2prada]

Re: ADA LCA Tejas - IV

Have you heard of F-4 phantoms being used as target drones? They are non FBW. Any ac can be configured for remote piloting. Long back NASA flew a B707 for crash testing in similar manner.

We are planning on doing the same for our older Mig-21s.All drones today are stable.

 

[Kunal Biswas]

Re: ADA LCA Tejas - IV

All fighters have to go through wind tunnels, their aerodynamics designs are important ..

In that sense most are aero dynamic stable, The question is how much efficient is one design over other and what is the role that they intended for ..

==============

IAF presently use MIG-23 as drones for EW and other purposes, They dont use PTA so much ..

Other than passenger planes and civilian cargo planes the stable aerodynamic configuration has no use in these days.

Have you heard of F-4 phantoms being used as target drones? They are non FBW. Any ac can be configured for remote piloting. Long back NASA flew a B707 for crash testing in similar manner.

 

[CuriousBen]

Re: ADA LCA Tejas - IV

We are planning on doing the same for our older Mig-21s.All drones today are stable.

I think modifying Mig 21 to operate remotely ( unmanned ) would be a very difficult proposition. However it is not impossible.

If I were to calculate this, the most complex task will be to land, followed by take-off .

 

[ersakthivel]

Re: ADA LCA Tejas - IV

Have you heard of F-4 phantoms being used as target drones? They are non FBW. Any ac can be configured for remote piloting. Long back NASA flew a B707 for crash testing in similar manner.

While F-4 was used as target practice, F-16 without pilots can be used as unmanned combat vehicles piloted by fly by wire software with full combat capabilities. That is a lot different from from simple drones. Read the report in full.

 

[Twinblade]

Re: ADA LCA Tejas - IV

I had vowed not to get into arguments with those who lack the very basic knowledge of aerodynamics and have no knowledge of things they consider themselves to be experts on.

Use the ignore option like everyone else does. Works like a charm.

 

[ersakthivel]

Re: ADA LCA Tejas - IV

I too am making a vow on the birth day of Gandhi,

I am not going get into arguments with people who can take a look at an aircraft's wing sweep angle and say whether it is RSS or not,

Also only due to the over weight issues the F-16 after blk 30 became stable fighter, not by any God gifted discovery that after a decade of operations it's designers have chosen to make it stable to overcome the pitfalls of the unstable design.

People who throw muck on RSS fly by wire platform do so due to incredible ignorance about the latest trends in military aviation which places it's bet on not straight line top speed but agility with a lower top speed.

Why?

because even if some one flies at mach 2.2 for a few seconds he cannot escape a long range BVR within it's no escape zone.

So designers are going for low wing loading designs that while reducing flat top line speed due to drag from more surface area, it gives the fighter a fairly preferable LIFT to DRAG ratio which gives the fighter the ability to pull higher Gs in lesser seconds the basic principle behind the ground breaking delta config that is being pioneered on Mirage-2000 and being followed on Grippen , TYPHOON, RAFALE and LCA, F-22, FGFA or PAKFA.

Some use canards for vortice generation to give more lift at low speeds to improve low speed handling and lower landing speeds like RAFALE, TYPHOOn, GRIPPEN some use cranked delta like TEJAS.

So if people want to use low wing loading design they have to design their fighters as some kind of Deltas because that is the only shape that permits more wing area within the safe area that won't be affected by shock cone generated by the fighter when it crosses the sound barrier.

it goes without saying that the delta shaped wing can be placed for the purpose of more lift only after the center of the fuselage because that is where there is a large area available for higher wing area that won't be buffeted by the turbulence generated by the super sonic shock cone.

Only with more lift per KG conferred by the high wing area low wing loading design the modern fighters can pull more Gs quickly to change their direction suddenly while trying to throw out the mach 4 speed BVR and WVR missiles.

The key is Instantaneous turn rate- the number of degrees the fighter can turn in a second , Which will always be higher for RSS Fly by wire Deltas than the stable compound wing fighters.

