AIRCRAFT HYDRAULIC SYSTEMS

1. AIRCRAFTS AIRCRAFTS
HYDRAULIC SYSTEMHYDRAULIC SYSTEM
YASH VARDHANYASH VARDHAN
09128401240912840124

2. INTRODUCTIONINTRODUCTION

Hydraulics is based on the fact that Hydraulics is based on the fact that
liquids are incompressibleliquids are incompressible

Hydraulic system is a system where Hydraulic system is a system where
liquid under pressure is used to liquid under pressure is used to
transmit energytransmit energy

In it a hydraulic pump converts In it a hydraulic pump converts
mechanical power to hydraulic powermechanical power to hydraulic power

An actuating cylinder converts An actuating cylinder converts
hydraulic power to mechanical hydraulic power to mechanical
power.power.

3. A SIMPLE HYDRAULIC SYSTEMA SIMPLE HYDRAULIC SYSTEM

4. DEVICES USING HYDRAULIC DEVICES 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 doors Bomb 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 with The oil is in contact with
both sides of the piston both sides of the piston
head but at different head but at different
pressures. High pressure pressures. High pressure
oil may be pumped into oil may be pumped into
either side of the piston either side of the piston
head. head.

The selector valve The selector valve
determines to which side determines to which side
of the actuating cylinder of the actuating cylinder
the high pressure oil (red the 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 VALVE SYSTEM RELIEF VALVE

PRESSURE REGULATORPRESSURE REGULATOR

7. POWER SYSTEMPOWER SYSTEM

8. RESERVOIRRESERVOIR
FUNCTIONSFUNCTIONS

Holds reserve supply oil to account for Holds reserve supply oil to account for
normal leakage, emergency supply of oil, normal leakage, emergency supply of oil,
volume changes, thermal contraction of volume changes, thermal contraction of
oil,oil,

Provides pressure head on the pump, a Provides 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 to air space for expansion of the oil due to
temperature changes temperature changes
etcetc

9. RESERVOIRRESERVOIR
CONSTRUCTIONCONSTRUCTION

Material: 5052 aluminiumMaterial: 5052 aluminium

Size: takes into account all oil Size: takes into account all oil
volumes in operational volumes 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 &
mounting mounting

10. ACCUMULATORSACCUMULATORS
PRINCIPLEPRINCIPLE

Gas valve lets in Gas valve lets in
compressed gas at ½ compressed gas at ½
system pressuresystem pressure

Diaphragm pops up & Diaphragm pops up &
oil is sent through oil is sent through
systemsystem

When system When system
pressure>accumulator pressure>accumulator
pressure, diaphragm pressure, diaphragm
deploys deploys

11. ACCUMULATORSACCUMULATORS
USESUSES

Absorbs the shocks due to rapid pressure Absorbs the shocks due to rapid pressure
variations in a hydraulic system variations in a hydraulic system

Helps maintain a constant pressure within Helps maintain a constant pressure within
the hydraulic system the hydraulic system

Helps the hydraulic pump under peak Helps the hydraulic pump under peak
pressure loads pressure loads

It is an emergency source of power It is an emergency source of power

Spherical shape is preferred for Spherical shape is preferred for
accumulators accumulators

12. POWER PUMPSPOWER PUMPS
FUNCTIONFUNCTION

Is to change mechanical horsepower to Is to change mechanical horsepower to
hydraulic horsepower hydraulic horsepower
TYPESTYPES

Gear pumps: move fluid based upon the Gear pumps: move fluid based upon the
number of gear teeth and the volume number of gear teeth and the volume
spacing between gear teeth.spacing between gear teeth.

Piston pumps: move fluid by pushing it Piston pumps: move fluid by pushing it
through the motion of the pistons within through the motion of the pistons within
the pump the pump

13. POWER PUMPSPOWER PUMPS
PRINCIPLES OF GEAR PRINCIPLES OF GEAR
PUMPSPUMPS

The liquid from the The liquid from the
reservoir is pushed reservoir is pushed
between the gear between the gear
teeth. teeth.

The oil is moved The oil is moved
around to the other around to the other
side by the action of side by the action of
the drive gear itself the drive gear itself
and sent through the and sent through the
pressure line. pressure line.

14. POWER PUMPSPOWER PUMPS
PRINCIPLES OF PRINCIPLES OF
RECIPROCATING RECIPROCATING
PISTON PUMPPISTON PUMP

As the cylinder block As the cylinder block
rotates, space rotates, space
between the block and between the block and
the pistons increase, the pistons increase,
letting in more oil. letting in more oil.

As the block rotates As the block rotates
from bottom dead from bottom dead
center, the reverse center, the reverse
occurs and the pistons occurs and the pistons
push oil out through push oil out through
the outlet the outlet

15. SYSTEM RELIEF VALVESYSTEM RELIEF VALVE
PRINCIPLEPRINCIPLE

The adjustment The adjustment
screw is set for a screw is set for a
certain pressure certain pressure
value P2. value P2.

When the pressure When the pressure
increases, the increases, the
poppet will move poppet will move
up, forcing the up, forcing the
excess liquid inexcess liquid in

16. Douglass Pressure RegulatorDouglass Pressure Regulator

high pressure oil from high pressure oil from
the power pump the power pump
opens valve C and opens valve C and
also act on piston A also act on piston A

piston A pushes Ball B piston A pushes Ball B
off seat D, the oil goes off seat D, the oil goes
through passage D through passage D
into the center into the center
chamber back to the chamber back to the
reservoir. reservoir.

17. HAND PUMPSHAND PUMPS

18. Selector Valves Selector 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 landing for 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 valve Position (2) is the position of the selector valve
upon retraction of the landing gear or the raising upon retraction of the landing gear or the raising
of the flaps of the flaps

19. FLOW EQUALISERFLOW EQUALISER

If wing air loads on one If wing air loads on one
wing are greater than on wing are greater than on
other, during wing sweep other, during wing sweep
back or sweep forward, back or sweep forward,
motion occurs unevenly.motion occurs unevenly.

To synchronize wing sweep To synchronize wing sweep
back or sweep forward flow back or sweep forward flow
equaliser usedequaliser used

flow equalizer is made up of flow equalizer is made up of
two power pumps placed two power pumps placed
side by side in which the side by side in which the
drive gears of both pumps drive gears of both pumps
are connected are connected

20. ACTUATION CYLINDERACTUATION CYLINDER

The function is to take The function is to take
the pressure & hydraulic the pressure & hydraulic
fluid flow & change them fluid flow & change them
into linear or rotary into linear or rotary
motion. motion.

Single piston double rod Single piston double rod
is an equal displacement is an equal displacement
cylinder used in aileron cylinder used in aileron
system or automatic system or automatic
guidance system guidance system

Double piston-double rod Double piston-double rod
actuating cylinder used actuating cylinder used
in bomb bay doors in bomb bay doors

21. ADVANTAGESADVANTAGES

It is lighter in weight than alternate existing It is lighter in weight than alternate existing
systems. systems.

It is dead beat, that is, there is an absence of It is dead beat, that is, there is an absence of
sloppiness in its response to demands placed on sloppiness 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 fire It is not a shock hazard; it is not much of a fire
hazard. hazard.

It can develop practically unlimited force or It can develop practically unlimited force or
torque. torque.

22. CONCLUSIONCONCLUSION
Hydraulic systems determine flight Hydraulic systems determine flight
worthiness, usability and reliability.worthiness, usability and reliability.