2. INTRODUCTIONINTRODUCTION
Hydraulics is based on the fact thatHydraulics is based on the fact that
liquids are incompressibleliquids are incompressible
Hydraulic system is a system whereHydraulic system is a system where
liquid under pressure is used toliquid under pressure is used to
transmit energytransmit energy
In it a hydraulic pump convertsIn it a hydraulic pump converts
mechanical power to hydraulic powermechanical power to hydraulic power
An actuating cylinder convertsAn actuating cylinder converts
hydraulic power to mechanicalhydraulic power to mechanical
power.power.
4. DEVICES USING HYDRAULICDEVICES USING HYDRAULIC
SYSTEMS IN AIRCRAFTSSYSTEMS IN AIRCRAFTS
Gun turretsGun turrets
Auto pilotAuto pilot
Shock absorption systemsShock absorption systems
Dive, landing, speed and flap brakesDive, landing, speed and flap brakes
Bomb bay doorsBomb bay doors
Doors and hatchwaysDoors and hatchways
Landing gears, wing flaps, etc…Landing gears, wing flaps, etc…
5. PRINCIPLES OF OPERATIONPRINCIPLES OF OPERATION
Governed by Pascal’s lawGoverned by Pascal’s law
The oil is in contact withThe oil is in contact with
both sides of the pistonboth sides of the piston
head but at differenthead but at different
pressures. High pressurepressures. High pressure
oil may be pumped intooil may be pumped into
either side of the pistoneither side of the piston
head.head.
The selector valveThe selector valve
determines to which sidedetermines to which side
of the actuating cylinderof the actuating cylinder
the high pressure oil (redthe high pressure oil (red
colored side) is sent.colored side) is sent.
6. PARTS OF THE POWER SYSTEMPARTS OF THE POWER SYSTEM
RESERVOIRRESERVOIR
ACCUMULATORACCUMULATOR
FILTERFILTER
POWER PUMPPOWER PUMP
SYSTEM RELIEF VALVESYSTEM RELIEF VALVE
PRESSURE REGULATORPRESSURE REGULATOR
8. RESERVOIRRESERVOIR
FUNCTIONSFUNCTIONS
Holds reserve supply oil to account forHolds reserve supply oil to account for
normal leakage, emergency supply of oil,normal leakage, emergency supply of oil,
volume changes, thermal contraction ofvolume changes, thermal contraction of
oil,oil,
Provides pressure head on the pump, aProvides pressure head on the pump, a
place to remove air or foam from liquid,place to remove air or foam from liquid,
air space for expansion of the oil due toair space for expansion of the oil due to
temperature changestemperature changes
etcetc
9. RESERVOIRRESERVOIR
CONSTRUCTIONCONSTRUCTION
Material: 5052 aluminiumMaterial: 5052 aluminium
Size: takes into account all oilSize: takes into account all oil
volumes in operationalvolumes in operational
requirements, thermal expansion,requirements, thermal expansion,
leakage, etc.leakage, etc.
Shape: domed cylindrical shape,Shape: domed cylindrical shape,
due to ease of construction &due to ease of construction &
mountingmounting
10. ACCUMULATORSACCUMULATORS
PRINCIPLEPRINCIPLE
Gas valve lets inGas valve lets in
compressed gas at ½compressed gas at ½
system pressuresystem pressure
Diaphragm pops up &Diaphragm pops up &
oil is sent throughoil is sent through
systemsystem
When systemWhen system
pressure>accumulatorpressure>accumulator
pressure, diaphragmpressure, diaphragm
deploysdeploys
11. ACCUMULATORSACCUMULATORS
USESUSES
Absorbs the shocks due to rapid pressureAbsorbs the shocks due to rapid pressure
variations in a hydraulic systemvariations in a hydraulic system
Helps maintain a constant pressure withinHelps maintain a constant pressure within
the hydraulic systemthe hydraulic system
Helps the hydraulic pump under peakHelps the hydraulic pump under peak
pressure loadspressure loads
It is an emergency source of powerIt is an emergency source of power
Spherical shape is preferred forSpherical shape is preferred for
accumulatorsaccumulators
12. POWER PUMPSPOWER PUMPS
FUNCTIONFUNCTION
Is to change mechanical horsepower toIs to change mechanical horsepower to
hydraulic horsepowerhydraulic horsepower
TYPESTYPES
Gear pumps: move fluid based upon theGear pumps: move fluid based upon the
number of gear teeth and the volumenumber of gear teeth and the volume
spacing between gear teeth.spacing between gear teeth.
