CHAPTER ONE

BACKGROUND OF Addis Ababa BOLE INTERNATIONAL AIRPORT

1.1. Brief history of the company

Addis Ababa Bole International Airport is a public enterprise serves the city of Addis Ababa,
Ethiopia. The airport is located in the Bole area, 6 km (3.7 mi) south east of Addis Ababa City
Centre. Formerly known as Haile Selassie I International Airport, it is the main hub of Ethiopian
Airlines. It is currently accommodates more than 150 flights per day that the facilities at this
airport are serving an average capacity of over 3,500,000 passengers per annum.

The Bole International Airport currently has two terminals with a total of 12 gates and an
elaborate modern supporting infrastructure consisting of numerous aircraft stands, aero-
bridges and check-in desks enabling smooth air traffic movements. Other passenger
convenience facilities at these terminals include a post office, a bank, currency exchange
counters, bars, restaurants, a VIP lounge, a duty free shop and various gift stalls for last minute
purchases. Private metered taxis and mini buses are readily located outside the terminal
building providing convenient downtown travel for passengers.

Factory Owner:The owner of Addis Ababa Bole International Airport is Government, means it is
under the control of the Federal Democratic Republic of Ethiopia Privatization and Public
Enterprise Supervising Agency.

Vision: The vision of this company is to be the leading Airport service provider in Africa and to
provide standardized service as international overall the world.

Mission: Its mission is providing quality airport infrastructure and qualified, safe, fast and
comfortable services to the customers. This plays a great role in development of air transport
through the country.

Objective: To construct, maintain and administer aerodromes in Ethiopia which is safe, reliable
and efficient. And to coordinate passengers and develop non-aeronautical services in the
aerodromes that is subject to the performing of security activity by the relevant body. In
accordance with the national aviation security program, it strives to ensure in the aerodrome to
issue directive regarding airport facilitation to coordinate and control the work.

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1.2 Its main service and users
1.2.1 Its main service

The main service of Bole airport is air transportation system as an international. So it gives the
service of air transport system from place to place in the country and from our country to
another country.
As generally the main services that the company provides can be divided in to two: aeronautical
and non aeronautical service. Non aeronautical services are those facilities including the
operation of restaurants, hotels, banking, shopping, car parking, a host of support facilities and
others. Aeronautical services include:
 Security screening and detection service
 Check in desk service
 Baggage traveling service
 Passenger boarding and leaving service
 Airfield ground lighting service

1.2.1.1 Security screening and detection service

Security screening and detection is the process of displaying and detecting materialssuch as
gun, bomb, sharp materials and etc that are unnecessary to travel from place to place or
country to country. For this purpose walk through metal detectors, x-ray machines and
explosive detection machines are used. When passengers pass through this walk through metal
detectors, it detects them. X-ray machines and explosive detection machines are used to detect
the baggage when they pass through it. But explosive detection machine is rejecting the
baggage by itself if there is unnecessary material in it.

1.2.1.2 Check in desk service

This includes different services such as;

 Checking passport card
 Giving flight information such as flight time

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  Checking the weight of the baggage
 Giving code for the baggage
 Packing materials etc.

1.2.1.3 Baggage traveling service

This service is the service of taking baggage from check in to an aircraft at departure or from
aircraft to carousel conveyor at arrival. Different conveyer such as weight, feeder, collector,
carousel and others are used for this purpose. At departure, after the weight of the baggage
taken, the weight conveyor pass it to feeder and then to collector conveyor. This collector
conveyor collect the baggage from all feeder at each check in desk and transfer it to main
conveyor which take the baggage to carousel. In other hand when we see at arrival, the cart
takes the baggage from aircraft to the main conveyor at arrival. Then this conveyor takes
baggage to carousel conveyor. Therefore the passengers take their baggage at this station by
passing it through x-ray machines.

1.2.1.4 Passenger boarding and leaving service

Passenger boarding and leaving is the process of go in to the aircraft and come out from the
aircraft. So this service is given for the passengers for boarding from building (apron) to aircraft
or leaving from aircraft to building (apron). For this purpose the company mainly uses
Passenger boarding bridge which is a telescoping passage way that can be driven from a parked
position beside the terminal to the aircraft itself. Additionally the company also uses different
cars those have their own stairs which used for the purpose of boarding to and leaving from
aircraft.

1.2.1.5 Airfield ground lighting service

Airfield ground lighting service is the service that concerns with the lighting system on the run
way which is used to communicate the pilot and air traffic controller (ATC) in order to take off
and landing safely by giving information to the pilot using the color of lighting mounted on the
run way. So there are many light mounted on and beside of the run way. Those light have
different color such as white, green, red, blue and yellow color. Therefore each color of these
light mounted there has its own meaning. These light have also different intensity and each of

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them has their own separate transformer. This airfield ground lighting system has its own
substation and all things controlled and varied from there to give correct service for pilot.

