AIRCRAFTS HYDRAULIC AIRCRAFTS HYDRAULIC SYSTEMSYSTEM

INTRODUCTIONINTRODUCTIONHydraulics is based on the fact that

liquids are incompressibleHydraulic system is a system where

liquid under pressure is used to transmit energy

In it a hydraulic pump converts mechanical power to hydraulic power

An actuating cylinder converts hydraulic power to mechanical power.

A SIMPLE HYDRAULIC A SIMPLE HYDRAULIC SYSTEMSYSTEM

DEVICES USING HYDRAULIC DEVICES USING HYDRAULIC SYSTEMS IN AIRCRAFTSSYSTEMS IN AIRCRAFTS

Gun turrets Auto pilot Shock absorption systems Dive, landing, speed and flap brakes Bomb bay doors Doors and hatchways Landing gears, wing flaps, etc…

PRINCIPLES OF OPERATIONPRINCIPLES OF OPERATIONGoverned by Pascal’s lawThe oil is in contact with

both sides of the piston head but at different pressures.  High pressure oil may be pumped into either side of the piston head.

The selector valve determines to which side of the actuating cylinder the high pressure oil (red colored side) is sent.

PARTS OF THE POWER PARTS OF THE POWER SYSTEMSYSTEMRESERVOIRACCUMULATORFILTERPOWER PUMPSYSTEM RELIEF VALVE PRESSURE REGULATOR

POWER SYSTEMPOWER SYSTEM

RESERVOIRRESERVOIR

FUNCTIONSHolds reserve supply oil to account for

normal leakage, emergency supply of oil, volume changes, thermal contraction of oil,

Provides pressure head on the pump, a place to remove air or foam from liquid, air space for expansion of the oil due to temperature changes

etc

RESERVOIRRESERVOIRCONSTRUCTION Material: 5052 aluminium Size: takes into account all oil

volumes in operational requirements, thermal expansion,

leakage, etc. Shape: domed cylindrical shape,

due to ease of construction & mounting

ACCUMULATORSACCUMULATORS

PRINCIPLEGas valve lets in

compressed gas at ½ system pressure

Diaphragm pops up & oil is sent through system

When system pressure>accumulator pressure, diaphragm deploys

ACCUMULATORSACCUMULATORSUSES Absorbs the shocks due to rapid

pressure variations in a hydraulic system

Helps maintain a constant pressure within the hydraulic system

Helps the hydraulic pump under peak pressure loads

It is an emergency source of power Spherical shape is preferred for

accumulators

POWER PUMPSPOWER PUMPSFUNCTION Is to change mechanical horsepower

to hydraulic horsepower TYPES Gear pumps: move fluid based upon

the number of gear teeth and the volume spacing between gear teeth.

Piston pumps: move fluid by pushing it through the motion of the pistons within the pump

POWER PUMPSPOWER PUMPS

PRINCIPLES OF GEAR PUMPS

The liquid from the reservoir is pushed between the gear teeth.

The oil is moved around to the other side by the action of the drive gear itself and sent through the pressure line.

POWER PUMPSPOWER PUMPSPRINCIPLES OF

RECIPROCATING PISTON PUMP

As the cylinder block rotates, space between the block and the pistons increase, letting in more oil.

As the block rotates from bottom dead center, the reverse occurs and the pistons push oil out through the outlet

SYSTEM RELIEF VALVESYSTEM RELIEF VALVE

PRINCIPLEThe adjustment

screw is set for a certain pressure value P2.

When the pressure increases, the poppet will move up, forcing the excess liquid in

Douglass Pressure Douglass Pressure RegulatorRegulator

high pressure oil from the power pump opens valve C and also act on piston A

piston A pushes Ball B off seat D, the oil goes through passage D into the center chamber back to the reservoir.

HAND PUMPSHAND PUMPS

Selector Valves Selector Valves Position (1) is the position of the selector valve,

for example, upon the extension of the landing gear or the lowering of flaps.

Position (2) is the position of the selector valve upon retraction of the landing gear or the raising of the flaps

FLOW EQUALISERFLOW EQUALISER

If wing air loads on one wing are greater than on other, during wing sweep back or sweep forward, motion occurs unevenly.

To synchronize wing sweep back or sweep forward flow equaliser used

flow equalizer is made up of two power pumps placed side by side in which the drive gears of both pumps are connected

ACTUATION CYLINDERACTUATION CYLINDER The function is to take the pressure

& hydraulic fluid flow & change them into linear or rotary motion.

Single piston double rod is an equal displacement cylinder used in aileron system or automatic guidance system

Double piston-double rod actuating cylinder used in bomb bay doors

ADVANTAGESADVANTAGES It is lighter in weight than alternate

existing systems. It is dead beat, that is, there is an absence

of sloppiness in its response to demands placed on the system.

It is reliable; either it works or doesn't. It can be easily maintained. It is not a shock hazard; it is not much of a

fire hazard. It can develop practically unlimited force or

torque.

CONCLUSIONCONCLUSION

Hydraulic systems determine flight worthiness, usability and reliabity.