Aircraft Construction

Basic section Plain flap Figure 3-9. Weight-shift control aircraft use the shifting of weight Split flap for control. portions of the trailing edge of the control surface. These movable trim tabs, which are controlled from the flight deck, reduce control pressures. Trim tabs may be installed on the ailerons, the rudder, and/or the elevator. Slotted flap A second type of empennage design does not require an elevator. Instead, it incorporates a one-piece horizontal stabilizer that pivots from a central hinge point. This type of design is called a stabilator and is moved using the control wheel, just as the elevator is moved. For example, when a pilot pulls back on the control wheel, the stabilator pivots so the trailing edge moves up. This increases the aerodynamic Fowler flap tail load and causes the nose of the airplane to move up. Stabilators have an antiservo tab extending across their trailing edge. [Figure 3-11] The antiservo tab moves in the same direction as the trailing edge of the stabilator and helps make the stabilator less Slotted Fowler flap sensitive. The antiservo tab also functions as a trim tab to relieve control pressures and helps maintain the stabilator in the desired position. Vertical stabilizer Figure 3-8. Types of flaps. Horizontal stabilizer Empennage Rudder The empennage includes the entire tail group and consists of fixed surfaces, such as the vertical stabilizer and the Trim tabs horizontal stabilizer. The movable surfaces include the rudder, the elevator, and one or more trim tabs. [Figure 3-10] The rudder is attached to the back of the vertical stabilizer. During flight, it is used to move the airplane’s nose left Elevator and right. The elevator, which is attached to the back of the horizontal stabilizer, is used to move the nose of the airplane Figure 3-10. Empennage components. up and down during flight. Trim tabs are small, movable 3-6