Afr 1041 Aircraft Hydraulic Pneumatic Lecture Presentation 2

7/30/2019 Afr 1041 Aircraft Hydraulic Pneumatic Lecture Presentation 2

1/269

MALAYSIAN INSTITUTE OF

AVIATION TECHNOLOGY

HYDRAULIC & PNEUMATICAFR 1041

BY:ABDULLAH HJ MOHD NOOR


2/269

PRINCIPLES OF HYDRAUL IC

Hydraulic Preface. Preface.

With the free and almost unlimited power available in

flowing water, much early human industry was locatedalong the rivers. People used water for transportation anddiverted water to flow over large wooden waterwheels andturned shafts inside factory buildings. Pulleys and beltsdrove the lathes and drill presses from these water drivenshafts.

As we modernized, the basic daily routine technology isimplemented into aircraft system to simplify and smoothenthe operation of it.


3/269

PRINCIPLES OF HYDRAUL IC

Hydraulic Design. Design.

Hydraulic fluid is design to fulfill aircraft needs. Most

aircraft use some form of hydraulic and pneumaticsystem, ranging from a simple braking system to amultiplex engine driven pump system and providing ameans of operation of large aircraft components.

The operation of landing gear, flaps, control-boost

system and other components is widely accomplish byhydraulic power system. Pneumatic systems are used insome aircraft design to perform the same type ofoperation performed by hydraulic systems. However,the majority of aircraft that have pneumatic system usethem only as backup system for the operation of

hydraulic components when the hydraulic system failed.


4/269

HYDRAUL IC REVIEW OF

TERMS

AREA

FORCE

DISTANCE/STROKE

VOLUME/DISPLACEMENT

WORK POWER


5/269


TERMS

AREA

A measurement of a surface.

In aircraft hydraulics, the technician is concerned with

the areas of piston heads.Knowing this area, the amount of force required to

actuate a mechanism can be determined.

Area is generally measured in square inch/square feet

in English system and in square centimeters /squaremeters in Metric system.


6/269


TERMS

AREA


7/269


TERMS

FORCE

The amount of push, pull or twist on an object.

The force in a hydraulic system is derived from the

pressure acting on the area of a piston head.In English system, force is measured in pounds (lbs), in

the Metric system, it is measured in grams, kilograms or

Newton (N).

To measure the force of hydraulic, we must be able todetermine force per unit area and this is called

pressure and is measured in pounds per square inch

(psi) or kilopascals (kPa).


8/269


TERMS

DISTANCE/STROKE

A measurement of distance of a piston.

The distance/stroke is being expressed in inches or feetin English system and centimeters or meters in the

Metric system.


9/269


TERMS

DISTANCE/STROKE


10/269


TERMS

VOLUME & DISPLACEMENT.Is a measurement of quantity of fluid available or the

amount of fluid moved.

Volume/displacement is expressed in cubic inches or

cubic feet in English system and cubic centimeter or

cubic meters in Metric system.


11/269


TERMS

VOLUME & DISPLACEMENT.


12/269


TERMS

WORK.Is the product of a force multiplied by the distance over

which the force acts.

Work is simply forces times distance and does not

considered time.

Work is being expressed in such unit as foot-pounds,

inch-pounds or inch-ounces in English system and in

Metric system work is measured in meter-kilograms orcentimeter-grams.


13/269


TERMS

POWER.Power is a measure of the amount of work done in a

given period of time and horsepower is the standard unit

for mechanical power.

One horsepower is 33,000 foot pound of work in 1

minute or 550 foot-pounds of work done in 1 second.

One horsepower is also equal to 746 watts of electrical

power.


14/269


RELATIONSHIPS

Relationship between Force, Pressure & Area.

In English system, Force is measured in pounds, Area is

in square inches and Pressure is in pounds per square

inch.The amount of force a fluid power system can produce

is determined by the amount of pressure used and the

area on which the pressure is acting.


15/269


TERMS


Force = Pressure X Area

Area = Force Pressure

Pressure = Force Area


16/269


RELATIONSHIPS

Relationship between Volume, Area & Distance.

With this relationship, you can find the amount of fluid

needed to move a piston of a specific given distance.Finding the distance a given amount of fluid will move

the piston or the size of the piston needed for a given

distance of movement when the volume is known.


17/269


TERMS

Relationship between Volume, Area & Distance.

Volume = Area X Distance

Area = Volume Distance

Distance = Volume Area


18/269


TERMS

Relationship between Height & Pressure/HydrostaticParadox.

The pressure of a static fluid exerts is determined by theheight of the fluid and has nothing to do with its volume.

For example, if the height of a liquid in a piece of inchtubing is exactly the same as the height of the liquid in a 100gallon tank, the pressure at the bottom of the tube will beexactly the same as the pressure at the bottom of the tank.

Neither the shape of the container nor the amount ofwater has any effect on the pressure. Pressure is determinedonly by the density of the fluid and by the height of the topof the fluid above the bottom of the container.


19/269


TERMS


Pressure = Density X Height


20/269


RELATIONSHIPS

The Law of Conservation of Energy.Energy cannot be created or destroyed, but we can change

the form of the energy in order to use it and when the energyform is changed, we exactly have the same amount ofenergy we started with.

Most mechanical devices produce less work than is put intothem. This is because of friction or inefficiency, but the totalenergy output is the same as the total input energy input.

Energy in fluid power system may be in one or two form,which is potential or kinetic.

Potential energy in a fluid power system is expressed in thepressure of the fluid and kinetic energy is expressed in thevelocity of the moving fluid.


21/269


RELATIONSHIPS

Pascals Law. Explains the way power is transmitted in a closed

hydraulic or pneumatic system.

Stated in simple terms, Pascals Law says that pressure inan enclosed container is transmitted equally and

undiminished to all parts of the closed container and it

acts at right angles to the walls that enclose it.

Amount of pressure increase by multiplying the area ofthe piston by the force caused by the weight. It is the same

on every single of the gages regardless of their position in

the system or of the shape of the container.


22/269


RELATIONSHIPS

Pascals Law. Pascals Law theory is proven in automobile a hydraulic

brake that provides equal braking action.

For example, when the brake pedal is pressed, the pressureis transmitted equally to each of the wheel regardless of

the distance between the brake master cylinder and the

wheel cylinder.


23/269


RELATIONSHIPS

Pascals Law.


24/269


RELATIONSHIPS

Pascals Law.


25/269


RELATIONSHIPS

Bernoullis Principles. When fluid is not in still condition (such as being explain

in Pascals Law), means it is moving, it is best to be

explain and proven by Bernoullis Principle. Bernoullis Principles explain the basic principle that

explains the relation between kinetic energy and potential

energy in fluids that are in motion.

Its explain the relationship between pressure and velocityin a stream of moving fluid. The total energy in the fluids

is made up of potential and kinetic energy.


26/269


RELATIONSHIPS

Bernoullis Principles.

