Hydraulics Flashcards
Amber Electric Hydraulic Pump OVERHEAT Lights
Hydraulic Fluid used to cool and lubricate electric motor driven pump has overheated
OR
Pump itself has overheated
Amber Hydraulic pump LOW PRESSURE lights
Output pressure LOW
Note: When Fire switch pulled, LOW PRESSURE light DEACTIVATED
Explain ON and OFF position Electric Hydraulic Pump Swicthes
ON - powers associated electric driven pump
Off - electric power removed from pump
Explain ON and OFF position for
ENGINE Hydraulic Pump Switches
ON - DEENERGISE Blocking valve in pump to allow pump pressure to enter
OFF - ENERGISES blocking Valve to block pump flow output
Why should ENGINE hydraulic pumps remain ON at shutdown?
To prolong solenoid life
As ON position DEENERGISES blocking Valve
How is Hydraulic Quantity displayed?
Via MFD SYS in Lower DU
Indicates digital percentage (0-106%)
Where else can hydraulic quantity displayed?
Displayed at each reservoir in the main wheel well
How is Hydraulic Pressure indicated and what is it’s Normal and Maximum pressure?
Via MFD SYS
Normal pressure - 3000 PSI
Max pressure - 3500 PSI
What hydraulic pressure is indicated when both ENG and ELEC hydraulic pumps for the same system is OFF?
May Indicate hydraulic RESERVOIR pressure
Normally LESS THAN 100 PSI
What does RF (white) indication mean?
Hydraulic quantity BELOW 76%
When is RF (white) indication valid?
- On the ground + both engine shutdown
- After Landing with flaps up during taxi-in
What happens when FLIGHT CONTROL Switches to STDY RUD?
Activates Standby pump
Opens standby rudder shutoff valve to pressurise standby rudder power control unit
What happens when FLIGHT CONTROL Switches to OFF?
Closes flight control shutoff valve isolating,
1. Ailerons
2. Elevators
3. Rudder
From associates Hydraulic system pressure
Why is FLIGHT CONTROL Switches positioned ON?
Guarded position - normal operating position
What does Flight Control LOW PRESSURE lights indicate?
Indicates low hydraulic system (A or B) pressure to ailerons, elevators and rudder
When is Flight Control LOW PRESSURE lights DEACTIVATED?
When FLIGHT CONTROL switch positioned to STBY RUD
AND
Standby rudder shutoff valve opens
What does STANDBY HYDRAULIC LOW QUANTITY light indicate?
Low quantity in standby hydraulic reservoir
Always armed
What does STANDBY HYDRAULIC LOW PRESSURE light indicate?
Standby pump output pressure is LOW
Armed only when standby pump operation selected
OR
Automatic standby function activated
Explain ALTERNATE FLAPS master switch positions
OFF (guarded position) - normal operating position
ARM - closes TE flap bypass valve, activates standby pump, arms ALTERNATE FLAPS position switch
What does STBY RUD ON light indicate?
Standby Hydraulic system is commanded to pressurise standby power control unit
How many hydraulic system does B737-800 have?
System A, B and Standby
Can System A/B power all flight control with no decrease in airplane controllability?
TRUE
Where is each hydraulic reservoir located?
Main wheel well area
How are System A and B pressurised?
Bleed Air
What is the Purpose pressurisation at the reservoirs?
Ensure positive fluid flow to all pumps
Systems pressured by A Hydraulics?
Ailerons - rudder - elevators
Flight spoilers (2,4,9,11)
Ground Spoilers ( 1,6,7,12)
Alternate brakes
No. 1 Reversers
Autopilot A
Normal steering
Landing gear
Power transfer unit
Systems pressured by system B?
Ailerons - rudder - elevators
Flight spoilers (3,5,8,10)
LE Flap and Slats
TE Flaps
Normal brakes
No.2 reverser
Autopilot B
Alternate steering
Landing gear transfer valve
Autoslats
Yaw damper
Advantage Engine Driven pump Vs Electric Driven Pump?
Engine pump Supplies 6 times fluid volume of electric pump
What happens when ENG driven hydraulic pump OFF?