1.2.2 Users of company’s service

The main end users of this company’s service are passengers. They may be our county citizens
or foreign people from different country. Over 3,500,000 passengers are using this service per
annum to transport from place to place or from country to country. In other hand the end users
of airfield ground lighting are pilot for landing and take of purpose. So more than 150 pilots are
use this service per day. Additionally, many people use this service (cargo) to transfer different
materials from one country to another country.

1.3 Overall organization and work flow of the company

To meet its objectives and fulfilling its duties and responsibilities, the company has organized as
shown diagram bellow.
Engineering instructor: Its functions are:
 To built new airports in the country
 To repair and maintain the old airports
 To provide mechanical, electrical, electromechanical supports for planting airports
 To give professional advice and supports for services related to airports etc

Information technology services: Its functions are:

 To enable the company’s information comparable with modern technology
 To provide computer software and modern technology for servants
 To give related maintenance
 To provide enough information for the company’s society

Addis Ababa bole international airport administration:The main functions of this

administration are:
 To provides human resources and required materials
 To bring comfortable, fast and safety services in this airport
To carry out these function, it organized in to four groups as block diagram shown below.

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 Technical and maintenance group: Under this group there are three sections. These are:
1. Electromechanical section: This section works mechanical and electrical system. It
includes:
 Baggage handling system
 Passenger boarding bridge system
 Escalators and elevators and
 Automatic sliding door
2. Airfield ground lighting section: Is a section that makes a suitable condition for the
aircraft to takeoff, landing and parking.
3. Security screening and detection section: It is a section that works function of checking
and controlling unauthorized materials such as weapon, knife, bomb and others. For this
purpose it uses:
 X-ray machines
 Explosive detection system
 Closed circuit television
Ministerand
 Walk through metal detector of transport
others.

Work administrator board

General Manager

Engineering and regional airport

Plan &office AABIA administrationCorporate service office
market development cooperator

Plan group Finance service property administrator service

Procurement&
Human resource& development service
ITRegional
service airport instructor
Engineering instructor
Statistic group

Market development group Procurement group

Employer administrator group
Engineering group

Store& distribution group

Customers service &contract administration group
Construction & installation group General maintenance group

Airport master plan group Leveling& training group

Promotion & communication group
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 Security screening & Detection section
Electromechanical section AGL section

Fig 1- block diagram of overall organization and work flow of the company

CHAPTER TWO
OVERALL INTERNSHIP EXPERIENCE

2.1 How we get into the company

The University Industry Linkage (UIL) announced the students to find the internship host by
themselves. Hence the UIL prepared the internship application request paper for the students.
The department gave us some orientation on how to choose Host Company. For instance they
orient us to consider about economic condition of the company environment since the money
funded for this program is not enough to survive. Based on this and other information, we
choice Bole International Airportcompany and got it after some process.

2.2 Working section in the company

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There are different working sections in this company. From those sections we work in three
sections. These are
1. Electromechanical systems (EMS)
2. Security screening and detection system
3. Airfield ground lighting (AGL) and digital control system.

2.2.1 Electromechanical systems (EMS)

Electromechanical systems (EMS) are physical structures characterized by interaction between

electromagnetic fields and inertial bodies. This section contains five sub sections which
describes five different objects that use electromechanical systems. These are
 Passenger boarding bridge system,
 baggage handling systems,
 escalators,
 elevators and
 Automatic sliding door systems.

2.2.1.1 Passengers boarding bridge

Passenger Bridge is a telescopic apron drive bridge with two extension tunnels. It is a
telescoping passage way that can be driven from a parked position beside the terminal to the
aircraft itself. These apron drive bridges come in a variety of lengths and options ,depending on
the needs of the airport .It is driven using PLC controls mounted on a console in a cab that is
separated from the passenger walk way.A jet way systems truss passenger boarding bridge is a
convenient way to board and leave an aircraft and keeps passengers safe from rain,snow, jet
blast, noise, and dust. It also separates the passengers from the aircraft’s ground crews.

Operation system of passenger boarding bridge is controlled from operator control console
which is located in the left side of the cab .It has all the controls needed to operate the
passenger bridge.

First of all powering up the system is required.To do this first turn the control current switch to
the one position that light up the control current lamp. After that push start up button situated
in control panel and this makes the system ready for operation .Then go to touch display unit
and enter password to gate menu screen that:

Pass word Enter Aircraft type screen pulling aircraft.

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After that the hidden push button on the left side of control panel must be pushed. Now the
system is ready for operation that we can move the bridge.

To move the bridge the following requirement must be fulfilled:

 The emergency stop must be inactivated.
 Protective cable must be attached.
 Manual/auto leveling switch must be in the manual position.
 There must be no obstacle within one meter of the drive unit.
 Start up light must be ON.
 Hydraulic pressure must be OK.
 Key lock must be inactive.
 Aircraft stopped lamp must be ON or pulling aircraft button has been pushed on the
touch display unit.

