Hydraulics Flashcards
Electric Hydraulic Pump OVERHEAT (amber)
hydraulic fluid used to cool and lubricate the electric pump has overheated or the pump itself is overheated
Hydraulic pump LOW pressure light (amber)
output pressure of associated pump is low
Engine Hydraulic pump switches
ON- de energizes blocking valve in pump to allow pump pressure to enter system
OFF- energizes blocking valve to block pump output
should remain ON at shutdown to prolong solenoid life
Normal pressure and maximum pressure of hydraulic system
Normal- 3000 PSI
Max- 3500PSI
White RF indication on DU
76%
Flight control switches (STBY RUD, OFF, ON)
STBY RUD- activates standby pump and opens standby rudder SOV to pressurize standby rudder PCU
OFF- closes flight control SOV isolating ailerons, elevators and rudder from associated hydraulic pressure
ON- normal operating position
Flight control low pressure lights (amber)
low hydraulic system A or B pressure to ailerons rudder and elevator
deactivated when associated FLIGHT CONTROL switch is position to STBY RUD
STANDBY HYDRAULIC LOW QUANTITY (amber)
indicates low quantity in standby hydraulic reservoir
always armed
standby hydraulic low pressure (amber)
indicates output pressure of standby pump is low
armed only standby pump operation is selected manually or automatically
ALTERNATE FLAPS master switch
Off- normal position ARM- closes TE flap bypass valve activates standby pump arms alternate flaps position switch
STBY RUD ON (amber)
indicates standby hydraulic system is commanded to pressurize the standby rudder PCU
Components powered by hydraulic system A
Ailerons Rudder Elevator and elevator feel flight spoilers (two on each wing) ground spoilers alternate brakes No. 1 thrust reverser Autopilot A normal nose wheel steering landing gear PTU main deck cargo door
Components powered by hydraulic system B
ailerons rudder Elevator and elevator feel flight spoilers (two each wing) LE flaps and slats TE flaps normal brakes No. 2 thrust reverser Autopilot B alternate nose wheel steering landing gear transfer unit autoslats yaw damper
where are the heat exchangers for the cooling of the hydraulic fluid?
Exchanger for system A in the main fuel tank 1
exchanger for system B in the main fuel tank 2
What happens if a hydraulic leak develops in the system A engine driven pump or its related lines?
the quantity will go to approx 20% full and pressure is maintained by the electric pump
what happens if a hydraulic leak develops in system A electric drive hyd pump or related lines?
quantity in reservoir decreases to 0
What happens if a leak develops in either pump line or component of B?
Quantity will decrease until it reads 0, HOWEVER, the fluid remaining in the B reservoir is enough for PTU operation
the PTU operates automatically when:
system B engine drive pump drops below limits
airborne
flaps less than 15 but not up
What is the landing gear transfer unit and when does it operate?
Supplies the volume of hydraulic fluid needed to raise the landing gear at the normal rate when system A engine drive pump volume is lost.
Operates when:
- airborne
- engine 1 RPM drops below a limit value
- landing gear lever positioned up
- landing gear is not up and locked
What does the standby hydraulic system power?
thrust reversers
rudder
LE flaps and slats (extend only)
standby yaw damper
What happens when FLT control switch is placed in STBY RUD
- activates electric standby pump
- closes related flight control SOV to shut off pressure to aileron, elevator, rudder
- opens standby rudder SOV
- deactivates the flight control low pressure light
- allows standby system to power rudder and thrust reversers
- illuminates STBY RUD ON, master caution, FLT cont lights
What happens when you position ALTERNATE FLAPS switch to ARM?
- activates electric standby pump
- closes TE flap bypass valve
- arms alternate flaps position switch
- allows standby system to power the LE flaps and slats and T/Rs
When is automatic operation of the standby hydraulic system activated
loss of system A or B
flaps extended
airborne or wheel speed greater than 60
FLT control switch A or B ON
OR
Main PCU Force Flight Monitor trips
What will happen if there is a leak in the standby hydraulic system?
the standby reservoir quantity will decrease to 0 and the system B fluid level will decrease to 70% full
When does the standby hydraulic system LOW QUANTITY light illuminate?
when the quantity is approx half empty
what might cause variations in hydraulic quantity indications in normal operations?
system pressurizing after engine start.
raising or lowering gear or LE devices
cold soaking
What is the minimum fuel for ground operation of electric motor drive pumps in each main fuel tank?
1675 lbs
What is the purpose of the PTU?
The PTU will supply the additional volume of hydraulic fluid needed to operate the autoslats and LE flaps at the normal rate when system B hydraulic pump volume is lost. It uses system A pressure to power the hydraulic motor driven pump, which pressurizes system B fluid. Operates automatically when:
- System B engine driven pump hydraulic pressure drops below limits
- airborne
- flaps are less than 15 but not up
During normal operations, variations in hydraulic quantity indications may occur in the following situations:
-system becomes pressurized after engine start
-raising or lowering landing gear or LE devices
-cold soaking occurs in long periods of cruise
These have little effect on operations
If the hydraulic system is not properly pressurized, foaming can occur at high altitudes. What indications might you see?
- pressure fluctuations
- blinking of related LOW PRESSURE lights
- MASTER CAUTION and HYD annunciator lights may also momentarily illuminate
