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AST 473 Cessna Citation II Hydraulic Power System - PowerPoint PPT Presentation

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AST 473 Cessna Citation II Hydraulic Power System. Dr. R. Kurt Barnhart. Hydraulic System. One Pump per engine Operates: Landing gear Speedbrakes Thrust reversers (optional). Hydraulic System Operation. Open Center- no pressure buildup- bypasses unused output back to reservoir

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hydraulic system
Hydraulic System
  • One Pump per engine Operates:
    • Landing gear
    • Speedbrakes
    • Thrust reversers (optional)
hydraulic system operation
Hydraulic System Operation
  • Open Center- no pressure buildup- bypasses unused output back to reservoir
  • System Pressurized upon component activation
  • Electric firewall shutoff valves- cockpit
  • Reservoir pressurized to provide adequate pressure at altitude
hydraulic system operation1
Hydraulic System Operation
  • Fluid filtered:
    • Prior to reservoir
    • Prior to sub-system (landing gear, etc.)

Annunciator lights:

-low fluid level- reservoir

-low pressure

-when system pressurized

hydraulic system operation2
Hydraulic System Operation
  • Reservoir (figure 13-1):
    • Located in tailcone on engine carry through beam
    • Pressurized to 15 – 16 psi via hyd. Pressure- small piston in reservoir neck.
    • When system not under pressure- internal spring gives 2.7 – 4.0 psi pressure.
hydraulic system operation3
Hydraulic System Operation
  • Visual indicator on reservoir:
    • Full- .5 Gal. Fluid
    • Overfull- .65 Gal.
    • Refill- .2 Gal.- Illuminates amber “HYD LEVEL LO” annunciator
    • Relief valve- on top of reservoir opens @30 psi to prevent overpress.- can be manually activated for system maintenance
hydraulic system operation4
Hydraulic System Operation
  • Pumps- constant volume gear driven- accessory section rated at 3.25 gpm. Ea. Operates when engine on- either pump can operate all sub-systems
  • System Bypass valve- spring loaded open- routes pump output to return line- valve energized closed (electric) to produce system pressure- valve fails open
  • Mechanical relief valve- in parallel w/ bypass valve opens @ 1,500 psi as a backup.
hydraulic system operation5
Hydraulic System Operation
  • Firewall Shutoff Valves:
    • Installed in supply line of ea. Pump.- electric- controlled by ENG FIRE switchlights
    • Normally open valve- closed for fire or mx.
    • Position indicated by respective F/W SHUTOFF annunciators
hydraulic system operation6
Hydraulic System Operation
  • Filters- 3; 2 for fluid leaving pumps/1 filters return fluid prior to reservoir return.- Each has a bypass valve- opens @ 100 psi if clogged- no cockpit indication
  • Flow Switches- in ea. Pump press. Line- controls the HYD PRESS (or FLOW) LO L/R. Limits:
    • .35 - .55 gpm- Light on
    • 1.33 gpm- Light off
    • Check valve prevents backflow into pump
hydraulic system operation7
Hydraulic System Operation
  • Operation:
    • When No demand- bypass valve open- to rtn.
    • HYD FLOW LOW annunciators extinguish on eng. Start.
    • Upon any demand- bypass valve closes- HYD PRESS ON annunciator illuminates- system press. Limited to 1,500 psi by relief valve
    • When operation completed pressure builds- bypass valve opens (spring)- system depressurizes- HYD PRESS ON annunciator extinguishes
hydraulic system operation8
Hydraulic System Operation
  • Loss of a pump indicated by the HYD PRESS LOW annunciator
thrust reversers
Thrust Reversers
  • Optional- most have;- target type- assist in deceleration on landing.
  • Deployed and held in position by system pressure
  • Upon stowing- hyd. Press. Is isolated and they are held in stow by an overcenter condition of the operation mechanism
thrust reversers1
Thrust Reversers
  • Protection- Solenoid lock in throttle quadrant- prevents power application during reverse until full reverser deployment
  • Throttle feedback system moves FCU lever and throttle to idle during inadvertent deploy
  • Reverser operation limited to gnd. Op only via the left squat switch.
    • After inadvertent deploy- mx. Check needed to determine cause and check linkage rigging
thrust reversers2
Thrust Reversers
  • Control- via reverser levers piggy-backed on throttles- 3 positions
    • Full fwd. (stow)
    • Reverse idle (detented)
    • Full aft. (reverse)
    • When lever moved to reverse idle- solenoid lockout mechanism prevents further aft lever movement until reverser fully deployed.
thrust reversers3
Thrust Reversers
  • Microswitch in throttle quadrant gives electrical control.
    • Switch closed- when reverser moved from stow applying power to:
      • Close hydraulic bypass valve and pressurize system
      • Open hydraulic isolation valve to provide pressure to reverser system
      • Energize reverser control valve to deploy position provided either squat switch is closed (ground).
thrust reversers4
Thrust Reversers
  • Each Reverser- 3 lights on glareshield
    • ARM- circuit completed by pressure switch = hyd. Press. Available to reverser control valve
    • UNLOCK- circuit completed by microswitch- closes when reverser mechanism initially moves from (mechanically) locked stowed pos.
    • DEPLOY- incicates reverser door mechanism has reached fully deployed pos.
    • Electrical power- left reverser- left. Ext. bus, rt. Reverser- rt. Crossover bus.
thrust reversers5
Thrust Reversers
  • Operation- After lndg.- throttles idle- nosewheel on ground:
    • Raise thrust reverser levers to idle deploy detent
    • ARM and HYD PRESS ON lights come on
    • Closely followed by UNLOCK then DEPLOY lights
    • Reverser lever solenoid lock- release
thrust reversers6
Thrust Reversers
  • Next:
    • Reversers can be moved aft to accel. Engine directly via fuel control- thrust levers held @ idle by mechancal interlock in pedestal
    • During reverse thrust- ARM, UNLOCK, DEPLOY, and HYD PRESS ON lights all stay on
thrust reversers7
Thrust Reversers
  • As 60 KIAS go to idle reverse- maintain this position as needed for drag and thrust attenuation
  • To stow reverser:
    • Reverser levers fully forward and down- energizes control valve to “stow” (directs hyd. Pressure to stow side of reverser actuators
    • DEPLOY light goes out followed by UNLOCK, ARM, and HYD PRESS ON lights- indicates Stow position.
thrust reversers8
Thrust Reversers
  • Caution: DO NOT attempt re-stow on Takeoff if reversers inadvertently deploy- throttle linkage damage may occur- loss of power
  • Caution: Reverser deployment @ higher than normal lndg. Speeds causes nose up pitching tendency- counter w/ yoke or else may porpoise & damage nose wheel.
thrust reversers9
Thrust Reversers
  • EMER STOW- bypasses normal sequencing system used for:
    • Inadvertent deployment
    • Normal Stow failure
emer stow operation
  • 2 position switch- ea. Reverser- inboard of reverser lights- labled “STOW SW”
    • EMER- closes hydraulic bypass valve and energizes control valve to stow position
    • NORMAL
emer stow operation1
  • If reversers deployed when EMER STOW selected:
    • HYD PRESS ON light comes on & reverser lights extinguish in sequence:
      • DEPLOY
      • UNLOCK
      • (HYD PRESS ON and ARM lights stay on in stow position- reverser held in stow position with continuous pressure as overcenter lock may be inop.- mx. check before next flight)
emer stow operation2
  • If either ARM or UNLOCK comes on in flight- MCAW system triggers
  • NOTE: If fire switch light pushed (test or eng. Fire)- isolation valve de-energizes closed & hydraulic reverser operation not possible.