9.2 Utility Hydraulics SH.PDF

UNITED STATES ARMY AVIATION CENTER FORT RUCKER, ALABAMA 24 April 2018 STUDENT HANDOUT CH-47F UTILITY HYDRAULIC SYSTEM 9.2 (MTP) H47F40...

UNITED STATES ARMY AVIATION CENTER FORT RUCKER, ALABAMA 24 April 2018 STUDENT HANDOUT CH-47F UTILITY HYDRAULIC SYSTEM 9.2 (MTP) H47F4000 PROPONENT FOR THIS STUDENT HANDOUT IS: 110 Aviation Brigade, 223-A, MTPC ATTN: ATZQ-ATB-CA Fort Rucker, Alabama 36362-5000 FOREIGN DISCLOSURE RESTRICTIONS: FD 2 - The materials contained in this course have been reviewed by the course developers in coordination with the USAACE Foreign Disclosure Officer, Fort Rucker, AL foreign disclosure authority. This course is releasable to military students from foreign countries on a case-by-case basis. Foreign countries desiring to place students in this course must meet one or more of the following criteria: (1) Own (a specific piece of equipment); (2) Have a signed Letter of Intent (LOI); (3) Have waiver from HQDA; (4) Have USG release for training; (5) etc. THIS PAGE INTENTIONALLY LEFT BLANK. 2  MAINTENANCE TEST FLIGHT UTILTIY HYDRAULIC SYSTEM TABLE OF CONTENTS Page TERMINAL LEARNING OBJECTIVE....................................................................................................................... 4 SECTION II, INTRODUCTION................................................................................................................................... 4 SECTION III, PRESENTATION.................................................................................................................................. 5 LSA 1 – GENERAL COMPONENTS AND DESCRIPTION....................................................................... 5 LSA 2 – APU RELATED HYDRAULIC COMPONENTS........................................................................ 13 LSA 3 – PRESSURE & RETURN CONTROL MODULE & UTILITY BOOST PUMP............................... 15 LSA 4 – POWER TRANSFER UNITS, CARGO HOOK & HOIST/WINCH SUB-SYSTEMS..................... 17 LSA 5 – WHEEL BRAKE SUB-SYSTEM............................................................................................... 28 LSA 6 – POWER STEERING/SWIVEL LOCK SUB-SYSTEM................................................................. 32 LSA 7 – CARGO RAMP AND DOOR SUB-SYSTEM............................................................................. 38 SUMMARY......................................................................................................................................................... 44 3 Terminal Learning Objective: Correlate the components, functions, and operational characteristics of the CH-47F Action: Utility Hydraulics System to maintenance testing procedures and indicators. Given TM 1-1520-271-10 Operator`s Manual for Army CH-47F Helicopter; TM 1- 1520-271-23&P Interactive Electronic Technical Manual Field Maintenance for Condition: Helicopter, Cargo Transport CH-47F including Repair Parts and Special Tools List (EM 0281); a computer with Interactive Multimedia Instruction (IMI) installed; a slideshow presentation; and the CH-47F Utility Hydraulic System Student Handout Correlation includes:  Review the purpose of the Utility Hydraulic System.  Review the Utility Reservoir/Cooler.  Review the APU Start Accumulator, APU Motor/Pump, Utility Pump, and the Auxiliary Ground Power Unit (AGPU). Standard:  Review the Pressure Control Module (PCM), and the Return Control Module.  Review the seven subsystems of the utility hydraulics (engine starters 1 & 2, brakes, power steering, swivel locks, ramp, Power Transfer Units (PTU) winch, and the center cargo hook. Classroom: Use care when handling training aids and or operating electronic devices. Safety Job Performance: Observe all WARNING, CAUTIONS, and NOTES that are published in Requirements: the operator’s manuals, student handouts and abide by all other safety regulations. Risk Assessment Low. Level: It is the responsibility of all Soldiers and DA civilians to protect the environment from damage. Environmental Considerations: Students should recycle all materials possible, e.g., paper, printer cartridges, soda bottles, cardboard, etc. Each student will be evaluated on this block of instruction during the written examination. Evaluation This will be a criterion type examination requiring a GO on each scoreable unit. You will have 3 hours for the exam 4  SECTION II. INTRODUCTION The utility hydraulic system provides hydraulic power during normal operations and in emergency situations to the aircraft’s wheel brakes, power steering, swivel locks, centering cams, cargo ramp & door, center cargo hook, cargo/rescue winch, power transfer units, engine starters and APU start subsystems. The Maintenance Test Pilot must be familiar with the operational, maintenance and troubleshooting aspects of utility hydraulic system and it’s subsystems to assure overall mission success 5  SECTION III PRESENTATION 1. Learning Step / Activity 1. General Component and Description. Utility Hydraulic System Schematic (Frame 1000) a. The utility hydraulic system supplies hydraulic power to operate seven aircraft subsystems. These subsystems include: (1) Engine Start (2) Cargo Ramp and Door (3) Power Transfer Units (4) Cargo/Rescue Winch (5) Center Cargo-Hook Release (6) Wheel Brakes (7) Power Steering and Swivel Locks b. In addition, the system can power both flight control hydraulic systems during ground and emergency operations. c. The normal operating system pressure is 2500-3500 PSI, and a system return pressure of 60-90 PSI. 6  (Frame 1010) d. There are four sources of power for the utility hydraulic system. (1) APU start accumulator (2) APU motor/pump (3) Utility hydraulic boost pump (on the #2 side of the aft transmission) (4) Auxiliary Ground Power Unit (AGPU) e. The utility system capacity is 5.6 gallons. (Frame 1020) f. The components we will discuss in this section include: (1) Hand Pump (2) Electric Pump for the Utility System Hydraulic Accumulator (EPUSHA) (3) Emergency Utility Pressure Valve 7  (4) Fill Module (5) Utility Reservoir/Cooler (6) Utility Cooler Fan (7) Utility Hydraulic Accumulator (bootstrap) (8) Reservoir Depressurization Valve Hand Pump (Frame 1030) g. Hand Pump (1) Located right side of ramp area at STA 535. (2) The handle telescopes to give more leverage. (3) The hand pump is a two stage hand pump which is primarily used to pressurize the APU start accumulator to start the APU. (4) In an emergency, the hand pump can be used to operate some of the utility subsystems. (5) The hand pump moves.97 cubic inches or hydraulic fluid per cycle up to a pressure of 1800-2000 PSI on the APU start accumulator. (6) Moves.59 cubic inches of fluid per cycle above 2000 PSI. 8  Electric Pump for the Utility System Hydraulic Accumulator (Frame 1040) h. Electric Pump for the Utility System Hydraulic Accumulator (EPUSHA) (1) Consists of an electric pump and pump control box to provide a less labor intensive means of pressurizing the APU start accumulator. (2) Has a max continuous run time of 5 minutes. Minimum cool-down time of 10 minutes is required once max run time is reached. (3) Electric Pump: (a) Located right side of ramp area at STA 539. (b) Pressurizes the APU Start Accumulator for APU start. (c) The electric pump is a fixed displacement, radial piston, electric motor driven pump. (d) Operates on 18 to 32 VDC supplied by the aircraft battery. (e) The pump is equipped with a pressurization switch that deactivates the pump once 2,950-3,050 PSI is reached on the APU start accumulator. (f) Incorporated within the pump is a thermal switch which deactivates the pump if an internal temperature of 300 °F is reached. Once the temperature drops below 270°F, safe operation of the pump may resume. (4) Control box: (a) Located right side of ramp area at STA 581. (b) Has a three position switch, START, STOP and center (NEUTRAL). (c) Placing the switch to the START position activates the pump. (d) To manually deactivate the pump, place switch to the STOP position. (e) Has a voltage sensing relay that shuts down the pump if the aircraft battery voltage drops below 20 VDC. 9  NOTE: Multiple EPUSHA operations may deplete the aircraft battery to the point that the APU cannot be started. To ensure battery power is available to start the APU, the number of EPUSHA operations should not exceed five. The actual number of operations will depend on battery condition, temperature and pump condition. EPUSHA Schematic (Frame 1050) (5) The pressure switch is normally closed, electrically opened. It activates at 2950-3050 pounds per square inch gauged (psig) to supply an over pressurization signal to the electrical receptacle. The switch is released and 24 VDC is removed from the circuit and the operation of the EPUSHA pump stops. The pressure switch deactivates at pressures below 2950-3050, turning on the pump. (6) In the event of an EPUSHA failure, the hand pump may still be used to pressurize the APU start accumulator. Emergency Utility Pressure Valve (Frame 1070) i. Emergency Utility Pressure Valve (1) Located at right side of ramp area STA 540. 