It is this key ITR which enables a fighter to quickly point its nose in the direction of enemy fighter and fire their high off bore sight within visual range missiles in close combat, not the quicker cart wheeling in circles capacity endowed by higher STR,

The key factor to know is not the number of Gs the fighter can pull ultimately, It is the G ONSET RATE i.e the rate at which higher Gs set in on a fighter aiding it in a higher ITR sudden turn.

It is always higher for RSS fly by wire fighter. If you have any doubts you can visit some authentic sites on F-16 XL like

http://www.airforcemag.com/MagazineArchive/Pages/1983/November 1983/1183f16xl.aspx

Hillaker said that the objective of the F-16XL program was to achieve a logical evolution from the basic F-16 that would provide significant improvements in all mission performance elements. At the same time, it would retain the fundamental F-16 advantage of low procurement and operating costs. Although the principal improvements were to be in range and payload capabilities, simultaneous improvements in all other mission elements were to be given equal emphasis.

For example, survivability was to be a prerequisite to longer range. Higher military power (non-afterburning) penetration speed, lower observables, increased maneuver agility, and reduced vulnerable area increased the survival rate so as to be consistent with a longer-range/deeper-penetration capability.

Many of the improvements resulted from the design team's innovative approach to integrating the weapons and airframe rather than hanging weapons on in the conventional high-drag, destabilizing manner.

So the RSS fly by wire F-16 XL is an evolution over the Stable F-16 after block 30 onwards not a regression.

and find out how the higher G ONSET RATE on F-16 XL opposed to normal F-16 helps the tighter performance of F-16 XL over the normal F-16 in all parameters apart from high powered engine and other things.

Without even understanding the basic principles that led to the evolution of RSS fly by wire fighters few people are dumping on RSS as repeatedly sold shit. I can not go on long duels with them forever. I have already done that once in tejas mk-2 thread. There is no point in dumping it here again.


And lastly I am not going to use ignore option either, because many posters on whom I want to use the button post such hilarious, entertaining stuff that I don't want to miss the fun!!!!!!!!!

 

[ersakthivel]

Re: ADA LCA Tejas - IV

The Revolutionary Evolution of the F-16XL

For a decade and a half, many fighter tacticians have stressed the paramount importance of being able to sustain a high turn rate at high Gs. The rationale was that with such a capability, enemy aircraft that cannot equal or better the sustained turn rate at high Gs could not get off a killing shot with guns or missiles.


With developments in missiles that can engage at all aspects, and as a result of having evaluated Israeli successes in combat, the tacticians are now leaning toward the driving need for quick, high-G turns to get a "first-shot, quick-kill" capability before the adversary is able to launch his missiles. This the F-16XL can do. Harry Hillaker says it can attain five Gs in 0.8 seconds, on the way to nine Gs in just a bit more time. That's half the time required for the F-16A, which in turn is less than half the time required for the F-4. The speed loss to achieve five Gs is likewise half that of the F-16A.


All of these apparent miracles seem to violate the laws of aerodynamics by achieving greater range, payload, maneuverability, and survivability. Instead, they are achieved by inspired design, much wind-tunnel testing of shapes, exploitation of advanced technologies, and freedom from the normal contract constraints.


The inspired design mates a "cranked-arrow" wing to a fifty-six inch longer fuselage. The cranked-arrow design retains the advantages of delta wings for high-speed flight, but overcomes all of the disadvantages by having its aft portion less highly swept than the forward section. It thus retains excellent low-speed characteristics and minimizes the trim drag penalties of a tailless delta.


Although the wing area is more than double that of the standard F-16 (633square feet vs. 300 square feet), the drag is actually reduced. The skin friction drag that is a function of the increased wetted (skin surface) area is increased, but the other components of drag (wave, interference, and trim) that are a function of the configuration shape and arrangement are lower so that the "clean airplane" drag is slightly lower during level flight, and forty percent lower when bombs and missiles are added. And although the thrust-to-weight (T/W) ratio is lower due to the increased weight, the excess thrust is greater because the drag is lower – and excess thrust is what counts.