After all the above conditions are fulfilled, we can drive to predetermine position by using
buttons situated in control panel. By using the controller for ‘forward-back ward’ and the
control wheel for ‘steer left-steer right’, the bridge can be loaded to pre determined basic
position on the apron. With help of the ‘rotate left ‘and ‘rotate right ’ buttons, rotate the cabin
so that there is approximately 90 degree angle between the cabin door opening and aircraft
center line in the apron. By using ‘raise’ and ‘lower’ buttons, the height of the cabin can be fine
tuned manually.

To docking to passenger to aircraft first roll up door from roll up button for better visibility and
then drive the bridge to predetermined position by using control panel. By using bellows out
button, the canopy (bellows) is extended and the protective cable must be removed. Then open
the aircraft door and set door shoe below opened aircraft door. Then after, manual/auto
leveling switch has been turn to auto leveling position and auto leveler automatically moves out
and connects to aircraft. So the docking is completed and the passengers can be start boarding
to or leave from the aircraft. After boarding to or leave from aircraft completed, it has been go
back to its privies position and by pressing ‘log off’ buttons, the power can be removed from
the bridge.

Basic components of passengers boarding bridge are the following.

 Cabin
 Canopy
 Roll up door
 Control panel

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  Door shoe
 Auto leveler
 Protective cable
 Stairs
 Drive unit
 Telescopic tunnels and so on.

Cabin: Cabin is the component that connects to aircrafts fuselage operation. It can rotate
around its centre point, in order to secure proper alignment with different aircrafts. It contains
canopy, roll up door, control panels, protective cable, protective edge, door shoe and auto
leveler.

Cabin Canopy
Tunnels
Drive
column

Rollup door

Protective
edge
Stair
Rotunda Drive unit

Fig 2- Components of boarding bridge

2.2.1.2 Baggage handling system

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The baggage handling system is the system that is intended for transporting those goods for
which it is designed. Therefore at an airport baggage handling system is used to transport the
baggage from place to place. This system has many conveyors which has their own motor and
control box. So each and every can be controlled manually or automatically. But the whole
system can be controlled from general control panel. It shall used only in accordance with the
instruction and in a fault-free condition from a safety view point.

A baggage-handling system has three main jobs:

 Move bags from the check-in area to the departure gate

 Move bags from one gate to another during transfers
 Move bags from the arrival gate to the baggage-claim area.

The BHS Consists of: -

 Departure system,
 Arrival system
 Supervisor system
 Baggage Operator system
 Check-in desk operators
 manual inspection operators
 X-Ray equipment systems.

A baggage-handling system is kind of like a road system in a city: The conveyors are like the
roads and your bag is like the car. Baggage-handling and road systems share these properties: a
conveyor is blocked (a traffic jam, of sorts), baggage can be routed around the
blockage.Baggage starts and ends its journey on conveyors (just as you start your drive to work
on roads). Unlike a road system, however, a baggage-handling system makes all of the decisions
about where a bag is going. The BHS operated only when all protection equipment has been
fitted and is functioning. The component operating panel is used to starting, stopping, resetting,
and etc the system.System started from the MISor via push buttons up on the main control
panel (OP). Before starting system all relevant e-stop system must be checked that healthy and
in the reset state. It must be checked that no associated fatal alarms active for example,
suspected HBS tracking or sensor fault.

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The system will be start from downstream to upstream order. When one or more areas are
starting-up an audible and visible alert will be active for a few seconds. So when system
starting-up the system or an individual area a horn on top of the main control cabinet sounds
and the flash light flashes for 5 seconds.

The system may be stop work by two causes/events; during the conveyor stop/ energy save
and the Emergency stop period. During the conveyor stop, the baggage progressively clears
from upstream to downstream and cleared conveyors are stopped.

EDS

Carousel
Collector

Check in
desk
Main
conveyor Feeder

Fig 3- baggage traveling system and its component

2.2.1.3 Escalators

An escalator is a moving staircase for transporting people between floors of a building. It is a

machine equipped with moving steps resembling a staircase usually seen in a workplace or
public building. They are powered by constant-speed alternating current motors. The core of an
escalator is a pair of chains, looped around two pairs of gears. An electric motor turns the drive
gears at the top, which rotate the chain loops. A typical escalator uses a 100 horsepower motor
to rotate the gears. The motor and chain system are housed inside the truss, a metal structure
extending between two floors.

Instead of moving a flat surface, as in a conveyer belt, the chain loops move a series of steps.
The coolest thing about an escalator is the way these steps move. As the chains move, the steps

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always stay level. At the top and bottom of the escalator, the steps collapse on each other,
creating a flat platform. This makes it easier to get on and off the escalator. Each step in the
escalator has two sets of wheels, which roll along two separate tracks. The upper set (the
wheels near the top of the step) are connected to the rotating chains, and so are pulled by the
drive gear at the top of the escalator.

The other set of wheels simply glides along its track, following behind the first set.The tracks
are spaced apart in such a way that each step will always remain level. At the top and bottom of
the escalator, the tracks level off to a horizontal position, flattening the stairway. Each step has
a series of grooves in it, so it will fit together with the steps behind it and in front of it during
this flattening.