10  (2) Manually operated (3) In the OPEN position it: (a) Allows the APU start accumulator or the hand pump (in some emergencies) to pressurize the utility system. (b) During power off operations, pressure from the APU start accumulator can be used to operate the winch, wheel brakes, and the cargo ramp and door subsystems. Hydraulic Fill Module (Frame 1080) j. Fill module (1) Used to service all three of the aircraft hydraulic systems. (2) The systems are normally serviced from this module but can also be serviced by an auxiliary ground power unit (AGPU). (3) Servicing can be accomplished while the system is in a static or operating condition, by pumping the fluid into the return portion of the selected system. NOTE: MIL-PRF-82382 has a higher flash point which provides a greater margin of safety than MIL-PRF-5606. The two fluids are fully compatible; however, the presence of more than 3 percent MIL-PRF-5606 will reduce the fire-resistance of MIL-PRF-82382 proportionately. (4) Use fire-resistant hydraulic fluid MIL-PRF-82382 (Primary). (5) Use hydraulic fluid MIL-PRF-5606 (Alternate) when MIL-PRF-82382 is not available or in temperatures below -50ºF (-46ºC). 11  Hydraulic Fill Module Schematic (Frame 1100) (6) Selecting the utility system will allow hydraulic fluid to pass through the return control module, return filter, and then into the reservoir/cooler. NOTE: Do not let the fluid level go below the site glass of the fluid level or air will be inducted into the hydraulic system being serviced. (7) The fill module includes a filter screen that will catch particles of 0.0035 or greater in size. (8) The fill module has a 1 quart capacity. (9) A site glass located at the bottom of the fill module is used as a visual level indicator. Utility Reservoir/Cooler (Frame 1110) k. Utility Reservoir/Cooler (1) Located in the hydraulics compartment of the aft pylon, on the right side. (2) Stores and cools hydraulic fluid for system operation. 12 (3) Is larger in size when compared to the flight hydraulic reservoir/cooler, and has a capacity of 5.6 quarts. (4) The utility reservoir/cooler is identical in operation to the No.1 and No.2 flight hydraulic reservoir/cooler, allowing the temperature sensor, thermal switch and relief valves to be interchangeable with all three reservoir/coolers. Visual Fluid Level Indicator (Frame 1120) (5) A visual fluid level indicator provides a mechanical means of determining the actual fluid level in the reservoir. Linear Variable Differential Transducer (Frame 1140) (6) A linear variable differential transducer (LVDT): (a) Located in the center of the reservoir, inside the visual fluid level indicator. (b) Indicates the level of fluid inside the reservoir based on the position of the floating piston that divides the fluid from the air. (c) Transmits the fluid level reading to the indicator on the maintenance panel. (d) Adjustable at AVIM (ASB) level only. 13  Utility Reservoir Level Indicator (Frame 1150) (e) A signal conditioner is internal to the indicator on the maintenance panel which inverts the 24/28 VDC to 8 VAC and sends it to the LVDT. (f) The LVDT receives the 8 VAC and returns a voltage proportional to the fluid level back to the indicator. (g) The conditioner circuits within the indicator rectify this return voltage back into VDC, and produce the proper indication. Reservoir/Cooler Bleed Relief Valve (Frame 1160) (7) Bleed/relief valve: (a) Protects the reservoir from over-pressurization. (b) Manually operated to bleed air from the reservoir. (c) Begins to open automatically at 100 PSI, and is fully opened at 125 PSI. (d) Fluid is drained through the HYDR COMPT DRAIN on the #2 side of the ramp area. 14  Reservoir/Cooler Bypass Valve (Frame 1170) (8) Bypass/relief valve: (a) Located between the return port and the supply port of the reservoir. (b) When the return pressure to the cooler exceeds supply pressure to the pump by over 20 PSI, the fluid will bypass the cooler. This will happen if the cooler became clogged or the fluid is thick (high viscosity) which will take increased amount of pressure to push the fluid through the cooler during cold weather. Bypass Valve Schematic (Frame 1170) (c) Relief valve is fully open at 25 PSI. (d) Relief valve closes and reseats itself at 20 PSI, allowing fluid to enter the cooler. 15  Reservoir/Cooler Temperature Bulb (Frame 1180) (9) Temperature Bulb: (a) Transmits an electrical signal to the utility hydraulic system fluid temperature indicator on the maintenance panel. (b) Located in the supply port of the reservoir/cooler. (c) As the temperature of the fluid increases, the temperature bulb resistance increases. The indicator circuit repositions the pointer to balance the circuit. (d) Powered by 28 VDC Reservoir/Cooler Thermal Switch (Frame 1190) (10) Thermal Switch: (a) Located on the supply port of the reservoir/cooler. (b) Controls the cooler fan operation. (c) Fluid temperature reaches 63° C (146°F) the fan is activated. (d) The fan is deactivated at 54° C (129°F). 16  Thermal Switch Schematic (Frame 1190) Utility System Hydraulic Cooler (Frame 1200) (11) Cooler Section: (a) Mounted on the top of the reservoir. (b) Hydraulic fluid passes through the cooler into the reservoir, prior to being supplied to the pumps. (c) Fluid is cooled by drawing air through the cooler assembly using an electrical fan. 17  Utility Hydraulic Cooler Fan (Frame 1210) l. Cooler Fan: (1) Located in the upper portion of the aft pylon, STA. 534 water line 120 butt line 0. (2) Connected to the cooler assembly by flexible ducting. Circuit Breakers for the Utility Cooler Fan (Frame 1220) NOTE: If No.1 AC or DC system fails with no bus-tie, the utility oil cooler fan will not function. (3) Two sources of electrical power are required for operation. The cooler fan uses 115 VAC from the No.1 AC bus, and is controlled by the 28VDC thermal switch on the reservoir/cooler through the 140K2 relay. (4) The UTIL HYD COOLING BLOWER circuit breaker, located on the No.1 AC bus, operates the fan. (5) The UTIL BLO CONTR circuit breaker, located on the No.1 DC bus, controls power to the thermal switch on the reservoir/cooler. 18  140K2 Relay (Frame 1220) (6) The 140K2 relay is located inside the aft pylon hydraulics compartment on the back wall No.1 side. When it receives the 28VDC from the thermal switch, it allows the 115VAC to the cooler fan. Utility Hydraulic Accumulator (Frame 1230) m. Utility hydraulic accumulator (bootstrap): (1) It is a 25 cubic inch accumulator located inside the aft pylon hydraulics compartment aft of the utility reservoir/cooler. (2) Maintains a head pressure of 60 PSI on the reservoir/cooler when the utility boost or APU motor/pump is not operating to prevent pump cavitation. (3) It must be depressurized to get an accurate reading of its pre-charge. (4) Applies the pressure to the back side of the piston at approximately 3000 PSI (or what the pressure in the accumulator) using a small area, and pushes on the fluid which has an area that is 50 times larger. Supplying that 60 PSI continuous flow to the APU Motor/Pump to prevent pump cavitation. Once the pumps are operating, the system pressure of 3000 PSI maintains supply fluid pressure. 