B737NG Hydraulic power

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B737NG Hydraulic systems overview

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B737NG Hydraulic power

  1. 1. B 737 NG Ground School.See the aircraft study guide at www.theorycentre.comThe information contained here is for training purposes only. It is of a general nature it isunamended and does not relate to any individual aircraft. The FCOM must be consulted forup to date information on any particular aircraft.
  2. 2. HYDRAULIC POWER
  3. 3. IntroductionThe airplane has three hydraulic systems: A, B and standby. The standbysystem is used if system A and/or B pressure is lost. The hydraulic systemspower the following airplane systems:• flight controls• leading edge flaps and slats• trailing edge flaps• landing gear• wheel brakes• nose wheel steering• thrust reversers• autopilots.Either A or B hydraulic system can power all flight controls with no decreasein airplane controllability.Each hydraulic system has a fluid reservoir located in the main wheel wellarea. System A and B reservoirs are pressurized by bleed air. The standbysystem reservoir is connected to the system B reservoir for pressurizationand servicing.Pressurization of all reservoirs ensures positive fluid flow to all hydraulicpumps.
  4. 4. FWDMAIN WHEEL WELLA SYSTEMHYDRESERVOIRB SYSTEMHYDRESERVOIR STANDBY SYSRESERVOIRRIGHT HANDMAIN GEAR.
  5. 5. A Hydraulic SystemComponents powered by hydraulic system A are:• ailerons• rudder• elevator and elevator feel• flight spoilers(two on each wing)• ground spoilers• alternate brakes• No. 1 thrust reverser• autopilot A• normal nose wheel steering• landing gear• power transfer unit (PTU)
  6. 6. B Hydraulic SystemComponents powered by hydraulic system B are:• ailerons• rudder• elevator and elevator feel• flight spoilers(two on each wing)• leading edge flaps and slats• autoslats• trailing edge flaps.•normal brakes• No. 2 thrust reverser• autopilot B• alternate gear retraction only.• alternate nose wheel steering• yaw damper
  7. 7. Standby Hydraulic SystemThe standby hydraulic system is provided as a backup if system A and/or B pressure is lost.The standby system can be activated manually or automatically and uses a single electricmotor–driven pump to power:• thrust reversers• rudder• leading edge flaps and slats (Full extend only)• standby yaw damper.
  8. 8. A and B Hydraulic System PumpsBoth A and B hydraulic systems have an engine–driven pump and an AC electricmotor–driven pump. The system A engine–driven pump is powered by No. 1engine and system B engine–driven pump is powered by No. 2 engine. Anengine–driven hydraulic pump supplies a much larger fluid volume than the relatedelectric motor–driven hydraulic pump.The ENG 1 (system A) or ENG 2 (system B) pump ON/OFF switch controls theengine–driven pump output pressure. Positioning the switch to OFF isolates fluidflow from the system components. However, the engine–driven pump continuesto rotate as long as the engine is operating. Pulling the engine fire switch shuts offthe fluid flow to the engine–driven pump and deactivates the related LOWPRESSURE light.
  9. 9. Controls solenoid on thepump. NORMALLY ONSolenoid cold. Extends life.
  10. 10. Controls solenoid on thepump. NORMALLY ONSolenoid cold. Extends life.Off energises solenoidand blocks flow fromthe pump.Re-routes to the casedrain and Fuel oil heatexchanger.EDP 36 GPM (145 L) at 3,000 PSI
  11. 11. EDP output less than 1,300 PSI.
  12. 12. EDP output less than 1,300 PSI.Inhibited if FIRE SWITCH PULLED!
  13. 13. A and B Hydraulic System PumpsThe ELEC 2 (system A) or ELEC 1 (system B) pump ON/OFF switch controlsthe related electric motor–driven pump. If an overheat is detected in eithersystem, the related OVERHEAT light illuminates, on some aircraft the powermay be removed from the pump and the LOW PRESSURE light will illuminate.NOTE; System A electric pump is labelled ELECT 2 because it is powered by ACtransfer bus 2.
