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an Arimid$^{®}$ fiber and the outer sheets are coated Phenolic$^{®}$ is common as well. In fact, a myriad of other material combinations such as those using fiberglass, plastic, Nomex$^{®}$, Kevlar$^{®}$, and carbon fiber all exist. Each honeycomb structure possesses unique characteristics depending upon the materials, dimensions, and manufacturing techniques employed. Figure 1-39  shows an entire wing leading edge formed from honeycomb structure. 

## Nacelles 

Nacelles (sometimes called “pods”) are streamlined enclosures used primarily to house the engine and its components. They usually present a round or elliptical profile to the wind thus reducing aerodynamic drag. On most single-engine aircraft, the engine and nacelle are at the forward end of the fuselage. On multiengine aircraft, engine nacelles are built into the wings or attached to the fuselage 

at the empennage (tail section). Occasionally, a multiengine aircraft is designed with a nacelle in line with the fuselage aft of the passenger compartment. Regardless of its location, a nacelle contains the engine and accessories, engine mounts, structural members, a firewall, and skin and cowling on the exterior to fare the nacelle to the wind. 

Some aircraft have nacelles that are designed to house the landing gear when retracted. Retracting the gear to reduce wind resistance is standard procedure on high-performance/ high-speed aircraft. The wheel well is the area where the landing gear is attached and stowed when retracted. Wheel wells can be located in the wings and/or fuselage when not part of the nacelle. Figure 1-40  shows an engine nacelle incorporating the landing gear with the wheel well extending into the wing root. 

<img src='content_image/590160.jpg'>