19  (Frame 1240) n. Utility Reservoir Depressurization Valve: (a) Located on the right side of the ramp area STA 555. (b) OPEN position allows the utility hydraulic accumulator to be depressurized when the APU start module depressurization valve is pressed. Is also used in conjunction with the EMERG UTIL PRESS to completely depressurize the utility hydraulic system. Check on Learning 1. The hand pump moves.97 cubic inches of hydraulic fluid per cycle up to a pressure of _______ PSI. A. 1600-1800 B. 1800-2150 C. 1800-2000 D. 2150-3000 2. Which component transmits the utility reservoir cooler assembly fluid level reading to the indicator on the maintenance panel? A. Visual fluid level indicator B. Linear variable differential transducer C. Fluid level switch D. Cooler bypass valve 3. The utility system provides hydraulic pressure to operate how many aircraft subsystems? A. Seven B. Eight C. Ten D. Nine 20 4. At what temperature is the fluid in the utility reservoir/cooler assembly when the cooler fan is activated? A. 63° F B. 54° C C. 63° C D. 54° F 21 2. Learning Step / Activity 2. APU related Hydraulic Components Reference: IETM- Helicopter Introduction/Equipment Description and Data/Utility Hydraulic APU Start Accumulator (Frame 2000) a. APU Start Accumulator: (1) Located in the ramp area to the right of the aft transmission at STA 555. (2) Primarily used for APU starting, during power off conditions can be used to operate the winch, wheel brakes, and ramp operations. (3) Basic characteristics: (a) Weighs 28lbs. dry. (b) 30 inches long (c) 375 cubic inch displacement (d) Withstands up to a.50 caliber projectile APU Start Accumulator Cut-Away (Frame 2010) 22 (4) Contains three chambers: (a) Air charge Chamber (section 1) holds the air or nitrogen gas pre-charge which is used to force the pressurized fluid to the utility system or the APU motor/pump. (b) Hydraulic pressure chamber (section 2) holds the pressurized fluid. (c) Hydraulic return chamber (section 3) holds return fluid. (5) The piston is vented through a hole between the piston seals; through a tube that runs to a port in the piston shaft; and out the end of the aft end of the accumulator. A sintered bronze screen filters the vented air. (Frame 2010) (6) The accumulator has a gauge and charge valve on the end of the accumulator. (a) Precharge is IAW the chart in the checklist, usually 1800-2000 PSI. Must depressurize accumulator to get correct precharge reading. (b) Should read 3000 PSI on preflight. APU Start Module (Frame 2030) 23 b. APU Start Module: (1) Located in the ramp area on the No.2 side of the right aft transmission door, STA 570. (2) Controls the APU start accumulator and the mode of operation of the APU motor/pump during the APU start sequence. (a) The APU start module accumulator is used to sequence the APU motor pump to shift into the motor mode to facilitate APU starting. (b) The APU start module is 5.75 cubic inches. (3) Primary function is to supply start signal pressure and pressure to the APU motor/pump. (4) Secondary function is to depressurize the APU start and utility hydraulic accumulators so that the utility system can be repaired. (5) Contains: (a) Accumulator pressure gauge indicates pressure in the APU start accumulator, should indicate approximately 3000 PSI on Preflight. (b) APU start module accumulator provides signal pressure to the shuttle valve on the APU motor/pump. During APU acceleration the accumulator keeps pressure in the signal line to prevent the motor/pump from changing from a motor to a pump before the APU is at its rated speed of 90%. (c) Depressurization valve is used to depressurize the utility system. Both EMER UTIL PRESS and Utility Reservoir Depressurization Valves must be open to depressurize the entire system. (d) APU start solenoid valve is controlled by the ESU using the APU start switch. It releases pressure to the pressure operated valve and pressure to the signal port of the APU motor pump simultaneously. APU Start Module Schematic (Frame 2040) (e) Pressure operated valve sends fluid from the APU start accumulator through the pressure line of the APU motor/pump. (f) Controlled by the solenoid valve, it is a slow opening mechanical valve that prevents shearing of the shaft between the APU motor/pump and the APU reduction drive. 24  APU Motor/Pump (Frame 2050) c. APU motor/pump: (1) Provides utility system pressure for engine start, ground operations and can be used in an emergency should the boost pump on the aft transmission fail during flight. (2) Mounted on the axial pad of the APU at STA 594. (3) It has a shearable shaft, which will shear at 1270 inch pounds of torque. (4) Has two modes of operation: (a) Motor mode: it drives the APU as a motor during the starting sequence and has a constant delivery stage. (b) Pump mode: driven by the APU operation and has a variable delivery stage providing 3350 PSI at 11.5 GPM. (5) Has five hydraulic ports: (a) A supply port with a fluid pressure of 60 PSI, except during APU starting which is 3000 PSI. (b) A pressure port with a fluid pressure of 3350 PSI. (c) A signal pressure port, which receives hydraulic pressure from the APU start module, positioning a spool valve to change the motor/pump to the motor mode to facilitate APU starting. (d) Case drain port with a flow rate not to exceed 1.0 GPM +.25 GPM. (e) Seal drain port allows hydraulic fluid or oil leakage between the motor/pump and the APU to be drained from the system. 25  APU Motor/Pump Schematic (Frame 2070) (6) The APU motor/pump’s mode of operation is controlled by two means, hydraulic and electrical. The motor mode is accomplished through the electronic sequencing unit (ESU), the APU start module and then to the motor/pump. (a) The ESU receives 28 VDC signal from the APU START switch. (b) The ESU then sends that 28 VDC signal to the APU start module pilot solenoid valve causing it to open. (c) The APU start module pilot solenoid valve releases pressure from the APU start module accumulator through the start signal line while simultaneously opening the pressure operated valve, which releases pressure from the APU start accumulator. (d) Start signal fluid flows to the spool valve changing the pressurized fluid from the APU start accumulator to the yoke actuator, changing the wobble plate and converting the motor/pump into the motor mode. Concurrently, pressurized fluid from the APU start accumulator begins to turn the motor. (e) At approximately 20% N1, the minimum power mode, the APU start accumulator is depleted and the wobble plate moves to a neutral position. (f) The pump mode occurs when the APU reaches 90% N1 speed, sensed by the ESU. The ESU removes the 28VDC to the APU start module pilot solenoid valve, causing it the close. This removes the pressure in the signal line allowing the spool valve to remove the pressure from the yoke actuator, thus the motor/pump turning back into a pump. Check on Learning 1. Which component stores fluid under pressure for APU starting? A. APU start module B. Utility reservoir pressurization accumulator C. APU start accumulator D. Utility hydraulic pump 26 2. The APU motor pump port with a fluid pressure of 3350 PSI is the ______ port. A. Case Drain B. Signal pressure C. Pressure D. Supply 27 3. Learning Step Activity 3. Pressure Control Module, Return Control Module & Utility Boost Pump Reference: IETM- Helicopter Introduction/Equipment Description and Data/Utility Hydraulic Pressure Control Module (Frame 3010) a. Pressure Control Module: (1) Located in the aft cabin area on the forward left hand side of STA 534 former assembly, adjacent to the No.9 drive shaft. (2) Controls the flow of all pressure fluid throughout the utility system and its subsystems. (3) Routes fluid first through a filter and then into five separate branches and incorporates isolation capabilities with the use of pilot solenoid valves. Filter Bowl Assembly (Frame 3020) (4) The filter bowl assembly is separated into three areas: Filter Bowl, Visual Contamination Indicator and a Filter Change Electrical Transmitter. (a) The filter bowl contains a five micron disposable filter. 28  (b) A differential pressure indicator (DPI) button extends when a pressure differential exceeds 75 PSID + 10, which is measured by the difference between the inlet and outlet pressures of the filter element. (c) Pressure differential may be caused by filter contamination or by pressure surges. (d) A differential pressure switch, mounted on the bottom of the filter bowl, activates the utility FLTR CHNG PRESS light on the maintenance panel when the DPI button has extended. Utility Pressure Transmitter (Frame 3030) (5) Pressure Transmitter: (a) Provides the pressure signal to the indicator on the maintenance panel. (b) Is an electro-mechanical device, receives 28VDC from the No.2 DC bus. Pressure Control Module High Pressure Relief Valve (Frame 3040) (6) High Pressure Relief Valve: 29  (a) Prevents the pressure control module from over-pressurization in the event of a high-pressure state. (b) Starts to open at 3500 PSI, is fully open at 3850 PSI to relieve the high-pressure state inside the module. (c) The relief valve is totally mechanical; once the mechanical pressure of the valves internal spring over-rides the hydraulic pressure, the valve will close. Utility Pressure Switch (Frame 3050) (7) Pressure Switch: (a) Controls the UTILTY HYD PRESS LO caution annunciator on the MFD to illuminate or extinguish. (b) Illuminates the caution annunciator at 1800 PSI of descending pressure. (c) Extinguishes the caution annunciator at 2300 PSI of ascending pressure. Engine Start Solenoid Valves (Frame 3060) (8) No.1 and No.2 engine start pilot solenoid valves: 30  (a) Control the engine start pressure operated valves to open. (b) Receives 28 VDC from its respective DC essential bus when activated by the engine start switch on the overhead console. (c) The part number for the No.1 and No.2 pilot solenoid valves are different. They are not interchangeable because the wiring set-up in each pilot solenoid valve is different. The pilot solenoid valves are wired into an interlock feature which prevents both energized at the same time. This allows only one engine to be motored with the switches in the MOTOR position. Engine Start Pressure Operated Valve (Frame 3070) (9) No.1 and No.2 engine start pressure operated valves: (a) Allow pressurized fluid to flow to their respective engine starters during engine start sequence. (b) Totally mechanical valves (slow opening). (c) Normally closed, hydraulically opened by its respective pilot solenoid valve. (d) Spring-loaded to the closed position. 