Lesson 4: Aircraft Primary Flight Control Surfaces/ Basic structure of an airplane
AILERONS of an aircraft.
An aileron, Figure 12, is a movable control surface. They are found in pairs located in or attached to the outer wing’s trailing edge on both sides of the aircraft. Their primary purpose is to control the aircraft around the longitudinal axis – or roll – by creating unequal or opposing lifting forces on opposite wings.
ELEVATORS of an aircraft.
Attached to the horizontal stabilizer, the elevator, Figure 12, may be one piece or two. If two pieces, they are located on either side of the centerline of the aircraft. Elevators operate together, both going up or down at the same time and are used to control the pitch of the aircraft around the lateral axis.
RUDDER of an aircraft.
The rudder, Figure 12, is an upright control surface used to control the aircraft about the vertical axis. It is hinged to the trailing edge of the vertical stabilizer and is deflected left and right to induce yaw.
ELEVONS of an aircraft
Elevons, Figure 13, are often found on flying wing and delta wing aircraft. They combine the function of the elevators and the ailerons into one control. They act independently for roll and together to control pitch. Elevons can be found on the B-2 bomber.
RUDDERVATORS of an aircraft
Ruddervators are a “V”, Figure 14, or butterfly tail that replaces the standard tail configuration with two surfaces set at an angle to the horizontal. These surfaces control pitch by working together and yaw by working asymmetrically. The F-117A and the refueling boom on the KC-135 are examples of this configuration.
STABILATORS of an aircraft
As aircraft capability and speed increase, especially up to and beyond the speed of sound, a wider range of control is required than can be obtained with simpler types of controls. With the advent of the stabilator, the entire horizontal stabilizer is built in one piece and is pivoted for pitch control. Examples include the century series fighters like the F-100 and F-105, the F-4 and the T-38. The stabilator set the stage for the high performance fighters we have in the current AF inventory.
DIFFERENTIAL STABILIZERS of an aircraft
Are used on high-speed aircraft such as the F 15, F-16, and B-1 (see figures 15 and 16). A differential stabilizer acts as a stabilator to control the pitch of the aircraft; however, each side is also able to move independently of the other. This allows the “stabs” to assist ailerons with roll control. This is significant at high speeds where it provides flight control functions normally handled by the controls on the wings, and allows us to further combine flight controls on the wings for weight reduction (see “flaperons” below).
TRIMMING STABILIZER of an aircraft
(with elevators). Figure 17. Also known as variable incidence stabilizers, these controls are used on aircraft that need a wider range of control forces for different flight conditions. In such cases, the horizontal stabilizer is built to allow changes in the angle of incidence for the entire horizontal stabilizer while maintaining integrated conventional elevators.
CANARDS of an aircraft
A canard is a horizontal stabilizer mounted forward of the wing instead of aft. See Figure 18. At high angles of attack, the canard creates high-energy vortices that wash over the wing delaying boundary layer separation hence stall.