Structural design considerations and examples of structural layout design of wings The purpose of this section is to provide some guidelines and examples of how the structural layout design and integration of the wing structure into the airplane can be accomplished. The material in this section is organized as follows:
Typical sapar, rib and stiffener spacings. Examples of wing structural arrangements Example of wing/fuselage integration Example of wing cross section design Examples of lateral control mechanizations Examples of high lift device mechanizations Examples of wing skin gages Maintenance and acces requirements.
Chapter 7 contains a procedure for preparing the overall structural arrangement of an airplane. For additional insight into airplane structural arrangements, the reader should consult chapter 8. TYPICAL SPAR, RIB AND STIFFENER SPACINGS. The actual structural arrangement of spars, ribs and skin stiffeners depends very mucho on the type of airplane subjected. The reader should refer to refs. 11, 19 and 23 for detailed information on the types of loads to which airplane structures are subjected. Reference 20 contains detailed methods for the preliminary structural analysis of wing structures. Figure 4.49 defines the locations of major structural components for wings.
Wing spar locations: most airplane wings use a so-called torque-box (wing box) as the main load carrying component. The torque box should be located to take maximum advantage of the structural height available within the airfoil contours. This will save weight. A front spar, a rear spar and an upper and lower skin normally close off the torque box. The spar locations are often constrained by requirements for high lift devices. Typical spar locations are: Front spar: 15-30 percent chord Rear spar: 65-75 percent chord
Multiple spar construction is often applied in the case of fighter wings. The F16 wing has 11 spars, 5 ribs and a machine-tapered skin without stiffeners. Wing Rib locations: To help stabilize torque box skins and to serve as attachment points for leading edge skins, trainling edge skins and/ or flaps, ailerons and spoilers, wing ribs are used. Typical rib spacings are:
Light airplanes: 36 inches Transports: 24 inches Fighters and trainers: rib spacings vary widely Ribs are always required at those spanwise locations where stores are attached to a wing. Examples of such ribs are shown in section 4.3. Wing stiffener spacings: These vary widely and depend on the relative stiffness of the wing skin. For example spacings see sub-section 4.2.2. 4.2.2 Examples of wing structural arrangements. A procedure for arriving at the overall structural arrangement for any new airplane is given in chapter 7. Figures 4.50 through 4.59 present examples of wing structural arrangements for the following airplanes:
Note that in most of these structural arrangements the wing stations of major structural elements are defined. A complete structural arrangement must contain that information. The structural arrangement for the P166 and the CL 215 are given in their entirety.