31  PTU, Cargo Hook, & Hoist/Winch Solenoid Valve (Frame 3080) (10) PTU, Hook and Hoist/Winch pilot solenoid valve: NOTE: Any of the four toggle switches, when selected, will break the ground to the pilot solenoid valve; which results in the solenoid valve de-energized closed and the pressure operated valve opened. Should a situation develop, such as a hydraulic leak between the pressure control module and either the PTU’s, center cargo hook or the hoist/winch, it would be necessary to turn all four switches to the OFF position to successfully isolate the hydraulic leak. (a) Controls the PTU, Center Cargo Hook and Hoist/Winch pressure operated valve to close when energized. (b) Normally closed, when the aircraft is shutdown or when a loss of the No.1 DC bus occurs without a bus tie. (c) Electrically energized open as soon as the No.1 DC bus comes on line, which closes the pressure operated valve and removes pressure from the three subsystems. (d) This allows emergency hoist/winch operations in the event of a dual generator failure. (e) De-energized closed when power is applied to the No.1 DC bus AND when one or more of the following four switches are toggled: (1) No.1 PTU switch in the ON position. (2) No.2 PTU switch in the ON position. (3) Cargo hook switch in the ARM position. (4) Hoist/Winch switch in the PILOT or REMOTE position. 32  (Frame 3090) (11) PTU, Hook, and Hoist/Winch pressure operated valve: (a) Normally opened, hydraulically closed. (b) Controlled by the PTU, Hook, and Hoist/Winch pilot solenoid valve. (c) Is a mechanical valve, spring loaded to the open position; this allows emergency hoist/winch operations in the event of a dual generator failure. (d) When in the open position, allows pressurized fluid from the utility system to flow to the PTU’s, center cargo hook and the hoist/winch solenoid valves. Pressure Control Module Schematic (Frame 3100) 33  Brakes and Power Steering Solenoid Valve (Frame 3110) NOTE: The brakes/power steering and ramp pilot solenoid valves are always in the ON position unless selected to the OFF position using their respective isolation switch in the cockpit. It is important to remember that electrical power is required to keep the solenoid valves closed; so if the APU generator or main generators are turned OFF or fail off-line the solenoid valves would automatically open and allow the sub-system(s) to function. (12) Brake and Power Steering pilot solenoid valve: (a) Isolates the brakes and power steering sub-systems in the event of a leak or evident loss of hydraulic fluid from the system. (b) Normally open, electrically closed. (c) Controlled by 28 VDC from the No.1 DC bus. (Frame 3120) 34  (13) Ramp pilot solenoid valve: (a) Isolates the ramp sub-system in the event of a leak or evident loss of hydraulic fluid from the system. (b) Normally open, electrically closed. (c) Controlled by 28 VDC from the No.1 DC bus. Utility Return Control Module (Frame 3140) b. Return Control Module: (1) Located in the aft cabin area on the forward right hand side of STA 534, adjacent of the No.9 drive shaft. (2) Receives return hydraulic fluid from the utility system and its sub-systems, and then routes that fluid to the reservoir/cooler. Except for when using external power, that fluid is routed back to the external power source (AGPU) bypassing the reservoir/cooler. (3) Includes a return filter assembly, the APU motor/pump fault indicator, the utility hydraulic boost pump fault indicator, various check valves and the ramp transfer valve. (4) The main purpose of the return control module is to provide a central collection point for all fluid returning from the various sub-systems while keeping those sub-systems isolated from each other. 35  Utility Return Filter Bowl Assembly (Frame 3150) (5) The filter bowl assembly is separated into three areas: Filter Bowl, Visual Contamination Indicator and a Filter Change Electrical Transmitter. (a) The filter bowl contains a five micron disposable filter. (b) A differential pressure indicator (DPI) button extends when a pressure differential exceeds 75 PSID + 10 and will bypass the filter at 130 PSID, which is measured by the difference between the inlet and outlet pressures of the filter element. Bypass will continue until the differential pressure decreases to 115 PSID and below. (c) Pressure differential may be caused by filter contamination or by pressure surges. (d) A differential pressure switch, mounted on the bottom of the filter bowl, activates the utility pressure FLTR CHNG RTN light on the maintenance panel when the DPI button has extended. Utility Pump Fault Indicators (Frame 3160) 36 (6) Pump fault indicators: (a) Two indicators mounted on the return module. (b) The top indicator is for the APU motor/pump. (c) The bottom indicator is for the utility boost pump. (d) The DPI extends when a flow rate of 1.0 GPM + 0.25 GPM is exceeded through case drains, with a differential pressure of 22 PSI existing. (e) When the DPI extends it closes the switch which activates the respective PUMP FAULT light on the maintenance panel, indicating an impending pump failure. Ramp Transfer Cylinder (Frame 3170) (7) Ramp transfer cylinder pertains directly to ramp operation. (a) Compensates for additional fluid flow for the ramp actuating cylinders during ramp operation. (b) Isolation of this function is maintained during ramp operation. (c) Operating pressure of 60 PSI return pressure. 37  Utility Boost Pump (Frame3180) c. Utility hydraulic boost pump: (1) Mounted to and driven by the aft transmission on the No.2 side of the accessory drive pad. (2) Provides a constant nominal output pressure of 3000 PSI, with a variable flow rate of 0 to 16 GPM. (3) The coupling shaft has a shear torque of 1650-2050 inch pounds. (4) It is the same hydraulic pump as the No.1 and No.2 flight control hydraulic system pumps. (5) Consists of four hydraulic ports: (a) Supply port supplies hydraulic fluid to the pump at 60 PSI from the reservoir/cooler. (b) Pressure port supplies hydraulic fluid to the utility system at 2900-3100 PSI. (c) Seal drain port allows hydraulic fluid or oil leakage between the pump and the aft transmission to drain from the system. (d) Case drain port carries the fluid that passes between the pistons inside of the pump and the piston housing. When the rate of flow exceeds 1.0 GPM + 0.25 GPM, the pump fault indicator on the return module will extend and illuminate the PUMP FAIL light on the maintenance panel. 38  Utility Boost Pump Schematic (Frame 3190) (6) The hydraulic fluid flow is provided by drawing in fluid from the supply port into the pistons. (7) The piston stroke is adjusted by the positioning of the swashplate which varies the amount of fluid drawn in and pressurized. (8) The swashplate is adjusted by an internal piston inside the pump which holds the swashplate in a neutral position when there is no demand on the pump. (9) As demand is placed on the pump, the pressure to the internal piston is reduced allowing the swashplate to increase the pitch and increase the flow. (10) Additionally, the pump is lubricated and cooled by hydraulic fluid. Check on Learning 1. Which component controls the flow of all pressurized fluid throughout the utility system and its subsystems? A. Utility hydraulic pump B. APU start module C. Utility reservoir pressurization accumulator D. Pressure Control Module 39 4. Learning Step / Activity 4. Power Transfer Unit, Cargo Hook, and Hoist/Winch Sub-systems Reference: IETM- Helicopter Introduction/Equipment Description and Data/Utility Hydraulic Power Transfer Units (Frame 4000) a. Power Transfer Unit: (1) Provides pressure to operate the flight hydraulic systems during ground operations and have the capacity to pressurize the system in flight for landing the helicopter safely with minimal control inputs in the event of an in-flight emergency. (2) Each PTU consists of three sections: a manifold, a motor and a pump. (3) The manifold provides a connecting junction for fluid transfer to the motor and a mounting base for the motor and pump. (a) Drives the motor with pressurized hydraulic fluid supplied from the utility system. (b) Contains a flow limiter, which reduces the flow into the manifold from 5 GPM to 3 GPM. (c) Contains a pilot solenoid valve: 1. Controlled by 28 VDC from the respective power transfer (PWR XFER) switches mounted on the overhead console hydraulics panel. 