Utility Accumulator

TM 1-1520-238-10 2-54 Change 4 (6) Rotor Brake Solenoid Valves. Valves are controlled by a three-position switch OFF, BRAKE, and LOCK on the pilot PWR lever quadrant adjacent to the PWR levers (fig 2-19). When the switch is positioned to BRAKE, utility system pressure regulated to 337 psi is ap- plied to stop the rotor brake disc on the main transmission. When positioned to LOCK, the brake off solenoid valve traps 3000 psi pressure between the manifold and the ro- tor brake actuator. b. Utility Accumulator. The accumulator is a multi- purpose installation unique to the utility hydraulic system. It is located on the right side of the helicopter directly be- neath the APU. It stores hydraulic fluid at 3000 psi. The accumulator is charged by nitrogen gas. A gas storage tank supplies the charge and is serviced through a charg- ing port (fig 2-31). The utility hydraulic manifold pressure is used for rotor brake application, APU starting, and emergency use of flight control operation. 2.38.3 Hand Pump. A hand pump is installed next to the primary system GSE panel on the right side of the heli- copter. The pump provides one method of charging the fluid pressure in the utility accumulator as well as a meth- od for the ground crew to fill both the primary and utility reservoirs. Low pressure fluid entering the fill port is fil- tered by a 45 micron screen filter (before MWO 1-1520-238-50-52) or a 5 micron cartridge filter (after MWO 1-1520-238-50-52). A lever may be moved to any of three positions. This, in turn, will open one of three me- chanically operated check valves to the accumulator or to either reservoir. Section XV contains servicing instruc- tions. 2.39 PRESSURIZED AIR SYSTEM (PAS). The PAS cleans, pressurizes, regulates, and distributes air to the air turbine starters, fuel boost pump, fuel trans- fer pump, external fuel tanks, hydraulic reservoirs, heat exchangers, defog nozzles, engine cooling louver actua- tors, utility receptacle, ice detector sensor, and environ- mental control unit (ENCU). The pressurized air system has three sources of air: The primary source is the shaft driven compressor; the other sources are bleed air from the No. 1 engine and from an external air source. M01-137 UTILITY MANIFOLD CHARGING PORT Figure 2-31. Utility Manifold