In addition to rotating the main chain loops, the electric motor in an escalator also moves the
handrails. A handrail is simply a rubber conveyer belt that is looped around a series of wheels.
This belt is precisely configured so that it moves at exactly the same speed as the steps, to give
riders some stability. It is generally agreed that an escalator is the most efficient means to move
large numbers of people between floors. Direction of movement (up or down) can be
permanently the same, or be controlled by personnel.

Components of escalator are:

1. Electric motor
2. Drive gear
3. Handrail drive
4. Handrail
5. Step
6. Return wheel
7. Chain guide
8. Inner rail

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Fig 4- Components of escalators

2.2.1.4 Elevators
An elevator or lift is a type of vertical transport equipment that efficiently moves people or
goods between floors (levels, decks) of a building, vessel or other structures. Elevators are
generally powered by electric motors that either drive traction cables or counterweight systems
like a hoist, or pump hydraulic fluid to raise a cylindrical piston like a jack.

In Airport, an elevator is any type of conveyor device used to lift materials and passengers in a
continuous stream from floor to floor of building. Several types exist, such as the chain and
bucket elevator, hydraulic elevator, roped elevator and so on.

In roped elevators, the car is raised and lowered by traction steel ropes rather than pushed
from below.The ropes are attached to the elevator car, and looped around a sheave. A sheave
is just a pulley with a groove around the circumference. The sheave grips the hoist ropes, so
when you rotate the sheave, the ropes move too.The sheave is connected to an electric motor.
When the motor turns one way, the sheave raises the elevator; when the motor turns the other
way, the sheave lowers the elevator. In gearless elevators, the motor rotates the sheaves
directly. In geared elevators, the motor turns a gear train that rotates the sheave.The ropes
that lift the car are also connected to a counterweight, which hangs on the other side of the
sheave. The counterweight weighs about the same as the car filled to 40-percent capacity. In

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other words, when the car is 40 percent full (an average amount), the counterweight and the
car are perfectly balanced.

The purpose of this balance is to conserve energy. With equal loads on each side of the sheave,
it only takes a little bit of force to tip the balance one way or the other. Basically, the motor
only has to overcome friction -- the weight on the other side does most of the work. To put it
another way, the balance maintains a near constant potential energy level in the system as a
whole. Using up the potential energy in the elevator car (letting it descend to the ground) builds
up the potential energy in the weight (the weight rises to the top of the shaft). The same thing
happens in reverse when the elevator goes up. The system is just like a see-saw that has an
equally heavy kid on each end. Both the elevator car and the counterweight ride on guide rails
along the sides of the elevator shaft. The rails keep the car and counterweight from swaying
back and forth, and they also work with the safety system to stop the car in an emergency.

Fig.5- Simple Elevator Control System Inputs and Outputs

Components of elevators are:

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  Elevator car
 Hoist way.
 Machine/drive system.
 Control system.
 Safety system etc.

Fig 6- Elevators and its components

2.2.1.5 Automatic sliding doors

Automatic door is an automated movable barrier installed in the entry of a room or building to
restrict access or provide visual privacy. An automatic door control system, used with a
moveable door system wherein doors are moved between closed and opened positions by

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means of the rotary drive of an electric motor, comprises of a photo sensor to detect the
object.

The operation of automatic sliding doors is start with switch ON the main switch. The functions
of the door are set with a program selector, which is fitted close to the door in exit, auto, off etc
mode. In EXIT mode passenger can pass through door way from inside only and in AUTO mode
it is two way traffic, normal operation of the door. The sliding door operator works
electromechanically. The motor, control unit, transmission and optional emergency unit and
electromechanically locking device are all assembled in a compact drive module. The drive is
mounted inside a support beam with integrated cover.The motor and gearbox transmits
movement to the door leaves by means of a tooth belt.
The door leaf is fitted to a door adaptor carriage wheel fitting and hangs on a sliding track.
When an opening impulse is received by the control unit the motor starts and transmits
movement to the door leaves which move toward open position and when the door is fully
open the motor stops. The close starts when the hold open time has run out.

2.2.2 Security screening and detection system

In this section there are another five sub sections. These are:
 x-ray machines
 explosive detection systems
 fire alarm detection system
 walk through metal detection system and
 Closed circuit television (CCTV) system.

2.2.2.1 X-ray machines

X-ray machines are used to screen objects non-invasively. Luggages at airport are examined for
weapons, including bombs.

X-rays are a type of electromagnetic radiation - and are part of the spectrum which includes
radio and television waves, microwaves, infra-red, visible light, ultraviolet and gamma rays.
Like all forms of radiation on the spectrum, X-rays come in different wavelengths. A
conventional airport scanner works by passing a burst of X-rays through an object or person on
to an electronic sensor. Different materials absorb X-rays at different rates so that rays pass
relatively unimpeded through flesh, leather, plastic and cloth, but are absorbed by metal and
bone.

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An X-ray imaging system consists of an X-ray source or generator (X-ray tube), an image
detection system which can be either a film (analog technology) or a digital capture system. X-
ray photons are produced by an electron beam that is accelerated to a very high speed and
strikes a target.