The potential energy relates to the pressure of the fluid

and the kinetic energy relates to its velocity.

Bernoullis Principle tells us that as long as the total

energy in a flow of fluid remains constant, any increase in

the velocity of the fluid will results in a decrease in the

pressure that is exerted by the fluid.


27/269


RELATIONSHIPS



28/269


RELATIONSHIPS



29/269


RELATIONSHIPS

Differential Areas. Another aspect of force produced by fluid pressure is the

effects of differential areas.

For example, (linear type actuator) if fluid pressure isapplied to the piston head end connection, the piston will

move to the left and if the fluid pressure is applied to the

piston rod connection, the piston will move to the right.

If the two end connections are connected together and the

fluid is applied top the both side at the same time, the

piston will not remain stationary.

In fact, it will move to the left and this is because by the

area of the piston being reduced on one side by the

amount equal to the cross sectional area of the piston rod.


30/269


RELATIONSHIPS

Differential Areas.


31/269


RELATIONSHIPS

Brahmah's Principles. In an aircraft hydraulic system, Brahmah's Principles can

be applied to the movement of different loads using

actuators subject to one pressure. It is known that fluid pressure acts equally in all direction

and also that the load which can be moved by a piston

depends upon the pressure and the piston area.

Brahmah's Principles stated that under a given load, thesmaller the area it acts upon the greater the pressure

produced and the greater the area under pressure, the

greater the force available.


32/269


RELATIONSHIPS

Brahmah's Principles. For example, a very small weight added to the 200

Newton on the small piston will cause some of the fluid in

the small cylinder to flow to the larger cylinder. Now thelarge pistons plus the 400Newton weight will move

upwards.

Brahmah's Principles, which worked on theory, provided

mechanical advantage. He used a large area of piston at

the load end and a small area piston at the effort end.

In this way a small force raised a heavy load.


33/269


RELATIONSHIPS

Brahmah's Principles. This gain is offset by the greater distance through which

the effort (small piston) has to move compared with the

distance moved by the load (large piston).

In addition, the speed of the travel of the large piston will

be less than that of the small piston.


34/269


RELATIONSHIPS

Mechanical Advantage. Is the ratio of the load, which is moved to the applied

force and is gained at the expenses of distance moved bythe effort.

There are 2 major advantages, which is: Force can be transmitted over large distances.

Large gain in mechanical advantage made possible by varying thesize of the pistons.

A mechanical advantage is achieved in a hydraulic systemby having an output piston that is larger than the inputpiston. If a piston whose area is one square inch is presseddown with a force of one pounds, it will produce a

pressure of one pound per square inch and for every inch

it moves, it will displace one cubic inch of fluid.


35/269


RELATIONSHIPS

Mechanical Advantage. It is possible to have an application in an aircraft hydraulic

system that requires a large amount of movement but only

a small amount of force. When this is needed, a largepiston can be used to drive a smaller one.

All of the fluid moved by the large piston will enter the

cylinder with the small piston and move it a distance equal

to the volume of fluid divided by the area of the small

piston.


36/269


RELATIONSHIPS

Advantages and Disadvantages of Fluid PowerSystem.

Advantages:

Provides smooth and steady and accurate movement.

Lighter to the weight ratio. Hydraulic power/force will be confined to pipe lines

and components associates only.

Ability of varying the speed of mechanical operationsby means of motors.

Ease of installation & less space required (pipe linesbetween components can go around obstructions).

Elimination of backlash between components.

Ease of inspection and maintenance.

Almost 100% efficient.


37/269


RELATIONSHIPS

Advantages and Disadvantages of Fluid

Power System.

Disadvantages:

Fluids are in closed container and undergo anexpansion due to hot temperature.

Incase of hydraulic leakage will results to corrosion to

metals and swelling to rubber for instance.

Hazards to humans body and organs if accidentallyinhale or in-touch with.

Required a special care and maintenance taken.


38/269

Hydraul ic f luids

Hydraulic Fluid Characteristic.

Viscosity.

Chemical Stability. Flash Point.

Fire Point.

Freezing Point.


39/269

Hydraul ic f luids

Hydraulic Fluid Characteristic.Viscosity.

Internal resistance of a fluid which tends to prevent its from

flowing.

Low viscosity will have high flow rate.

Excessive viscosity will add load and excessive wear of parts and

low viscosity is also contributing to rapid wear of parts which

subjected to heavy loads due to excessive friction. Therefore a

correct viscosity for particular hydraulic operation is required and

to be determined.

Viscosity is inversely proportional to temperature.

SayBolt Universal Viscosimeter is a standard instrument for

testing petroleum product and lubricant. Tests are usually made at

temperature of 100oC, 130oC and 210oC.


40/269

Hydraul ic f luids

Hydraulic Fluid Characteristic.Viscosity.

The time used for the test is seconds and time requiredfor exactly 60cc of the fluid to flow through and

accurately calibrated orifice is recorded as second,Saybolt universal.

Viscosity index is an arbitrary methods of stating therate of change in viscosity of a fluid will changetowards temperature.


41/269

Hydraul ic f luids


Chemical Stability.

The ability of a liquid to resist oxidation and

deterioration for long operating period. All liquids tend to undergo unfavorable chemical

changes under severe operating conditions and in this

case for example , when the system operates for a

considerably period of high temperatures.


42/269

Hydraul ic f luids


Flash point.

Temperature at which a liquid gives off vapor in

sufficient quantity to ignite momentarily (flash) when aflame is applied.

A high flash point is desirable for hydraulic fluids

because it indicates a good resistance to combustion

and a low degree of evaporation at normaltemperatures.


43/269

Hydraul ic f luids


Fire point.

Temperature at which a substance gives off vapor in

sufficient quantity to ignite and continue to burn whenexposed to a spark or flame.

As with flash point, a high fire point is desirable in

hydraulic fluids.

Freezing point. Temperature at which the liquid will solidify and

hardened because of a certain low temperature applied.


44/269

Hydraul ic f luids

Properties of an Ideal Hydraulic Fluid. Incompressible.

Low to medium viscosity.

Reasonable density variation with changes to

temperature. Low rate of change of viscosity with temperature

changes.

Wide working range of temperature (approximately -80oC to +70oC).

Good lubricating properties over the usual workingrange.

Low co-efficient of fluid expansion due to temperaturechanges.

Low freezing and high boiling point.


45/269

Hydraul ic f luids

Properties of an Ideal Hydraulic Fluid.

Non-flammable, which is high flash and fire point.

Non-corrosive and non-detrimental to seals.

Chemically stable with change in temperature andunder all operating condition.

Maximum resistant to oxidation (non sludging with

variation in temperature).

Should not be toxic if accidentally sprayed underpressure to operators.

Good storage life (either shelf or operation life).


46/269

Hydraul ic f luids

Types Of Hydraulic Fluids. VegetablesBase Fluid.

MineralBase Fluid.