  14. 14. TRANSFER BUS No 25.7 GPM (23.0 L) at 3,000 PSI
  15. 15. Hydraulic fluid used for cooling and lubrication of the pumps passes through aheat exchanger before returning to the reservoir. The heat exchanger for system Ais located in main fuel tank No. 1 and for system B is in main fuel tank No. 2.CAUTION: Minimum fuel for ground operation of electric motor-drivenpumps is 760 Kgs in the related main tank.Pressure switches, located in the engine–driven and electric motor–driven pumpoutput lines, send signals to illuminate the related LOW PRESSURE light if pumpoutput pressure is low. A check valve, located in each output line, isolates therelated pump from the system. The related system pressure transmitter sends thecombined pressure of the engine–driven and electric motor–driven pump to therelated hydraulic system pressure indication.
  16. 16. Elect 2 output pressureless than 1,300 PSI
  17. 17. Return line cooling fluid morethan 107° C.MOTOR case more than 113° C.
  18. 18. Pulling the engine fire switch shuts off thefluid flow to the engine–driven pump anddeactivates the related LOWPRESSURE light.HYDRAULIC SHUTOFF VALVES
  19. 19. System A Hydraulic LeakIf a leak develops in the engine–driven pump or its related lines, a standpipe in thereservoir prevents a total system fluid loss. With fluid level at the top of the standpipe, thereservoir quantity displayed indicates approximately 20% full.System A hydraulic pressure is maintained by the electric motor–driven pump.If a leak develops in the electric motor–driven pump or its related lines, or componentscommon to both the engine and electric motor–driven pumps, the quantity in the reservoirsteadily decreases to zero and all system pressure is lost.EDP SupplyELECT 2 supply100% 21.6 L (5.7 Gal)76% 17.7 L (4.7 Gal) RF20% 8.5 L (2.3 Gal) Standpipe
  20. 20. System B Hydraulic LeakIf a leak develops in either pump, line or component of system B, the quantitydecreases until it indicates approximately zero and system B pressure is lost. Thesystem B reservoir has one standpipe which supplies fluid to both theengine–driven pump and the electric motor–driven pump. However, with fluidlevel at the top of the standpipe, fluid remaining in the system B reservoir issufficient for power transfer unit operation.A leak in system B does not affect the operation of the standby hydraulic system.EDP SupplyELECT 1 supplyPTU supply100% 31.1 L (8.2 Gal)76% 26.0 L (6.9 Gal) RF72% 25.1 L (6.6 Gal) Balance line0% 4.9 L (1.3 Gal) Standpipe
  21. 21. REFILL Indication (RF) (white)Illuminated (white) – hydraulic quantity below 76%.Note: Valid only when airplane is on ground with both enginesshutdown or after landing with flaps up during taxi–in.
  22. 22. Standby Hydraulic SystemThe standby hydraulic system is provided as a backup if system A and/or Bpressure is lost. The standby system uses a single electric motor–driven pump topower:• thrust reversers• rudder• leading edge flaps and slats (extend only)• standby yaw damper.The standby system can be activated two ways manually or two ways automatically
  23. 23. LOW QUANTITY lightindicates 50% or less in theSTBY Reservoir.When full the reservoir holds 13.3 litresof fluid (3.6 Gal)
  24. 24. Standby by pump is low pressure.Only armed when Pump iscommanded to run.
  25. 25. Standby Rudder SOV is open andSTBY RUD PCU is pressurised.
  26. 26. Manual OperationPositioning either FLT CONTROL switch to STBY RUD:• activates the standby electric motor–driven pump• shuts off the related hydraulic system pressure to ailerons, elevatorsand rudder by closing the flight control shutoff valve• opens the standby rudder shutoff valve• deactivates the related flight control LOW PRESSURE light when thestandby rudder shutoff valve opens• allows the standby system to power the rudder and thrust reversers.• illuminates the STBY RUD ON, Master Caution, and Flight Controls(FLT CONT) lights.
  27. 27. STANDBY HYDRAULIC SYSTEM CAN BE ACTIVATED IN 4 WAYSSTBY RUD switch Normal guarded ON.OFF position used for maintenance onlyCloses six flight control valves in the main wheel well.
