| AN 01-25CN-2 | PARAGRAPH 6 |
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6. ASSEMBLY.-Before assembly, thoroughly clean all parts and examine them carefully for signs of wear and damage and the presence of foreign matter such as metal chips, grit and dirt. In the event that any foreign matter is found, the complete hydraulic system should be drained and thoroughly cleaned. To assemble the electric motor-driven hydraulic pump, reverse the procedure specified above. (c) HYDRAULIC HAND PUMP-An auxiliary hand pump is installed on the right side of the cockpit and is used to maintain pressure in the hydraulic system in case of failure of the electric pump. 1 - TO DISASSEMBLE THE HAND PUMP. -REMOVAL.-The hand pump may be removed from the floor of the cockpit by disconnecting all hydraulic lines and removinig the four hold-down bolts. To disassemble the hand pump, refer to Figs. 96 and 97, for the listing of parts. First remove the rubber boot "T" and unscrew the gland retaining nut "S" with the wrench provided in the tool kit. Remove the pump handle shaft "Q". Only one end of the cylinder need be opened to remove the piston. Release the snap ring "N" which retains the discharge check and double seal packings, after which the piston "B" should pull out freely. The ball check at both ends of the piston.may be disassembled by removing the set screw "H" and unscrewing the retainer, "G~" The packing ring "D" and packing "C" may be removed if necessary for replacement. The spring "T" and 'hardened steel check ball "E" may also be removed. The check ball and spring may be removed from the discharge check and double seal packing assembly, by unscrewing the retainer "M" The piston and retainers should be pulled straight out to prevent scoring the cylinder wall and the packings in turn when reassembled in the cylinder. 2. TO ASSEMBLE THE HAND PUMP.-- To assemble the hand pump, reverse the procedure noted in the paragraph above. Before the ball checks are reseated, clean both the ball and seat thoroughly, place the ball on the seat, and tap lightly. In assembling the rubber packings, care must be taken not to damage the feather edges of the packings, for a small cut will cause unsatisfactory pump performance. The best results for installing packings will be obtained by thoroughly wetting the packings and mating the parts with hydraulic fluid (Spec. 3586). |
Test the hand pump after assembly as follows: pump must deliver one quart for 80 strokes (40 cycles) maximum at 500 p.s.i. pressure. When a pressure of 2500 p.s.i. is applied to either of the three ports with the other ports plugged, the pump must not leak more than 5 drops per minute.
(d) CONTROL VALVE.-The control valve assembly consists of two operating handles on two cam shafts which operate a series of poppet valves for the control of the fluid flow. (See Fig. 102.) (e) RESTRICTED FITTINGS AND CHECK VALVES-A restricted fitting is installed in the flap system in the control valve boss from the return line. When the flaps are being raised, because of the air loads on the flaps in the "'down" position, they will go up automatically as soon as the control valve is moved to the "up" position. The 3/64-inch diameter orifice in the restricted fitting controls the flow of fluid in this condition and regulates the rate at which the flaps may move upward. (f) CHECK VALVE. 1. A check valve is installed in the pressure line from the motor-driven pump in the fuselage. This valve is located on the left side of the airplane and may be reached through the stowage compartment door. Its purpose in the system is to prevent by-passing the hand pump pressure through the electric pump when the hand pump is operated. 2. TO DISASSEMBLE THE CHECK VALVE. a. Insert the check valve in a vise with aluminum-covered jaws, at the nut face on the upper end of the valve body. Turn the stop nut off the valve with a suitable wrench. b. Pull the snap ring with a snap ring wrench or a pair of light pliers. c. The bushing, spring, and valve will now fall out when the valve is released from the vise and turned bottom side up. (See Fig. 98.) |
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