SyntheticHydrocarbonBase Fluid. Phosphate EsterBase/ SyntheticBase Fluid.


47/269

Hydraul ic f luids

VegetablesBase Fluid. Known as MIL-H-7644 or DTD 900/4081.

Essentially made of castor oil and alcohol and used in

older aircraft. Although is similar to automotive brake fluid, it is not

interchangeable.

Dyed blue or golden yellow for identification.

Uses natural rubber seals.


48/269

Hydraul ic f luids

VegetablesBase Fluid. If any contamination occurs, the system of this type of

fluid is flushed with alcohol.

MIL-H-7644 is a flammable fluid its strips paint andattack synthetic rubber. It also toxic in a fine sprays

mist.

They are considered obsolete and are not generally

found in any hydraulic power system but may still befound in some older brake system.


49/269

Hydraul ic f luids

MineralBase Fluid.

Known as MIL-H-5606 or DTD 585.

Basically a kerosene-type petroleum product.

Dyed red color for identification. Used in many systems, especially where the fire hazard

is comparatively low.

It have good lubricating properties and additives to

inhibits foaming and at the same time prevent theformation of corrosion.

Mineral base fluid has the advantages of increased fire

resistance compared to vegetables hydraulic fluid.


50/269

Hydraul ic f luids

MineralBase Fluid. If contamination occurs, the system using this type of

hydraulic fluid can be flushed with naphtha, varsol or

Stoddard solvent. Neoprene seals and hoses may be used with MIL-H-

5606 or synthetic rubber, leather or metal composition

seals and hoses is also an option.

MIL-H-5606 is a flammable type of hydraulic fluid.


51/269

Hydraul ic f luids

SyntheticHydrocarbonBase Fluid. Known as MIL-H-83282 or MIL-H-81019.

As a replacement for the familiar red oil or known asMIL-H-5606.

Dyed red for identification but has synthetichydrocarbon base rather than kerosene type petroleum

base.

Compatible will all material used with MIL-H-5606

hydraulic fluid. A main advantage of MIL-H-83282 is that it is fire

resistant.

MIL-H-81019 is used in extremely low temperatureand operational at a temperature as low as -90oF.


52/269

Hydraul ic f luids

Phosphate EsterBase/ SyntheticBase Fluid.

Known as MIL-H-8446 or Skydrol.

Mostly utilized in transport category aircraft and very

fire resistant (although it is fire resistant, it is not fire

proof) such as high performance piston engine and

turbine powered aircraft.

Under certain condition, Skydrol will burns (at very

high temperature).

Dyed light purple for identification and slightly heavier

than water.


53/269

Hydraul ic f luids

Phosphate EsterBase/ SyntheticBase Fluid. Seals and hoses used with this type of fluids are made

from Butyl, synthetic rubber, ethylene propylene orTeflon or fluorocarbon resin.

It is very susceptible to contamination (water) becauseit absorbs moisture from atmosphere and must be keptin tight seal containers.

If contaminated, the system should be flushed withtrichloroethylene.

MIL-H-8446 can sustain operation at wide range ofoperating temperature, from approximately -65oF tomore than 225oF.

The continual development of more advanced aircrafthas resulted in modification to the formulation of

phosphate ester-base fluids.


54/269

Hydraul ic f luids

Phosphate EsterBase/ SyntheticBase

Fluid.

The continual modification of the fluid specification

has resulted in the utilization of Type I, II, III and nowType IV fluids.

Currently there are 3 grades of Skydrol in use, which is

Skydrol 500B4, Skydrol LD-4 and Skydrol 5.

Typical examples of current Type IV fluids are SkydrolLD-4 and Skydrol 500B4.

Two distinct classes of Type IV hydraulic fluid exist

and the class definition is according to the airframe

manufacturer hydraulic specification.


55/269

Hydraul ic f luids

Phosphate EsterBase/ SyntheticBase

Fluid.

The classes are, Class 1 which is low density and offers

some advantage in jumbo jet transport aircraft whereweight is a prime factors (Skydrol LD-4) and Class 2 is

high density and possess handling characteristic that

are beneficial in some hydraulic system (Skydrol

500B4).

Skydrol 5 is more compatible with painted surfaces

than the other types of Skydrol.

MIL-H-8446 or Skydrol is non-flammable.


56/269

Hydraul ic f luids

Effects of Fluid Friction. Types of fluids flow:

Laminar flow (the flow is smooth and straight inline).

Turbulence flow.

When there is a resistant of fluid friction, there isalways lost of power and energy (reduction in pressurethrough out of pipeline).

As velocity of fluid increase the resistance to flowincrease and temperature increases.

Any restriction in a pipeline will increase liquidvelocity and produce turbulence in which resulting inreduce pressure downstream of restriction.


57/269

Hydraul ic f luids

Effects of Fluid Friction.

Friction between the fluid and wall of the pipelines

depends on:

Velocity of the fluid in the pipelines. The bore, length and internal finish of the pipelines.

The number of vent in the pipeline and the radius

of the bent.

The viscosity of the fluid (friction increase willfollowed by increase in viscosity).


58/269

Hydraul ic f luids

Compatibility of Hydraulic Fluids. Due to the difference in composition, hydraulic fluid

must not be mixed.

The seals used with any particular fluid are not useable

with or, tolerant of any other difference types of

hydraulic fluid.

Should an aircraft hydraulic system is accidentally

service with other than the specific fluid, the system must

be immediately drained and flush with an appropriateflushing solvent.

Aircraft manufacturer will give instruction regarding the

action to be taken with regard to the seals in the system.


59/269

Hydraul ic f luids

Compatibility of Hydraulic Fluids.

For example:

Skydrol does not appreciably affect common aircraft metal

such as aluminum, silver, zinc, magnesium, cadmium,

iron, stainless steel, bronze, chromium and others inconjunction that the fluid is kept free from contamination.

Thermoplastic resin (commonly used as tubing insulator

for electrical and fluid lines) may be softened chemically

by Skydrol.

Skydrol 5 has less effect on painted surface than the other

types of Skydrol.

Skydrol will attack polyvinyl chloride and must not be

allowed to drip on the electrical wiring as it will break

down the insulation.


60/269


61/269

Hydraul ic f luids

Hydraulic Fluid Contamination. Contamination of aircraft hydraulic system can

seriously affect the operation of the aircraft operation.

There are 2 principle/types of contamination thataffects the aircraft hydraulic system:

Particulate Contamination.

Soluble or Liquid Contamination.


62/269

Hydraul ic f luids

Hydraulic Fluid Contamination. Particulate Contamination.

Identification of where small pieces of solid matter

are present in the system.

Resulting from the introduction of particles from

external sources or particles produced within the

system itself.

Filters in the system generally remove particlesfrom the system.

Contamination of a system occurs when, filters

element becomes blocked or filter element ruptures.


63/269

Hydraul ic f luids


Particulate contamination can be minimized by:

Blanks all lines and parts when components are

removed and lines disconnected.

