system, and associated sensing and controlcomponents. The trailer has towing and steeringcapabilities and its own braking system. A collapsibleair ducting hose connects to the aircraft and providesconditioned air.A/M32C-21 AIR CONDITIONER.—TheA/M32C-21 air-conditioner (fig. 9-27) is a mobile,four-wheel, trailer-mounted, electrically powered,self-contained unit powered by a 30-horsepower,440-volt, 3-phase, 60-hertz ac electric motor that is anintegral part of the six-cylinder reciprocating typecompressor. A 30- to 50-foot external power cable, a30-foot collapsible duct hose for aircraft connection, acollapsible tow bar for towing and steering, tie-downrings, and a manual parking brake are provided.Hydraulic JacksHydraulic jacks are frequently used in aircraftmaintenance. Maintenance of the tires, wheels, brakes,and struts requires part or all of the aircraft to be liftedoff the deck. The entire aircraft must be lifted off thedeck to perform operational testing of the landing gear.Different types and sizes of hydraulic jacks areneeded. Some typical hydraulic jacks are described inthe following paragraphs. The basic types areillustrated in figure 9-28.AIRCRAFT AXLE JACKS.—The aircraft axlejack (fig. 9-28, view A) is a portable, self-contained,hydraulically operated unit. These jacks are used toraise the landing gear wheels off the deck to performmaintenance operations. The lift, a component of thebase of the jacks, consists of three rams and an outercylinder. A rectangular tank welded to the base formsthe fluid reservoir.AIRCRAFT TRIPOD JACKS.—The aircrafttripod jack (fig. 9-28, view B) is a portable,self-contained, hydraulically operated jack. Thesejacks are used for raising the wing, nose, or tail of anaircraft. When used in sufficient numbers and at therequired jacking points, this jack can lift the completeaircraft off the deck. The jack consists of three mainassemblies—a hydraulic cylinder, a tubular steel tripodleg structure with caster wheels, and a hydraulic pumpassembly. The cylinder and ram are raised by manuallyoperating the hydraulic pump.Maintenance PlatformsPerforming maintenance on aircraft does notalways occur at ground level and often requires the useof a maintenance platform. There are several differentmodels to use depending on type of aircraft, themaintenance requirement, and location. Two commonmaintenance platforms are the B-2 maintenanceplatform and the B-4 maintenance platform.B-2 MAINTENANCE PLATFORM.—The B-2maintenance platform (fig. 9-29) is a fixed height,9-17ANF0929HYDRAULICCYLINDERBARRELLOCKBARRELGROOVESHYDRAULICRESERVOIRTOWBARJACKSCREWHYDRAULICPUMPSHYDRAULICLINESFigure 9-29.—B-2 maintenance platform.
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