2. Normally closed , electrically opened 3. Controls the pressure operated valve. (d) Contains a pressure operated valve: 1. Directs fluid flow through the PTU. 2. Totally mechanical valve, spring-loaded to the closed position and hydraulically opened by the pilot solenoid valve. (4) A fixed displacement motor is driven by hydraulic fluid from the manifold, powers the pump utilizing a splined shaft. (5) There is no fluid transfer between the motor and pump. (6) A fixed displacement pump pressurizes the flight control hydraulic system(s) with a nominal pressure of 3000 PSI. (a) The supply port has a fluid pressure of 60 psi. 40  (b) The pressure port has a fluid pressure of 3000 psi. (c) The case drain port has a flow rate not to exceed 1.0 GPM ±.25 GPM. (d) A sealed drain port permits fluid leakage between the motor and the pump to be drained back into the respective hydraulic system. Power Transfer Unit Schematic (Frame 4020) Center Cargo Hook (Frame 4030) b. Center cargo hook: (1) The center cargo hook is an electro-hydraulic-pneumatic operated assembly. (2) Normally operated open using 3000 PSI of hydraulic pressure from the utility hydraulic system. (3) During normal operations the 2100 PSI nitrogen pre-charge is used to close the hook and keep the hook closed. 41  Center Cargo Hook Chambers (Frame 4040) (4) The center cargo hook actuating cylinder contains four chambers: (a) Chamber A contains air at atmospheric pressure and is vented out to the atmosphere. (b) Chamber B holds the emergency release charge of 2100 PSI of nitrogen or air. (c) Chamber C is the chamber that is momentarily filled with the air charge when the EMERG REL ALL switch is activated, opening the center hook; during normal operation the chamber is vented to the atmosphere. (d) Chamber D is the chamber that hydraulic fluid is forced into to open the hook during normal operation 42  Normal Operation Schematic (Frame 4050) (5) The pressure is directed between the floating cylinder and the hydraulic piston. This moves the floating cylinder and piston upward, opening the hook. Emergency Operation Schematic (Frame 4060) (6) The EMERG REL ALL switch is a guarded switch that opens all three hooks regardless of the HOOK SEL switch position. (a) Setting the switch to REL ALL energizes an emergency hook release relay. 43  (b) The emergency hook release relay then energizes electrical release solenoids in the forward and aft hooks and a solenoid valve in the center hook. (c) The solenoid valve in the center hook releases the air charge stored in Chamber B, transferring the charge to Chamber C opening the hook in the same manner as using hydraulic fluid. This charge is held in Chamber C for 10 seconds, and then released into the atmosphere. (d) After emergency release, the forward and aft hook will re-latch automatically; while the center hook must be manually reset and recharged with nitrogen or air to 2100 PSI. (e) A single activation of the emergency release system does not use all of the air charge; theoretically the center hook can continue to be used. Normal/Emergency Micro-switch (Frame 4070) (7) There are two micro-switches attached to the hook. (a) The normal/emergency release micro-switch is located at the top of the hook so that the cylinder will contact it when the hook is open. (b) This contact will illuminate the MID HOOK OPEN caution annunciator on the MFD. The switch is normally open, mechanically closed. 44  Manual Release Micro-switch (frame 4070) (c) The manual release micro-switch is located on the left side of the hook so that the rotating cam can remain in contact with it. Once the cam loses contact with the micro-switch, the MID HOOK OPEN caution annunciator on the MFD will illuminate. The switch is normally closed, mechanically opened. Center Cargo Hook normal Release Hydraulic Solenoid Valve (Frame 4080) (8) The normal release hydraulic solenoid valve: (a) Located in the tunnel area at STA 334 (b) When the valve is energized, the valve opens and provides utility hydraulic system pressure to the hook actuating cylinder. (c) The center cargo hook release system incorporates a check valve on the return side to help prevent excessive fluid loss of fluid in the event of a break or rupture in the fluid line to the cargo hook. 45  (Frame 4090) (9) During normal and emergency release operations, the hook pivots around the cam locks as the actuating cylinder is extended and retracted. (Frame 4100) (10) During manual release operations, the mechanical cam lock mechanism is released allowing the hook to pivot off the hook cylinder rod. After the hook has been manually released it must be manually reset by pushing up on the tip of the hook and re-locking into position. 46  (Frame 4110) c. Cargo hoist/winch system components: (1) An internal winch, which has a 3,000 pound capacity but is capable of up to 12,000 pounds with the aid of pulley blocks. When used in hoist operations, the load capacity is limited to 600 pounds due to structural limitations on the airframe. (2) Weight capacities with the aid of pulley blocks: (a) No pulley block (straight pull) – up to 3,000 pounds. (b) 1 Pulley block – up to 6,000 pounds. (c) 2 Pulley blocks – up to 9,000 pounds. (d) 3 Pulley blocks – up to 12,000 pounds. Hoist/Winch Mode Selector (Frame 4110) 47 (3) The cargo hoist/winch has two modes of operation, cargo and rescue. (a) Controlled by a selector lever mounted to the motor assembly. (b) Cargo mode – has a reel speed of 20 feet per minute (fpm). (c) Rescue mode – has a reel speed of 100 fpm. (4) The cargo hoist/winch has limit switches installed to prevent winch overloading and structural limitations of the airframe. (a) Overload limit switch opens the circuit when the load on the cable exceeds 3100-3200 pounds when the winch is being reeled in. (b) Out limit switch will stop when the winch cable is reeled out 150 feet and there is 2½ to 3½ wraps of cable remaining on the drum. (c) Cargo mode: In limit switch will stop the winch with 3 feet of cable reeled out. (d) Rescue Mode: In limit switch will stop the winch with 28.5 feet of cable reeled out. (5) When the manual override knobs are used, the cable limit switches are disabled. As a result, care is necessary to prevent reeling the cable too far in or out. (Frame 4130) (6) A mechanical braking device automatically locks the cable drum when power is OFF, preventing the loss of load control through cable payout. 48  (Frame 4140) (7) Hoist/Winch shutoff solenoid valve: (a) Supplies hydraulic pressure from the utility system to the winch, the brake release and the hoist/winch control valve. (b) Normally closed, electrically opened with 28 VDC from the No.1 DC bus. (c) Has the capability of being locked in the open position manually so that the system can be operated in the event of an electrical failure. (8) Hoist/Winch control valve: (a) Directs hydraulic fluid to the motor for the selected movement of REEL IN or REEL OUT. (b) Contains a threaded manual control knob that is used, in conjunction with the knob on the shutoff valve, to reel in or out in the event of an electrical failure. (c) Within the valve is a load compensator which relieves hydraulic shock loads back to the return when the servo motor is cycled. Hoist/Winch Pressure Reducer (frame 4160) 49 (9) A pressure reducer is installed between the Hoist/Winch control valve and the motor on the REEL OUT hydraulic line. This reduces the pressure from 3,000 PSI to 750 PSI. Hoist/Winch Switch (Frame 4170) (10) Hoist MSTR switch (overhead panel): (a) When the switch is set to REMOTE, electrical power from the No.1 DC energizes the winch arming switch on the control grip. When the arming switch is pressed, the winch cable switch (also on the control grip), is energized, allowing the winch reeling speed to be controlled at the hoist operator’s grip. (b) When the switch is set to PLT, electrical power energizes the hoist control switch on the overhead panel, which gives the pilot control of the hoisting system. (c) When the switch is set to OFF, electrical power is removed from the hoist control switch at both stations. 