Use clean containers for storing componentsremoved from aircraft.

Ensure hydraulic fluid is free from contamination

when used as a lubricant for o rings duringassembly of components.

Service hydraulic system reservoir from containersthat is clean and free from contamination.


64/269

Hydraul ic f luids


Particulate contamination usually consists mainly

of metal and seal particles.

The common sources of particles usually from

internal damage of hydraulic pumps.

Pump pressure filter and case drain return filter

normally trapped these particles, whenever a pump

is replaced because of damage or suspected

damage, these filters should be replaced.


65/269

Hydraul ic f luids

Hydraulic Fluid Contamination. Soluble or Liquid Contamination.

The effects of chemical or solvent action that

affects the system.

Can be in form of deposit and cause erosion of

valves and internal corrosion components.

Chlorinated compound causes hydraulic system

valve to erosion and causes internal leakage,

overheating and followed by low hydraulic

pressure.


66/269

Hydraul ic f luids

Hydraulic Fluid Contamination.

Soluble or Liquid Contamination.

Soluble or Liquid contamination can be minimized

by:

Avoid using chlorinated solvents when cleaning

hydraulic system components.

Ensure that components being removed from aircraft,

repaired and replaced are handled and stored in

accordance with the highest standards of cleanliness. Always service hydraulic system with the correct

fluid.

Do not allow the hydraulic system to be overheated.


67/269

Hydraul ic f luids


Introduction of engine oil or DTD 585/MIL-H-5606 that uses ester based fluid causes seals to

swell and possibility form a gelatinous material andreduce the fire resistance of the fluid.

Contamination of ester based fluid with free(undissolved) water can results in formation ofcorrosion on steel parts of components.

Hydraulic system overheating accelerates with thedecomposition of ester based fluids forming acidscauses etching of metal in system components.


68/269

Hydraul ic f luids


Overheating of hydraulic system can be caused byexcessive internal leakage in components and

partially blocked pump case drain return filters. Skydrol will turns to dark brown color when

overheated and considered not serviceable andmust be drained and flushed.

Hydraulic system and test rigs should be check fortotal acidity and water contents to ensure it is stillin appropriate aircraft manufacturer recommendedlimits.


69/269

Hydraul ic f luids

Handling Hydraulic Fluids. Skydrol fluid does not present any particular health

hazard when used as recommended.

Skydrol has a very low order of toxicity when taken

orally or applied to the skin in liquid form. It causes pain on contact with eye tissue and other

areas of sensitive skin, but animal studies and humanexperience indicate that it causes no permanentdamage.

First aid treatment for eye contact includes flushing theeyes immediately with large volume of water and theapplication of anesthetic eye solution. If pain persists,the individual should see a physician as soon as

possible.


70/269

Hydraul ic f luids

Handling Hydraulic Fluids. If mist or fog form, Skydrol is quite irritating to nasal

or respiratory passages and generally produces

coughing and sneezing.

Such irritation does not persist after exposure is

terminated. Silicone ointment, rubber gloves and

careful washing procedures should be utilized to avoid

excessive repeated contact with Skydrol in order to

avoid solvent effect with skin.


71/269

Hydraul ic f luids

Handling Hydraulic Fluids. In addition to any other instruction given in the airplane

manufacturer manuals, the following precaution should be

observed in the use of hydraulic fluids:

Mark each aircraft hydraulic system to show the type offluid to be used in the system (especially on filler cap or

filler valves).

Never service an aircraft hydraulic system with type of

fluid different from that shown on the instruction plate.

Make certain that hydraulic fluids and fluid containers

are protected from any kind of dirt.

Never allowed hydraulic fluid of different types to

become mixed.


72/269

Hydraul ic f luids

Handling Hydraulic Fluids (cont). Do not expose fluids to high heat or open flames.

Vegetables base and mineral base fluids are highly

flammable.

Avoid contact with the fluids.

Wear protective gloves and a face shield whenever

handling phosphate ester based fluid or working

around hydraulic lines that are under pressure.


73/269

END OF STAGE 1.


74/269

System components

HYDRAULIC RESERVOIR.

A tank or container designed to stored sufficient

hydraulic fluids for all hydraulic system normaloperation, emergency operation or the system is not

in operation. Usually equipped with a standpipe that

drawn fluid in normal operation and drawn fluid for

emergency from the bottom of the tank.


75/269

System components

HYDRAULIC RESERVOIR.

Integral type.

In-line type.


76/269

System components

Integral type reservoir.

Type of reservoir that has no housing.

Usually found in small aircraft that fly at lower

altitudes (below 1500 ft) and usually not a

pressurized type.

Example of an integral type reservoir is the Brake

Master Cylinder.

A reservoir that combined with a pump.

The upper portion of the Brake Master Cylinder

serves as the reservoir and the lower portion serve

as the pump basically to operate the brake.


77/269

System components

Fig 13-12: Integral type reservoir.


78/269

System components

In-line type reservoir.

Type of reservoir that have its own housing.

Connects to others hydraulic components bymeans of tubing or hydraulic lines.

The most common type of reservoir and

most can be found as pressurized and non-

pressurized. Used on aircraft that demands high hydraulic

fluid requirement.


79/269

System components

Fig 13-11: In-line type reservoir.


80/269

System components

HYDRAULIC RESERVOIR. Pressurizing the reservoir.

1) The most basic rule of hydraulics states that fluid

cannot be pulled, it only can be pushed. At sealevel (14.7psi) of atmosphere provides the force to

push the fluid from the reservoir to the pump.

2) As altitude increase, atmospheric pressure

decreases and with little or no pressure on thefluid, it tends to foam and causing air bubbles to

form in the low part of the system.


81/269

System components

HYDRAULIC RESERVOIR. Pressurizing the reservoir (cont).

3) When aircraft operating at high altitude, the pump

will be starved for fluid unless some means ofpressurizing is used. Therefore, to provide acontinuous supply of fluid to the pumps, thereservoir is pressurized.

4) Methods of pressurizing the reservoir:

Turbine engine bleed air.

Venturi type aspirator or venturi tee .

springs attached to the reservoir piston.

electric pump


82/269

System components


Turbine engine bleed air.

i. Can be used to pressurize the reservoir.

ii. It will be fed to the pressure regulator to

establish the proper pressure into the top of

the reservoir.

iii. Usually used to maintain a pressure of

between 40 -45lbs/sq.in


83/269

System components

FIG XX: Turbine engine bleed air methods.


84/269

System components


Venturi type aspirator or venturi tee .

i. The low pressure section of the venturi draws

air into the reservoir and increases thepressure.

ii. The use of air pressure acting directly on thefluid eliminates the need for any elaboratechambering of the reservoir.

iii. The reservoir is simple pressurized, with theair settling out to the top of the airtightreservoir.

iv. Usually used to maintain a pressure of

between 30 - 35lbs/sq.in.


85/269

System components

FIG 5-22: Venturi type aspirator or venturi tee methods .