The larger yet more efficient wing provides a larger area for external stores carriage. At the same time, the wing's internal volume and the lengthened fuselage enable the XL to carry more than eighty percent more fuel internally. That permits an advantageous tradeoff between weapons carried and external fuel tanks.


Through cooperation with NASA, more than 3,600 hours of wind-tunnel testing refined the shapes that Harry Hillaker and his designers conceived. More than 150 shapes were tried, with the optimum design now flying on the two aircraft at Edwards.


As an additional technology, the XL's wing skins are composed of an advanced graphite composite material that has a better strength-to-weight ratio than aluminum, is easier to form to the compound wing contours, and has higher stiffness to reduce undesirable flexibility effects.

Cleared to climb to 30,000 feet, Jim applied afterburner and back pressure. Our weight was diminished only by the fuel used for takeoff and the brief excursion out of the pattern. We climbed at more than 20,000 feet per minute, leaping from 4,000 to 27,000 feet in sixty-seven seconds. Jim eased the power back while turning into the supersonic corridor and getting cleared by Edwards Control to begin a supersonic run. Jim applied afterburner and the aircraft accelerated smoothly from Mach 0.95 through 1.0 and to 1.2 in seconds. Even with the heavy bomb load aboard, the aircraft went supersonic without a tremble. Handling characteristics at mach 1.2 with the heavy ordnance load were remarkably similar to those of the standard F-16 without bombs.


Jim pulled the throttle back to military power. The aircraft continued to coast supersonically for a long period before the mach meter showed that we were once again subsonic at 0.97.


Next, we maneuvered at slow flight speeds and high angles of attack, demonstrating the F-16XL's agile handling in that corner of the performance envelope. With airspeed below 150 knots, Jim invited me to try a roll to the left. Pressure on the side-stick controller resulted in a fast roll, with no sensation of lagging because of the heavy payload. Release of pressure stopped the roll immediately. I tended to "ratchet," and tried to end the roll with opposite pressure. That's unnecessary with the F-16XL's system, as Jim demonstrated. I tried it again, more smoothly this time.

In the loaded configuration, the F-16XL can penetrate at low level at airspeeds fifty-to-ninety knots faster than the basic F-6 when similarly configured. In fact, at every corner of the performance envelope, the aircraft has power in reserve, according to members of the Combined Test Force at Edwards.

Next, we conducted simulated weapons passes on a ground target, using the continuously computed impact point system (CCIP) displayed on the HUD. With this system, even this novice pilot, who has difficulty with a non-computing gun-sight, achieved on-target results. Attack maneuvers resulted in G forces ranging to +7.0. With the heavy bomb load aboard, the F-16XL is cleared for maneuvers up to +7.2 Gs, compared with 5.58 Gs in the F-16A. This demonstrates how the designers were able to increase the aircraft weight while maintaining structural integrity and mission performance.


We returned to Edwards to land on Runway 22. Touchdown speed was 170 knots. When Jim deployed the drag chute, its effect was instantaneous, slowing us to less than eighty knots in less than 1,000 feet.


With the F-16XL, the US Air Force has the option to gain markedly improved range, payload, and survivability performance over current fighters. According to its designers, the F-16XL in production would have a unit flyaway cost of about fifteen to twenty percent more than the F-16C and D.

Just read the following sentence,

And although the thrust-to-weight (T/W) ratio is lower due to the increased weight, the excess thrust is greater because the drag is lower – and excess thrust is what counts.


So due to the necessity to support higher wing weight the empty weight increase leading to lower thrust to weight for tejas mk-1 than the latest F-16s in PAF.

But what counts is the drag is lower because of better lift to drag ratio provided by the large wing area higher weight delta wing which gives the fighter the critically important "excess thrust " as mentioned in the article and it is what counts in close combat and agility . not a blind reading of TWR figure of a fighter.

