**2.3 About this research**

Flight control systems for military aircraft have had and still have a very rapid evolution based on the needs of the air force in each country, on the rapid scientific and technical evolution that allows new and new improvements of military flight control systems. As presented, military aircraft are designed to be aerodynamically

#### *Military Aircraft Flight Control DOI: http://dx.doi.org/10.5772/intechopen.105491*

unstable to give them superior maneuverability in training or during air combat with enemy armed forces.

During the air maneuvers, the aerodynamic forces developed on the control surfaces and the fuselage of the military aircraft are very large, which requires strong, very fast, but also very safe flight control systems, considering the huge cost of these aircraft.

To make the flight control systems very secure, they are designed as multiredundant systems, and the actuators with which the control surfaces are operated are dimensioned to exceed the aerodynamic forces in any situation.

Of all the systems presented and analyzed, the most advanced, the lightest, and with increased protection from electromagnetic interference (EMI) and electromagnetic pulse (EMP) is the fly-by-light (FBL) flight control system.

In addition, the fiber-optic cable used in the fly-by-light flight control system has a much higher bandwidth, and a very high transfer speed of multiple signals, with the speed of light, it is incredibly difficult to intercept the signal without sectioning the cable, and finally, the diameter of the fiber-optic cable is smaller, which makes it possible to design a multiredundant flight control system without significantly increasing the weight of military aircraft.

The best flight control system for military aircraft is by far the fly-by-light (FBL) system, due to its extraordinary features highlighted above.

#### **3. Conclusions**

From the creation of the first aircraft (the Wright brothers, in [30]), or even earlier, pioneer inventors used empirical mechanical flight control systems to take off, fly, and land with aircraft designed by them. Since then, flight control systems have evolved continuously, at a very fast pace, as flight speed has steadily increased and the sound barrier has been overcome several times nowadays.

The fly-by-wire flight control system is much lighter than the previous flight control system because all the mechanical connections have been replaced with thin copper wires. Other advantages of the control system are lower weight, better reliability, damage resistance, and highly efficient control of a high-speed and highly maneuverable military aircraft, unstable designed to increase its maneuverability.

The fly-by-light flight control system uses fiber-optic cables and is widely used in data and telecommunications networks. Recently, glass has been replaced with special clear plastic that helps reduce weight even more significantly. Due to its major advantages, the fly-by-light flight control system is increasingly used in military aircraft as well as in commercial aircraft [16, 31–33].

Because the fly-by-light system has low weight, high bandwidth, compact size, and resistance to electromagnetic interference (EMI) and electromagnetic pulses (EMP), it is expected to become the next generation of flight control systems as it offers immunity to new more hostile military environments.

#### **Acknowledgements**

The work was carried out within contract no. 8 N/2019, code PN 19 01 04 01, supported by the Romanian Ministry of Research, Innovation, and Digitalization.