86/269

System components


Springs attached to the reservoir piston.

i. The spring force on the piston causes the

piston try to move downward, which

pressurized the reservoir.

ii. A system operating 3000lbs/sq.in canpressurize the fluid in the reservoir

approximately 60 lbs/sq.in.


87/269

System components

FIG 13-9: Springs attached to the reservoir piston methods.


88/269

System components


Electric pump.

i. Another method of pressurizing the

reservoir.

ii. Before the engine starts the inlets lines of

engines driven pumps are under positivepressure, which provides a positive supply of

fluid to the pump and reduces pump wear


89/269

System components

FIG 5-23: Electric pump methods.


90/269

System components


5) Providing sufficient fluid to make up for normal

losses of fluid seepage past seals.6) Are not designed to be completely filled, they

must allow for an air space above the fluid level toallow for expansion of fluid being heated duringoperation.

7) Means of checking the fluid level and beingreplenished, quantity indicating methods may bein a form ofdipstick on the filler cap or mayconsists of remote indicating system that displaythe quantity of fluid in flight deck/cockpit.


91/269

System components


8) A sight gauge or sight glass may be attached

to the reservoir to provide and indication of

accumulation of air in the reservoir.

9) Replenishment of fluid may be accomplished by

adding fluid directly to the reservoir through a

filler opening.

S


92/269

System components

HYDRAULIC PUMPS.

A mechanical devices or components that

designed to provide or supply hydraulic fluid tothe actuators drawn through the lines. It does

not create the pressure but the pressure is

produced when the flow of hydraulic fluid is

restricted. Operation principle either by manualsor mechanical power (electric motor or aircraft

engine).

S


93/269

System components

HYDRAULIC PUMPS.

Hand pumps.

I. Single action hand pump.II. Double action hand pump.

Powered pumps.I. Constant Displacement pumps.

II. Variable Displacement pumps.

S t t


94/269

System components

HYDRAULIC PUMPS. Hand pumps.

I. Single action hand pump.

Move fluid only on one stroke of the piston only.

When the handle is move/stroke to one direction,the piston inside the pump will make a movementcreates a low pressure condition and draws fluidfrom the reservoir through a check valve into thecylinder.

When the handle is move/stroke towards the otherway, the piston forces the fluid to drawn outthrough the discharge check valve and produce amovement (at the actuators).

S t t


95/269

System components

FIG 13-17 :Single acting hand pump.

S t t


96/269

System components

HYDRAULIC PUMPS. Hand pumps.

II. Double action hand pump.

Most commonly used in aircraft hydraulic systemsbecause of their greater efficiency.

Also called piston rod displacement pump,

because its pumping action is caused by the

difference in area between the two sides of the

piston in which one side of the piston has lesssurface area because of the piston rod.

Move fluid in every single stroke made.

S t t


97/269

System components

FIG 5-24 :Double acting hand pump.

S t t


98/269

System components

HYDRAULIC PUMPS.

Powered pumps.

I. Constant Displacement pumps.

1) Vane type.

Classed as a positive-displacement pump

because of its positive in moving fluid.

Move a large volume of fluid (about 300 psi) but

does not produce a very high pressure. Consists of slotted rotor located off-center within

the cylinder of the pump body with rectangular

vanes that are free to move radially in each slot.

S t t


99/269

System components

HYDRAULIC PUMPS. Powered pumps.


1) Vane type (cont). As the rotor turns, the vanes are caused to move

outward by centrifugal force and contact the smoothinner surface of the casing.

Since the rotor is eccentric with respect to the casing,

the vanes form chambers that increase and decreasein volume as the rotor turns.

The inlet side of the pump is integral with the side ofthe casing in which the chambers are increasing involume. Thus the fluid is forced to enter the chambersbecause of the low pressure created by the expanding

chambers.

S t t


100/269

System components

HYDRAULIC PUMPS.

Powered pumps.


1) Vane type (cont).

The fluid is carried around the casing to the point

where the chambers begin to contract and this

section of the casing is connected to the output

port of the pump. The contraction of the chambers forces the fluid

into the outlet port and system.

S t t


101/269

System components

FIG 5-24 :Vane type pump.

S stem components


102/269

System components

HYDRAULIC PUMPS.

Powered pumps.


2) Gear type.

Classed as a positive-displacement pump

because each revolution of the pump will deliver a

given volume of fluid (provided that the pump is

not worn or no leakage). Moves a medium volume of fluid under a pressure

of between 300 psi and 1500 psi.

Example of a gear type pump in aircraft is spur-

gear type.

System components


103/269

System components



2) Gear type (cont). Consists of two gears that are driven by the power

source, which could be an engine driven or anelectric motor drive.

One gear is meshed with and driven by the other

gear and rotates together. As the gear rotates together, the fluid enters the

IN port to the gears, where it trapped between thegear teeth and carried around the pump case tothe OUT port.

System components


104/269

System components

HYDRAULIC PUMPS.

Powered pumps.


2) Gear type (cont).

The fluid cannot flow between the gears because

of their closely meshed design, therefore it is

forced out through the OUT port.

System components


105/269

System components

FIG 5-24 :Gear type pump.

System components


106/269

System components

HYDRAULIC PUMPS.

Powered pumps.


3) Gerotor type.

A combination of internal and external gear pump.

Consists of a housing containing an eccentric-shaped

stationary linear.

Containing an internal gear rotor having 5 wide teeth ofshort height and having 4 spur driving gear with narrow

teeth.

The 4 tooth-spur gear is driven by an engine accessory

drive and as turns, it rotates the 5 internal gear rotors.

System components


107/269

System components



3) Gerotor type (cont). As the gear and the rotor turns, the space between the

teeth gets larger on one side and smaller on the other.

A plate with two crescent-shaped openings covers the

gear and the rotor and forms the inlet and outlet ports

of the pump. The opening located above the space that gets larger

as the gear and the rotor turn is the inlet side of the

pump and the opening above the space that gets

smaller as the teeth come into mesh is the outlet of the

pump.

System components


108/269

System components

FIG 13-21 :Gerotor type pump.

System components


109/269

System components

HYDRAULIC PUMPS.

Powered pumps.


4) Piston type.

Most widely used on modern aircraft.

Uses on hydraulic system that requires a relatively

small volume of fluid under pressure of 2500 psi or

more often use fixed-angle, multiple-piston pumps. Consists of seven or nine axially-drilled holes in the

rotating cylinder block of the pump.

Each hole contains a close fitting piston attached to a

drive plate by a ball jointed rod.

System components


110/269

System components



4) Piston type (cont). The cylinder block and the piston are rotated as a unit

by a shaft that is driven from an engine accessorydrive.

The housing is angled so that the piston on one side of

the cylinder block is at the bottom of their stroke whilethe piston on the other side of the block is at the top ofthe stroke.