  28. 28. STANDBY HYDRAULIC SYSTEM CAN BE ACTIVATED IN 4 WAYS1. Either STBY RUD switch to STBY RUD.Stand by rudder valve opens.Standby pump runs.
  29. 29. STANDBY HYDRAULIC SYSTEM CAN BE ACTIVATED IN 4 WAYSStandby PUMP delivers 3.7 GPM @ 2,700 PSIAC TRANSFER BUS No 2
  30. 30. Positioning the ALTERNATE FLAPS master switch to ARM• activates the standby electric motor–driven pump• closes the trailing edge flap bypass valve• arms the ALTERNATE FLAPS position switch• allows the standby system to power the leading edge flaps andslats and thrust reversers.
  31. 31. STANDBY HYDRAULIC SYSTEM CAN BE ACTIVATED IN 4 WAYS2. Alternate Flaps Master switch to ARM.
  32. 32. Automatic OperationAutomatic operation is initiated when the following conditions exist:• loss of system A or B, and• flaps extended, and• airborne, or wheel speed greater than 60 kts, and• FLT CONTROL switch A or B Hydraulic System ON (Normalguarded position.)
  33. 33. STANDBY HYDRAULIC SYSTEM CAN BE ACTIVATED IN 4 WAYS3. Auto Activated Low pressure in SYS A or B. Flaps Not UP. With; Wheel speed more than 60 Knots. Or Air mode.This automatically activates the standbyrudder in a critical flight phase.
  34. 34. Automatic Operationthe main PCU Force Fight Monitor (FFM) tripsAutomatic operation:• activates the standby electric motor–driven pump• opens the standby rudder shutoff valve• allows the standby system to power the rudder and thrustreversers.• illuminates the STBY RUD ON, Master Caution, and FlightControls (FLT CONT) lights.
  35. 35. STANDBY HYDRAULIC SYSTEM CAN BE ACTIVATED IN 4 WAYS4. Auto Activated If Main Rudder PCU Force FightMonitor trips.Automatically activates the STBY rudderif system A rudder PCU and system BPCU are trying to move the rudder inopposite directions (Force fight)
  36. 36. Indicates low hydraulic pressure to flight controls.RudderAileronsElevator
  37. 37. Indicates low hydraulic pressure to flightcontrols.RudderAileronsElevatorINHIBITED; If Standby RudderPCU is Pressurised.<1,300 PSI
  38. 38. Standby Hydraulic System LeakIf a leak occurs in the standby system, the standby reservoir quantitydecreases to zero. The LOW QUANTITY light illuminates when thestandby reservoir is approximately half empty. System B continues tooperate normally, however, the system B reservoir fluid levelindication decreases and stabilizes at approximately 72% full.
  39. 39. Power Transfer UnitThe purpose of the PTU is to supply the additional volume of hydraulicfluid needed to operate the autoslats and leading edge flaps and slatsat the normal rate when system B engine–driven hydraulic pumpvolume is lost. The PTU uses system A pressure to power a hydraulicmotor–driven pump, which pressurizes system B hydraulic fluid. ThePTU operates automatically when all of the following conditions exist:• system B engine–driven pump hydraulic pressure drops below limitsLess than 2,350 PSI• airborne• flaps are less than 15 but not up. (Some aircraft flaps not up)
  40. 40. POWER TRANSFER UNIT(PTU)Hydraulic MotorHydraulic PumpHYD SYS AHYD SYS BPRESSReturnSuctionPRESS
  41. 41. PTU; Used to assist the movement of the leading edge Flapsand Slats. Will assist Auto slat operation.
  42. 42. PTU; Used to assist the movement of the leading edge Flapsand Slats. Will assist Auto slat operation.Control valve OPENAir Mode.T/E Flaps between UPand 15EDP PRESSURE LESSTHAN 2,350 PSI
  43. 43. Landing Gear Transfer UnitThe purpose of the landing gear transfer unit is to supply the volume of hydraulicfluid needed to raise the landing gear at the normal rate when system A engine–driven pump volume is lost due to an engine failure. The system B engine–drivenpump supplies the volume of hydraulic fluid needed to operate the landing geartransfer unit only when all of the following conditions exist:• airborne• No. 1 engine RPM drops below a limit value (N2 less than 50%)• landing gear lever is positioned UP• either main landing gear is not up and locked.The electrical pump is able to raise the landing gear but only slowly. With an enginefailure between V1 and gear up a clean aircraft is very desirable as quickly aspossible.
