Ac Fluid Assignment

8/8/2019 Ac Fluid Assignment

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EMIRATES AVIATION COLLEGE

KHAIRUNNISA, HAIFA,

JASIM AND FAZAL AIRCRAFT FLUID SYSTEMS Page 1


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KHAIRUNNISA, HAIFA,


TABLE OF CONTENTS

Introduction page 2

A320 Hydraulic system page 3-4

y Green system page 5

y Blue system page 5

y Yellow system page 5

y Power Transfer Unit page 6

y Ram Air Turbine page 6

y Fire Shut off valve page 6

y Fire control system in general page 7

Secondary Flight Controls

y Fly by wire page 8

y Computers page 8-9

y Spoilers page 10

y Roll spoiler page 11

y Speed brake control page 11-12

y Ground spoiler control page 12

y Full extension (rejected take off phase) page 12

y Full extension (landing phase) page 12

y Partial extension page 12-13

y Retraction page 13

y Flaps and slats page 16

y Flap disconnection detection page 16-17

y Configuration page 17

y Alpha lock function slats page 17-18

y Power supply for slats\ flaps page 18

y Slat mechanical drive page 18

y Flap mechanical drive page 18-19

y THS (Trimmable Horizontal Stabilizer) page 20-21

Problem faced by A320 page 23

Conclusion page 24

References page 25


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INTRODUCTION

In this assignment, we are familiarizing with the A320 general hydraulic system,

component structure and the secondary flight control system in full constructionand operation details.

First lets have a general introduction on Airbus A320.

The airbus 320 is a single aisle medium range airliner which belongs to A320

family which made its first entry in 1988. There are more than 3400 aircraft of this

family in service now.

The first subsonic airline to have a fly-by-wire technology is the A320. This

system is controlled by five dedicated computers.

Electronic signaling and hydraulic jacks are used in combination to operate the

primary and secondary flight controls. High safety Standard is ensured in the

flight.

There are two passenger doors on the port side and service doors on the

starboard side in the main cabin of A320. It enables to carry bulk cargo and

containers.

This airbus offers various features like advanced technology, improved operating

economics, different passenger capacities and wider single aisle cabins.

Because of the advanced technology used in A320, it is much widely used as a

replacement over many earlier versions of Boeing aircrafts. (*1)

(*2)


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(*3)


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A320 HYDRAULIC SYSTEM

There are three hydraulic systems in the aircraft namely blue, green and yellow

systems. They are continuously operating and have its own hydraulic reservoir..The fluid in each system cannot be transferred to another. At normal conditions,

the operating pressure is 3000 psi which reduces to 2500psi when powered by

RAT (Ram Air Turbine). Three of the systems supply for various needs of the

flight controls..

Each system has its own accumulator which helps to maintain constant pressure

in the system, priority valve which cut off hydraulic power from heavy load users

when the pressure in the system is low.

All the three systems are kept between a distance apart to avoid and reduce

problems like engine or tire burst or from any other damage.

When the engines starts operating, all the three systems start supplying hydraulic

power.

In case when the main pumps cannot be used, we can pressurize the systems

with one or more of the auxiliary systems.

During maintenance, all the three hydraulic systems can be pressurized from an

external hydraulic supply. These connections can be installed on the ground

service panels.

On ground,

Yellow hydraulic system can be pressurized by yellow electric pump while Green

hydraulic system can be pressurized by using yellow electric pump by means of

Power Transfer Unit (PTU). Blue electric pump can pressurize the blue hydraulic

system.


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THE GREEN SYSTEM

The Green system is pressurized by a pump driven by engine 1. If this engine fail

to work or the green system pump is not operational, the green system will

pressurize by Power Transfer Unit (PTU) which is reversible.

THE BLUE SYSTEM

The blue system is pressurized by an electric pump. During emergency or during

power failure, a pump driven by a RAT pressurizes this system.

THE YELLOW SYSTEM

The yellow system is pressurized by an electric pump and this allows yellow

hydraulic to be used when the engines are not working. Similar to green system,

yellow system can be pressurized by reversible PTU. In case due to the

unavailability of electric power, crew members can pressurize yellow system by ahand pump thereby to operate cargo doors.

