I'm always forced to compare LCA to that of F-16XL whenever comparison was made LCA with other planes(like JF-17) with simple wing form or which is not double delta.
Reason is, F-16XL brings out the difference it could make between a double delta plane and a delta plane or simply a conventional wing form with tailplane which is F-16.
There is no other example. It a standard proof how much a difference a double delta with RSS/FBW could make from an conventional F-16 as F-16XL is modified F-16 retaining the basic characteristics of F-16.
So for those like Das who thinks to make LCA a modern version of Ajeet instead of Tejas, although it may not be actually comparable, i like to put it in terms of F-16XL, how much we could have lost if we have chosen a conventional wing design instead of double delta as in Tejas.
http://www.airforce-magazine.com/Magazi ... f16xl.aspx
Harry J. Hillaker was chief project engineer for the advanced versions of the F-16. Harry has been involved in the advanced design of every major aircraft produced at Fort Worth since 1942. He served as YF-16 deputy chief engineer and director of F-16 deputy chief engineer and director of F-16 marketing before turning to leading the F-16XL design effort. The advanced designs that led to the F-16XL were undertaken with company funds and with the cooperation of the National Aeronautics and Space Administration (NASA) and USAF.
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.
To say that Hillaker’s design team achieved its objectives is an understatement. Example: For an air-to-surface mission, the F-16XL can carry twice the payload of the F-16A up to forty-four percent farther, and do it without external fuel tanks while carrying four AMRAAM (Advanced Medium-Range Air-to-Air Missiles) and two Sidewinder AIM-9 infrared missiles. With equal payload/weapons and external fuel, the mission radius can be nearly doubled. When configured for a pure air-to-air mission, an F-6XL with four AMRAAMs and two AIM-9s can go forty-five percent farther than an F-16A and can do so while conducting a combat action that is equal to thirty percent of its internal fuel.(Check the comment from IAF exclaiming how such a small plane, Tejas, having such a long leg and that is just Mark-I)
As for penetration and survivability, the F-16XL can dash supersonically with a load of bombs at either high or low altitude. It can climb at high rates with the bombs aboard. And it has a speed advantage of up to eighty-three knots over the F-16A at sea level at military power setting and 311 knots on afterburner at altitude while carrying a bomb load.(Check the news of Tejas clocking highest speed a sea level for Indian fighter jets)
Two additional capabilities of the F-16XL contribute to survivability. First is improved instantaneous maneuver ability coupled with greatly expanded flight operating limits (with bombs), and second is reduced radar signature resulting from the configuration shaping. (I don't have to say anything, it is obvious.)
Importance of High Turn Rate
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. (Though we haven't heard on this scale, it is well established, Tejas can make tight turn much more comfortable than Mirage-2000.)
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.
and there is still Mark-2 yet to come.
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