Hydraulic Systems of Aircrafts

1. BASIC HYDRAULICS

2. What is Hydraulics?
• Hydraulics is derived from the Greek
word
- Hydor meaning Water
- Aulos meaning Pipe

3. Hydraulic System
• Means of transmitting energy from one
area to another efficiently
• Energy transmitted can be divided into
two basic disciplines
> Hydraulics – Employing pressurized
liquid
> Pneumatics - Employing
Compressed gas
• We would be only be discussing
hydraulics i.e. fluid mechanics

4. HYDRAULICS DEFINED
FURTHER…
Fluid Mechanics is the physical science and technology of the static
and dynamic behavior of fluids.
• Hydraulics is a topic in applied science and engineering dealing with
the mechanical properties of liquids. Fluid mechanics provides the
theoretical foundation for hydraulics, which focuses on the
engineering uses of fluid properties.

5. PASCAL’S LAW
Pascal Law – which is the basis for all
hydraulic systems, is named after the French
Scientist – Blaise Pascal, who established
the law.

6. Pascal’s LawPascal’s Law
It states that “ Pressure exerted anywhere in a confinedIt states that “ Pressure exerted anywhere in a confined
fluid is transmitted equally in all directions throughout thefluid is transmitted equally in all directions throughout the
fluid.fluid.
• The basic idea behind all hydraulic system is based upon thatThe basic idea behind all hydraulic system is based upon that
principle & can be simply stated as:principle & can be simply stated as:
• Force applied at one point is transmitted to another pointForce applied at one point is transmitted to another point
using anusing an incompressible fluid.incompressible fluid.

7. Working Principle of a HydraulicWorking Principle of a Hydraulic
PressurePressure

8. Functions of Hydraulic OilFunctions of Hydraulic Oil
• It transmits power.It transmits power.
• It lubricates moving partsIt lubricates moving parts
• It seals clearancesIt seals clearances
between moving partsbetween moving parts
• It dissipates heat i.e.It dissipates heat i.e.
cooling purposescooling purposes

9. Force that is applied at one point isForce that is applied at one point is
transmitted to another point using antransmitted to another point using an
incompressible fluidincompressible fluid
• In this drawing, two pistons (green) fit into two glassIn this drawing, two pistons (green) fit into two glass
cylinders filled with oil (blue) and connected to onecylinders filled with oil (blue) and connected to one
another with an oil-filled pipe. If you apply a downwardanother with an oil-filled pipe. If you apply a downward
force to one piston (the left one in this drawing), then theforce to one piston (the left one in this drawing), then the
force is transmitted to the second piston through the oilforce is transmitted to the second piston through the oil
in the pipein the pipe

10. Hydraulic System PartsHydraulic System Parts
• Reservoir/TankReservoir/Tank
• AccumulatorAccumulator
• FilterFilter
• Hydraulic PumpHydraulic Pump
• Directional Control ValveDirectional Control Valve

12. Tank / Reservoir
First a tank is needed to store the hydraulic oil
Reservoir/Tank- Properties
Storing oil
It dissipates heat
It allows foreign particles to settle
down
Baffle separates inlet line with the
return line and allows the air
bubbles to escape

13. AccumulatorAccumulator
• Absorbs the shocks due to rapid pressureAbsorbs the shocks due to rapid pressure
variations in a hydraulic systemvariations in a hydraulic system
• Helps maintain constant pressure withinHelps maintain constant pressure within
hydraulic systemhydraulic system
• Can be used as an emergency source ofCan be used as an emergency source of
powerpower

14. PUMPSPUMPS
• Hydraulic Pump is the most importantHydraulic Pump is the most important
component in the hydraulic system.component in the hydraulic system.
• Function of the Hydraulic Pump is to convertFunction of the Hydraulic Pump is to convert
Mechanical Energy to Hydraulic EnergyMechanical Energy to Hydraulic Energy
• Hydraulic Pump are classified in twoHydraulic Pump are classified in two
categories:categories:
- Hydro-dynamic- Hydro-dynamic
- Hydro-static- Hydro-static

15. Tank
Pump
Now we need a pump to create flow
Pump
Two types of hydraulic pumps are
most commonly used:
- Rotary Pumps
- Reciprocating Pumps

