A complete wheel assembly is shown in figure 11-3. The wheel casting is the basic unit of the wheel assembly. It is to this part that all other com-ponents are assembled and upon which the tire is mounted.

Figure 11-1.Typical divided (split) wheel assembly.

The demountable flange is attached to the wheel to simplify tire removal and installation. The remountable flange lockring secures the flange to the wheel. The flange is fitted into a groove in the wheel casting.

The bearing cups are shrink-fitted into the hub of the wheel casting, and are the parts on which the bearings ride. The bearings are tapered roller bearings. Each bearing is made of a cone and rollers. This type of bearing absorbs side thrust as well as radial loads and landing shocks. These bearings must be cleaned and lubricated in accordance with the NAVAIR 04-10-1 manual.

A three-piece grease retainer keeps the grease in the inboard bearing and keeps out dirt and moisture. It is composed of a felt seal and inner and outer closure rings. A lockring secures the assembly inside the wheel hub.

The hubcap seals the outboard side of the hub. It is secured with a lockring. On some aircraft, the hubcap is secured with screws.

All wheels designed to be used on the main landing gear are equipped with braking components. These components are attached to the wheel casting. They may consist of either a brake drum or brake drive keys. The wheel shown in  figure 11-3 is

Figure 11-2Demountable flange wheel.

Figure 11-3.Typical wheel assembly.

equipped with drive keys. This wheel is designed for disc brakes.

The trend in the military is toward smaller, faster, more powerful aircraft with increased load carrying capabilities. This means heavier loads and higher landing speeds. The friction of long landing rollouts and taxiing causes heat to be absorbed by the wheel. Because of the heat, possible wheel failure may occur. This may damage equipment and injure personnel. To prevent this situation, aircraft manufacturers have developed a safety device called a fusible plug. The fusible plug contains an alloy that will melt and permit the tire to deflate. This action occurs in the event the wheel is exposed to excessive heat. Wheels that contain fusible plugs should have a metal tag affixed that reads "Fusible Plugs Installed."