13 Hydraulics Flashcards
🟧 OVERHEAT
- in ELEC 2/1
HYD fluid (to cool and lubricate the electric motor driven pump) has overheated or pump itself has overheated
- power automatically removed from AC electrical driven pump
ENGINE HYDRAULIC PUMP SWITCH
- ON
O - de-energizes blocking valve in pump to allow pump pressure to enter system
- should always remain on at shutdown to prolong solenoid life
Hydraulic system quantity
Hydraulic system pressure
- when both pumps off:
Q - indicates 0%-106% digitally
P - normal pressure 3000 PSI, max pressure 3500 PSI
W - indication may read hydraulic system reservoir pressure, normally < 100 PSI
HYD refill indications
- when valid:
- when illuminated:
V - ONLY when aircraft on ground with both ENG shutdown or after landing with flags up during taxi-in
I - hydraulic quantity below 76%
FLIGHT CONTROL SWITCH
STBY RUD = activates standby pump and opens standby rudder shutoff valve to pressurize STBY rudder PCU
Which HYD system to pressurize ALL flight controls
EITHER A or B, with NO decrease in controlability
HYD ENG DRIVEN PUMP
-failed
- switched to OFF
HYD ELECTRIC DRIVEN PUMP
ENG - provides 6 times HYD fluid compared to electric
- FAIL: ELEC pump on and HIGH demand on system: can result in low pressure
- operates as long as ENG is still operating
ELEC - AC electric motor-driven pump
Pulling ENG fire switch
shuts off HYD fluid to ENG driven pump
Heat exchanger
- why
- located
used for cooling and lubrication of pumps through heat exchanger before turning to reservoir.
- System A: main tank 1
- System B: main tank 2
MIN fuel quantity for ground operation of electric motor-driven pump
760 KG in related main tank
Check valve
system pressure transmitter
C - isolates related pump from Hydraulic system
S - sends combined pressure (ENG+ ELEC) to HYD system pressure indicator
SYSTEM A LEAK
- in ENG pump
- in ELEC pump
ENG: due to standpipe the quantity will NOT drop more than 20%, system A pressure (below 20%) will be maintained by ELEC pump
ELEC: quantity slowly decreases to 0 and the pressure will be lost
SYSTEM B LEAK
- in ENG pump or ELEC pump
- standpipe
Quantity INDICATIONS will decrease to 0% and the B pressure will be lost
Standpipe: will make sure if EITHER pump B Leakes and indications read 0, the fluid remaining (below standpipe) will be sufficient for PTU operation
Does a leak in HYD B effect STBY HYD SYSTEM
NO
POWER TRANSFER UNIT
- purpose
- uses what to power what
- operates when:
P - Supply additional HYD fluid when ENG pump B is inoperative
- User SYS A pressure to power hydraulic motor driven pump which than pressurizes HYD B fluid
- operates when all of these occur:
- SYS B ENG driven pump hydraulic pressure drops below limits
- airborne
- flaps NOT up
Landing Gear Transfer Unit
- purpose
- supply
- when operating
P - SYS A ENG pump lost, it supplies the volume of HYD fluid needed to raise the landing gear
S - SYS B ENG pump supplies the volume of HYD fluid needed to operate the LGTU when ALL of these occur:
- airborne
- No 1 ENG RPM drops below a limit value
- landing gear lever in UP position
- either main landing gear NOT up + locked
STBY HYD SYSTEM
- activated manual: positioning either FLT CTRL switch to STBY RUD:
- activates STBY ELEC
- closes FLT CTRL Shutoff valve, this deactivates LOW PRESSURE light
- opens STBY RUD valve
- allows STBY system to power rudder + thrust reversers
- illuminates STBY RUD ON, MASTER CAUTION + FLT CTRL lights
STBY HYD SYSTEM
- activates automatic: initiated when:
- automatic operation:
- loss of system A OR B, and
- flaps extended, and
- airborne or wheel speed > 60 KTS, and
- FLT CONTROL switch A or B HYD system ON
—– OR —— - Main PCU FFM (Force Flight Monitor) trips
- activates the STBY ELEC motor-driven pump
- opens STBY rudder shutoff valve
- allows STBY system to power rudder + thrust reversers
- illuminates STBY RUD ON, MASTER CATUION, FLT CTRL LIGHTS
LEAK in STBY HYD system
- decrease quant
- system B
STBY reservoir quantity decreases to 0, when STBY reservoir reaches half empty > 🟧 LOW QUANTITY
SYS B continues to operate normally, but reservoir B decreases until 70%
Variations in HYD Quantity
- during normal operation
- not pressurized properly at higher altitudes
During normal operation:
- system becomes pressurized after ENG start
- raising/lowering landing gear of LE devices
-cold soaking occurs during long periods of cruise
Foaming can occur:
- HYD pressure fluctuations
- LOW PRESSURE light blinking
- MASTER CAUTION + HYD
