A quick first assessment of the Chinese Wonder jets 27/12/24                             

 Prof. Prodyut Das

Iss.2 Dated 28/12/24 (updates in colour.) 

Iss.3/4/5.    29/12/24.


There was much chirping and twittering in Indian dovecotes at the release on 26/12/24 of pictures purporting to be not just one but two Chinese stealth aircraft accompanied by much “and the widows of Ashur are loud in their wails/and Idols are broke in the temples of Baael”. Actually the Chinese aircraft, unless the pictures released are some kind of elaborate fake, are quite modest. If they are fakes then my congratulations to the poster; the last time the Chinese put out pictures of a “futuristic” fighter it looked like a Swiss Army Knife. These look sensible.

There is nothing remarkable about the Chinese aircraft unless it is colonial surprise of the sort “How could the bloody Chinks do it?”. The aircraft- actually are yet more ( JF 17 earlier) excellent examples of good frugal engineering applied by men who grew up knowing that their future well-being rested on meeting parameters and deadlines.

I do not think the j 36 (?)  aircraft shown, for all their sleekness and swept wings, are supersonic. Supersonic flight does strange things to stability. The Horten Brothers, in the 1930s had clearly demonstrated that, unlike Dr. Lippisch finned tail less designs, a finless aircraft is possible- in subsonic aircraft e.g. HO 229 but I cannot remember seeing too many finless supersonic aircraft. If the Chinese aircraft is supersonic, it will need an installed thrust of something between that of a Mya-4,and a Hustler. As a lazy guess around 300 kN minimum.

Perhaps the Chinese approach is “brilliant” because of its simplicity, frugality and the ability to think from fundamentals and -then-trust what one finds. If at all stealth works, then stealth is an allotropy of performance. Combined with AI weapons- the platform becomes a transporter much like a 30 kt frigate being the transporter of a hypersonic Brahmos- a simple subsonic aircraft will do. In any case a Military supersonic aircraft will run out of fuel within minutes or like the Concorde be 60 mts long, have 350 sq. mts of wing area and be limited to cruise at 16,000 mts. You will note that a picture published the next day shows absence of DSI or any Variable Geometry intakes. It indicates that the Chinese doctrine does not consider Close combat or any sustained supersonic capability i.e. The aircraft is not a fighter. The original Vulcan despite being a ‘50s technology aircraft with metal manufacturing, gaps in the sheet metal and kinks all along the Leading edge reportedly had a low RCS largely because  on its shape. The Chinese design being much smaller and is  properly shaped should have an RCS ( pi x (window)2 ) may be a twentieth of the Vulcan’s say the aircraft would first appear on the screen may be when less  than a minute away from overhead . Not the best but there you have something that has a fighting chance specially when you have stand off AI missiles and don't HAVE to come over head.

The Chinese approach was more like “what if current 5th, gen. technology was applied to a 2nd generation airframe like say the Vulcan” (which, BTW, used bicycle chains and sprockets to operate the lift spoilers!). Shorn of the high- altitude cruise requirement (16,000 mts) of the Vulcan would reduce the size of the wing benefitting weight but losing the advantage of buried engines, and given more modern engines with their lower fuel demands, the propulsion system weight would go down leading to further reduction in wing size and weight. The end result of a few cycles of such a process is an aircraft like what the Chinese have shown. It uses more "robust stealth" i.e. stealth that is dependent on small size, shape, faceting, angles rather than fancy coatings-  So it is quite possible that we have the large bomb bay size similar to the Vulcan but tailored to Chinese GWs. Incidentally a stealth aircraft Bomb- bay would be quite a challenge to design. Despite the “tubbiness” of the fuselage it is probably- like Petter’s Lightning and the Gnat- quite expertly area ruled, combined with the lack of DST for the intakes;  it indicates a high subsonic machine

The wing is vaguely reminiscent of the SAAB Draken with a sharp inboard sweep and a lower sweep outboard and a reverse taper on the TE- a good balance of tailoring the RCS signature and the AR. Again, the sweep not for speed but for stealth; very practical and clear headed aerodynamically and indicating a design cruise speed of around M = 0.85. The kink in the leading edge would increase RCS but the whole business of RCS reduction in India has been developed into a religious cult. It is really not as difficult at all that but nor is it about a mythical “invisibility”. I have not been able to work out the aspect ration but it should be more than 2.5 given the reverse taper on the T.E again indicating a sustained high-speed cruise.. 

