[0:08]Alright, let's nail down aircraft primary flight controls, once and for all. Aircraft flight control systems consist of primary and secondary systems. The ailerons, elevator, and rudder constitute the primary control system and are required to control an aircraft safely during flight. On the other hand, wing flaps, leading edge devices, spoilers, and trim systems constitute the secondary control system. and improve the performance characteristics of the airplane or relieve the pilot of excessive control forces. I will leave these secondary flight controls for future lessons. In this video, let's focus on primary flight controls. In order to perfectly learn about the flight controls and their effects on flight, you first need to know what center of gravity is. Center of gravity or CG of an aircraft is simply the point where the aircraft would balance. Imagine trying to balance a plane in your hand, like you do for a pencil. The exact point where you can balance the aircraft in all three dimensions is the center of the gravity of an aircraft. It's the point about which the aircraft will rotate. Now, with this said, if you somehow apply any force away from the CG, then the aircraft will rotate about its CG. The CG is more like a fulcrum point, if you will, and the farther away the force is from the CG, the less force it is required to rotate. It's basic physics. Okay, now that you know the aircraft rotates about the center of gravity, let's make the three axes, which we all know of, about the center of gravity so that it would be easier to understand. The three axes are named longitudinal axis, lateral axis, and vertical or normal axis. These names are pretty important for your exams and even for the overall knowledge. But it's easy to remember, along the length, long itudinal axis. Along the width, lateral axis, and along the height, vertical axis. With these information in mind, the flight controls and how they work are a piece of cake. Let's start with ailerons. Why ailerons? Cause it will be easy later, believe me. And also cause it will be an alphabetical order. Anyways, the ailerons are the flight control surfaces at the outboard trailing edge of each wing and move in opposite direction from each other. If the one side goes up then the other side will go down and vice versa. This will create different lift forces in each wings. The one with the aileron down will have increased lift and the one with ailerons up will have reduced lift. Now we have up and down acting forces and away from the center of the gravity. The net effect? The aircraft will roll. That is to say it will rotate about its longitudinal axis. It's easy, isn't it? And if you don't know, how does the up and down movement of aileron cause the lift forces to increase or reduce, first watch this video on aerodynamics forces in flight? It's the most basic and best lesson you can get. All right, let's move on to our next flight control surface, elevator. The elevators are the flight control surfaces that are situated at the tail part of an airplane exactly on a trailing edge of the horizontal tail and move up and down simultaneously unlike the ailerons. As they move up or down, which is achieved through linkages in older aircrafts and through fly-by-wire systems in modern airliners, there is a net up or down force. When the elevator moves down, it increases the chamber, and hence the lift on the horizontal stabilizer will increase. This increment in lift will create an upward force away from the center of gravity. Result? The aircraft will rotate nose down about its CG. In the same way, the nose can be pointed up just by moving the elevators up. Remember all the pilot is doing by pulling on the control stick is moving the elevators up or down. The remaining part is done by the aerodynamics. Okay, now let's move to our last, but not the least primary flight control surfaces, rudder. Rudder is the surface that is located at the tail part on a vertical stabilizer and can rotate side to side about its hinge axis. They are simply the elevators turned vertical.
[4:16]But unlike the elevators, rudders are controlled by the rudder pedals on an aircraft, not through control stick, though the mechanisms are about the same. Okay, when the rudder is deflected to the left as seen here, then the aerodynamic force to the right is created. It's the same as the creation of more lift as the elevator does, but it's sideways. And as the force is created to the right and away from the center of gravity, the nose will then rotate towards left. Quite simple, isn't it? One last quick tip. Notice that we came alphabetically, ailerons, elevators, and rudders. When we normally talk of the axes we say it longitudinal, lateral and vertical. I don't know why, but we do say it like that. So, if we go alphabetically like ailerons, elevators and rudders, then it will be easier to remember because they respectively rotate the aircraft about longitudinal, lateral and vertical axis. So, next time, will you know which control surface is for which axis? I hope you guys also got to know about how the aircraft maintains its required alignment. For more simple and basic explanations on some curious topics of airplane, subscribe to our channel Curious About Planes. We have more cool educational videos coming up. Stay tuned.