Two Spoilers are positioned by Servo jack and they receive hydraulic

power from green, blue or yellow hydraulic system.

Both the green and blue hydraulic systems provide power for the slats.

While both the green and yellow hydraulic systems provide power for the

flaps.


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PowerTransferUnit ( PTU )

The yellow system can pressurize the green system and vice versa by a power

transfer unit which is bidirectional. This works automatically when there is a

differential pressure greater than 500psi between green and blue systems.

Ram AirTurbine ( RAT) :

When there is unavailability of power or when the engines are not working, RAT

can be used as a replacement. It is coupled with a hydraulic pump. It can be

brought down manually from the overhead panel. It can be returned back to

position only when the aircraft is on ground.

During normal operation, the short term demands can be satisfied by an

accumulator thereby helping to maintain the constant pressure of the

system.

FIRE SHUT OFF VALVE

Both the green and yellow systems have its own fire shut off valves which is

placed above the Engine driven pumps. They can be closed with the help of Fire

push buttons. (*4)


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Flight Control System In General :

Flight control system surfaces are made up of different composite materials

except slats. They are made of aluminum alloy. All the flight controls are

controlled by electric means and actuated hydraulically.

Trimmable Horizontal stabilizers help in the long term activity of pitch control.

Spoilers 2, 3, 4 and 5 on each wing help in roll control along with aileron.

Spoilers 2, 3 and 4 are used for the speed braking function. This function helps to

increase the drag. All the spoiler surfaces are involved for the function of ground

spoilers. This function is activated in order to destroy lift at touchdown or cases of

rejected take-offs.

Slats, flaps along with primary control, aileron is used for achieving high lift. On

each wing, there are two flaps and five slats placed from wing root to wing tip.These are also used for lift augmentation during take-off and landing.

(*8)


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SECONDARY FLIGHT CONTROLS

FLY BY WIRE

Until the introduction of fly by wire technology by the A320, all other aircrafts

were controlled via mechanic Bowden cables that ran through the entire aircraft.

But with this innovative technology, pilots can make use of simple side sticks for

giving orders. The term fly by wire originated from the idea that the movements of

flight controls are converted into electric signals which is transmitted through

wires. In order to produce ordered response, the movements of actuators are

determined by computers.

In A320 family, both the primary and secondary flight controls are operated

electrically. But in case, there is a power supply failure, the aircraft can be

controlled mechanically until emergency power supply come into action.

With the use of fly by wire technology, it not only reduces the tasks of pilots

helping to concentrate in other duties, but also ensures high safety in commercial

aircrafts. With the use of computers for flight controls, cost is reduced. The

engines are also under supervision always thereby optimizing thrust and feeding.

It also reduces weight and less fuel consumption all leading to less cost.

Another advantage of A320 was its wide cabins compared to other aircrafts,

which enables it to have more spacious seats and thereby helping to have great

passenger capacity.(*5)

COMPUTERS

There are mainly three types of computers which are used for flight control. They

are as follows:

y ELAC (Elevator Aileron Computer) : There are two ELACs which gives

commands for the operation of normal elevator, aileron and stabilizer.

Mainly for primary control.


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y SEC (Spoiler Elevator Computer) : there are three SECs in the control

system for achieving the control of spoilers. While two are used for

controlling of stabilizer and elevator.

y FAC (Flight Augmentation Computer) : They are used in electrical rudder

control and for specified speed calculation.

Besides these, there are other control computers used;

Two SFCCs (Slats Flaps Control Computer) and two FCDCs (Flight Control Data

Concentrator). These help in getting information from control computers like

ELACs and SECs and transfer to ECAM.

(*9)


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(*9)

SPOILERS

Three SECs are used for controlling the spoiler panels which are placed on each

wing. They are hydraulically powered. They can be powered by either of the

green, blue or yellow systems. With the help of side stick controllers speed brake

control lever, these surfaces can be manually controlled.

They can also be automatically controlled in autopilot or load alleviation function.

For ground spoilers, all the five spoiler panels are being used. Along with the

primary control (aileron) , the four outboard spoilers help in roll control .

While the middle spoiler panels are used for the operation as speed brakes.

When there is a fault detected, the associated spoiler will automatically retract. In

case with the loss of electric power, the spoiler will remain with same deflection

or a little less due o the aerodynamic forces pushing it down.

