We can do that. But that does not mean I am going to let the Chinese off the technical hook. We will let the silent readers decide who is the more credible.
Mr. Asok said that the J-20 have a variable DSI system. Nowhere have I said there are technical barriers to that. In fact, I provided my first jet, the F-111, as proof of that system.
Mr. Asok said that the variable DSI system would 'optimize' airflow into the engines. Never mind that the word 'optimize' have been abused to death by those who do not know what they are talking about but tries to portray themselves as knowledgeable.
Air is not uniform in density. Everyone who took basic science in high school know that. As altitude increases, air density decreases. This means airflow in aerodynamics forces and in jet engine operations will be negative affected. Negative as in decrease in efficiency and performance output. This is why rockets carries their own oxidizers -- oxygen -- in the fuel mixture.
http://www.braeunig.us/space/propel.htm
As the rocket gains altitude, its flight will not be affected by the lack of oxygen to burn.
Going back to the J-20 and its claim to have a variable DSI system...
Q: As the jet fighter changes in altitudes, often unplanned, how would this variable DSI system know the available air density ?
A: Air data probes, specifically pitot and static.
https://www.grc.nasa.gov/www/k-12/airplane/pitot.html
Air data is needed for the flight control computer (FLCC) to calculate flight control surface displacement.
But the problem now is that because an aircraft is a complex body, airflow over its complex surfaces will be different in both velocity and pressure. Further, the physical structures themselves will create a variety of airflow behaviors. A jet engine inlet is a tunnel or tube, essentially trapping airflow, whereas the wing will simply let airflow travels over its surface.
So if this variable DSI bump is supposed to change its shape and dimension to optimize airflow into the engine, the system
MUST have localize pitot/static air sensors. That pitot/static probe in front or on the size of the radome is for airflow that is in first contact with the aircraft. This is for raw airspeed and altitude information. As airflow travels the fuselage, its velocity and pressure changes. This means the inlet cannot use air data information from the nose where airflow velocity and pressure are different.
Sure...This variable DSI system can use
CALCULATED air data information from the nose air data, but this is a high risk proposition because of the need for maneuvers where airflow will be different in diverse areas of the aircraft.
Therefore, the best, safest, and most accurate air data information for this variable DSI system must be independent of what the main pitot/static probe in the forward fuselage area have. Each engine inlet must have its own independent pitot/static sensor as close to the inlet entrance as possible, and each inlet must have its own independent air data computer to alter the DSI bump. The F-111 have it. The F-15 have the same layout.
Assuming the J-20 do have this variable DSI bump system, I doubt that the J-20 engineers are that much of risk takers to use calculated air data from a different part of the jet.
So where are the components for this variable DSI bump system ?
What I wrote above is clear evidence that I do know what I am talking about. You will
NEVER find comparable technical information on basic system configuration from the Chinese members here. They have neither the aviation experience nor even basic education in the aviation fields to inform the readers this way.
The Chinese claimants maybe correct, but that would be from luck, not from experience and/or education.
