The flight controls consist of various services around the aircraft that manipulate the aerodynamic forces on the plane, allowing the pilot to control the aircraft. Aircraft flight controls are broken into two systems, primary and secondary flight controls. Primary flight controls are simply those flight controls that the pilot primarily uses to control the airplane.
The three primary flight controls are the ailerons, elevator, and rudder. Secondary flight controls, on the other hand, are used to change the airplane's performance and lighten the pilot's workload. The two secondary flight controls that we'll discuss are the flaps and trim.
The pilot controls the ailerons and elevator with a yoke or stick and the rudder with the rudder pedals. In most general aviation airplanes, as the pilot moves the controls, he or she is moving steel cables or pushrods connected through other linkages that physically move these controls. As the control service is deflected, the airflow is changed, which results in an aerodynamic force changing the airplane's path through the air.
Let's investigate the three primary flight controls in more detail. The ailerons are located on the back end of the wings out towards the tip and control the aircraft's roll or bank. When the pilot moves the controls to the left, The left aileron is deflected up, creating a downward force, and the right aileron is deflected down, creating an upward force. This results in the airplane rolling to the left.
The opposite would happen if the pilot were to move the controls to the right. The elevator is attached to the back of the horizontal stabilizer and controls the airplane's pitch, which allows the airplane to climb or descend. When the pilot moves the controls forward or aft, the elevator rotates, deflecting the air and creating a force that results in the airplane's pitch changing. If the pilot pulls back on the controls, the elevator will move up, creating a force that pushes the tail of the airplane down, thereby making the nose pitch up and causing the airplane to start climbing.
Finally, the rudder, which is controlled by the rudder pedals, is attached to the back end of the vertical stabilizer. As the pilot pushes on one of the rudder pedals, a cable connected to the rudder allows the rudder to move. Just like the other flight controls, as air moves around the deflected rudder, a force is applied, making the airplane yaw.
Simply, if the pilot pushes the left rudder pedal, the nose of the airplane will slide to the left. The easiest way to envision this is to think of an airplane suspended on a string above the ground. push as hard as you could towards the right, what do you think would happen?
The tail of the airplane would move to the right, and the nose would move to the left. It's that simple. We use the rudder in coordination with the ailerons to turn the airplane.
The primary flight controls then fundamentally work the same. The pilot moves a control in the cockpit, which through cables and other linkages moves that control. As that control is moved, the airflow around it gets deflected, creating a force that is and results in the airplane either rolling, pitching, or yawing.
In order to help improve the performance of the airplane and make the pilot's job easier, most general aviation airplanes are equipped with flaps and trim, known as secondary flight controls. Let's examine these further. The flaps are located on the backside of the wing, close to the fuselage. They are primarily used to help increase lift during takeoff and landing.
The pilot controls the flaps by moving a lever in the airplane which either electrically moves the flaps by a motor like on the Cessna 172 or the pilot manually moves the flaps using a lever like on the Piper Arrow. In either case as the pilot extends the flaps the shape of the wing changes which increases lift. This allows the airplane to fly at slower air speeds and make steeper approaches to landing.
This is extremely beneficial during takeoff from a short runway because it allows the airplane to take off at a slower speed, meaning it will use less runway. During landing, the pilot uses flaps to allow the airplane to land at a slower airspeed, using less distance to decelerate and stop. The other secondary flight control that we'll discuss is trim. The trim is used to make the pilot's job easier. and allows the airplane to essentially fly itself with fewer control inputs by the pilot.
The Cessna 172, like most training airplanes, has two trims. One that the pilot can directly control through cables on the elevator, and the other, a ground-adjustable tab on the rudder. The elevator trim is typically controlled through a wheel inside the cockpit that is labeled nose down or nose up. As the pilot moves this wheel, the cables will adjust the elevator trim tab, which is located on the aft or back end of the elevator. Usually during takeoff, the trim tab is in its neutral position, which means it is just about flush with the elevator.
As the pilot climbs, however, he or she may trim the airplane to help relieve control pressure and prevent pilot fatigue. If he or she wants to climb at a specific airspeed, then the trim can be adjusted to maintain that airspeed. The rudder has a ground-adjustable trim tab.
That simply means that it can only be adjusted while on the ground, as the pilot... has to manually move it. The rudder's ground adjustable tab helps the pilot during climb because of the left turning tendencies that the plane has while climbing.
We'll talk more about those turning tendencies in a future lesson. It is obvious that the flight controls are a necessity for the pilot to fly the airplane. The pilot manipulates these flight controls in order to achieve the desired performance out of the airplane. Now, that we have a basic understanding of the components of the airplane and how the pilot controls different surfaces, let's go under the hood of the airplane and investigate the power plant.