As the pump rotates of a turn, half of the pistonsmove from the top of their stroke to the bottom and thepiston on the other side of the block move from the

bottom of their stroke to the top.

System components


111/269

System components



4) Piston type (cont). A valve plate that has two crescent-shaped

openings covers the ends of the cylinder. Thepump outlet port is above the pistons that aremoving up and the inlet port is above the pistons

that are moving down. As the piston move down in the cylinder block,

they pull fluid into the pump and as they move up,they force the fluid out of the pump into thesystem.

System components


112/269

System components

FIG 5-28 :Piston type pump.

System components


113/269

System components

FIG 13-23 :Piston type pump.


114/269

END OF STAGE 2.

System components


115/269

System components

HYDRAULIC PUMPS.

Powered pumps.


1) Stratopower Demand/Axial piston type.

A pump that does not move a constant amount of fluid

each revolution but only the amount of the system will

accept.

By varying the pump out put, the system pressure canbe maintained within the desired range without the use

of regulators and relief valve.

Variable-displacement pump can turn without any fluid

being forced into the system.

System components


116/269

System components



1) Stratopower Demand/Axial piston type (cont). To prevent overheating, these pumps are usually

bypassing some fluid back to the reservoir so there willalways be some flow of fluid to cool the pump.

An unloading valve of some sort is needed whenconstant-displacement pumps is being used but thesame force used to control this valve may be used tocontrol the output of a variable-displacement pumpwithout no need for separate control valve.

One of the more popular types of variable-displacement pump used for high pressure aircraft is

the Stratopower demand type pump.

System components


117/269

System components

HYDRAULIC PUMPS.

Powered pumps.


1) Stratopower Demand/Axial piston type (cont).

This type of pump is consists of 9 axially orientated

cylinder and piston.

The piston is driven up and down inside the cylinder by

a wedge-shaped drive cam and the piston pressagainst the cam with ball joint slippers.

The physical stroke of the piston is the same

regardless of the amount of fluid demanded by the

system but the effective length of the stroke controls

the amount of fluid moved by the pump.

System components


118/269

System components

FIG 5-29 :Stratopower Demand type pump.

System components


119/269

System components

FIG 5-29 :Stratopower Demand type pump.

System components


120/269

System components

HYDRAULIC FLOW CONTROL

VALVES/AUTOMATIC CONTROL VALVES.

Fluid must be made to flow accordingly to a definiteplan and must be rigidly controlled. Acts like switch

in an electrical system. Some allow fluid to or

prevent it from flowing. Others direct flow from one

device to another and still others regulate the rate offlow.

System components


121/269

System components


VALVES/AUTOMATIC CONTROL VALVES. Selector Valves.

Check Valves.

Orifice Check Valve.

Metering Check Valve.

Orifice or Restrictor Valve.

Sequence Valve.

Shuttle Valve.

Priority Valve.

System components


122/269

System components


VALVES/AUTOMATIC CONTROL VALVES. Flow Equalizer.

Quick Disconnect Valve.

Hydraulic Fuse.

System components


123/269

System components


VALVES/AUTOMATIC CONTROL VALVES. Selector Valves.

Rotary type.

Poppet type, Closed Center.

Poppet type, Open Center.

Spool or Piston type.

System components


124/269

System components

HYDRAULIC FLOW CONTROLVALVES/AUTOMATIC CONTROL VALVES.

Check Valves.

Allowing fluid to flow in one direction but prevents itsfrom flowing in the opposite direction.

Made in two general design to serves two differentneeds:

In-Line Interconnected with other components bymeans of tubing or hose. This type of check valvecompletes itself or has its own housing.

Integral Check valve is not complete itselfbecause it does not have its own housing. This typeof valve is actually an integral part of some majorcomponents and shares the housing of thatcomponents.

System components


125/269

System components


Check Valves.

Types of check valves are: Ball type.

Cone type.

Swing type.

System components


126/269

System components

FIG 13-51:Ball type check valves.

System components


127/269

System components

FIG 13-51:Cone type check valves.

System components


128/269

System components

FIG 13-51:Flap type check valves.

System components


129/269

System components


Orifice Check Valves.

Some application require full flow of fluid in one

direction but rather than blocking or preventing the

fluid flowing in the opposite direction, these allow fluid

to flow through the valve at restricted rate and orifice

(allows full flow in one direction and restrict the flow in

the other direction) check valve is used. Usually used in LANDING GEAR SYSTEM to slow

down the extension of the gear and yet allow it to

retract as quickly as possible.

System components


130/269

Syste co po e ts


Orifice Check Valves (cont).

When the selector valve is placed in GEAR-DOWN

position, the up locks release the landing gear and it

falls out of the wheel well.

The weight of the gear and the force of air blowing

against the wheel as it drop down try to speed up the

extension.

System components


131/269

y p


Orifice Check Valves (cont).

The orifice check valve restricts the flow of the fluid

coming out of the actuator and prevents the landing

gear from dropping too quickly.

When the selector valve is placed in the GEAR-UP

position, the fluid flows into the actuator GEAR-UP line

through the orifice check valve in its restricteddirection and full flow raises the Landing Gear.

System components


132/269

y p

FIG 13-51:Orifice type check valves.

System components


133/269

y p


Metering Check Valves.

Sometimes called a one way restrictor.

Serves the same purpose as orifice check valve,

however the metering check valve is adjustable

whereas orifice check valve is not.

Consists of housing, a metering pin and check valve

assembly. The pin is adjusted to hold the ball slightly off its seat.

System components


134/269

y p


Metering Check Valves (cont).

By adjusting the metering on top of the housing in and

out with a screwdriver, the rate of which the fluid can

return from the actuating cylinder is controlled.

This happens because the position of the metering pin

changes the width of the opening between the ball and

its seat.

System components


135/269

y p

FIG 13-53:Metering check type check valves.

System components


136/269

y p


VALVES/AUTOMATIC CONTROL VALVES. Orifice/Restrictor Valves.

Orifice is merely an opening, passage or hole. Arestrictor can be described as an orifice or similar to

an orifice.

A variable restrictor is an orifice that can be changed

in size so it s effect can be altered. The size of a fixed orifice must remain constant,

whereas a variable restrictor permits adjustment to

meet changing requirement.

System components


137/269

y p


VALVES/AUTOMATIC CONTROL VALVES. Orifice/Restrictor Valves (cont).

The purpose of an orifice or a variable restrictor is tolimit the rate of flow.

The orifice causes the mechanism being operated by

the system to move more slowly.

An orifice of this construction may be placed in ahydraulic line between a selector valve and an

actuating cylinder to slow the rate of the movement of

the actuating cylinder.

System components


138/269

y p


VALVES/AUTOMATIC CONTROL VALVES. Orifice/Restrictor Valves (cont).

A variable restrictor meanwhile horizontal port and avertical, adjustable needle valve.

The size of the passage through which the hydraulic

fluid must flow may be adjusted by screwing the

needle valve in or out. The fact that the passage can be varied in size is the

featured that distinguished the variable restrictor from

the simple fixed orifice.

