krash
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a higher thrust engine would consume more fuel and reduce the range of an already short legged plane even further.
It's a little bit more complicated than that.
Firstly, the consumption can be controlled by applying lesser thrust when higher thrust is not needed. Sort of like what airliners do, they never fly at max speeds/thrust unless need be. They usually fly at speeds that are most economical for fuel consumption. If the JF-17 is currently applying x kN for cruising, it would still apply only x kN for cruising after the engine is upgraded. You want that extra bit of thrust so that when you do need it you aren't left hanging, especially when it's a kill or be killed situation.
Secondly, when thrust is increased on an engine it is usually safe to assume that both dry and wet thrust ratings are increased. This means that for a range of thrust values the aircraft will now consume less fuel as compared to before. For example, according to Wikipedia the RD-93 has a dry thrust rating of 50 kN and a wet thrust rating of 81.3 kN. Right now if the pilot were to apply 60 kN of thrust (or any other amount beyond 50 kN) the afterburners would kick in causing the fuel consumption to go through the roof. If the dry thrust of the engine were to be increased from 50 kN to, say, 65 kN then applying 60 kN of thrust, when need be, would not engage the afterburners and the fuel consumption would be a lot more affordable. This would be true with the entire thrust range from 50 kN to 65 kN. In fact, the increase in max dry thrust will most likely increase the max wet thrust as well, which in turn should result in lesser fuel consumption, compared to before, from 65 kN till 81.3 kN as well, only less dramatically.
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