Boeing Hydraulics PDF

TM (QT) 1-1520-263-10 SECTION VI. HYDRAULIC AND PNEUMATIC SYSTEMS 2-53. HYDRAULIC SYSTEMS INTRODUCTION 2-54. PRIMARY HYDRAULIC SYSTEM The hydraulic systems consist of two independent sys-...

TM (QT) 1-1520-263-10 SECTION VI. HYDRAULIC AND PNEUMATIC SYSTEMS 2-53. HYDRAULIC SYSTEMS INTRODUCTION 2-54. PRIMARY HYDRAULIC SYSTEM The hydraulic systems consist of two independent sys- The primary hydraulic system (Figure 2-67) provides hy- tems: the primary and the utility. They are similar but draulic pressure to the primary side of all four flight con- not identical, and have separate as well as shared func- trol servoactuators. Only the primary sides of these tions. servo actuators have electrohydraulic valves that allow the FMC to affect the flight controls. The primary hy- draulic equipment includes a hydraulic pump, manifold, and servoactuators. During APU start or shortly afterwards dur- a. Primary Hydraulic Pump. The primary hy- ing the Flight Controls IBIT, the crew may draulic pump is mounted on the left side of the trans- experience a primary hydraulic pressure ex- mission accessory gearbox. The pump is a constant ceedance. When this event occurs, the pilot pressure, variable displacement design, driven by the will receive an ADVISORY (PRI HYD PSI HI) transmission accessory gear train. within five seconds and then be able to view the primary hydraulic pressure on the MPD b. Primary Hydraulic Manifold. The primary man- Engine page as soon as electrical power ifold stores, filters, and regulates the flow of hydraulic comes on-line. This overpressure condition fluid, provides pressure, dirty filter, and low level indi- may dissipate on its own or may continue. cations. The manifold reservoir is pressurized on the As soon as the behavior is noticed, the pi- return side by IPAS air acting on the manifold reser- lot should move any of the flight controls to voir piston. This prevents pump inlet cavitation. Ser- generate sufficient hydraulic flow and return vicing crews introduce fluid to the reservoir through the the hydraulic pressure to normal operating Ground Support Equipment (GSE) connections or the range. If the primary hydraulic overpres- hand pump. The primary hydraulic system fluid capacity sure condition persists after moving the flight is approximately 7 pints. The reservoir stores approxi- controls, shutdown the APU and replace the mately 2 pints. primary hydraulic pump IAW IETM proce- dures. Note that an exceedance and fault (1) Air Bleed Valve. The air bleed valve is will only be logged if operation at 3400 psi used to deplete the pressurized air from the manifold or greater continues after 60 seconds (total) reservoir for system repair or service. of APU operation. If this occurs, the IETM special inspection for a hydraulic system (2) Reservoir Low Level Indicating overpressure shall be performed. Switch. A reservoir low level switch is activated by the manifold reservoir piston. The PRI HYD LEVEL LOW Extended ground operation on APU power caution displays when the minimum operating level is can result in elevated hydraulic temperature detected. that may result in a “Pylon Actuator Fail” fault. If encountered, the APU should be shut down NOTE or the engine started. The failure may be The hydraulic dirty filter indicator button on the cleared by cycling the power of the affected Hydraulic manifold may pop after APU start. Missile or Rocket system from OFF to ON The button may be reset one time. If the but- once the hydraulic temperature is reduced. ton pops a second time, maintenance must be Extended ground operation on APU power performed. can result in elevated hydraulic temperatures that may damage hydraulic seals. External (3) Manifold Pressure and Return Fil- leakage and/or diminished performance may ters. Filters on both manifold pressure and return result. Due to the lack of temperature indi- sides have mechanical dirty filter indicators for visual cation for the hydraulic system, the operat- inspection. These indicators operate on differential ing limits and monitoring described in Section pressure. Only the return filter has a bypass valve 5-5.b shall apply. provision. In addition to the mechanical/visual indica- tors both filters contain electrical switches that provide NOTE signals to generate the PRI HYD BYP caution. Failure of the primary hydraulic system will re- sult in the loss of BUCS and SCAS functionality. (4) Fluid Level Indicator. A fluid level indica- tor in the manifold housing allows visual inspection of the reservoir fluid level. 