Chapter 13 - Hydraulics Flashcards
Hydraulic Pumps
Engine Driven Pumps - EDP
4 Seperate pumps each providing 3000psi
Demand Pumps - DP
4 Seperate pumps automatically operate during periods of high demand or if the EDP fails.
DP #1 & #4 are pneumatically powered
DP #2 & #3 are electrically powered
AUX - AP
Electrically powered on system 4 for use on the ground to power the brakes.
SYS FAULT light
Low Pressure
Low Fluid Quantity
High Fluid Temperature
NOTE - FAULT light for Sys.4 will go out when AUX pump is turned on however the PRESS light will remain illuminated.
Demand Pump PRESS light
DP selector is OFF or AUX
DP output pressure is low
DP failed
Demand Pump selector knob
AUTO
- DP operates when respective EDP output pressure is low
- Fuel Control Switch is placed to cutoff
- Engine Fire Handle is pulled
- DP #1 & #4 also operate when flaps are in transit on ground or when flaps are out of up inflight
AUX (System 4)
- Operates on ground until related EDP pressurizes system
- Respective DP push switch is off
- Does NOT turn off when EDP pressurizes system
EDP Switch
(Push Switch)
ON - EDP pressurizes system
No Light - OFF
PRESS - Low EDP pressure
Hydraulic Quantity
Hydraulic Pressure
Hydraulic Temperature
All 3 display on the STAT page on the DSP
QUANTITY
Displays as a percentage of full - 1.00 full
RF [ReFill] will display on ground when at or below 0.75
LO will appear on ground and inflight at 0.34
PRESSURE
Displays in PSI
TEMPERATURE
Temperature in ºC
Reservoirs
Independent reservoirs supply fluid to each hydraulic system. The bleed air system pressurizes the reservoirs to prevent pump cavitation and ensure positive flow during high demand conditions.
Brake Accumulator Panel
Hydraulic Pressure for the Brakes come from System 4
BRAKE SOURCE Light - All brake sources have low pressure
HYD BRAKE PRESS Guage - Brake Accumulator Pressure
System 1 Powers?
Inboard Trailing Edge Flaps
Body Gear Actuation
Nose Gear Actuation
Body Gear Steering
Nose Gear Steering
Alternate Brakes
Left Outboard Elevator
Left Inboard Elevator
Left Outboard Aileron
Left Inboard Aileron
Upper Rudder
Center Autopilot
System 2 Powers?
Alternate Brakes
Stabilizer Trim
Elevator Feel
Lower Yaw Damper
Right Autopilot
Spoilers 2, 3, 10 & 11
System 3 Powers?
Stabilizer Trim
Elevator Feel
Upper Yaw Damper
Left Autopilot
Spoilers 1, 4, 9 & 12
System 4 Powers?
Outboard TE Flaps
Wing Gear Brakes
Normal Brakes
Spoilers 5, 6, 7 & 8
Minimum in-flight speed with a failed engine where windmilling engine provides hydraulic power
160 KIAS
What is the normal source for the brakes?
System 4
If pressure is lost on System 4 will the BRAKE SOURCE light illuminate?
NO
If system 2 and/or 1 have sufficient pressure and automatic switching to alternate brakes
occurs, the light will not illumintate.
System 4, 1 and 2 must be low.
When do the demand pumps come on without a loss of pressure from the EDPs?
Inflight
- Flaps out of up
On the ground
- Flaps are in transit
Will the SYS FAULT light go out when the aux pump pressurizes?
Yes
Why do we prssurize system 4 for for pushback with the aux pump?
For primary brakes through normal brake system.
ADP and EDP lights remain illuminated.
Why do we pressurize system 1 with the Demand Pump for pushback?
Nose wheel steering and brake backup.
You are now ready for pushback. You select the Demand pumps to auto and demand pump 4 to aux. Which pumps are electric and which are air driven?
DP 1 is pneumatically powered
AP is electrically powered
The Demand Pump Selectors for System 1 and 4 are in AUTO. What will cause them to activate?
• Engine pump output is low
• Fuel Control Switch is in cutoff
• Flaps in transit on the ground
• Flaps out of up in flight
The Auxiliary Hydraulic Pump(s) are powered by what bus or busses?
The Ground Handling Bus.
The number 4 Auxiliary Hydraulic Pump is selected on. Is the number 4 SYS FAULT light illuminated
No.
Name the power sources for the Demand pumps?
• Number 1 and 4 are air driven
• Number 2 and 3 are electric
What causes the hydraulic SYS FAULT light to illuminate?
• Low hydraulic system pressure
• Low hydraulic reservoir quantity
• Excessive hydraulic fluid temp
What is the minimum hydraulic quantity for dispatch?
.80 as indicated on the secondary EICAS HYD synoptic or STAT display
What is the implication of a BRAKE SOURCE light illuminated in flight?
You have lost hydraulic systems 4, 1 and 2
Hydraulic System 1 is unpowered. What major components are now unavailable?
• Nose and Body Gear hydraulic operation
• Nose and Body Gear steering
• Inboard Trailing Edge Flap hydraulic operation
• Autopilot Center
• Left outboard Elevator
• System 1 Alternate brakes
Hydraulic System 1 EDP is leaking. The EICAS advisory message “HYD PRESS ENG 1” is displayed. You look on the STATUS Page and see that the system 1 quantity indicates zero. Is Hydraulic System 1 still powered? If so, why?
• Yes
• The ADP draws its supply from the reservoir bottom. The EDP draws its supply from the reservoir at a level above the bottom, but coincident with the zero index of the quantity indication.
Why does RF display next to the hydraulic quantity indication? Where is it displayed? Will it display in flight?
• Indicates that refill of the hydraulic reservoir is required
• It is displayed on the Secondary EICAS Status Page and Hydraulic Synoptic
• No
What does a hydraulic reservoir quantity indication of .80 mean, as displayed on the Secondary EICAS display?
80% of normal service level
Why are the hydraulic reservoirs pressurized by the bleed air system?
To prevent pump cavitation
To ensure positive flow during high demand conditions
How does pulling a fire switch affect the hydraulic system?
Related hydraulic fluid shutoff valve closes
The EDP depressurizes.
The related demand pump operates.
What drives the Auxillary Pump system 4 is driven by?
Electrically via the Ground Handling Bus
During preflight, the minimum hydraulic quantity is?
.80
When is the Auxillary Hydraulic Pump available?
Only on the ground
During preflight, the most likely indication that a hydraulic system needs refilling is?
The lower EICAS Status page with magenta RF next to hydraulic quantity.
The HYD SYS FAULT light on the overhead panel illuminates due to:
- Low hydraulic system pressure.*
With a DP selector ON the associated pump will run?
Continuously
The engine driven pump on hydraulic system 1 should run when?
Engine 1 is rotating
An illuminated demand pump PRESS light may indicate?
The associated aux pump is running and pressure is normal.