So ADA was right in choosing the evolutionary design pioneered by RSS- Fly by wire F-16 XL and that is why IAf is ordering tejas in hundreds , not due to charity motives,

Now charmers who counsel the use of "IGNORE" option "which works like a charm !!!!!!!!!" and vowing to never to get into argument with guys pushing "Repeatedly Sold Shit as Relaxed Static Stability" can take the center stage and tear apart my arguments like the famous or (infamous !!!!) Rahul Gandhi episode of tearing apart the ordinance in a press conference!!!!!!!!!!!

 

[Decklander]

Re: ADA LCA Tejas - IV

A-320 does complete autoland in Cat-3b conditions including coming to full stop on ground after landing. And it lands better than what most pilots can do.

 

[ersakthivel]

Re: ADA LCA Tejas - IV

@ersakhivel,
I had asked you many questions earlier and except for garbage you dished out nothing. Let me ask those questions again and let us have a fair & healthy debate if you may please.
1. Why has cranked delta design not been applied to anyother fighter tilldate including the latest stealth designs?
2. I have searched the net and cud not find any mention of RSS for F-22 & F-35, can you post the true picture?
3. What do you have to say about F-20 which had two crashes due to very high onset of G resulting in G-LOC of pilots.
4. 42* sweepback gives a particular point of MAC which is generally about 25% chord, the look at F-22 & F-35 airframe clearly shows that they are most likely stable designs. Pls compare the position of F-16 wing w.r.t to these fighters and also of highly swept designs like F-16XL, M2K & Tejas and pls tell me in which flight conditions will they be stable and in which they will be unstable?
5. Does an RSS ac remain RSS thruout its flight envelope?
If you can maintain the dignity for a healthy debate, I promise, I will respond with grace.

Relaxed stability - Wikipedia, the free encyclopedia

The latest generation of fighter aircraft often employ design elements which reduce stability to increase maneuverability.[clarification needed] The BAE Harrier GR7/GR9 employs a significant and obvious anhedral angle to its wings, this reduces the inherent lateral stability of the wings mounted high on the fuselage.
A less stable aircraft requires smaller control deflections to initiate maneuvering; consequently drag and control surface imposed stresses will be reduced and aircraft responsiveness will be enhanced. Since these characteristics will typically make control by the pilot difficult or impossible, an artificial stability will typically be imposed using computers, servos, and sensors as parts of a fly by wire control system.

ARTIFICIAL STABILITY & FLY-BY-WIRE CONTROL

One of the most basic requirements for a fighter aircraft is manoeuverability. Prior to the age of supersonic aircraft, the problem of finding the optimal amount of stability was fairly straightforward, however the necessary aerodynamics for supersonic flight began to introduce complications. Modern supersonic aircraft tend to have thin wings with relatively short span. This alters the mass distribution in the aircraft, most of the mass is distributed along the fuselage, increasing moments of inertia in pitch and yaw.

The result is an aircraft very easy to roll, if not unstable in roll, but reluctant in pitch and yaw, which is hardly desirable for tight manoeuvering. An illustration of that class of aircraft would be the F-105 Thud, quote "...it doesn't turn very well.... it rolls beautifully ...".

One possible solution to this problem would be lowering the aircraft's static stability, particularly in pitch. This can be achieved by shifting the centre of gravity aft of the centre of lift, thereby creating a nose-up pitching moment, which will assist in rotating the aircraft's nose into a tight turn. However, the resulting loss in stability must be countered and this is the task of artificial stability.

Both the GD F-16 and the Mirage 2000 employ this means of improving manoeuverability, Rockwell's HiMAT technology demonstrator also uses artificial stability.

