The Model HSU-1 fluid service unit (fig. 4-9) is operated similarly to the H-250-1 unit, except that it has a fluid-holding capacity of 3 gallons. Like the H-250-1 servicing unit, the HSU-1 accepts a standard 1-gallon container and uses it as a fluid reservoir. Additionally, it contains an integral 2-gallon reservoir assembly. Three-micron filtration is incorporated to ensure delivery of contamination-free fluid. The integral 2-gallon reservoir assembly is made of anodized cast aluminum and (along with a hand pump assembly) is mounted to a cast aluminum base. The lower can piercer is mounted on top of the reservoir and allows fluid to flow from the installed 1-gallon container into the reservoir, automatically replenishing it. A sight gauge indicates the fluid level of the reservoir. It reads from 0 to 2 gallons, in 1/4-gallon increments. An indicated level of 2 gallons or less means that the 1-gallon container is empty and can be removed for replacement. A capped deaeration port is located on top of the reservoir to permit bleeding the air from the pump and output hose. Can holder and handle assemblies are mounted above the 2-gallon reservoir. The can holder positions the installed 1-gallon fluid container directly above the reservoir, and also provides a means of placing the handle assembly over the container top. The handle assembly is hinged to a bracket on the can holder assembly. It is provided with a spring-loaded latch to lock the handle in the closed position. In addition to the carrying handle itself, the handle assembly contains an upper can piercer, a vent check valve, and a filter. A vent hose is connected between the top of the reservoir (sight gauge) and the upper can piercer.

Fluid is delivered by a single-action, piston hand pump that displaces 1.5 fluid ounces per full stroke at 0 to 250 psi. The pump is operated with a sliding pump handle, which is held in the extended or retracted position by a spring-loaded ball detent. A replaceable 3-micron (absolute) disposable filter on the pump base removes particulate contamination from the hydraulic fluid being delivered to the suction side of the pump. The filter unseats a shutoff valve, which closes the suction port whenever the filter element is being replaced The HSU-1 service unit is equipped with a 7-foot service hose connected to the units fluid output port at the pump assembly. The hose assembly ends with a short bent-tube assembly for direct connection to fill fittings on the aircraft or components being serviced. A 3-micron, in-line filter is located between the hose end and the tube. This prevents reverse-flow contamination and serves as a final filter. When the fluid service unit is not in use, it is stored by wrapping the hose assembly around the can holder assembly and fastening the tube end to the hose storage fitting on the base.

The Model 310 fluid service cart (fig. 4-10) is a hand-propelled, mobile unit designed to service

Filtered fluid from the hand pump is routed to an air trap assembly, which contains a special chamber that removes any free air present in the fluid. The air trap assembly contains a manual bleed valve for venting collected air and a 0- to 300-psi pressure gauge for monitoring output pressure. Fluid is delivered to the system or component being serviced by a 15-foot service hose. A 3-micron, in-line filter assembly is located near the discharge end of the service hose to ensure against system contamination.