50  Hoist/Winch Sub-system (Frame 4180) (11) The cable cutter is attached to a pulley and must be used during hoisting operations through the compartment at STA 334. (a) The attachment point for the rescue pulley is structurally limited to 600 pounds. (b) The cartridge is an electrically fired shell that forces a punch that cuts the cable and remains in the cable cutter housing, trapping the remaining cable. Check on Learning 1. How many micro switches are on the center cargo hook? A. 3 B. 2 C. 1 D. 0 2. With the winch in RESCUE mode, how much cable will remain when the in-limit switch activates? A. 28.5 FT B. 18.5 FT C. 20 FT D. 3 FT 51 5. Learning Step / Activity 5. Wheel Brake Sub-system Reference: IETM- Helicopter Introduction/Equipment Description and Data/Utility Hydraulic Wheel Brake Sub-system (Frame 5000) a. The Wheel Brake Sub-system consists of a pressure reducing valve, an accumulator, four master cylinders, two transfer valves, a parking brake valve and six self-adjusting disk brake assemblies on each wheel. (1) Braking is provided on all wheels when both pilot’s or copilot’s brake pedals are depressed. (2) The right pedal operates the right brakes and the left pedal the left brakes Brake Reducer (Frame 5010) b. Pressure reducing valve: (1) Reduces pressure from 3000 PSI to 1390 PSI. 52  (2) Located on the left side of the aft drive shafting support structure, STA 502. Brake Accumulator (Frame 5020) c. Fluid continues through the tunnel area to a check valve, located under the No.1 tunnel cover; this check valve prevents the brake sub-system from being depleted in case of a utility system failure. d. Brake accumulator is located on the No.1 side of the forward pylon, STA 120. (1) A 25 cubic inch accumulator, with a pre-charge of 600 PSI to 850 PSI. (2) Provides approximately 3 brake applications in the event of a utility system failure or isolation. Brake Master Cylinders (frame 5030) e. Master cylinders contain brake pedals that allow hydraulic pressure to flow from the brake system into the master cylinder and then to the remaining components of the sub-system. (1) Four master cylinders, which will provide pressure when depressed. The further they are depressed, the more pressure that will flow to the wheel brakes. (2) Two for the left side brakes, one for the pilot and one for the co-pilot. 53 (3) Two for the right side brakes, one for the pilot and one for the co-pilot. Brake Master Cylinder Schematic (Frame 5030) (4) When the brakes are released, pressurized fluid in the brake cylinders is released back through the return port of the master cylinders. (5) Contains three ports: (a) Pressure port, which receives 1390 PSI for operation. (b) Brake pressure port, which allows a variable amount or pressure out dependent upon the amount of pedal that has been applied. (c) Return port, which allows the pressurized hydraulic fluid from the brake cylinders to be returned into the utility system once the brakes are released. (6) The left or right pedals can be applied independently, or simultaneously. Both pilot and copilot brakes cannot be applied at the same time. (7) As the brakes are depressed, springs located in the bottom of the master cylinder open an internal check valve which allows 1390 PSI into the master cylinder. This check valve also prevents system pressure from entering the return system during brake application, but allows fluid flow out the return port when the brakes are released. 54  Brake Master Cylinder Schematic with Brakes Applied (Frame 5040) (8) As the cylinder rod compresses, it actuates a valve that first opens allowing 1390 PSI into a reservoir, then closes trapping the hydraulic fluid in the reservoir. (9) As the cylinder rod end continues downward transferring this pressure to the wheel brake assemblies. Brake Master Cylinder Schematic with Brakes Released (Frame 5040) (10) Releasing the brake, removes pressure allowing internal springs to decompress the upper piston and cylinder rod and decompression of the lower pin and check valve, allowing return fluid action. 55  Brake Transfer Valve (Frame 5050) f. The transfer valves are located behind the canted console and to the left of the parking brake valve, STA 36. (1) Two transfer valves: (a) One for the brakes on the right side (b) One for the brakes on the left side. (2) Transfer valves allow only one master cylinder to apply brake pressure to its respective side, thus preventing over-pressurization of the brake cylinder seals. Brake Transfer Valve (Frame 5050) 56  Parking Brake Valve (Frame 5060) g. The parking brake valve maintains brake pressure on the brake cylinders when the brakes are in the set position in both static and dynamic operations. (1) Contains two thermal compensators, one for each side. (a) Each contains a large spring and a piston. (b) Parking brake cylinders are used to lock hydraulic pressure between the parking brake cylinders and the wheel brakes. In addition, it will not allow the fluid to flow to the return port of its respective master cylinder. (c) Maintains parking brake pressure constant over a wide range of temperatures. (d) The brakes can be released by one brake pedal, the right pedal. This automatically opens the parking brake valve, retracts the parking brake handle, and puts out the caution light. The pressure used to set the parking brake is routed through the right parking brake cylinder. Both brake pedals will be used to set and release the parking brakes. (2) Contains a micro-switch that is activated when the parking brake handle is pulled providing a ground through the switch to DCU1, which illuminates the PARKING BRAKE ON advisory light indicating that the parking brakes are engaged. 57  Wheel Brake Assembly (frame 5070) h. Wheel brake assembly: (1) Each assembly contains: (a) The brake housing has three cylinders which receive hydraulic pressure for the master cylinders. (b) Six brake linings, which directly contact the brake disc when the cylinder is pressurized during brake applications. (c) One brake disc, which is inserted into the brake assembly and interlocked into the wheel assembly. (2) When the brake pedals are pressed, fluid under pressure flows through the valves into each brake respective side brake assemblies. (3) Within each brake assembly, the pressurized fluid presses three floating brake pads against the brake disc that rotates with the wheel. (4) The floating brake pads press the rotating disc against three fixed pads on the opposite side of the disc, thus stopping the wheel. Check on Learning 1. In the event of a utility system failure or isolation, the brake accumulator; located at STA 120 on the #1 side of the forward pylon provides approximately _______ brake applications. A. 2 B. 3 C. 4 D. 1 2. The pressure used to set the parking brakes is routed through the _______ parking brake cylinder(s). A. Right B. Both C. Left D. All four 58 6. Learning Step / Activity 6. Power Steering/Swivel Lock Sub-system Reference: IETM- Helicopter Introduction/Equipment Description and Data/Utility Hydraulic Power Steering/Swivel Lock Sub-system (Frame 6000) a. Landing Gear Assy. (1) The aft right landing gear is hydraulically operated and electrically controlled by a control knob on the power steering control box. The three position SWIVEL LOCK switch and the STEERING CONTROL panel control the operation of the power steering and the swivel locks. (2) Hydraulic power to operate the power steering actuator and the swivel locks is supplied by the utility hydraulic system through the utility pressure control module to a separate power steering and swivel lock module. 59  Power Steering Control Box (Frame 6010) b. Power steering control box: (1) Swivel lock control switch is a three position switch; LOCK, UNLOCK and STEER. The switch positions are arranged so that the power steering system cannot be energized and used with the swivel locks engaged. (a) The LOCK position energizes the swivel lock and centering cam solenoid valve on the power steering and swivel lock module. (b) The UNLOCK position de-energizes the power steering circuits in the control box and the power steering actuator, simultaneously maintaining the swivel locks in the disengaged position. (c) The STEER position applies 28 VDC to the circuits in the power steering control box, the power steering hydraulic solenoid valve to allow hydraulic power to the system and to the out of phase switch. (d) If the wheel goes beyond its left or right limit, the switch will close and provide a ground for relay 137K1. This will shut off hydraulic pressure to the power steering actuator and illuminate the POWER STEERING annunciator on the MFD. 60  (Frame 6020) (2) Power steering is accomplished by rotating the control knob a given amount in the desired direction. (a) A control knob is spring-loaded to a zero turn angle. (b) Turning the knob to the right for a right turn will induce the right aft wheel to turn counterclockwise or to the left 82°. (c) Turning the knob to the left for a left turn will induce the right aft wheel to turn clockwise or to the right 58°. (d) The index marks around the knob indicate degrees of knob rotation to the left and right in increments of 30°. The index marks do not represent wheel turn angle; they are there for reference only. (3) Contains a fail-safe module and relay that monitors the steering electrical circuits. (a) The module monitors the system for shorts and/or opens. If a short or open occurs, the fail-safe module provides a ground for the 137K1 relay. (b) With the 137K1 relay energized, the hydraulic valve is shut off and the POWER STEERING annunciator on the MFD will illuminate. This prevents the system from going into a hard-over condition. (c) The POWER STEERING caution annunciator indicates that the power steering circuits have failed or that the aft right wheel has exceeded the turning limits. (d) To reenergize the power steering system, the aft right wheel must be returned to within operating limits and the swivel switch must be recycled. 