13. Hydraulics Flashcards
Engine Hydraulic Pump Switch
- ON: De-energizes blocking valve in pump to allow pump pressure enter system,
- OFF: Energizes blocking valve and isolates fluid flow from the system components,
- However the EDP continues to rotate as long as the engine is operating,
- Should remain ON at shutdown to prolong solenoid life
HYDRAULIC System QUANTITY Range
0-106%
HYDRAULIC System PRESSURE Indications
- Normal: 3000psi,
- Maximum: 3500psi,
- When pumps OFF: Normally less than 100psi
RF Indications
- Refill shows when hydraulic quantity < 76%,
- Valid only when airplane on ground with both engines shutdown or,
- After landing with Flaps Up during taxi-in
FLIGHT CONTROL Switches
- STBY RUD: Activates Standby Pump and opens Standby Rudder SOV to pressurize Standby Rudder PCU,
- OFF: Closes Flight Control SOV isolating ailerons, elevators
Flight Control LOW PRESSURE Lights Deactivation
- When associated FLIGHT CONTROL switch is positioned to STBY RUD,
- And Standby Rudder SOV opens
STANDBY HYDRAULIC LOW QUANTITY and LOW PRESSURE Lights
- LOW QUANTITY: Always armed, illuminates when the reservoir approximately half empty,
- LOW PRESSURE: Armed only when standby pump is operating
ALTERNATE FLAPS Master Switch
ARM:
- Closes Trailing Edge Flap Bypass Valve,
- Activates Standby Pump and,
- Arms ALTERNATE FLAPS position switch
STBY RUD ON Light
Standby hydraulic system is commanded to pressurize the Standby Rudder PCU
Hydraulic Fluid Reservoirs
- Located in the Main Wheel Well area,
- Pressurized by bleed air,
- Standby reservoir connected to System B reservoir
Hydraulic System Joint Powered Components
- Ailerons, rudder, elevator,
- Elevator Feel,
- Flight Spoilers (A 2, 4, 9, 11 / B 3, 5, 8, 10)
- Thrust Reversers (A1, B2),
- Autopilot
Only Hydraulic System A Powered Components
- Ground Spoilers (1, 6, 7, 12),
- Alternate Brakes,
- Normal Nose Wheel Steering,
- Landing Gear,
- Landing Gear Transfer Valve,
- Power Transfer Unit
Only Hydraulic System B Powered Components
- Leading Edge Flaps and Slats,
- Trailing Edge Flaps,
- Normal Brakes,
- Alternate Nose Wheel Steering,
- Landing Gear Transfer Valve,
- Autoslats,
- Yaw Damper
Hydraulic System Pumps
- Engine Driven Pumps supplies approximately 6 times more fluid volume than Electric Motor Driven Pumps,
- Loss of an EDP and high demand may cause LOW PRESSURE for EMDP and Flight Control LOW PRESSURE light,
- EMDP powered by AC power,
Hydraulic Fluid Cooling
- Passes through Heat Exchanger located in Main Fuel tanks (1 for A, 2 for B),
- Minimum fuel for ground EMDP operation is: 760KG in the related Main Tank
Hydraulic Leaks
System A:
- If EDP or its related lines: Standpipe prevents total loss. Quantity shows 20% full,
- EMDP maintains System A pressure,
- If EMDP or its related lines or joint lines: All system pressure is lost
System B:
- If either pump, line or component: Quantity indicates approximately zero,
- Standpipe provides enough fluid for Power Transfer Unit operation,
- Leak does not affect Standby Hydraulic operation
Standby:
- Quantity decreases to zero,
- System B fluid level indication decreases and stabilizes at 70% full
Power Transfer Unit
- Supplies the additional volume of hydraulic fluid to operate Autoslats and LE Flaps & Slats at normal rate,
- When System B EDP is inoperative,
- Uses System A pressure to power a hydraulic motor driven pump,
- Which pressurizes System B hydraulic fluid
PTU Automatic Operation Conditions
- System B EDP pressure drops below limits,
- Airborne,
- Flaps “1, 2, 5, 10” or for SFP aircraft not UP
Landing Gear Transfer Unit
- Supplies volume of hydraulic fluid to raise the Landing Gear at normal rate,
- When System A EDP volume is lost,
- System B EDP supplies the required the volume of hydraulic fluid to operate Landing Gear Transfer Valve,
LGTU Automatic Operation Conditions
- Airborne,
- No. 1 Engine RPM drops below a limit value,
- Landing Gear Lever is UP,
- Either Main Landing Gear is not up and locked
Standby Hydraulic System Powered Components
- Thrust Reversers,
- Rudder,
- Leading Edge Flaps and Slats (extend only),
- Standby Yaw Damper
Standby Hydraulic System Manual Operation
By positioning either FLT CONTROL switch to STBY RUD:
- Allows Standby System to power: the Rudder and Thrust Reversers
By positioning ALTERNATE FLAPS switch to ARM:
- Allows Standby System to power: LE Flaps and Slats
Standby Hydraulic System Automatic Operation
- Loss of System A or B and,
- Flaps Extended and,
- Airborne or wheel speed greater than 60KT and,
- FLT CONTROL switch A or B ON,
- OR: The Main PCU Force Fight Monitor (FFM) trips,
- Allows Standby System to power: the Rudder and Thrust Reversers
Hydraulic Quantity Variations
- When the system becomes pressurized after engine start,
- Raising or lowering the Landing Gear or Leading Edge Devices,
- Cold soaking occurs during long periods of cruise
Hydraulic LOW PRESSURE Light Flickering
Foaming can occur at higher altitudes if the hydraulic system is not properly pressurized