16. ROTARY & RECIPROCATINGROTARY & RECIPROCATING
TYPESTYPES
• Common Pumps in Rotary type are:Common Pumps in Rotary type are:
- Gear Pumps- Gear Pumps
- Vane Pumps- Vane Pumps
• Reciprocating type is given by:Reciprocating type is given by:

18. ACTUATORSACTUATORS
• An actuator is a mechanical device forAn actuator is a mechanical device for
moving or controlling a mechanism ormoving or controlling a mechanism or
system. An actuator typically is asystem. An actuator typically is a
mechanical device that takes energy &mechanical device that takes energy &
converts it to a desirable form for usage orconverts it to a desirable form for usage or
application.application.
Actuator
Pump
Tank

19. ACTUATORS Contd…ACTUATORS Contd…
• There are mainly two types ofThere are mainly two types of
Actuators:Actuators:
- Linear actuators- Linear actuators
Used to operate trailing edge flaps, trim tabs, elevator,Used to operate trailing edge flaps, trim tabs, elevator,
rudder, aileron etc.rudder, aileron etc.
- Rotary actuators- Rotary actuators
Used in air conditioning, landing gears and fuelUsed in air conditioning, landing gears and fuel
systemssystems

21. Types of ValvesTypes of Valves
• There are three main types ofThere are three main types of
Valves:Valves:
- Pressure Control Valves (relief- Pressure Control Valves (relief
valves, pressure regulating valve,valves, pressure regulating valve,
pressure reducing valve)pressure reducing valve)
- Directional Control Valves (check- Directional Control Valves (check
valve)valve)
- Flow Control Valves (needle valve,- Flow Control Valves (needle valve,
throttle check valve etc.)throttle check valve etc.)

24. Relief valveRelief valve
• This is simply a pressure relief valve. If aThis is simply a pressure relief valve. If a
malfunction in the system causes themalfunction in the system causes the
pressure to rise too high, the relief valvepressure to rise too high, the relief valve
opens and the fluid simply passes back toopens and the fluid simply passes back to
the reservoir. In virtually all automotivethe reservoir. In virtually all automotive
power steering pumps, the relief valve ispower steering pumps, the relief valve is
built into the pumpbuilt into the pump

25. Tank
Pump
Actuator
Hydraulic System – some applications of
the basic components

26. FILTERSFILTERS
• There are basically threeThere are basically three
types of Filterstypes of Filters
- Suction line filters- Suction line filters
- Pressure line filters- Pressure line filters
- Return line filters- Return line filters

27. Why is filtration necessary?Why is filtration necessary?
• Impurities in the HydraulicImpurities in the Hydraulic
system affect the componentssystem affect the components
of the hydraulic system andof the hydraulic system and
shorten their service life.shorten their service life.
• Reduction in service life of theReduction in service life of the
components occurs in twocomponents occurs in two
ways:ways:
- Wear and Tear- Wear and Tear
- Breakdown of component- Breakdown of component
Filters are used to remove theFilters are used to remove the
smallest insoluble particlessmallest insoluble particles
and keep the hydraulic systemand keep the hydraulic system
cleanclean

28. Devices Employing HydraulicDevices Employing Hydraulic
System in AircraftsSystem in Aircrafts
• Landing gearsLanding gears
• Fuel systemsFuel systems
• Air conditioningAir conditioning
• Control Surfaces e.g. elevators, flaps, spoilers, aileronsControl Surfaces e.g. elevators, flaps, spoilers, ailerons
etc.etc.
• Doors and hatchwaysDoors and hatchways
• Shock absorption systemsShock absorption systems
• Bomb bay doorsBomb bay doors
• Gun turretsGun turrets
• Auto pilotAuto pilot

32. Some Hydraulic SymbolsSome Hydraulic Symbols

33. SO, IN HYDRAULICS, AS IN LIFE,SO, IN HYDRAULICS, AS IN LIFE,
REMEMBER YOUR BASICS & NEVERREMEMBER YOUR BASICS & NEVER
GIVE UPGIVE UP
AND LIFE SHALL BE FULL OFAND LIFE SHALL BE FULL OF
HAPPINESSHAPPINESS