X-ray machines work by applying controlled voltage and current to the X-ray tube, which results
in a beam of X-rays. The beam is projected on matter. Some of the X-ray beam will pass through
the object, while some is absorbed. The resulting pattern of the radiation is then ultimately
detected by a detection medium including rare earth screens (which surround photographic
film), semiconductor detectors, or X-ray image intensifiers. When baggage is placed on the
conveyor, it is moved into the machine by the operator. There is an infrared transmitter and
receiver assembly to detect the baggage when it enters the tunnel. This assembly gives the
signal to switch on the generator and signal processing system.
The signal processing system processes incoming signals from the detector and reproduce an
image based upon the type of material and material density inside the baggage. This image is
then sent to the display unit.

Fig 7- X-ray image of a backpack

2.2.2.2 Explosive detection system

EDS and EDX are also x-ray electrical machines which detect and scan expected explosive and
chemically forbidden materials. Decision is not only on the hand of the operator but also the
machine detects forbidden materials based on the atomic number of their content. Like
conventional x-rays they also have image processing and displaying sub systems for operator
decision in addition to auto detection.

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First, each bag is uniquely identified as it enters the system at the Bag Identification Point. This
bag identification (ID) is accomplished by the Customer to track bags through the system. Next,
each bag is automatically scanned by the EDX Mainframe at the Level 1 Inspection Point. The
Mainframe automatically clears or rejects the bag. All bags continue down the same conveyor,
while bag ID and data for rejected bags are sent to a Level 2 Workstation.

The rejected bag data is displayed on an available Level 2 Workstation Display Monitor for
analysis by an Operator. Here, the Operator manually clears or rejects the bag. Information on
bags cleared after the Level 2 inspection is returned to the Mainframe and sent to the Baggage
Control System.Bags rejected at the Level 2 Decision Point are diverted by the Baggage Control
System to a Level 3 Inspection Point for inspection by an independent system or an Operator at
a Level 3 Workstation.

2.2.2.3 Fire detection and alarm systems

A key aspect of fire protection is to identify a developing fire emergency in a timely manner,
and to alert the building's occupants and fire emergency organizations.This is the role of fire
detection and alarm systems. Depending on the anticipated fire scenario, building and use type,
number and type of occupants and criticality of contents and mission, these systems can
provide several main functions:

 They provide a means to identify a developing fire through either manual or automatic
methods.
 They alert building occupants to a fire condition and the need to evacuate.
 They transmit an alarm notification signal to the fire department or other emergency
response organization.
 They may also shut down electrical, air handling equipment or special process
operations, and they may be used to initiate automatic suppression systems.

i) Photoelectric detector

The principle of using a light source and a photosensitive sensor arranged so that the rays from
the light source do not normally fall onto the photosensitive sensor. The light signal is

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processed and used to convey an alarm condition when it meets preset criteria.In the normal
case, the light from the light source on the left shoots straight across and misses the sensor.
When smoke enters the chamber (the light path), however, the smoke particles scatter the light
and some amount of light hits the sensor.

A – Light Source

B – Photo Sensor

Fig8- Light Scattering Smoke Detection process

ii) Ionization detector

Ionization smoke detectors use an ionization chamber and a source of ionizing radiation to
detect smoke. This type of smoke detector is more common because it is inexpensive and
better at detecting the smaller amounts of smoke produced by flaming fires. Inside the
ionization detector is a small amount (perhaps 1/5000th of a gram) of Americium-241. The
radioactive element americium is a good source of alpha particles. An ionization chamber is
very simple. It consists of two plates with a voltage across them, along with a radioactive source
of ionizing radiation.

The principle of using a small amount of radioactive material to ionize the air between two
differentially charged electrodes to sense the presence of smoke particles. Smoke Particles
entering the ionization volume decrease the conductance of the air by reducing ion mobility.
The reduced conductance signal is processed and used to convey an alarm condition when it
meets preset criteria.

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The alpha particles generated by the americium have the following property: They ionize the
oxygen and nitrogen atoms of the air in the chamber. To "ionize" means to "knock an electron
off of." When you knock an electron off of an atom, you end up with a free electron (with a
negative charge) and an atom missing one electron (with a positive charge). The negative
electron is attracted to the plate with a positive voltage, and the positive atom is attracted to
the plate with a negative voltage (opposites attract, just like with magnets). The electronics in
the smoke detector sense the small amount of electrical current that these electrons and ions
moving toward the plates represent. When smoke enters the ionization chamber, it disrupts
this current -- the smoke particles attach to the ions and neutralize them. The smoke detector
senses the drop in current between the plates and sets off the horn.

iii) Heat/Thermal detector

Heat detectors are the oldest type of automatic fire detection device. They also are the slowest
in fire detecting. A heat detector is best situated for fire detection in a small confined space
where rapidly building high-output fires are expected, in areas where ambient conditions would
not allow the use of other fire detection devices, or when speed of detection is not a prime
consideration. Heat detectors are generally located on or near the ceiling and respond to the
convected thermal energy of a fire. They respond either when the detecting element reaches a
predetermined fixed temperature or to a specified rate of temperature change. In general, heat
detectors are designed to operate when heat causes a prescribed change in a physical or
electrical property of a material or gas.

iv) Projected Beam-Type Detector:

It is a type of photoelectric light obscuration smoke detector wherein the beam spans the
protected area.When smoke particles enter the light path, some of the light is scattered and
some of the light is absorbed, thereby reducing the light reaching the receiving sensor. The
light reduction signal is processed and used to convey an alarm condition when it meets preset
criteria.