Fourth-generation jet fighter - Wikipedia, the free encyclopedia

During the period in question, maneuverability was enhanced by relaxed static stability, made possible by introduction of the fly-by-wire (FBW) flight control system (FLCS), which in turn was possible due to advances in digital computers and system integration techniques. Analog avionics, required to enable FBW operations, became a fundamental requirement and began to be replaced by digital flight control systems in the latter half of the 1980s.
An aircraft with negative static stability can therefore be made more maneuverable. At supersonic airspeed, a negatively stable aircraft can exhibit positive static stability due to aerodynamic center migration.[1][6] To counter this tendency to depart from controlled flight—and avoid the need for constant minute trimming inputs by the pilot—the 4th gen aircraft has a quadruplex (four-channel) fly-by-wire (FBW) flight control system (FLCS). The flight control computer (FLCC), which is the key component of the FLCS, accepts the pilot's input from the stick and rudder controls, and manipulates the control surfaces in such a way as to produce the desired result without inducing a loss of control

All sites refered explicitly states that after the Mirage-2000 and YF-16 most of the new fighter designs 0f 4.5 the gen and 5th gen are Relaxed static stability.

Do you have a single source to prove that F-22 has a stable flight profile?

The reason after blk-30 F-16 became stable was increase in weight due to modern requirements, not because of the superiority of the Stable design over RSS.

Of it is so the french and europeans too would have moved to Stable flight profile for their TYPHOONs, RAFALEs and Grippens

I see no reason why US will go back from RSS design for it's most advanced fighter plane of the century.

http://members.tripod.com/aviation_corner/f22page.html

The Lockheed Martin/Boeing F-22 Raptor was designed as an Advanced Tactical Fighter to replace the McDonnell Douglas F-15 Eagle. In 1981, the ATF requirement called for a fighter combining low-observability or stealthy design, the ability to cruise over long ranges at supersonic speed without afterburning, a very high degree of aerial agility and STOL-capability with the aid of two-dimensional thrust vectoring, a fly-by-light control system for a relaxed-stability airframe, and an advanced nav/attack system using artificial intelligence to filter data and so reduce the pilot's workload while improving his grasp of tactical situation.

http://defenseissues.wordpress.com/tag/f-22/

With introduction of thrust-vectoring F-22 and Su-35, many claims have appeared, such as that thrust vectoring aircraft are most maneuverable in the world and that addition of thrust vectoring alone guarantees that fighter in question will be unrivalled in maneuverability, excepting of course other thrust vectoring aircraft.

These claims hold that addition of thrust vectoring by itself is enough to turn otherwise-sluggish fighter aircraft into supreme air-to-air machine. Things are more complex than that, however; effectiveness of thrust vectoring depends on aircraft's aerodynamic configuration, speed and altitude.

To discuss thrust vectoring, we must first know how non-TVC aircraft behave. Major parameters that impact aircraft's performance are:

weight
lift, which can be approximated through wing loading
excess thrust, determined by thrust to weight ratio
drag

One of advantages of thrust vectoring is allowing aircraft to enter and recover from a controlled flat spin, yawing aircraft without worrying about rudder, which looses effectiveness at high angles of attack. However, aircraft using close coupled canards instead of thrust vectoring have also demonstrated flat spin recovery capability, example being Saab Gripen.

But while thrust vectoring reduces drag during level flight, thus increasing the range, close-coupled canards add drag and decrease lift unless aircraft is turning, thus improving the range.