2-67 Change 2 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 (5) Pressure Sensing Switch. A pressure Rotor brake switch senses primary system pressure and notifies the crew of a low fluid pressure condition by displaying the AWS turret PRI HYD PSI LOW caution. Ammunition handling system (6) Pressure Transducer. A pressure trans- APU start motor ducer measures hydraulic pressure on the pressure side Tail wheel unlock actuator of the manifold and displays these values on the ENG and SYS pages. External stores elevation actuators Emergency hydraulic system accumulator (7) Servoactuators. One side of the four flight control servoactuators is positioned through the use of Equipment includes a hydraulic pump, manifold, accu- hydraulic pressure from the primary hydraulic system. mulator, and servoactuators. The pump is mounted on the right side of the transmission accessory gearbox. 2-55. UTILITY HYDRAULIC SYSTEM The significant difference in the primary and utility hy- draulic system is the manifold. The utility hydraulic system (Figure 2-68) provides hy- draulic pressure to the utility side of all four flight con- trol servoactuators. This system also provides hydraulic pressure to the following: Change 2 2-68 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 Figure 2-67. Primary Hydraulic System 2-69 Change 2 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 Figure 2-68. Utility Hydraulic System Change 2 2-70 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 a. Utility Hydraulic Manifold. The utility manifold (7) Reservoir Low Level Switch. A reservoir is installed on the aft main fuselage deck on the right low level switch is activated by the manifold reservoir side. It stores, filters, supplies, and regulates the flow of piston. The UTIL HYD LEVEL LOW caution is displayed utility hydraulic fluid. Demands on the utility system are when the low level switch detects a low level condition. greater than those on the primary system, and the utility manifold is larger. The utility manifold incorporates the NOTE utility accumulator hydraulic pressure transducer and ro- The hydraulic dirty filter indicator button on the tor brake solenoids not duplicated on the primary man- Hydraulic manifold may pop after APU start. ifold. The button may be reset one time. If the but- ton pops a second time, maintenance must be (1) Low Level and Auxiliary Isolation performed. Valves. The low level and auxiliary isolation valves permit hydraulic fluid to flow to external stores, ammo carrier drive, and AWS turret. If reservoir fluid level (8) Manifold Pressure and Return Fil- decreases significantly, the reservoir piston, driven ters. Filters on both manifold pressure and return by IPAS air, closes the low level valve. The auxiliary sides have mechanical dirty filter indicators for visual isolation valve, which normally requires two sources of inspection. These indicators operate on differential pressure to permit fluid flow, then closes and denies pressure. Only the return filter has bypass provisions. hydraulic power to the AWS turret, external stores In addition to the mechanical/visual indicators both actuator, and ammo carrier drive. filters contain electrical switches that provide signals to generate the UTIL HYD BYP caution. (2) Shutoff Valve. A shutoff valve in the pres- sure line to the directional servo and tail wheel unlock (9) Fluid Level Indicator. A fluid level indica- actuator is actuated by the low level switch in the utility tor in the manifold housing allows for visual inspection system reservoir. The utility side of the directional servo of the reservoir fluid level. actuator and the tail wheel unlock actuator become in- operative if a low utility system fluid level is sensed. (10) Pressure Sensing Switch. A pressure switch senses utility system pressure and informs the (3) Accumulator Isolation Valve. The accu- crew of a low fluid pressure condition by generating the mulator isolation valve normally isolates accumulator UTIL HYD PSI LOW caution. pressure from the rest of the utility system but allows system flow from the pump to pass through a portion of NOTE the valve to the utility side of the tandem