61  Power Steering Adjustment Screw (Frame 6040) (4) Power steering adjustment via an Adjustment screw on the left side of the box. (a) Used during taxi checks to adjust steering alignment of deviations of more than 10° for 100 feet in the STEER position and more than 5° for 100 feet in the LOCK position. (b) The adjustment screw will only be used to make minor corrections in deviations. It is not to be used to correct major corrections in deviations, such as 3 or more. (5) Provides AFCS interface capability. (a) Moving the swivel switch from the LOCK position will disable the heading hold capability of the AFCS. (b) The YAW axis check, during AFCS hover checks, requires that swivel switch to be placed in the UNLOCK position. The hover check determines if the aircraft can change heading and not capture a heading with YAW dampening present. Power Steering Module (Frame 6050) 62 c. Power steering and swivel lock module contains four components. (1) Power steering pilot solenoid valve: (a) Allows fluid to flow to the power steering actuator when the swivel switch is placed to STEER. (b) Normally closed and electrically opened, 28 VDC. (2) Swivel lock pilot solenoid valve: (a) Allows fluid to flow to the swivel lock housing and centering cams on both aft landing gear assemblies. (b) Normally closed and electrically open, 28 VDC. (3) The check valve is used in the system to prevent back flow between the two solenoid valves. (4) Has a 5.75 cubic inch accumulator that: (a) Reduces surges and supplies a constant pressure when large demands are placed on the system. (b) Provides pressure to lock the swivel locks in the event of a utility system failure or isolation of the brake and power steering/swivel lock sub-system. (c) Pre-charge 1400 PSI, must be depressurized to get accurate reading of pre-charge. Should read 3000 PSI during pre-flight. (d) To depressurize the power steering and swivel lock module; hydraulic power on, isolate the brakes and power steering using the BRAKE/STEER switch, and cycle the swivel lock switch from LOCK to UNLOCK 5 times. Power Steering Actuator (Frame 6060) d. The power steering actuator assembly includes the following components: (1) The servo valve directs fluid to either extend or retract the piston rod which turns the landing gear for steering. (2) The feedback potentiometer is part of the piston rod assembly and is used to send signals to the power steering control box through the use of bridge circuit. (3) The cam and wheel centering assembly houses an out of phase switch which is activated when the wheel exceeds the 82° right turning angle or the 58° left turning angle. (4) The steering lever is attached to the upper spline of the aft right landing gear housing and connected to the power steering actuator rod end. It is used to rig the actuator for steering alignment. 63  Swivel Lock Schematic (Frame 6070) e. There are two swivel lock actuators located on the aft landing gear, and contains two hydraulic ports. (1) Hydraulic pressure is routed through the power steering/swivel lock module to the upper port of the actuator. The pressure displaces a spring-loaded piston inside the swivel housing downward to engage the swivel lock in a detent. (2) When the switch is set to UNLOCK, hydraulic pressure is removed from the upper port of the actuator and applied to the lower port. The piston within the swivel housing is moved upward, releasing the swivel lock from the detent and allowing the wheel to swivel freely. (3) The swivel locks are spring-loaded into the unlock position. Therefore, when the hydraulic system is shut down, the locks are disengaged and the wheel is free to turn. Wheel Centering Cam (Frame 6080) f. Centering Cams: (1) Each aft landing gear assembly contains a centering cam. 64  (2) Hydraulically assists the aft landing gear to be placed into a trail position so the swivel locks can be locked and engaged while off the ground. Wheel Centering Cam Schematic (Frame 6080) Check on Learning 1. Power steering adjustment is done via an Allen head screw on the _______ of the box. A. Right side B. Center C. Back D. Left Side 2. The power steering control box contains a fail-safe module and relay that monitors the steering electrical circuits. If a short or open occurs, the fail-safe module provides a ground for which relay? A. 134K1 B. 137K1 C. 135K1 D. 136K1 65 7. Learning Step / Activity 7. Cargo Ramp and Door Sub-system Reference: IETM- Helicopter Introduction/Equipment Description and Data/Utility Hydraulic Cargo Ramp and Door Sub-system (Frame 7000) a. The cargo ramp and door sub-system consists of: (1) Ramp control valve (2) Two actuating cylinders (3) Pressure actuated door override valve (4) Sequence Valve (5) Cargo door motor (6) Transfer cylinder on the return control module (7) Overhead HYD Panel b. The door is an integral part of the cargo ramp; references made to the cargo ramp will be understood to include the door and its related movements. c. Hydraulic pressure is used to only unlock the actuating cylinders and to raise the ramp, therefore the ramp free falls down. 66  Ramp Control Valve (Frame 7010) d. Ramp Control Valve: (1) Located on the right side of the ramp area, STA 486. (2) It is equipped with a slide assembly controlled either by a handle, internal UP or internal DN solenoid valves. (a) The internal UP or DN solenoid valves provide control in EMERG by applying hydraulic pressure to the respective ends of the slide assembly. (b) When the RAMP PWR switch on the overhead panel is set to ON, the solenoid valves are off, pressure is removed the ends of the slide assembly and the ramp control valve is controlled by the handle. (3) The ramp control valve has three positions/functions: (a) The STOP position locks all fluid, pressure and return, between the actuating cylinders and the ramp control valve. (b) The DN position routes pressurized fluid to the actuating cylinders to unlock the mechanical locks, routes fluid to the top of the actuating cylinders and to the return control module. (c) The UP position routes pressurized fluid to the actuating cylinders and at the same time routes return fluid to the transfer cylinder on the return control module. 67  Ramp Control Valve Schematic (Frame 7020) (d) When the control valve is operated to STOP, pressurized fluid is cutoff and port C3 is open to return. (e) When the control valve is operated DN, pressurized fluid flows through port C3 to the ramp unlock port in the actuating cylinders. Port C1, C2 and return are open to allow fluid to transfer from the bottom to the top of the actuating cylinders during freefall of the ramp. (f) When the control valve is operated UP, pressurized fluid flows from port C2 through the pressure actuated valve into the bottom of the ramp actuating cylinders. The rising pistons force fluid through both upper lines to ports C1 and C3 and onto the return port in the control valve. Ramp Actuating Cylinder (Frame 7030) 68 e. Ramp Actuating Cylinders: (1) Two of them, located on the left and right side of the ramp area, STA 502. (2) Identical and each cylinder has a stroke of 16.2 inches (3) Incorporates a locking assembly that locks the ramp in no other position than the full up position. (4) The ramp locking system is adjustable. (5) Each cylinder has three ports: (a) UNLOCKING PORT – The uppermost port, uses pressurized fluid to mechanically unlock the locking mechanism that secures the ramp in the full up position. The lock requires 400 PSI to unlock the locks. (b) RAMP DOWN PORT – The second port from the top, is used when lowering the ramp. This port allows return fluid to enter the top of the actuating cylinder from the ramp control valve. (c) RAMP UP PORT – The bottom port, used to retract the actuating cylinder using pressurized fluid routed from the ramp control valve. Ramp Pressure Actuated Valve (Frame 7050) f. The pressure actuated door override valve is a spring-loaded, hydraulically operated, four-way valve. (1) Located on the right side of the ramp area, STA 502 (just under the maintenance panel). (2) Hydraulic pressure generated by the cargo door motor actuates the valve so that ramp operation will momentarily stop to facilitate cargo door operations. This action will not take place if the sequence valve is manually locked into position. (3) When the cargo ramp control valve lever is operated, fluid flows through ports C and D to (or from) the lower ports on each actuating cylinder. When the sequence valve is actuated, return fluid from the door motor flows into port A. There is a 180 PSI relief valve, located in the pressure actuated valve that prevents the 60-90 PSI return fluid from continuing to return. This moves the spool and shuts off ports C and D, causing a hydraulic lock. The cargo ramp stops until the door fully extends or retracts. When the pressure in the return line builds up to 180 PSI, the relief valve opens and the fluid flows to return. 