Tejas is good, but not as good as initially thought. Tejas Mk 2 still does not have DSI which JF-17 has. DSI is the first 21st century jet technology.
so DSI alone can make a a all metal fighter go invisible ?
or can DSI hide heat and electro magnatik & radar signature ?
or can DSI boost power of a fughters engine and increase its power to wieght ratio ?
well at best DSI can onli hide frontal heat signature from incoming heat seaking missiles and thats it what helps in real terms is power to wieght ratio , range , EWsuites , RADAR and agility and type of wepons on a pertikular fighter
PAK-FA doesn't have it because Russia does not have such a technology. All American and Chinese jets developed since year 2000 use it.
DSI is not the onli thing that reduces heat and radar signatures its more deu to overall shape , use of carbon composites in body & RAM coating
as for US fighters they also use better radar ,avioniks and wepons (where india has an uppar hand against PAF) and LCA has most ofindo- western hybrid Radar , wepons ,engine & EW suits + its the onli fighter which uses such a huge ammount or carbon composites in its overall bady & wieght (next onli to dreamliner in %)
now why is india still devloping LCA .......... the contemporary aircraft of LCA developed in other countries are JAS-39 by Sweden, FA-50 by South Korea and JF-17 by Pakistan / China. The engines installed in these aircraft (except that of JF-17) are GE-404 series engines.
LCA parameters, such as empty weight, all up weight (except that of JAS-39), thrust, speed (except that of JAS-39) are better than those of the other aircrafts.
Similarly, development / unit cost of LCA are less than those of JAS-39 and FA-50 but more than that of JF-17. However, LCA’s Ferry Range is less than those of other aircrafts."