Can i ask one question please, tell me on thing which fighter jet using fixed air intake go beyond Mach-2+, and why Lockheed Martin is saying that DSI worked under the Mach-2 and don't worked well beyond Mach-2, are they (Lockheed Martin) is right or you @undertakerwwefan
Can i ask one question please, tell me on thing which fighter jet using fixed air intake go beyond Mach-2+, and why Lockheed Martin is saying that DSI worked under the Mach-2 and don't worked well beyond Mach-2, are they (Lockheed Martin) is right or you @undertakerwwefan
Rumors for J-20's DSI is not fixed, its variable or can move forward and backward, and its on a fixed intake like testing on F-16 which lacks variable ramps and splitter plates to go beyond Mach-2+ (Fixed intake+ DSI) can't reach Mach-2+ @undertakerwwefan
F-35 has enough T/W ratio to go beyond Mach-2+ but it can't do that for 2 reasons 1,Its using high bypass ratio turbofan which prohibited super cruise and go beyond Mach-2 and 2, its using Fixed+DSI intake @undertakerwwefan
i asked senior Chinese members in J-20 discussion Here on PDF on Chinese Defense section long time a go,, they said that there were rumors that J-20 using Variable DSI intake to achieve Mach-2+ performance @undertakerwwefan
so you're saying Chinese can't innovate new things @undertakerwwefan 
i asked senior Chinese members in J-20 discussion Here on PDF on Chinese Defense section long time a go,, they said that there were rumors that J-20 using Variable DSI intake to achieve Mach-2+ performance @undertakerwwefan
The main job for DSI is not to save weight but provide smoother air flow to the engine without using variable ramp intake s and fixed intakes but it extra advantage is to save weight @undertakerwwefan
Probability is there that J-20 is using variable DSI intake @undertakerwwefan
Rumors are the only thing these 'senior' Chinese guys know how to do.
The diverterless intake system would be a half cone and to expand this structure to slow down supersonic air would involve complex moving mechanisms.
Rumors are the only thing these 'senior' Chinese guys know how to do.
A variable DSI would be even more complex in mechanics than a variable ramp. The reality is that the F-111 already done it.
Do you see that long green colored spear-like thing? It is called a 'spike' on the F-111.
You can see three vertical lines on its body. It means the spike is made of three parts. The last part of the spike ends at the white colored structure.
At the tip of the spike, barely in the photo, is a pitot-static probe. The probe measure airspeed (pitot) and altitude (static) at the intake and have the direct effect on the spike's operations. Each intake have its own pitot-static probe and is called the 'local Mach' probe. The reason why each intake must have its own pitot-static sensor is because air flow over an aircraft is not always uniform, especially if the aircraft is maneuvering. So for the F-111 to have effective Mach 2+ speed at low altitude, each intake should have its own air data, hence the individual pitot-static probes.
What the spike does is move aft and expands (blossom). That is why the spike is a 3-parts structure. As the spike blossoms or gets physically larger, it slows down supersonic air for the engine, which you can see in the photo.
You can see additional views of the F-111's intake spike here...
http://www.f-111.net/models/inlets/index.htm
Here is a wiki source for the spike system...
https://en.wikipedia.org/wiki/Inlet_cone
The diverterless intake system would be a half cone and to expand this structure to slow down supersonic air would involve complex moving mechanisms.
In order to fully expand the intake spike, maintenance would have to simulate higher airspeed and altitude at the local Mach probe. This is done with a test tool call the TTU-205.
https://www.testvonics.com/ttu-205.html
The local pitot-static probe is covered and pressurized air is created for pitot and de-pressurized air is created for static. The tester can simulate pitot-static air from ground zero to 100,000 ft and from zero airspeed to Mach 3.
The J-20 do not have a variable DSI as far as all known images. For starter, these 'senior' Chinese forum members do not have any aviation experience in the first place, so all they have are speculations, and technically baseless ones at that.
So you're saying Chinese can't innovate new things @undertakerwwefan ???
May be inside DSI bump @undertakerwwefan
May be inside DSI bump @undertakerwwefan
Are you the engineer in CAC @undertakerwwefan
that J-20's DSI haven't enough space @undertakerwwefan 