Energises blocking valve to block pump output
However, Pump continues to rotate
What happens when pulling engine fire switch for related system?
Engine drive Hydraulic LOW PRESSURE light deactivated
Fluid flow to pump shuts off
What does ELEC hydraulic pump control?
Controls related Electric Motor pump
What happens if Loss of an engine drive pump?
High demand on electric pumps
Resulting in intermittent LOW PRESSURE for remaining electric pump
Flight control LOW PRESSURE light
MASTER CAUTION
FLT CONT & HYD annunciator
Other purpose of hydraulic fluid?
Cooling and lubrication of pumps
What happens to hydraulic fluid before returning to reservoir?
Passes through heat exchanger
Where are Heat exchangers located?
System A: Main fuel tank No.1
System B: Main fuel tank No.2
Minimum fuel for ground operation of ELECTRIC PUMPS?
760kg In related MAIN TANKS
What happens if leak develops in ENGINE pump Line for system A?
STANDPIPE in reservoir prevents total fluid loss
System A pressure is maintained by A ELECTRIC pump
What happens if leak develops in ELEC pump Line for system A?
Quantity is system A reservoir steadily decreases to ZERO
All system pressure lost
What happens if leak develops in either pump Line for system B?
Quantity indicates ZERO
System B pressure is LOST
Does System B leak affect Standby hydraulic Operation?
NO
Purpose of Power Transfer Unit (PTU)?
Supply Additional hydraulic fluid to operate autoslats, LE flaps and slats when system B ENG pump is inoperative
How does PTU operate?
Uses SYSTEM A pressure to power hydraulic pump that pressurises system B hydraulic fluid
PTU Automatic Operation criteria?
PTU operates automatically when;
- SYSTEM B ENG pump pressure drops below limits
- Airborne
- flaps not less than 15 but not up
Purpose of Landing Gear Transfer Valve?
Supply hydraulic fluid to RAISE landing gear when SYSTEM A ENG pump is lost
How does Landing Gear Transfer Valve Operate?
System B ENG pump supplies hydraulic fluid to transfer valve to raise gear
When does Landing Gear Transfer Valve Operate?
Airborne
No.1 Engine RPM drops below Limit (system A)
Landing gear lever UP
Either main gear not up and locked
How can Standby Hydraulic be Activated?
Manual or Automatic
How many Pumps does the standby hydraulic system contain?
A Single ELECTRIC MOTOR PUMP
What does Standby Hydraulic Pump power/ supply?
Thrust Reversers
Rudder
LE Flaps and Slats (extend only)
Standby yaw damper
Manual Operation of Standby Hydraulic system?
Position EITHER FLT CONTROL switch to STBY RUD
What is affected during Manual Operation of Standby Hydraulic System?
Standby ELEC pump activated
Standby rudder shutoff valve opened
Standby system to power rudder and thrust reverser
Illuminates STBY RUD ON, MASTER CAUTION, FLT CONT annunciator
——————-
Shuts off flight control shutoff valve
Deactivates flight control LOW PRESSURE light
How is Automatic Operation of Standby Hydraulic system initiated?
When
Loss of either A/B systems and,
Flaps extended and,
Wheel speed > 60kts or airborne and,
FLT CONTROL switch ON (guarded)
What is affected during Automatic Operation of Standby Hydraulic System?
Standby ELEC pump activated
Standby rudder shutoff valve opened
Standby system to power rudder and thrust reverser
Illuminates STBY RUD ON, MASTER CAUTION, FLT CONT annunciator
What is the Difference between Automatic and Manual Operation of Standby Hydraulic system?
During Automatic Operation,
Flight control shutoff valve for ailerons elevators and rudder is NOT SHUTOFF
FLT CONTROL LOW PRESSURE lights remain illuminated
———
Only when STBY RUD is position - above statement is changed
What happens when ALTERNATE FLAPS master switch is positioned ARMED?
Activated standby electric pump
Closes TE flaps bypass valve
Arms ALTERNATE FLAPS position switch
Allows standby system to power LE Flaps, slats and reversers