servoactuators. The accumulator should be checked on pre- flight and thru-flight inspections for a minimum (4) Override Solenoid. An override solenoid, of 2600 psi prior to APU start. de-energized closed, permits crew management of b. Utility Hydraulic Accumulator. The accumula- accumulator reserve pressure. Upon activation of the tor stores hydraulic fluid at 3000 psi. The accumula- EMERG HYD pushbutton, the override solenoid valve tor provides damping for fluid pressure changes, hy- energizes open and accumulator fluid passes to the draulic power for rotor brake application, APU starting, accumulator isolation valve via emergency routing. In and emergency flight control operation. The start valve this case, another portion of the accumulator isolation opens when the APU button is pressed to ON and closes valve permits accumulator fluid to flow to the utility side automatically at 60% APU speed. of the servoactuators. c. Utility Hydraulic Return Accumulator. The util- (5) Pressure Transducer. An accumulator hy- ity hydraulic return accumulator stores hydraulic fluid at draulic pressure transducer provides the crew with ac- 55 psi. The accumulator dampens hydraulic pressure cumulator pressure. During normal operation, the indi- surges caused by sudden actuation of the gun turret. cated pressure is the same as the utility hydraulic sys- tem. A pressure transducer measures hydraulic pres- d. Servoactuators. The four flight control servoac- sure on the pressure side of the manifold and transmits tuators are positioned through the use of hydraulic pres- this value for display on the ENG and SYS pages. sure from the utility hydraulic system. (6) Rotor Brake Solenoid Valves. The sole- e. Hydraulic System Hand Pump. A hand pump, noid valves are controlled by the RTR BRK switch on the next to the primary system GSE panel, provides one pilot POWER lever quadrant. When this switch is posi- method of charging fluid pressure in the utility accumu- tioned to BRK, utility system pressure is applied to stop lator as well as access for the ground crew to fill the the rotor brake disc on the main transmission. When primary and utility reservoirs. The control lever may be positioned to LOCK, the brake off solenoid valve traps moved to any of three positions. This opens one of three pressure between the manifold and the utility system ac- check valves to the accumulator or to either reservoir. cumulator. 2-71 Change 2 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 2-56. HYDRAULIC SYSTEM CONTROLS brake, if previously set at LOCK remains locked as long as accumulator pressure is available. Operation of the hydraulic system is automatic except in emergency situations, tail wheel locking/unlocking, and b. Tail Wheel Lock. Utility hydraulic pressure is rotor brake activation. Hydraulic system indications are used by the tail wheel lock actuator to unlock the tail displayed on the ENG and SYS pages. wheel. The tail wheel can be locked or unlocked from either crew station via the TAIL WHEEL panel or collec- tive grip tail wheel button. The tail wheel can also be locked or unlocked by ground crew using a handle pro- vided on the locking device. Do not place the RTR BRK switch in LOCK position with rotors turning. 2-57. HYDRAULIC SYSTEM RELATED MPD PAGES NOTE When engaging the rotor lock, pause in the a. ENG Page. The ENG page displays hydraulic BRK position until the RTR BRK advisory is dis- pressures for the following conditions. played prior to placing the switch in the LOCK position. The POWER levers will not advance (1) Ground Format. The primary, utility and past the ground idle detent with the rotor brake accumulator hydraulic pressures are displayed in the switch in the LOCK position. HYD PSI status window at the bottom of the ENG page when displaying the ground format (Figure 2-69). a. Rotor Brake. The rotor brake is a disc brake mounted at the aft end of the main transmission. The rotor brake reduces turnaround time for aircraft loading and servicing and prevents windmilling of the rotor sys- tem during gusty wind conditions. The RTR BRK switch on the pilot POWER lever quadrant has three positions: (1) OFF. With the switch at OFF, the only hy- draulic pressure to the brake is 30 psi from the IPAS which, when operating, pressurizes the return side of the utility hydraulic system. (2) BRK. When the switch is set at BRK, sole- noid