True .... Designing a FAC is not a painting on a paper ; i guess many have read it but for those who haven't, Read This :
The Chinese have made so many MiG 21 based derivatives that one can be forgiven for initially thinking it was yet another derivative with a nose job like the Qiang JiJi 5 ,surely one of the ugliest jet as I ever wish to see. This impression is quickly corrected by looking at the Table.
The JF 17 is no MiG 21 clone. It is altogether a more potent aircraft, reminiscent of the Northrop F 20 Tigershark. Though Yang Wei, the Chief Designer, did not have access to the F 20 he may have had opportunity to examine ex Vietnam Air Force F 5A aircraft or airframes and why not-only an arrogant fool will not “flatter” a good piece of engineering by imitating? Mitchell of Spitfire fame was “inspired” by the Heinkel He 70 Blitz’s graceful lines and Yang Wei may have been similarly “inspired” by Welko Gasich/Lee Begin’s work on the F5/F20 series. Northrop of course threw the game away by adding 80% more power and 20% more weight without changing the wing which remained the same as the F5 series. The figures of the wing loading speak for themselves. Digressing for a moment one sees the same reluctance in BAe to design a proper light strike aircraft using perhaps the Hawk systems in a Gnat derived airframe ( see Vayu III/2016- Going against the Wind) instead of trying to fob off native Air Forces with an inappropriate airframe too big for the job.
It would seem that the JF 17’s able Chief Designer Yang Wei carefully studied the F 20 concepts and made very well thought out “nips and tucks” type bespoke tailoring of the F20 design so that the JF 17 did not carry an extra ounce of fat or skin. Comparing the lengths the JF 17 is 0.53 mts longer but that is largely the difference between the F 404 and the RD 33 engine lengths. The empty weight of the JF 17 is 622 kgs. heavier but again if you factor in the weight differences of the two engine types and the additional 5.8 sq.mts of wing area that the Sino/Pak fighter carries the weight is commendable. The weights indicate that either the weight control supervision on the JF 17 was up to US/International design standards or Shri Wang Wei had enough domain expertise to tell the powerful PLAFAF faction where they got off regarding equipment fit standards of the JF 17! One can recount that when the US Navy wanted any additional equipment on the little A4, Douglas’s Ed Heinmann would reputedly take off fuel of weight equal to the additional equipment requested. Of such stories is aviation is made. One final point on weights that should make us think: The JF 17 is a larger aeroplane with a heavier engine and with an all metal structure and yet it is “as near as dammit” the same weight as the largely composite and smaller LCA Mk 1. That is an indication of how much we have erred and how much we can correct.
Having accomplished his weight control Wang Wei pulled off the first of his two
coups de main in that the generally conservative approach to the Northrop- like design was modified to a mid wing layout of increased wing area. Despite the weight penalty of longer u/c struts and ring frames to carry through the wing bending loads- an additional 42 kilos somehow comes to mind for the frames-it cured several big problems. The F 20 suffered in that though the warload was increased by twenty percent the low wing meant that fitting the store and the Ground clearance certifications must have been nail biting. The mid wing of the JF 17 avoided this easily and the larger wing area meant that the high induced drag of the F 20’ in high “g” turn and the increased CDo caused by the higher AoA, was lowered and dog fighting and general handling improved significantly. The F 20 gave the later F 16s a hard time during fly off competition and the JF 17 should be very much better. One will also note that sweet handling aircraft e.g. Hunter, MiG 21 and the Lightning were mid wing layouts which reduces or eliminates roll coupling and the JF 17 is a beneficiary. The second of his “
coups de Main” was the introduction of the DSI after seven years of parallel preliminary work. DSI reduced weight and drag. Summing up: a very competent airframe has been designed on the lines of the Northrop F 20 but as with the F22/F31 resemblance the Chinese design somehow manages to look more elegant and dainty!
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