Re: New JF-17/FC-1 thread
No, it's a compound delta with fixed forward surfaces:
This overcame some of the high AOA and stall problems of the Mirage III series.
No, I'm afraid that's not accurate. Firstly, a pure right-angled triangle delta is the
fighter.
Now the Mirage-2000 is not pure, but a clipped delta in which its right-angled triangle is left slightly incomplete, thus forming a trapezium. (
)
A compound delta is one which has one more edge in addition to the clip. The most common example is the
. It's wing has 5 prominent edges including the clip (6 edges if the lateral join with the exhaust is counted).
Similar to Draken, the
also shows 5 distinct edges including the clip.
This is a significant shift from the 'vanilla' delta of the Mirage-2000, which is simpler.
Draken's compound is concave (bent inwards) whereas the LCA's compund is convex (bent outwards).
The compound of the LCA is because the frontal edge which is in touch with the forward fuselage forms the crank.
crobato said:
You are assuming that canards are just for vortex formation. It is a lot more than that. Cranks and LERX are not functional lifting surfaces, canards are.
crobato, the crank of the LCA is used for vortix generation, if you referred to the pdf article I gave earlier "Radiance of the Tejas".
Canards can also be viewed as the tail-planes brought to the front (which is why their technical term is fore-planes). Pitching is meant to be done by
movable canards. That can't be said for fixed canards like in Su-30 MKI.
crobato said:
Canards create a pitching movement, cranks don't. The fact that you still have an elevon means you have to push the tail down (create negative lift) in order to push the nose up. This means you lose lift in a turn. Depressing the elevons also create drag, which means you lose speed.
I agree that movable canards are meant to create a pitching movement (cranks being unmovable, are not meant to do that anyway). But as canards are never in the same plane as the rest of the wing, forward-drag created by them is already an inherent impediment of the aircraft. So the canard aircraft is already cruising in the disadvantage of a drag, unlike in LCA.
Drag induced while turning by the delta in the LCA is compensated to quite an extent by vortex lift created by the cranks.
crobato said:
This assumes you are not bleeding speed from the turn, and this is certainly not true of tailless deltas.
I agree that speed is bled profusely. It is infact a tradeoff to achieve a high turn-rate in a much lesser AoA. But the bled speed is more than a conventional aircraft for the
same value of AoA. When an LCA already achieves the same turn at a much lesser AoA, it wouldn't have bled as much speed.
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The discussion has gone outside the scope of the topic of JF-17. To that effect, I can say that Russia definitely seeks to enter the Pakistani arms market and RD-93 may be an indirect and stealthy beginning.
The JF-17 does appear nearly as manoueverable as an F-16 in turning, but it doesn't appear to do a sustained complete vertical-climb probably because of low T/W ratio. Some weight reducing measures like composites or a high thrust engine may be urgently needed.