System components


139/269

y p

FIG 13-49:Orifice / restrictor type valves.

System components


140/269

y p


VALVES/AUTOMATIC CONTROL VALVES. Sequence Valves.

Sometimes called timing valve because it timescertain hydraulic operation in proper sequence.

A common example of the use of this valve is in a

landing gear system.

The landing gear door must be opened before thegear is extended and the gear must be retracted

before the doors are closed.

System components


141/269

y p

FIG 13-55:Sequence type valves.

System components


142/269


VALVES/AUTOMATIC CONTROL VALVES. Shuttle Valves.

Quite frequently that a hydraulic system it is necessaryto provide alternative or emergency sources of power

with which to operate critical parts of the system.

This is particularly true of landing gear in the case of

hydraulic pump failure. In this case of hydraulic failure, the landing gear

system is operated by an emergency hand pump and

sometimes by a volume of compressed air or gas

stored in high pressure air bottle.

System components


143/269


VALVES/AUTOMATIC CONTROL VALVES. Shuttle Valves (cont).

In either of the case, it is necessary to have a meansof disconnecting the emergency source of power andthe shuttle valve achieved it.

During normal operation, free flow is provided from thenormal system to the service and the emergency line

is blocked. When normal system pressure is lost and the

emergency is selected, the shuttle valve moves acrossbecause of the pressure difference, blocking thenormal line and allowing emergency pressure to theactuator.

System components


144/269

y

FIG 13-58:Shuttle type valves.

System components


145/269

FIG 13-59:Shuttle valves arrangement in system.

System components


146/269


VALVES/AUTOMATIC CONTROL VALVES. Priority Valves.

A valve that is similar to sequences valve that isoperated by hydraulic pressure rather than by a

mechanical means.

The valve is used to allow one actuator to operate and

complete its operation before allowing a secondcomponent to operate.

This action gives the first components a priority over

the second and resulting in the name priority valve.

System components


147/269


VALVES/AUTOMATIC CONTROL VALVES. Priority Valves (cont).

A priority valve is used for sequencing, but thesevalves are also used to give one component priority

over another component in unrelated operation.

For example, in some aircraft, a priority valve is used

to give the flight control actuators priority to the systempressure over the landing gear and flap systems.


148/269

System components


149/269

y p

FIG 13-61:Priority valves arrangement in system.


150/269


151/269


152/269


153/269

System components


154/269


Quick Disconnect Valves (cont).

A power pump can be disconnected from the

system and a hydraulic test stand connected its

place.

These valve units consists of two interconnecting

section coupled by a nut when installed in the

system. Each valve section has a piston and poppet

assembly and these are spring loaded to the

CLOSED position when the unit is disconnected.

System components


155/269

FIG 5-88:Quick Disconnect Valve

System components


156/269

HYDRAULIC FLOW CONTROL VALVES/AUTOMATICCONTROL VALVES.

Hydraulic Fuses.

Is a device designed to seal off a broken hydraulic lineand prevent excessive loss of fluid.

It permits normal flow in line but if the flow increasesabove an establish level.

The valve in the fuse closes in line and prevents furtherflow.

There are 2 types of hydraulic fuses.

One shuts off the flow after a specific amount of fluidhas flowed through it (volume).

The other one shut off the flow if the pressure dropacross the fuse indicates a broken line (pressure).

Fluid flowing in the reverse direction is not restrictedby hydraulic fuses.


157/269


158/269

END OF STAGE 3


159/269

END OF STAGE 3.

System components


160/269

HYDRAULIC PRESSURE CONTROLVALVES.

Pressure Switch.

Automatic Pressure Regulator/UnloadingValve.

Relief Valve.

Thermal Relief Valve. Pressure Reducer.


161/269

System components


162/269

FIG 13 29:Bourdon type pressure switch

System components


163/269

HYDRAULIC PRESSURE CONTROL VALVES. Automatic Pressure Regulator/Unloading Valve.

1) Designed to maintain a certain range of pressure within thehydraulic pressure.

2) Closed center hydraulic system requires an automaticregulator to maintain the pressure within a specified range and

to keep the pump unloaded when no unit in the system isactuated.

3) Usually the pressure regulator is designed to relieve thepressure on the pressure pump when it is not needed foroperating a unit in the system.

4) Some pressure regulators are also called unloading valves,

because they unload the pump when hydraulic pressure is notrequired for operation of landing gear, flaps or other sub-system.

5) Continuous pressure on the pump increases wear and thepossibility of failure.

6) There are 2 types of unloading valves which is the spool type

and the balanced type


164/269


165/269

System components


166/269

HYDRAULIC PRESSURE CONTROL VALVES. Relief Valve (cont).5) As the pressure in the line increases to a level

above that for which the valve spring is adjusted,the valve lifts off it seats and the fluid then flows

through the valve and out the return line.6) The pressure at which the relief valve lifts is called

crack ing pressure.

7) When several relief valves are incorporated in ahydraulic system, they should be adjusted in a

sequence that will permit each valve to reach itsoperating pressure.

8) Therefore, the highest pressure valves should beadjusted first then the other are adjusted in theorder of descending pressure values.

System components


167/269

Fig 5 48: Relief valve

System components


168/269

Fig 13 35: Relief valve construction

System components


169/269

HYDRAULIC PRESSURE CONTROL VALVES. Thermal Relief Valve.1) Quite similar to the regular system relief valve, however such

valves are installed in parts of the hydraulic system wherefluid pressure is trapped and may need to be relieved becauseof the increase caused by higher temperatures.

2) During the flight of an airplane, it is quite likely that fluid in

many of the hydraulic lines will be at low temperature.3) When the aircraft lands, this cold fluid will be trapped in the

landing gear system, the flap system and most probably theother associates system because selector valves are in theneutral or OFF position.

4) The fluid temperature increases due to warm air on the groundresults in fluid expansion and could cause damage unless

thermal relief valves are incorporated in the system.5) Thermal relief valves are adjusted to pressures that are above

those required for the operation of the system and thereforethey do not interfere with normal operation.


170/269

System components


171/269

HYDRAULIC PRESSURE CONTROL VALVES. Pressure Reducer (cont).6) When the actuator is in operation under reduced

pressure, the valve will vary its opening to meter thefluid at the speed required to maintain the desiredpressure.

7) Another type of pressure reducing valve is the de-boostervalve used in an aircraft brake system to reducesystem pressure.

8) In addition to reducing pressure it will provide for highervolume of fluid flow to the brakes for rapid application ofbraking forces.

9) A de-booster valve operates by the differential area oftwo pistons.

10) If a small area piston is connected by a rod to large areapiston, the two pistons will be capable of developingpressure in inverse proportion of their areas.


172/269

System components


173/269

Fig 13 37: Pressure reducing valve

System components


174/269

Fig 13 36 : Reducing valve arrangement

System components


175/269

HYDRAULIC ACTUATORS. Linear Actuators.