Spoilers are used for roll control, in addition to that, they also are used as speed

brakes and ground spoilers.

When the speed brakes are extended, in the ECAM it will display a green SPD

BRK memo.

Spoilers are positioned by Servo jack who receives hydraulic power from green,

blue or yellow hydraulic system. They are controlled by Spoilers Elevators

Control (SEC) 1, 2 or 3.


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When there is no electrical control or if a fault is detected, spoilers are

automatically retracted to zero position by the system. When there is loss of

hydraulic power, the spoiler is retained with the deflection it had at the time of

loss or lesser.

ROLL SPOILER

One of the main activity of spoiler is Roll control. This is achieved by four roll

spoilers which are placed on the upper wing surfaces along with an aileron. The

surfaces are controlled electrically and they are actuated by means of

independently supplied hydraulic jacks.

Depending upon the signals from the electrical Flight Control Computer or from

the autopilot, the roll spoilers are positioned. When the side stick is moved, it will

produce a signal to both ELAC and SEC. from the SEC, the signal is passed to

the servo jacks. This will ensure whether the spoilers are in the right position.

During the flight (cruising), due to gusts, there will be vertical acceleration. This

can be compensated with the help of two outer spoilers combined with the

ailerons. This function is known as the Load Alleviation Function (LAF) and can

be achieved by the electrical FCC (Flight Control Computer). This function will be

implemented in the SEC and ELAC. When there is vertical acceleration, the four

different accelerometers which are installed will give the control computers with

the values of acceleration. And with this, spoilers are deployed in order for the

normal cruising of aircraft. (*10)

SPEED BRAKE CONTROL

The speed brakes which are actually spoilers 2, 3 and 4 are controlled by the

speed brake lever. But the extension of speed brakes is inhibited in cases like

when there is any fault with SEC1 and SEC3, when the flaps are in full

configuration, when Elevator has fault etc. When this inhibition occurs while the

speed brakes are being extended, they are retracted automatically until the pilot

resets the lever.


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A symmetric speed brake surface will be inhibited in case when there is a failure

of speed brake surface on any of the wings.

GROUND SPOILER CONTROL

Ground spoilers are Spoilers 1 and 5. Similar to the speed brakes, when there is

failure of ground spoiler surface, a symmetric of it on other wing is inhibited.

The Ground spoilers can be armed by pulling the speed brake control lever up.

FULL EXTENSION: (REJECTED TAKE OFFPHASE)

The ground spoilers will automatically extend if the speed exceeds 72knots and

ground spoilers are armed after both thrusts are set to idle state. When the

exceed 72knots and the ground knots are not armed, the ground spoilers are

automatically extended as soon as when one thrust lever remains at idle.

FULL EXTENSION-LANDING PHASE:

During landing time, when both the main landing gears touch down, the ground

spoilers will automatically extend only if they are armed and all the thrust levers

are set at idle state.

In case, when the main landing gears have touched down while the ground

spoilers are not armed, the ground spoilers will extend as soon as one of the

thrust lever remaining at idle and reverse is selected on one engine.

PARTIAL EXTENSION

Keeping one engine at idle and reverse being selected on one engine, the

ground spoilers will be partially extended with an angle of 10degree. Also the

main landing gear strut should be compressed.

This will decrease the lift thereby eases the compression of the other main

landing gear strut and then leads to full extension of ground spoilers.


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RETRACTION

The ground spoiler will retract only after landing or after an aborted take-off and

only if the ground spoilers are not armed. (*6)

y In a manual flight, the maximum speed brake deflection for spoilers 3

and 4 are 40owhile that for spoiler 2 is 20 o.

y But whereas,when there is an autopilot engaged the maximum

speed brake deflection changes for spoilers 3 and 4 to 25 o and for

spoilers 2, it is 12.5 o. This is achievedwith halfdeflection of speed

brake.


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*A close look at the inner workings of the spoiler during the landing of anAirbus A320.** (*7)


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(*8)


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FLAPS AND SLATS

In each wing, there are five slat and two flap panels. They can be electrically

controlled and are actuated hydraulically when pilots give input from the flapslever. The Command sensor units transmit signals from the flaps lever position to

the SFCCs (Slat Flap Control Computers). Basically, by moving the flaps lever, it

rotates the input shaft of CSU thereby converting mechanical demand into

electrical signals and these are later transmitted to SFCCs.