69  (Frame 7060) (4) A manual override knob, located on the bottom side of the valve, is provided in the event of a valve or ramp system malfunction. Should the chain or cable break, the pressure actuated valve has to be overridden to operate the ramp. Ramp Sequence Valve (Frame 7070) g. The ramp sequence valve is a spring-loaded, four-way valve that controls the sequence of the cargo ramp and door operation. (1) Its internal valve is activated by an adjustable plunger which is mounted to the ramp assembly, or by the manual operator knob on the top of the sequence valve. (2) A locking pin on the sequence valve allows the cargo ramp to be raised or lowered with the cargo door locked in position, extended or retracted. Normal operation is with the locking pin in the vertical position. With the locking pin set horizontally, the valve cuts off fluid flow to the door motor. The position of the door remains fixed, regardless of cargo ramp movement. (3) When the cargo ramp is brought up, pressurized fluid flows through port D2 to operate the cargo door motor to extend the cargo door. Return fluid from the door motor flows through port D1 to return. 70  (4) When the cargo ramp is brought down, pressurized fluid from port D1 reverses the cargo door motor and retracts the cargo door. Return fluid from the cargo door motor now flows through port D2 to return. (5) A restrictor in the pressure line of the sequence valve limits the flow of fluid to the valve. Cargo Door Motor (Frame 7080) h. The cargo door motor extends or retracts the cargo door. (1) Controlled by the ramp sequence valve. (2) The motor is a fixed displacement, reversible, piston-type hydraulic motor. (3) There are three ports on the motor assembly: inlet, outlet, and case drain. (4) The motor can be manually operated using a crank handle stowed on the left side of the cabin behind the soundproofing, STA 320. (5) The motor extends or retracts the cargo door with the use of a chain, pulley and wire rope system. The door rides in and out on two trolleys with roller bearings. Ramp Transfer Cylinder (frame 7090) 71 i. The ramp transfer cylinder is used to store hydraulic fluid for use when the cargo ramp is lowered. When the ramp is raised the cylinder is recharged and any excess fluid is returned to the return control module through a check valve. Ramp Down Operation Schematic (Frame 7100) j. Description of operation when the lever is operated to the DN position: (1) Pressurized fluid releases the mechanical locks on each actuating cylinder. (2) As the ramp slowly falls under gravity, fluid is forced out of the cylinders through the pressure actuated valve to the control valve. (3) The control valve routes the fluid to the upper end of the cylinders. (4) As the ramps falls, the sequence valve is activated by an extended plunger. (5) The sequence valve routes pressurized fluid to the cargo door motor, retracting the door into the ramp. (6) As the door retracts, return fluid from the motor passes through the sequence valve and into the pressure actuated valve. (7) A relief valve in the pressure actuated valve boosts the pressure of this return to 180 PSI. This increased pressure moves a spring-loaded valve spool to block the fluid returning from the actuating cylinders, stopping the ramp after it has dropped about eight inches. (8) When the door is fully retracted, the motor stops. This relieves the pressure in the pressure actuated valve. (9) The valve spool returns to its original position and return flow from the cylinders resumes, allowing the ramp to continue falling. 72  Ramp Up Operation Schematic (Frame 7110) k. Description of operation when the lever is operated to the UP position: (1) Fluid is routed by the control valve through the pressure actuated valve to the bottom of the actuating cylinders. (2) The fluid retracts the cylinders to lift the ramp. (3) As the ramp rises, it strikes the sequence valve plunger activating the sequence valve. (4) The sequence valve allows pressurized fluid to operate the cargo door motor to extend the door. (5) As the door extends, return fluid from the cargo door motor is directed by the sequence valve to the pressure actuated valve, where is halts the ramp in the same manner as during ramp down operation. (6) When the cargo door is fully extended, the motor stops and relieves the pressure in the pressure actuated valve. And the ramp continues to travel until it is in the full up position. Overhead Hydraulic Panel (frame 7120) 73 l. Overhead HYD Panel: (1) The RAMP PWR and RAMP EMER switches mounted on the HYD panel control ramp hydraulic power and operation. (2) The RAMP PWR switch is a three position switch with OFF, ON, and EMERG functions. (a) Setting the RAMP PWR switch to OFF is used to isolate the cargo ramp sub-system. It applies power to the normally open pilot solenoid valve on the pressure control module, causing it to close. With the solenoid valve closed, it prevents fluid flow to the ramp control valve. (b) The RAMP PWR switch in the ON position allows hydraulic fluid at 3000 PSI to flow to the ramp control valve. If ramp operation is to be controlled from the ramp control valve handle, this switch must be in the on position. (c) When the RAMP PWR switch is set to EMERG, electrical power is directed to the RAMP EMER switch and energizes the internal UP and DN solenoid valves in the control handle. (3) The RAMP EMER switch is a guarded switch, momentary double throw switch which controls operation of the ramp control valve by the internal DN and/or UP solenoid valves in the ramp control valve. (a) There is a five second time delay relay installed on the overhead panel, and wired between the UP terminal of the RAMP EMER switch and the internal UP solenoid valve in the ramp control valve. (b) This time delay relay provides a means to keep the ramp traveling downward without having to hold the RAMP EMER switch in the DN position. Ramp Emergency Operation Down Schematic (Frame 7130) m. Description of operation when using the RAMP EMER switch to the DN position: (1) Basic cargo ramp and door hydraulic sub-system remains the same during emergency operations. (2) The ramp is lowered by lifting the RAMP EMER switch guard and moving the switch to the DN position. (3) This energizes the 5 second time delay relay and removes hydraulic power from the UP solenoid valve, allowing the DN solenoid valve to drive the slide assembly and handle of the control valve into the DN position. 74  Ramp Emergency Operation Up Schematic (Frame 7130) n. Description of operation when using the RAMP EMER switch to the UP position: (1) Moving the RAMP EMER switch to the UP position will stop the ramp from being lowered; and if held in the UP position, brings the ramp back up. (2) Hydraulic pressure directed by the UP solenoid valve causes the slide assembly and handle of the ramp control valve to move to the UP position. (3) When the RAMP EMER switch is released, power is applied to the DN solenoid valve which directs hydraulic pressure to the down end of the slide assembly. Pressure from the UP solenoid valve is neutralized, causing the slide assembly and handle to return to the STOP position. Check on Learning 1. The ramp control valve handle positions are labeled ______________. A. OPEN, CLOSE, and OFF B. UP, STOP, and DN C. UP, DN, and OFF D. UP and DN 2. The two ramp actuating cylinders contain the lock assembly that does not lock the ramp in any other position other than the ____________ position. A. Full Extend B. Full Down C. Full Secure D. Full up 75 76