I warmed particularly to the three engines. Turbines are horrible sfc wise when operating off design. Much energy (fuel) is wasted in compressing air and then dumping it which is why the US ( and of course , our GTRE)  is so keen in developing “variable cycle” engines. The three- engine formula is that you take off with all three and then shut down one or two as the flight progresses and the weight reduces all the while the working engines work at max. continuous power and therefore the optimised fuel burn gives a longer range than what would happen if all three engines worked severely off design. This reduces the size which directly results in, reduced RCS.

In my assessment the Chinese have developed- without using stunning technology a good sensible weapons carrier that does not cost the sky. The second design shown is a rival design ( always strongly recommended to keep costs an delays in control) with a higher aspect ratio.I close with two worries for debate;

i)                   Have the Chinese mastered FBW/computer- controlled yaw stability? The technology we can counter. How do we counter the confident spirit of original thinking?

ii)                 In the ‘fifties the British joke was that the logical replacement for the Lightning was a Vulcan with missiles. The Soviets, of course, had a long love affair with the self- contained long range interceptor e.g. the Yakovlev 28. The Chinese have just done that; turned the old British " joke" on its head. 

I hold that no current 5th.gen can shoot down an opposing 5th, Gen. If that is indeed right have the Chinese, by using ancient thoughts and the appropriate technology developed a 5th. Gen. “Sniper” a -something whose task is to kill opposing 5th. Gen. aircraft? If they plan to attack Taiwan they may need it. We should go along with this "new" concept rather than the AMCA which is neither here nor there, And I don't buy the argument that the Tejas Mk2 is the way to teh AMCA. That is BS. designed to protect the funds for a non performing organization who blame every one but themselves for their own troubles. 

What do we do now.

1.      Nothing. Take a deep breath and do nothing. Certainly, don’t hustled into getting 3 squadrons of Su 57 or F 35s , nice no doubt that these aircraft are. My caution is that the 5th. Gen acquired will not be able to detect and destroy the other side’s 5th generation.

2.      What we need to do is to set up a “Magic Carpet” detection system based on the philosophy by which the Navy hunts submarines i.e. by detection of Magnetic or Radio Frequency anomalies. These can be fully autonomous Ground based systems. Once the hostile is roughly located it should be possible to vector a 4th. Gen. aircraft which should find the 5th. Gen easy meat.

3.      Focus on getting the Mark 1A in numbers and put up a weight improvement team which will bring down the airframe weight down to about 2000 kgs.  The IAF needs perhaps 15 squadrons of this type and it is a pity that the nettle is not being grasped firmly and effort is not being put in to sort out the bungles. Of course the problem is that ADA thinks it has done an excellent job and this makes them believe that the basic platform i. e the Tejas cannot be improved further whereas another ton of weight can come off and that will give us a fair decent aircraft. 

4.      Forget about the Mk2. Either the forward fuselage is entirely redesigned or we repeat the farce of the MK 1 where we built prototypes to learn that kindergarten mistakes are more damaging than senior school mistakes which tend to be local and requires less correction. The Canard location in the Mk. 2 is pure kindergarten/ unnecessary bravado. We just must accept that the Tejas is a dead end and have a Mk.2 with just the longer fuselage and carefully controlled weight improvement so that the FBW is not too disturbed. You get the Idea.

5.      “AMCA ADA ka bus nahi” Let the private sector be funded to take over the “assets” and proceed thereafter. We harp on Chinese funds. Why not harp on Chinese Competing design buteaux ?

1.      How long will it take us to develop an aircraft similar to the Chinese aircraft ?. 3-4 years and 6000 crores should be enough with possibility of funds left over if we use all the current existing izedeliye and all our available resources and with respect for all our stakeholders. The other alternative- with the current structure-Never - even with any amount of funds if done by the existing systems.

T To close with a Parthian shot: Have you noticed the wing tips ? They end in points which generates no lift but add drag and weight. It also indicates that the Chinese are ( quite correctly) relying quite heavily on stealth rather than performance.

 TFurther Reading

The following links may be of interest:

https://prodyut7.blogspot.com/2024/03/the-frugal-5-th-generation-amca-indias.html

https://prodyut7.blogspot.com/2023/03/a-technology-demonstrator-for-subsonic.html

There are some two three more articles in the blog ProfProdyutdas2 on stealth aircraft if you are so inclined 


  

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