But to see what impact thrust vectoring has on combat performance, we have to take a look at parameters I have defined above. Mass of aircraft determines inertia – thus, heavier the aircraft is, longer it takes to switch from one maneuver to another quickly. This results in slower transients, making it harder for pilot to get inside opponent's OODA loop – in fact, mass is defined as a quantitative measure of an object's resistance to acceleration (to clear common mistake in terminology, acceleration can be in any direction – in fact, what is commonly called "deceleration" is mathematically defined as "acceleration"). But to actually turn, aircraft relies on lift. Lift is what allows aircraft to remain in the air, and when turning, aircraft uses control surfaces to change direction in which lift is acting, resulting in aircraft turning around imaginary point. It can be approximated by wing loading. But turning leads to increase in angle between air flow around the aircraft and the aircraft itself (this angle is called Angle of Attack), which results in increased drag. Increasing drag means that aircraft looses energy faster, and once fighter's level of energy decays below that of his opponent, he is fighting at disadvantage. Loss in energy can be mitigated by excess thrust, which can also be used (usually in combination with gravity, aka downwards flight) to recover lost energy. All of this leads to expression "out of ideas, energy and altitude", which basically means "I'm in trouble and have no way out". Nose pointing allows aircraft to gain a shot at opponent with gun, and was crucial for gaining a shot at opponent with missiles before advent of High Off Bore capability, which shifted requirements more in direction of ability to sustain maneuvers at or near corner speed (minimum speed at which aircraft can achieve maximum g loading; it is usually around M 0,6 – 0,9). It must be noted that, while lift and excess thrust of aircraft can be approximated by wing loading and thrust to weight ratio, heavier aircraft will require higher thrust to weight and lift to weight ratios to achieve same turn rates as lighter aircraft.

Thrust vectoring, as its name says, results in shifting of the thrust. Due to modern fighter aircraft's center of gravity and center of lift never being behind its nozzles, shift in thrust results in aircraft rotating around its center of gravity, resulting in massive increase in Angle of Attack. Thus, comparision non-TVC aircraft turning and TVC-equipped aircraft turning would look like this:

With standard loadout of 50% fuel, 2 Sidewinder, 4 AMRAAM, F-22 has wing loading of 313,5 kg/m2 and thrust-to-weight ratio of 1,29. For comparision, with same loadout, Eurofighter Typhoon has wing loading of 284 kg/m2 and thrust-to-weight ratio of 1,28; Dassault Rafale's values are 276 kg/m2 and 1,22. Su-27s values are 324 kg/m2 and 1,24. Thus, F-22 is inferior in wing loading to both Eurocanards, and has only slightly superior thrust-to-weight ratio compared to Typhoon. It is also only slightly superior to the Su-27 in wing loading, and somewhat more in thrust-to-weight ratio.

you can also see how important the wing loading is, Not just TWR alone defines the agility. Tejas has a very low wing loading as well

RSS os there for close combat speeds closer to mach 1. Every one knows that for supersonic flight the center of lift goes back and the fighter becomes stable.Since most fighters are not very maneuverable close to top speeds RSS is irrelevant ad most of the dog fights dont take place at mach 1.6 plus.

All new non canard deltas have two angles on their wing for their vortice generation needs to offset the less controllable behaviour at low speeds in pure deltas. This is what we call cranked delta on Tejas and diamond shaper wing in F-22 , cranked arrow in F-16 Xl.

If you too stop shooting from the hip like, "I will make sure you won't post about the superiority of RSS" and "I vow to stop arguing with " like stuff we can have a good debate,

Thanks.

 

[Decklander]

Re: ADA LCA Tejas - IV

@ersakhivel, I am still waiting for the reply to the pointed questions I asked. Regarding F-22, I had clearly stated that I have not found anything which states that it is RSS ac. I had asked you to post such data if you have it. Posting the reference data for making an aircraft does not mean the ac is RSS. The wiki which you seem to rely on very clearly states the RSS for every ac which has it but even that is silent on this aspect for F-22 & F-35.
have a look at trapezoidal wing form, it overcomes the problem of backward movement of CP with mach number. RSS allows the CP to move both sides of CG and its movement depends only on airspeed(AOA). Infact even the CG moves with fuel burn and load release. So no RSS ac is always RSS in flight.

 

[ersakthivel]

Re: ADA LCA Tejas - IV

All new non canard deltas have two angles on their wing for their vortice generation needs to offset the less controllable behaviour at low speeds in pure deltas. This is what we call cranked delta on Tejas and diamond shapeg wing in F-22 , cranked arrow in F-16 Xl. In Tejas the less swept wing at the wing root enables lift inducing vortices to be generated so that it gets a better lift to drag ratio.