Both the green and blue hydraulic systems provide power for the slats while both

the green and yellow systems powers the flaps. In case any of the system fails to

perform, only the associated slat and flap surfaces extend and retract at half

speed. But when the controlling computers fails, all the flaps and slats perform at

half speed.

During the cases of over speed, asymmetry or uncommanded movement, the

flaps or slats can be locked by four wing tip brakes which are hydraulically

operated, but these brakes can be reset only on reaching ground. Two SFCCs

control the system in which of them comprises of one slat and flap channel. In

each Power Control Unit (PCU), there are two hydraulic motors provide hydraulic

actuation.

The computers are used for monitoring slat and flaps drives and locking them

when necessary and in alpha lock function.

FLAP DISCONNECTION DETECTION:

This system prevents further operation of flaps when any failure is detected.

It has two sensors placed on each wing used for measuring differential

movement between outer and inner flaps. In each wing, there will be a sensor

unit (comprising two sensors) which are electrically controlled and actuated

mechanically.


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This works when an attachment failure is detected, it de-energizes the flap Power

Control unit thereby applying Pressure off brakes. And therefore, further

operations of flaps are prevented.

Configuration:

There are five positions for a flaps lever which are 0, 1, 2, 3 and full.

Two configurations which are Configuration 1 and 1+F configuration denotes

position 1.

This can be represented as:

(At 210 knots, it will be Zero flap when configuration 1+f is selected).

ALPHA LOCK FUNCTION SLATS

This helps in preventing slat retraction at low speed and high angle of attack

(alpha). In order to inhibit the slat retraction, SFCCs use corrected alpha.

Slat retraction from 1 to 0 is inhibited, when the airspeed is below 148 knots,

while the inhibition is removed when speed goes above 154 knots.


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But this alpha Lock function cannot take place on ground when speed is less

than 60 knots.

Power Supply for Slats/Flaps:

Electrical power supply for Flap Control systems are

y essential bus 401PP which supplies for SFCC1 flap channel, related PCU

solenoids and synchro and LVDT excitation voltages

y Normal bus 204PP

y Battery buses supplies WTB solenoids ( of SFCC 2).

SLAT MECHANICAL DRIVE

Slat operating mechanism is driven by actuators which receives power from

Power control Unit (PCU) by means of gearboxes and torque shafts. Through a

single output shaft, the slat transmission system is driven by the slat PCU. Both

the gearboxes and the actuator input shafts are rotated at same speed and

simultaneously.

In the slat transmission system, there are six gearboxes used in which torque

shaft alignment changes. The actuators produce the necessary torque and speed

reduction for the slats to work in desired way. The slats are placed to the forward

ends of the four tracks which run in guide rollers out of which only T2 and T3 are

driven where as the other tracks are used in inhibition of slat loss due to any

failure.

When abnormal operations like asymmetry are detected by the controlling

computers, SFCCs, the Wing Tip Brakes (WTB) stop the transmission.

FLAP MECHANICAL DRIVE

Flap transmission output shafts are driven by the flap PCU. Where there are

small angular changes, steady bearings are attached in order to support the

torque shafts. Torque shafts rotate and drive the gearboxes and actuator input


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shafts at same speed. Where there is a large change in torque shaft alignment,

one to one gearboxes are used for flap transmission. These gearboxes are of

three types: right angle gearbox, line gearbox and a 19 level gearbox.

At each track, an actuator operates the flap mechanism which provides torque

and speed reduction for a desired flap working. There is bi directional torque

limiter in each actuator to protect against over load. Similar to slat drive

mechanism, the WTBs stop the transmission when associated faults are

detected. The outboard flap is connected to the flap track carriage while inboard

flap is connected to track2 carriage, both by failsafe bolt. The inboard flap is also

connected to the pendulum assembly by the flap turn-on. The inboard and

outboard flaps are connected by means of interconnecting struts. There are also

flap disconnect sensors in the struts which helps in detecting flap disconnection.

