In this blog post, we will look at how flight control engineering improves aircraft stability and maneuverability, and what possibilities it opens up for future transportation and automation technologies.
Take a sheet of A4 paper. If you fold this paper in half to make a paper airplane, will it fly well? You don’t need to try it to know the answer. It won’t fly. This is because the paper airplane lacks basic flight stability. However, if you apply flight control engineering to this simple paper airplane, the story changes. Even a paper airplane can fly freely in the sky. So, what is flight control engineering, how does it stabilize unstable aircraft, and what new possibilities has it opened up? Let’s take a closer look in this article.
The importance of flight control engineering lies not only in the flight safety of aircraft, but also in its significant impact on maximizing aircraft performance and efficiency. In fields that require advanced technology, such as military aircraft, flight control engineering is no longer an option but a necessity. With advances in technology, flight control systems are becoming more sophisticated, enabling aircraft to perform increasingly complex missions.
To understand the principles of flight stability, let’s take a closer look at why the paper airplane mentioned earlier lacks flight stability. Four forces act on an airplane: lift, gravity, drag, and thrust. Lift is the force that pushes upward, while gravity is the force that pulls the airplane toward the ground. In general, lift increases with speed. Drag is the force that acts between the airplane and the air and hinders the airplane’s forward motion, while thrust is the force that propels the airplane forward by means of an engine or other device. The centers of these four forces are generally located at different points.
Let’s take the interaction between lift and gravity as an example. Imagine that the point where lift acts is ahead of the point where gravity acts. The lift acting on the front of the aircraft will lift the front of the aircraft, and the gravity acting on the rear will pull the rear down. As a result, the aircraft and its wings will be lifted upward. When the wings are lifted upward, the area of contact between the air and the wings increases, increasing drag. At this point, a stable paper airplane will slow down due to drag, which will reduce lift. When lift is reduced, the rotational force also weakens, causing the airplane to return to its original state. On the other hand, the wide wing area of the paper airplane in the example creates a very large drag, which reduces the speed excessively and causes it to lose lift. An airplane that loses lift will inevitably crash.
Here, we can imagine what would happen if we had a computer, sensors, and a motor that were light enough to attach to a paper airplane. With these, we would be able to fly the airplane without crashing. By attaching a small control surface that moves up and down behind the wings, when the airplane rises, the control surface is raised to make the airplane face downward, and conversely, when it falls downward, the control surface is lowered to make the airplane face upward. This shifts the point where lift acts by changing the airflow around the aircraft. If this is done quickly and precisely without interruption, stable flight is possible. This series of tasks is called “flight control engineering.” Simply put, flight control engineering is the technology of how to relate input and output. The controller receives the aircraft’s attitude obtained through sensors and the desired movements from the user, and outputs the movements of the engine and control surfaces to reduce the difference between the two. The key to a good controller is how to determine the output value for the input. The designed controller is simulated on a computer model and then implanted into the aircraft’s computer.
There is an aircraft that some people call an “iron” because of its flat shape. The B-2 bomber developed by Northrop Grumman in 1988 is a good example. It is well known that it takes off from a US Air Force base in Hawaii whenever North Korea provokes the US. Aircraft like the B-2, whose wings are part of the fuselage, are called “flying wings.” Flying wings are older than you might think. They were continuously attempted by the Nazis in the 1930s. However, none of the flying wing aircraft attempted before the B-2 were commercialized. This was because they could not fly properly due to the stability issues mentioned earlier. Unlike paper airplanes, commercial aircraft need to change direction, so the lack of a vertical tail was even more fatal. Nevertheless, aeronautical engineers did not give up on developing flying wing aircraft because of their unique advantages. Wing-in-ground effect aircraft boasted excellent stealth (technology that makes radar detection difficult) performance and flight efficiency that had never been seen before in any form. Another advantage was that the large fuselage area allowed them to carry a large amount of bombs or cargo.
In the 1980s, 50 years after wing-in-ground effect aircraft first appeared in the world, it was finally possible to develop a practical wing-in-ground effect aircraft thanks to advances in control technology. The B-2 uses a control technology called fly-by-wire (FBW). The name comes from the fact that the aircraft flies by means of electrical signals flowing through wires. In conventional aircraft, the pilot directly controls the control surfaces using hydraulic pressure, but with FBW, the pilot gives commands for direction and speed to a computer-based control system, which then performs the optimal control to keep the aircraft flying stably based on these values. This FBW technology keeps the aircraft stable by constantly moving the control surfaces even during horizontal flight. Before FBW technology, this had to be done constantly by the pilot, and even a small mistake could lead to a major accident due to the unstable structure of the wing.
Today’s aircraft are all products of control engineering, which has become one of the most important factors in aircraft design. The F-35 currently being developed by US aircraft manufacturer Lockheed Martin contains 15 million lines of control software, with software development costs accounting for 40% of the total development cost. The reason why companies are rushing to invest in control technology is that, even if it is not for unique aircraft such as the B-2, control technology can expand possibilities such as improved maneuverability and stability.
The development of control technology is not limited to improving existing aircraft. It is constantly creating new types of aircraft. The quadcopter, which has recently become widely available as a toy, is also the result of advances in control technology. As its name suggests, a quadcopter is an aircraft that flies freely using only four motors and propellers. Stabilizing a quadcopter is like balancing a stick on the tip of your finger. However, with control technology, it can be easily flown. Quadrotors are gaining attention for their simple structure, consisting of a frame, motors, and propellers. In June last year, Domino’s Pizza in the UK released a video demonstrating pizza delivery using quadrotors. In addition, countless new types of aircraft using control technology are appearing. The rapidly advancing world of control engineering gives us a glimpse of how much further aviation technology can develop in the future.
The development of flight control engineering is not limited to aircraft. It has great potential to be applied in various forms not only to future transportation but also to all aspects of human life. For example, the principles of flight control engineering can be applied to autonomous vehicles, drone delivery systems, and various automation systems in smart cities. The potential for application in such a wide range of fields means that flight control engineering will not be limited to aircraft control, but will become an important technology for solving various problems in the future.
In conclusion, flight control engineering is the essence of modern technology, enabling humanity to develop safer and more efficient flight, as well as various forms of transportation and logistics. The development of flight control engineering will continue unabated, and we must pay close attention to the new possibilities that this technology will create.