Piston pumps: move fluid by pushing itPiston pumps: move fluid by pushing it
through the motion of the pistons withinthrough the motion of the pistons within
the pumpthe pump
13. POWER PUMPSPOWER PUMPS
PRINCIPLES OF GEARPRINCIPLES OF GEAR
PUMPSPUMPS
The liquid from theThe liquid from the
reservoir is pushedreservoir is pushed
between the gearbetween the gear
teeth.teeth.
The oil is movedThe oil is moved
around to the otheraround to the other
side by the action ofside by the action of
the drive gear itselfthe drive gear itself
and sent through theand sent through the
pressure line.pressure line.
14. POWER PUMPSPOWER PUMPS
PRINCIPLES OFPRINCIPLES OF
RECIPROCATINGRECIPROCATING
PISTON PUMPPISTON PUMP
As the cylinder blockAs the cylinder block
rotates, spacerotates, space
between the block andbetween the block and
the pistons increase,the pistons increase,
letting in more oil.letting in more oil.
As the block rotatesAs the block rotates
from bottom deadfrom bottom dead
center, the reversecenter, the reverse
occurs and the pistonsoccurs and the pistons
push oil out throughpush oil out through
the outletthe outlet
15. SYSTEM RELIEF VALVESYSTEM RELIEF VALVE
PRINCIPLEPRINCIPLE
The adjustmentThe adjustment
screw is set for ascrew is set for a
certain pressurecertain pressure
value P2.value P2.
When the pressureWhen the pressure
increases, theincreases, the
poppet will movepoppet will move
up, forcing theup, forcing the
excess liquid inexcess liquid in
16. Douglass Pressure RegulatorDouglass Pressure Regulator
high pressure oil fromhigh pressure oil from
the power pumpthe power pump
opens valve C andopens valve C and
also act on piston Aalso act on piston A
piston A pushes Ball Bpiston A pushes Ball B
off seat D, the oil goesoff seat D, the oil goes
through passage Dthrough passage D
into the centerinto the center
chamber back to thechamber back to the
reservoir.reservoir.
18. Selector ValvesSelector Valves
Position (1) is the position of the selector valve,Position (1) is the position of the selector valve,
for example, upon the extension of the landingfor example, upon the extension of the landing
gear or the lowering of flaps.gear or the lowering of flaps.
Position (2) is the position of the selector valvePosition (2) is the position of the selector valve
upon retraction of the landing gear or the raisingupon retraction of the landing gear or the raising
of the flapsof the flaps
19. FLOW EQUALISERFLOW EQUALISER
If wing air loads on oneIf wing air loads on one
wing are greater than onwing are greater than on
other, during wing sweepother, during wing sweep
back or sweep forward,back or sweep forward,
motion occurs unevenly.motion occurs unevenly.
To synchronize wing sweepTo synchronize wing sweep
back or sweep forward flowback or sweep forward flow
equaliser usedequaliser used
flow equalizer is made up offlow equalizer is made up of
two power pumps placedtwo power pumps placed
side by side in which theside by side in which the
drive gears of both pumpsdrive gears of both pumps
are connectedare connected
20. ACTUATION CYLINDERACTUATION CYLINDER
The function is to takeThe function is to take
the pressure & hydraulicthe pressure & hydraulic
fluid flow & change themfluid flow & change them
into linear or rotaryinto linear or rotary
motion.motion.
Single piston double rodSingle piston double rod
is an equal displacementis an equal displacement
cylinder used in aileroncylinder used in aileron
system or automaticsystem or automatic
guidance systemguidance system
Double piston-double rodDouble piston-double rod
actuating cylinder usedactuating cylinder used
in bomb bay doorsin bomb bay doors
21. ADVANTAGESADVANTAGES
It is lighter in weight than alternate existingIt is lighter in weight than alternate existing
systems.systems.
It is dead beat, that is, there is an absence ofIt is dead beat, that is, there is an absence of
sloppiness in its response to demands placed onsloppiness in its response to demands placed on
the system.the system.
It is reliable; either it works or doesn't.It is reliable; either it works or doesn't.
It can be easily maintained.It can be easily maintained.
It is not a shock hazard; it is not much of a fireIt is not a shock hazard; it is not much of a fire
hazard.hazard.
It can develop practically unlimited force orIt can develop practically unlimited force or
torque.torque.
