PHAK 3-4

Empennage Powerplant Fuselage Wing Landing gear Figure 3-4. Airplane components. Bulkhead Stringers Longerons Struts Longerons Figure 3-5. Truss-type fuselage structure. independent of airspeed Nose-down force dependent upon airspeed Nose-up force Fixed Variable Vertical forces acting on an airplane in flight. CG CL Lift CG too far aft nose-down force Insufficient elevator If the CG is too far aft, there might not be enough elevator nose-down force at the low stall airspeed to get the nose down for recovery. Lift CG CL CG too far forward nose-up force Insufficient elevator If the CG is too far forward, there will not be enough elevator nose-up force to flare the airplane for landing. CG Lift CL Figure 3-3. Center of gravity (CG). flight. There are numerous wing designs, sizes, and shapes used by the various manufacturers. Each fulfills a certain need with respect to the expected performance for the particular airplane. How the wing produces lift is explained in Chapter 5, Aerodynamics of Flight. Wings may be attached at the top, middle, or lower portion of the fuselage. These designs are referred to as high-, mid-, and low-wing, respectively. The number of wings can also vary. Airplanes with a single set of wings are referred to as monoplanes, while those with two sets are called biplanes. [Figure 3-6] Many high-wing airplanes have external braces, or wing struts that transmit the flight and landing loads through the struts to the main fuselage structure. Since the wing struts are usually attached approximately halfway out on the wing, this type of wing structure is called semi-cantilever. A few high-wing and most low-wing airplanes have a full cantilever wing designed to carry the loads without external struts. The principal structural parts of the wing are spars, ribs, and stringers. [Figure 3-7] These are reinforced by trusses, I-beams, tubing, or other devices, including the skin. The wing ribs determine the shape and thickness of the wing (airfoil). In most modern airplanes, the fuel tanks are either an integral part of the wing’s structure or consist of flexible containers mounted inside of the wing.