Signals are processed from the sensors by Landing Gear Control Interface

(LGCIU) which transmits to SFCCs. When any attachment failure is detected,

system is stopped after de energizing the PCU. But here wing tip brakes are not

used. (*8)


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THS (TRIMMABLE HORIZONTAL STABILIZER)

The Trimmable Horizontal Stabilizer (THS) is operated by a THS actuator. It is

used to provide pitch-trim control of the aircraft. This horizontal stabilizer can be

either controlled electrically by any of the three motors or mechanically with the

help of a trim wheel. These trim wheels moves whenever the stabilizer moves.

They are located on the control pedestal. Green and yellow systems actuate it

hydraulically.

A Trimmable Horizontal Stabilizer actuator is an electro-hydraulic unit comprising

of a double load-path ball screw which are powered by means of hydraulic

motors (coupled together) which are servo controlled mechanically. Some of its


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components are two hydraulic motors, a pitch trim actuator, a fail-safe ball screw

jack, input shaft, gearbox, two hydraulic valve blocks etc.

Both the hydraulic motors receive fluid from different hydraulic systems and are

therefore independent. Through a power differential gear, hydraulic motors

transmit output force from it to the screw shaft. This helps in operating on one

circuit with half of the maximum speed. There is a comparison system in order to

make sure the immobilizing of THS actuators when control valve or control gear

loops get locked.

If there is loss of hydraulic power, the THS is fully immobilized by its actuator.

Normally, electric motors which are servo controlled by the ELAC 2 drives the

input shaft of stabilize actuator while the other motors are controlled by ELAC 1

or SEC1 and SEC2. But the input shafts can also be controlled mechanically

through mechanical linkage (moved by the hand wheels).

Mechanical control is rather preferred over electric control due the overriding

mechanism.

The THS position will be displayed on the lower ECAM display unit along with

hydraulic systems used for the actuator. A specific mark will be painted to the this

stabilizer and on the next aircraft structure. (*8)


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(*8)


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PROBLEM FACED BY A320

The largest airline companies operating A320 are JetBlue, Northwest, U.S.

Airways and United airlines.

There was instances in which the pilots pointed out that the Power Transfer

Unit (PTU) racket is not audible from the cockpit which lead to problems. And

the idea arose for providing with quieter machinery. As a result, in order to

reduce the PTU noise, airlines suggested crew members to run a separate

electric pump during a single - engine taxi. (*10)


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CONCLUSION

With the help of this assignment, we came to know more about airbus A320, its

general hydraulic system and secondary flight controls. The normal andabnormal operations have been discussed along with various back up systems.

We have also described the various secondary flight controls of A320 like the

spoilers, speed brakes, flaps, slats and THS ( Trimmable Horizontal Stabilizer) in

full construction and operation details.

With the help of schematic diagrams, indication statuses and illustrations, its

more understandable and this will help to know each component in detail.

Thus by doing this assignment, we gained a lot of information and working as a

team also was worthwhile.


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REFERENCES

(*1) Introduction: http://www.aerospace-technology.com/projects/a320/

(*2) Picture of A320:http://www.google.ae/images?hl=en&q=A320%20pictures&um=1&ie=UTF-

8&source=og&sa=N&tab=wi(*3) Hydraulic system picture:

http://www.vbirdva.nl/airbus/images/Completehydjpeg.jpg ,

(*4) Hydraulic system theory:

http://www.smartcockpit.com/pdf/plane/airbus/A320/systems/0033/

(*5) Fly by wire: http://en.wikipedia.org/wiki/Fly-by-wire ,

http://www.afc.aero/index.php?ILNK=produkte_a320_history&iL=2

(*6) Spoilers:

http://www.smartcockpit.com/pdf/plane/airbus/A320/systems/0031/

(*7) spoiler picture: http://en.wikipedia.org/wiki/Spoiler_(aeronautics)

(*8) A320 chapter 27.

(*9) Flight deck and system briefing for pilots.

(*10) Roll spoiler

http://www.dutchops.com/Portfolio_Marcel/Articles/Flight%20Controls/A320_Fli

ght_Controls/A320_Secondary_Flight_Controls.html

(*11) problem of A320:

http://www.salon.com/technology/ask_the_pilot/2006/01/20/askthepilot170

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