2.2.2.4 Walk through metal detector

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A metal detector is a device which responds to metal that may not be readily apparent. Metal
detectors have been a staple of airport security for decades. These tall, boxy metal detectors
are meant to be walked through and, theoretically, they will detect any metal objects that pass
through them.The simplest form of a metal detector consists of an oscillator producing an
alternating current that passes through a coil producing an alternating magnetic field. If a piece
of electrically conductive metal is close to the coil, eddy currents will be induced in the metal,
and this produces a magnetic field of its own. Therefore when another coil is used to measure
the magnetic field (acting as a magnetometer),the change in the magnetic field due to the
metallic object can be detected.

For the walk-through metal detector, the generated energy is in the form of a magnetic field.
The interaction of the generated magnetic field with certain types of objects in the portal
region of the detector and the ability to detect this interaction is the basis of operation for
walk-through metal detectors.An objects that are electrically conductive and magnetizable
such as metallic belt buckles, metal buttons, cardiac pacemaker, coins, metal-frame eyeglasses,
hearing aid, jewelry, keys, pens and pencils, shoes with metal arches or supports, metallic
surgical implants, undergarment support metal, metal zippers, and similar items, which would
significantly alter the signal produced are also detected.

2.2.2.5 Closed circuit television (CCTV)

Closed-circuit television (CCTV) is the use of video cameras to transmit a signal to a specific
place, on a limited set of monitors. It differs from broadcast television in that the signal is not
openly transmitted, though it may employ point to point, point to multipoint, or mesh wireless
links. CCTV systems may operate continuously or only as required to monitor a particular event.
A more advanced form of CCTV, utilizing digital video recorders (DVRs), provides recording for
possibly many years, with a variety of quality and performance options and extra features (such
as motion-detection and email alerts). More recently, decentralized IP-based CCTV cameras,
some equipped with megapixel sensors, support recording directly to network-attached storage
devices, or internal flash for completely stand-alone operation. Surveillance of the public using

2.2.3 Air field ground lighting (AGL) and digital control system
This system is concerns about lighting system on the run way which is used to communicate the
pilot and air traffic controller (ATC) in order to take off and landing safely by giving information
to the pilot using the color of lighting mounted on the run way. It is PLC aeronautical ground

21
lighting (AGL) control and monitoring system type that is an integrating system of modern &
proven design.

AGL include the following system

 Approach Threshold Runway End High Elevated Light
 Precision Approach Path Indicator (PAPI)
 Approach High intensity Inset light
 Runway Edge High Intensity Bidirectional Elevated Light.
 Taxiway Edge Medium Intensity Elevated light.
 Microprocessor controlled constant current Regulator(MCCCR)
 Series Transformer.
 Guidance signs.

In its operation 15kv is supplied to step down transformer and we get 400/380v from the
transformer this three phase voltage is supplied to the CCR (constant current regulator) it
controlled by micro controller based device. Every lighting system have their own CCR with
redundancy for reserve, they get supply from their own CCR. One CCR is used for the same type
of lighting system. CCR are not for use of supply only it has many propose, it can detect faults of
the lightening systems with the help of two detectors contained in the CCR.

All lights have their own transformer with different power rating and every transformers are
wired in series one to another.
Taxiway
light
PAPI Inset light

Approach
End light Cross bar
light
light

Fig 9- run way light

2.2.3.1 Approach, Threshold Runway End High intensity Elevated Light

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Electrical supply: Suitable for use in 6.6A airfield lighting circuits, normally supplied from one
100W, 150W or 200W series circuit isolating transformer. Power consumption is 100W, 150W
or 200W depending upon application.

Application Color Lamp power(w) Intensity (cd)

Approach White 150 23700

center line

Approach side row Red 150 7120

Threshold Green 200 10750

Threshold wing bar Green 200 10200

Runway End Red 45 2750

Table 1- Approach, Threshold Runway End High intensity Elevated Light

2.2.3.2 Approach High Intensity Inset Light

Use: as Approach center line, crossbars and side row barrettes.

Electrical power supply:6.6 A through a 300 W isolating transformer installed under the light or
in a separate housing.

23
 Approach center Colo Average intensity(cd)
line r

Approach center line &

crossbar

 0 to 475m White 22940

White 21600
 beyond 475m

Approach side-row Red 6260

Table 2-Approach High Intensity Inset Light

2.2.3.3 Combined Threshold and Runway End High Intensity Inset Light

Use: High intensity threshold and runway end.

