Hydraulic Flashcards
HYD QTY Display Values
- % of Full
- RF = Refill
- OF = Overfill
Ram Air Press light (Green)
- RAT deployed
* RAT producing hydraulic pressure
Components of Left Hydraulic System (757)
- Reservoir
- Eng Driven Pump (EDP) - primary pump
- Elec Driven Pump - provides additional power (operates full time)
- Power Transfer Unit (PTU)
- Hand Pump for Main Cargo Door
Systems powered by Left Hydraulic Sys
- Left Thrust Reverser
- Alt Brakes
- Left Autopilot
- Spoilers
- Right Aileron
- Elevators
- Rudder
- Rudder Ratio
- Left Yaw Damper
- Flaps and Slats
- Landing Gear
- Nose Wheel Steering
- Main Cargo Door
What happens to the HYD Sys when Engine Fire Switch is pulled
- HYD shutoff valve is closed
- pump depressurized
When does PTU operate?
- Left Engine Failure
- Left EDP low press
Purpose of PTU
- Back up for left Sys
- supplements left elec pump
- Draws fluid from below standpipe level in left reservoir
- Motor driven by Right Sys pressure
When activated what systems does the PTU drive?
- Flaps and Slats
- Landing Gear
- Nose Wheel Steering
- Main Cargo Door on ground via accessory panel PTU switch
Components of Right Hydraulic System (757)
- reservoir
- Electric Driven Pump (EDP)
- Elec Driven Pump - provides addition power (operates full time)
Systems powered by Right HYD System
- Right Thrust Reverser
- Normal Brakes
- Spoilers
- Right Autopilot
- Left Aileron
- Elevators
- Rudder
- Elevator Feel
- Stab Trim
- PTU motor
Reserve Brake Switch
- uses reservoir reserve fluid (below standpipe)
- Open reserve brake valve
- closes valve to other components
- activates elec driven pump
Components of Center HYD Sys (757)
- reservoir (maintains reserve fluid below standpipe for RAT pump)
- 2 x elec driven pumps
- RAT pump (back up)
When does the system shed the Center 2 pump?
- sheds automatically to reduce electrical loads
- when one generator running and both center electrical pumps ON (757)
- when one generator running and all 4 electric pumps ON/Auto (767)
Where is RAT located?
Faring in left Main Gear
When does RAT deploy and what does it power?
- Deploys MAN via switch or automatically when both engine fail above 80 knts
- provides adequate hydraulic power above 130 knts for:
- center Sys flight controls
- center autopilot
Electric Demand Pump Selector - AUTO (767)
- Left/Right Elec Demand pump operate when engine pump pressure is low
- Left Elec Demand pump is inhibited on the ground during engine start of either engine
- Right Elec Demand pump when Flaps 1, 5 ,15, 20
- Center air demand pump operates when both center electric pump pressures are low
- Center air demand pump operates when heavy load items are selected
- Center air demand pump operates when HDG operating (loss of both main AC busses)
Primary and Backup Hydraulic Pumps (767)
Left HYD:
Primary - L EDP
Backup - L Elec Demand Pump
Center HYD:
Primary - C Elec Pump 1 and 2
Backup - C Air Demand Pump
Right HYD:
Primary - R EDP
Backup - R Elec Demand Pump
Brake Source Light
- Norm and Alt Brake Press Low
- Only pressure from accumulator
Systems Powered by Center Hydraulic Sys (767)
- Tail Skid
- Hydraulic Driven Generator (HDG)
- Landing Gear
- Nose Wheel Steering
- Alternate Brakes
- Flaps and Slats
- Left Yaw Damper
- Rudder
- Elevator
- Elevator Feel
- Stab Trim
- Spoilers
- Left and Right Inboard Aileron
- Center Autopilot
- RAT pump
Which systems utilize reserve hydraulic fluid (standpipe fluid)
Left system:
− None
− (B757) Power Transfer Unit (PTU)
Center system:
− Reserve brakes and steering
− (B757) Ram Air Turbine (RAT)
Right system:
− None
− (B757) Reserve brakes
When does the Pitch Enhancement System (PES) operate?
o Operates if both left and center hydraulic systems fail
o Operates via yoke trim switches only
o Operates at 1/4 normal trim rate
o Powered by a Power Transfer Unit (PTU) which is:
- Driven by right hydraulic system
- Utilizes trapped fluid in left hydraulic system
When is the center air demand pump commanded to operate in AUTO (767)
− Center system pressure drops to a preset level – or – − High system demand operation: ♦ Flaps/slats ♦ Landing gear ♦ Speedbrakes/spoilers ♦ HDG signaled to operate