valves in the utility hydraulic manifold operate and applies 337 psi to actuate the brake. (3) LOCK. The LOCK position is used to pre- vent windmilling in strong winds and for locked rotor en- gine starts. When both engines are at idle and the switch is set to LOCK (full 3000 psi utility hydraulic pressure), the brake prevents the drive train and power turbine from being driven by the gas turbine. A system of three interlocks prevents the rotor brake Figure 2-69. ENG Page – Ground Format from being locked when the power levers are in any po- sition except IDLE or OFF. When rotors are stopped, the (2) Flight format. The primary, utility and ac- switch can be set to LOCK which causes the solenoid cumulator hydraulic pressures are displayed in the HYD valves in the manifold to de-energize and all available PSI status window in the upper portion of the ENG page utility hydraulic system or accumulator pressure to be when there is a low pressure condition sensed by any of applied to the brake. If aircraft power is lost, the rotor the hydraulic pressure sensing systems. Change 2 2-72 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 b. SYS Page. The following hydraulic pressures; 2-58. INTEGRATED PRESSURIZED AIR SYSTEM primary (PRI), utility (UTIL) and accumulator (ACC) are (IPAS) indicated on the SYS page (Figure 2-70): Pneumatic power for the IPAS (Figure 2-73) is gener- ated by dual engine bleed air, APU or AGPU air. The IPAS pressurizes, regulates, and distributes air to the following: Air turbine starter Fuel boost and transfer pumps Hydraulic reservoirs Ice detect probe aspirator Nitrogen inerting unit Engine firewall/cooling Utility receptacle Environmental Control System (ECS) a. Dual Engine Bleed Air. IPAS primary pneumatic power source is dual engine bleed air. Bleed air is pro- vided by both engines during normal operation. b. Single Engine Bleed Air. The secondary source of pneumatic power for the IPAS is single engine Figure 2-70. SYS Page bleed air. NOTE c. APU or AGPU Bleed Air. During aircraft power The following descriptions of the SYS page hy- up, APU bleed air is the pressurized air source and is draulic system indications give ranges of those used to start main engines. External air from an AGPU displays. Refer to Chapter Chapter 5 for system may be used to start engines via the external air recep- limits and restrictions. tacle. Each engine has a low and high pressure bleed air port. The high pressure port is used exclusively to PRI/UTIL/ACC PSI pressurize the hydraulic reservoirs and the low pres- sure port supports the remaining functions. Low pres- 0 - 6000 displayed in increments of 10 sure flow and pressure is controlled by the engine bleed psi pressure regulator and shutoff valve. High pressure flow and pressure is controlled by a restrictor and a regulator. 3410 - 6000 yellow ≥ 5 seconds red w/box 3310 - 3400 yellow ≥ 5 minutes red w/box NOTE Bleed air buttons are also located on the HIT 1260 - 3300 green page. 0-1250 red w/box d. IPAS Control. Control of IPAS is an integrated function provided by mission processors and the Electri- cal Power Management System (EPMS). The A/C UTIL page (Figure 2-71) and HIT page (Figure 2-72) provide BLEED AIR 1 and 2 on/off buttons. 2-73 Change 2 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 Figure 2-71. A/C UTIL Page (Pilot) Figure 2-72. HIT Page e. IPAS Advisories. Crewmembers are provided the following IPAS advisory messages: (1) Engine Bleed Air Fail. This advisory oc- curs when engine 1 and/or engine 2 pressure regulating shutoff valve is in the commanded position and the MMP commands the engine 1 and/or engine 2 bleed air shut- off valve open or closed and it does not move. (2) Engine Bleed Air Overtemperature. This advisory occurs when the MMP receives a bleed air overtemperature signal, and will display a BLD AIR HOT advisory on the EUFD. (3) Engine Bleed Air Off. This advisory will be displayed if it has been determined by the MMP that both engines' bleed air has been turned off. Change 2 2-74 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 Figure 2-73. Integrated Pressurized Air System (Sheet 1 of 2) 2-75 Change 2 Copyright © 2023 Boeing. Export Controlled Information  TM (QT) 1-1520-263-10 Figure 2-73. Integrated Pressurized Air System (Sheet 2 of 2) Change 2 2-76 Copyright © 2023 Boeing. Export Controlled Information