Electrical power supply: 6.6A, 300w/100w/200w
Lamps: Three 105w-6.6A cold mirror pre focus halogen 1000hours rated life at full intensity.

Application Color Average Intensity (cd)

1. Threshold Green 11780

2.Runway End L-850D Red 2600

3. Threshold Green 11800

Table 3-Combined Threshold and Runway End High Intensity Inset Light

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2.2.3.4 Precision Approach Path Indicator (PAPI)
The Precision Approach Path Indicator (PAPI) is a light system positioned beside the runway
that consists of two, three, or four boxes of lights that provide a visual indication of an aircraft's
(fixed wing or rotor wing) position on the glide path for the associated runway. The PAPI is
usually located on the left side of the runway and can be seen up to five miles during the day
and twenty miles at night. It has two or four lights installed in a single row instead of far and
near bars that would be characteristic of Visual Approach Slope Indicator (VASI).

Each box of lights is equipped with an optical apparatus that splits light output into two
segments, red and white. Depending on the angle of approach, the lights will appear either red
or white to the pilot. Ideally the total of lights will change from white to half red, moving in
succession from left to right side. The pilot will have reached the normal glide path (usually 3
degrees) when there is an even split in red and white lights. If an aircraft is beneath the glide
path, red lights will outnumber white; if an aircraft is above the glide path, more white lights
are visible.

Principles: The PAPI system consist of a bar of four units, each one of producing a light beam
divided into an upper white and a lower red sector .when roll guidance is not provided by other
visual aids, a bilateral, eight unit system may be used the transition from red to white is very
sharp, not exceeding 3 minutes of arc on the whole beam width.

The units are installed on a line perpendicular to the run way center line and are set in
elevation at varying angles; the difference between adjacent units is 20 minutes of arc. On the
correct approach slope, the pilot will see three units of the same color and only one of the
other color .when the deviation reaches 30 minutes of arc,the four units show the same color.

2.2.3.5 Taxiway Edge Medium intensity elevated light

Taxiway Edge Medium Intensity Elevated Light is used to deli mate the edge of air part
taxiways, holding body’s and aprons. Elevated lights are designed for the lighting of the taxiway
Edges and Apron Edge serving Runway of all categories. The fixture consists of a blue prism and
blue LED mounted on a yellow powder coated cast aluminum lamp housing.

25
Equipment data
Input current 6.6A
Lamp 30w/6.6A -EXL-quartz
Rated lamp life 1000hrs
Temp range of illumination -50C (-67F) to +55C (+1314F)
Humidity up to 100%

2.2.3.6 Microprocessor Controlled Constant Current Regulator (MCR)

Type:MCCR 2.5KVA to 30KVA J-Bus remote control

Use: The ADB MCR is a microprocessor controlled constant current Regulator specially designs
for the supply of air port lighting series loop at varies intensity level.

Components
 Auxiliary fuses
 Dual in/out terminals
 Thyristor pack
 Thyristor trigger and contactor on/off control PCB
 2-pole contactor
 Auxiliary supply transformer
 Plugs P2 and P7 for the Control Module
 Input current transformer

Electrical power supply

Rated power 2.5/4/5/7.5/10/12.5/20/25/30KVA
Rated input voltage 220/230/240/380/400/415 v
Rated frequency 50/60Hz
Series circuit current stand 6.6A also 20A for 25 and 30KVA

Operating principle: The MCR's operating principle is based on back to back coupled thyristors
controlling the supply voltage to the output transformer. A comparator determines the
thyristor firing angle to adjust the output current to a reference value. The reference value
varies with the selected brightness step.
The regulator consists of three main components:

26
 1) A power module
2) A control module
3) An output transformer

2.2.3.7 Series Transformer

Isolation transformers are used by airports worldwide to isolate high operating voltage for
constant operation of approach lighting used on airport runways. Its primary and secondary
winding are made of enameled copper wire & are completely separated from each other. This
is particularly important with required to the safety of the operating personnel. There is neither
direct contact nor a creeping path b/n the high voltage primary winding & the secondary
Winding.

Electrical characteristics
Power rating 30, 45, 65, 100, 150, 200& 300
Frequency 50/60 Hz
Primary current 6.6A
Secondary current 6.6A
Max primary service voltage 500v
Max secondary service voltage 600v

2.3 work flow in section

As mentioned before, this company starts its service from entrance and continues up to
boarding to aircraft. Therefore the work flow diagram is as shown bellow.

Waiting area
Walk through metal Passengers
Passengers
detector

Entrance (sliding door) Check in desk

X-ray machine Baggages Feeder conveyor

Baggages

Collector conveyor
Explosive detector machine
Carousel

Aircraft
27
Boarding bridge
Fig 10- block diagram work flow in section

2.4 Executed work

In electromechanical system section, different electrical equipments used in baggage handling

system, passengers boarding bridge system, escalators, elevators and automatic sliding door
systems are disassembled, checked and assembled. Docking the bridge to plane also executed.
Some failed equipments such as photo sensor, IC and others are also changed. In security
screening and detection section also different works such as assembling, disassembling,
baggage screening and changing failed section of the system such us power control board (PCB)
are executed. Additionally in Airfield ground lighting section the works such as insulation testing
by using megger, testing, stopping and starting constant current regulator (CCR), runway light
installation, changing failed separate transformer of each light etc are executed.

