GRAVITY (OVERWING) FUELING NOZZLE

The MD-1 (fig. 5-15) is the newer nozzle and will eventually replace all D-1 nozzles. Although physi- cally similar, they differ internally, as the collar on the MD-1 nozzle swivels independently of the body. On the D-1 nozzle, the body and collar are one unit. Because the MD-1 is scheduled to become the stan- dard pressure nozzle used in the fleet, it is the only one discussed here. The MD-1 pressure fueling nozzle consists of four major components. They are the collar assembly, the nose seal assembly, the body, and the valve oper- ating linkage. Collar Assembly The collar assembly holds the dust cover and the bumper. The dust cover is used to keep dust, dirt, and moisture out of the nozzle. The bumper is to provide additional protection to prevent accidental damage to the nozzle. The collar is attached to the body by 49 ball bearings. Nose Seal Assembly The nose seal assembly acts like a modified O- ring to seal the nozzle to the aircraft refueling connection and prevent leakage at the connection. It is made of metal and an O-ring type material. It also provides a housing for the poppet. Figure 5-15.—MD-1 Pressure fueling nozzle with nozzle adapter and strainer. Body The body houses the actuating linkage, indexing pins, collar lock pin, and the collar lock pin spring. It also has an opening to connect the sample connection and another opening to connect the actuating lever. The bottom of the body is attached to the inlet elbow by 39 bearings. Leakage between the body and other attached parts of the nozzle is prevented by O-rings. Valve Operating Linkage The valve operating linkage connects the actuat- ing lever to the poppet. When the actuating lever is rotated up and forward, the linkage pushes out the poppet and opens the nozzle. When the actuating lever is rotated backward and down, the linkage pulls the poppet back into the nose seal assembly and closes the nozzle. The poppet is made of Teflon®-coated cast alumi- num. A shroud on the bottom of the poppet eliminates turbulence while fueling. The nozzle poppet pushes on the aircraft fueling adapter poppet when opening, thereby opening the aircraft fueling adapter. GRAVITY (OVERWING) FUELING NOZZLE The gravity fueling nozzle (fig. 5-16) is manually controlled. Like the pressure refueling nozzle, it is attached to the end of a fuel hose by a nozzle adapter and quick-disconnect coupling. The nozzle outlet is inserted directly into the fuel tank. The nozzle is actually a valve for controlling the rate of fuel flow, and it closes automatically when hand pressure is released. When you move the control lever toward the noz- zle handle, fuel is allowed to flow through the nozzle. A dual valve in the nozzle allows a gradual opening or closing of the nozzle. The control lever presses against the valve stem and lifts a small valve disk that is held against its seat by a compression spring. When you open the smaller valve, you avoid a sudden flow of fuel (known as cracking the valve). After cracking, the continued action of squeezing the handle depresses the valve stem farther, and a shoulder on the stem meets the large disk assembly, opening the valve fully. In clos- ing the nozzle, the operation is reversed, and the larger valve disk closes first. The small stream still coming through the valve relieves the stress on the hose, which results if the complete flow is suddenly stopped. Fully releasing the control lever closes the 5-14