Center Of Gravity

This is more like very basic physics instead of military technology, so I want to talk about it. Plus, US has sealed the base design of F-35, so this post will not give them advantages in air superiority or supremacy, unless they want to redo everything. Previously, we talked about F-22 and Eurofighter and discussed why lack of high thrust has been a limiting factor for European fighters. So far, US and Russia have been the only 2 nations in the world to demonstrate the capability of high thrust in fighter engines. The question remains, why is US unable to produce highly maneuverable fighters despite high thrust? Why do European fighters and Russian fighters tend to be more maneuverable?

Center of gravity. High maneuverability is often achieved with all-moving tails, both horizontal and vertical. So far, Russia is the only country to adopt this design. What does that mean? The force to enable change in direction is exerted at the tail of a fighter, which implies that its center of gravity should move closer to its tail instead of its head. Why not just do that? Well, the traditional design of an airframe has its main wings in the middle to naturally maintain a balanced position in the air. If additional lift is required to maintain the balance of a jet, additional fuel is needed to do just that, because nothing is free in physics. So, how come Russian fighters don’t have a range issue? Well, they do, but it has more to do with their engine design. In any case, Russia still has a very good range with their fighters compared to the rest of the world. That’s why it’s not quite obvious. For stealth fighters that can’t see each other in the sky, maneuverability is a matter of life and death. If a trade-off is necessary, take just a little maneuverability instead of a little range. After all, range still matters.

Su-27 has a very optimized airframe in terms of aerodynamics. That its center of gravity is closer to its tail means that its main wings are supposed to be closer to the end as well. It is a near-perfect design to achieve all important performance characteristics for a jet fighter. This explains why all Russian fighters that come after Su-27 stick to this very one design. Eternity requires perfection. Su-27 is a very good example to demonstrate this principle. Even T-50 did not stray too far away from Su-27, which you can compare side by side.

So, why does China copy F-35 with J-31? Well, they are American fans. Don’t you know that?

Can you do better than Su-27? I think so. However, we need a mathematical formula to relate the 3-D shape of an airframe, including its mass distribution, to all desired performance characteristics, just so a supercomputer can solve the equation for us based on desired parameters, whose solution gives you the optimized shape for your needs. Perfection has to be proven, both mathematically and physically. How else can you be sure that it’s perfect?


About Run Song

Run Song (宋闰) is my pen name for the Moments of Poetry, a collection of poems about the greatest moments of life. If photography captures the greatest moments of life, poetry is the life behind them.
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