ENGINE MOUNTS

CHAPTER 1 AIRCRAFT CONSTRUCTION AND MATERIALS

Aviation Structural Mechanic (H&S) 3&2 - How airplanes are built and how to maintain them
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Figure 1-1.—Semimonocoque fuselage construction. The semimonocoque fuselage is constructed primarily of aluminum alloy; however, on newer aircraft graphite epoxy composite material is often used. Steel and titanium are found in areas subject to high temperatures. Primary bending loads are absorbed by the "longerons," which usually extend across several points of support. The longerons are supplemented by other longitudinal members, called “stringers.” Stringers are lighter in weight and are used more extensively than longerons. The vertical structural members are referred to as “bulkheads, frames, and formers.” These vertical members are grouped at intervals to carry concentrated loads and at points where fittings are used to attach other units, such as the wings, engines, and stabilizers. Figure 1-1 shows a modified form of the monocoque design used in combat aircraft. The skin is attached to the longerons, bulkheads, and other structural members and carries part of the load. Skin thickness varies with the loads carried and the stresses supported. There are many advantages in the use of the semimonocoque fuselage. The bulkheads, frames, stringers, and longerons aid in the construction of a streamlined fuselage. They also add to the strength and rigidity of the structure. The main advantage of this design is that it does not depend only on a few members for strength and rigidity. All structural members aid in the strength of the fuselage. This means that a semimonocoque fuselage may withstand considerable damage and still remain strong enough to hold together. On fighters and other small aircraft, fuselages are usually constructed in two or more sections. Larger aircraft may be constructed in as many as six sections. Various points on the fuselage are heated by station number. Station 0 (zero) is usually located at or near the nose of the aircraft. The other fuselage stations (FS) are located at distances measured in inches aft of station 0. A typical station diagram is shown in figure 1-2. On this particular aircraft, station 0 is located 93.0 inches forward of the nose. Quick access to the accessories and other equipment carried in the fuselage is through numerous doors, inspection panels, wheel wells, and other openings. Servicing diagrams showing the arrangement of equipment and the location of access doors are supplied by the manufacturer in the maintenance instruction manuals and maintenance requirement cards for each model or type of aircraft. Figure 1-3 shows the access doors and inspection panels for a typical aircraft. ENGINE MOUNTS Engine mounts are designed to meet particular conditions of installations, such as their location on the aircraft; methods of attachment; and size, type, and characteristics of the engine they are intended to support. Although engine mounts vary widely in their appearance and in the arrangement of their members, the basic features of their construction are similar. hey are usually constructed as a single unit that may be detached quickly and easily from the remaining structure. In many cases, they are removed as a complete 1-2

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