1) The ultimate function of a hydraulic or pneumaticis to convert the pressure in the fluid into work.

2) Linear actuators are made up of a cylinder and apiston.

3) The cylinder is usually attached to the aircraftstructure and the piston is connected to thecomponent that is being moved.

4) If two linear actuating cylinders with piston havingthe same cross sectional area but different lengthsof stroke are connected to the same source ofhydraulic pressure, they will exert equal amount offorce and move at the same rate of speed.

System components


176/269

HYDRAULIC ACTUATORS. Linear Actuators (cont).

5) But it will take them a different length of time to

reach the end of their stroke.

6) If the cylinders have different areas, but areconnected to the same source of pressure, they

will produce different amount of force.

7) The rate of movement of the piston in a linear

actuator can be controlled by restricting the fluidflowing into or out of the cylinder.

System components


177/269

HYDRAULIC ACTUATORS. Linear Actuators (cont).

8) There are 3 types of linear actuator, which is:

i. Single Acting.

Has a piston that is moved in one direction by hydraulic fluidand is returned by a spring force.

A single acting actuator is normally used as a locking device,

the lock being engaged by spring pressure and released by

hydraulic pressure.

The wheel cylinder in a shoe type brakes are good examples ofa single acting cylinder.

Hydraulic pressure moves the pistons out to apply the brakes,

but when the pedal is released, springs pull the shoes away

from the drum and move the piston back into the cylinder.

System components


178/269

HYDRAULIC ACTUATORS.


179/269

System components


180/269



181/269

System components


182/269


System components


183/269

HYDRAULIC ACTUATORS. Rotary Actuators.

i. Another type of actuator is rotary actuator.

ii. Perhaps the simplest type of the kind is rack and pinion

type.iii. Widely used to retract the main landing gear in the

popular high-performances single engine Cessna

aircraft.

iv. It consists of a rack of teeth cuts in its shaft and these

teeth mesh with those in pinion gear that rotates as thepiston moves in or out.

v. The rotation of the pinion shaft raises or lowers the

landing gear.

System components


184/269

HYDRAULIC ACTUATORS. Rotary Actuators (cont).

vii.A continuous rotational force can be obtained by

means of hydraulic motor with this type of

actuators.viii.Piston type hydraulic motor or vane type hydraulic

motor is an option and gives an advantages such

as:

Able to operate through a wide range of speeds(0rpm maximum) for the particular motor.

Variable speed electric motors can provide

some flexibility in the rate of actuation, however

they lose efficiency as speed increases.

System components


185/269


System components


186/269

HYDRAULIC ACTUATORS. Servo Actuators.

i. Is designed to provide hydraulic power to aid the pilot in

the movement of various flight controls.

ii. Such actuators usually incorporate and actuatingcylinder, a multiport flow control valve, check valve and

relief valve together with linkages.


187/269

System components


188/269

HYDRAULIC ACCUMULATOR.1) Is basically a chamber for storing hydraulic fluid under

pressure.

2) All accumulators consist of a high strength container divided

by some form of movable partition into two section or

compartments.

3) One compartment is connected to the hydraulic pressure

manifold and the other compartments are filled with either

compressed air or nitrogen.


189/269

System components


190/269

HYDRAULIC ACCUMULATOR (Cont).5) There are 3 types of accumulators and which is:

I. Diaphragm Type.

i. Consists of 2 steel hemisphere fastened together.

ii. Being separated by synthetic rubber (neoprene)diaphragm between two halves.

iii. The sphere is constructed in two parts, which are

joined by means of screw threads.

iv. A screen is placed at the fluid outlet inside the

sphere to prevent the diaphragm from beingpressed into the fluid outlet.

System components


191/269


I. Diaphragm Type (cont).

v. When the hydraulic pump is not operating, the

compressed gas forces the diaphragm over until

the air chamber fills the entire sphere.

vi. As hydraulic fluid is pumped into the accumulator,

the diaphragm is moved down, further compressing

the gas and storing the hydraulic fluid under

pressure.

System components

HYDRAULIC ACCUMULATOR


192/269

HYDRAULIC ACCUMULATOR.

System components


193/269


II. Bladder Type.

i. Consists of metal sphere.

ii. A bladder that is installed to separate the air andthe hydraulic fluid and being made out of heavy

neoprene bladder or bag.

iii. The bladder serves as the air chamber and the

space outside the bladder contains the hydraulic

fluid.iv. The bladder is filled with compressed air or

nitrogen and the hydraulic fluid is pumped into the

sphere on the outside of the bladder.


194/269

System components



195/269


System components


196/269


III. Piston Type.

i. Consists of steel or aluminum cylinder divided into

2 compartments by a free floating piston.

ii. Compressed air or nitrogen is put into one end of

the cylinder and the hydraulic fluid is put into the

other end.

iii. As more fluid is forced into the accumulator, the

piston is moved over and further compressing thegas and storing the hydraulic fluid under pressure.

System components



197/269


System components


198/269

HYDRAULIC ACCUMULATOR (Cont).6) Accumulators are charged with compressed air or nitrogen to

a pressure of approximately of 1/3 of the hydraulic system

pressure.

7) As the pump forces hydraulic fluid into the accumulator, the

gas is further compressed and it exerts a force on thehydraulic fluid, holding it under pressure after the system

pressure regulator has unloaded the pump.

END OF STAGE 4.


199/269

END OF STAGE 4.


200/269


201/269

System components

HYDRAULIC ACCUMULATOR AIR VALVES


202/269

HYDRAULIC ACCUMULATOR AIR VALVES.

System components


203/269

HYDRAULIC ACCUMULATOR AIR VALVES(cont).1) There are three types of air valves that may be used in

accumulator application.

ii. AN 6287-1.

Seals the air inside the accumulator by means of steel againststeel seal.

Have a valve core similar to AN 812 but have a swivel nut

around the stem.

The swivel nut is smaller compared to the body nut.

To charge the accumulator with this type of air valve, removethe protective cap and attach the charging pressure hose to

the valve and loosen the swivel nut for about one turn.

System components


204/269

HYDRAULIC ACCUMULATOR AIR VALVES(cont).1) There are three types of air valves that may be used in

accumulator application.

ii. AN 6287-1 (cont).

Loosening the swivel nut, backs the valve body off enough toallow air to pass into the accumulator.

To deflate the accumulator, remove the protective cap and

loosen the swivel nut about one turn and depress the stem of

the valve core.

CAUTION: When using this type of air valve, the air in theaccumulator is under high pressure. Dirt particles may be

blown into the skin or eyes and cause serious injury. To

prevent this danger, the valve core stem should always be

depressed with a special tool to deflect the escaping a

Afr 1041 Aircraft Hydraulic Pneumatic Lecture Presentation 2

Documents

Transcript of Afr 1041 Aircraft Hydraulic Pneumatic Lecture Presentation 2