Helicopter Components,  Sections, and Systems Chapter 4 Introduction Airframe This chapter discusses the components, sections, and systems  found on most modern helicopters. Helicopters come in a  variety of sizes and shapes, but most share the same major  components. The chapter introduces the major components/ sections of the helicopter and the systems that correlate  with each. Knowing how the components and systems  work on the helicopter enables the pilot to more easily  recognize malfunctions and possible emergency situations.  Understanding the relationship of these systems allows the  pilot to make an informed decision and take the appropriate  corrective action should a problem arise. The airframe, or fundamental structure, of a helicopter can be  made of either metal, wood, or composite materials, or some  combination of the two. Typically, a composite component  consists of many layers of fiber-impregnated resins, bonded  to form a smooth panel. Tubular and sheet metal substructures  are usually made of aluminum, though stainless steel or  titanium are sometimes used in areas subject to higher  stress or heat. Airframe design encompasses engineering,  aerodynamics, materials technology, and manufacturing  methods to achieve favorable balances of performance,  reliability, and cost.  [Figure 4-1]