  44. 44. How is Hydraulic system oil cooled?
  45. 45. How is Hydraulic system oil cooled?Hydraulic fluid used for cooling and lubrication of the pumps passes through aheat exchanger before returning to the reservoir. The heat exchanger for system Ais located in main fuel tank No. 1 and for system B is in main fuel tank No. 2.CAUTION: Minimum fuel for ground operation of electric motor-drivenpumps is 760 Kgs in the related main tank.
  46. 46. The hydraulic indication RF will be displayed.a) Only in flight with a reservoir quantity less than 76%.b) On the ground or in flight with a reservoir quantity less than 76%.c) On the ground with both engines shutdown.d) On the ground if any of the three reservoirs quantities are less than 76%.
  47. 47. The hydraulic indication RF will be displayed.a) Only in flight with a reservoir quantity less than 76%.b) On the ground or in flight with a reservoir quantity less than 76%.c) On the ground with both engines shutdown.d) On the ground if any of the three reservoirs quantities are less than 76%.
  48. 48. How can a loss of fluid from the standby system be identified?
  49. 49. How can a loss of fluid from the standby system be identified?Standby Hydraulic System LeakIf a leak occurs in the standby system, the standby reservoir quantity decreases tozero. The LOW QUANTITY light illuminates when the standby reservoir isapproximately half empty. System B continues to operate normally, however, thesystem B reservoir fluid level indication decreases and stabilizes at approximately72% full.50%72%
  50. 50. The PTU provides a back up source of hydraulic power to operate:a) Rudder, thrust reversers and L.E flaps.b) Autoslats.c) Autoslats and thrust reversers.d) Landing gear retraction.
  51. 51. The PTU provides a back up source of hydraulic power to operate:a) Rudder, thrust reversers and L.E flaps.b) Autoslats.c) Autoslats and thrust reversers.d) Landing gear retraction.
  52. 52. What flap settings will enable automatic operation of the PTU.a) Flap 15 only.b) Flaps less than 15 but not up.c) Any flap setting less than 15.d) Flaps more than 15.
  53. 53. What flap settings will enable automatic operation of the PTU.a) Flap 15 only.b) Flaps less than 15 but not up.c) Any flap setting less than 15.d) Flaps more than 15.
  54. 54. PTU; Used to assist the movement of the leading edge Flapsand Slats. Will assist Auto slat operation.Control valve OPENAir Mode.T/E Flaps between UPand 15EDP PRESSURE LESSTHAN 2,350 PSI
  55. 55. How is the reservoir for the standby hydraulic system pressurised.a) By hydraulic system B.b) Directly from B system reservoir.c) Directly from A system reservoir.d) Directly from the pneumatic system manifold.
  56. 56. How is the reservoir for the standby hydraulic system pressurised.a) By hydraulic system B.b) Directly from B system reservoir.c) Directly from A system reservoir.d) Directly from the pneumatic system manifold.System A and B reservoirs are pressurized by bleed air. The standbysystem reservoir is connected to the system B reservoir for pressurizationand servicing.Pressurization of all reservoirs ensures positive fluid flow to all hydraulicpumps.
  57. 57. What can the Standby hydraulic system power?
  58. 58. What can the Standby hydraulic system power?L.E Flaps and slats Full extendNo1 and No 2 Thrust reversersStandby rudderStandby Yaw Damper.
  59. 59. The END of Hydraulic PowerNow Take the test at www.theorycentre.comOr contact us for further information info@theorycentre.comTwo 16-cylinder engines combined generate 4400 hp, powering 14 hydraulic pumps.The reservoirs hold up to 3400 gallons of hydraulic fluidBucyrus RH400 Hydraulic Shovel

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