2.5 Procedures for the work executed in each section

In each section procedures followed are similar. Before performing each task we discuss on
safety with all workers in that sections.
After discussing on safety we introduced how things are performed. For instance what are
equipments found in each shop, what is their use, how we work on them, what is their principle
of operation etc. After being informed all these by observing and asking we participated in

28
performing work on equipment with technicians. Then after we have tried to perform some
works like starting, stopping, assembling, disassembling and checking with technicians.

2.6 Challenges we faced

We have faced certain problems during our four months staying in Addis Ababa Bole
International Airport.

During the apparent ship our challenges were: -

o It is too hard to live due to Financial problem.

o There is no separation of stream (focus area) to ask some questions, especially
no man power who specialized in control engineering.
o Some of the equipment in the company hasno manual and some of them has
very old manual so it is difficult to get information about them.
o We did not learn the theoretical knowledge and application of PLC, but almost
many control parts of the company works by using plc system.
o When any failure is happen in passenger boarding bridges, we can get the failure
by finding the place where the fail is occurred. This finding kills many times and
the bridge stop working for long time until the error is gotten.
o Escalators are run always sat the same speed,evenif there is a passenger or not.
Because of this reason the system wastesmuch energy without any use.
o There is the problem in Insulation Test in Air lighting system;When phase contact
with ground the resistance will be increase, so at this case the desired current
can’t reached at load .This can affect controlling of the current and voltage,in
another meaning the illumination of the lamp can be affected or can’t give
appropriate illumination .At this case The pilot can’t signify the light easily. To
solve this problem a Technician takes insulation test with megger test. The
megger test is tired and time killing system.
o They have not detector system when a plane takes off or land on Runway that
affect plane safety as well as a man pass the Runway during takeoff or landing
plane.
o The whole system of airfield ground light system has not automation room;
when one device defective we can’t easily seethat effect to get device defective

29
 place accurately that is headache for Technician to get exact defective part. It
also takes long time for searching problem a defective system.

2.7 Measures we have taken

As much as possible we have engaged with workers during work and observed the procedures
they took, asking them about the operation of the system and then involving into the task. We
have used internet a lot to understand the function, operation and internal parts of the plc. By
coming in times other than work time we were trying to improve our practical skill on plc. Also
the company’s supervisor was giving us a lecture on concepts which were new for most of the
student and we got idea that we can solve the real world problem & maintain some failed
machines by the knowledge we get both from the company and school.

CHAPTER THREE
CHALLENGE FACED OVERCOMING PROJECT

3.1 Objective

Objectives of the project are:

 To solve the problem of the company faced in power wastage.
 To reduce power wastage caused due to escalator running without considering the
absence of the passenger.

30
  Change the system’s stop and start mechanism from manual to automatically.
 To control running duration of the escalator.

3.2 Introduction

Escalators are common in airport now a day. Its core component is drive motor. Therefore
controlling the motor (drive unit) is in another hand controlling the overall escalator’s
operation. Controlling the running time of the drive motor is the basic aim of this project. To do
this 555 timer and two photo sensors are used. Both photo sensors are built at its top or
bottom level to detect the passengers to start (activate) the system. The 555 timer is used to
stop systems after adjusted time interval. Therefore this project aimed to control the escalator
automatically with considering the absence and presence of passengers.

3.3 Components used

 Motor
 Cyclo-converter
 555 timers
 Photo sensors
 Contactors.
 Resistance
 Capacitance

Cyclo-converter: is basically ac to ac power converters where the alternating voltage at supply

frequency is converted directly to a lower frequency without going through any intermediate dc
power conversion stage. It is used for the speed control of motors, constant frequency power
supplies, controllable reactive power supply for an ac system and induction heating system,
VSCF (variable frequency input and constant frequency output) generation. So in our case, it is
used as a variable frequency variable speed drives for AC machines. The input of the cyclo-
converter is connected to a power supply with fixed frequency and the machine to be driven is
connected to the output of the cyclo-converter. Since in induction and synchronous motors the
speed is directly proportional to the supply frequency, the speed can be effectively controlled
by controlling the input frequency.

Generally the speed (revolution per minute) of the motor is calculated by:
RPM= 120f

31
 P
Where RPM- revolution per minute
f- Frequency
p- Pole
So by varying the value of frequency we can vary the speed of the motors.

Fig 11- circuit of Cyclo-converter

555 timer: is a highly stable circuit capable of functioning as an accurate time-delay generator
and as a free running multivibrator. When used as an oscillator the frequency and duty cycle
are accurately controlled by only two external components, a resistor (R) and a capacitor (C).

A Mono stable timer Circuit produces one pulse of a set length in response to a trigger input
such as a push button. The output of the circuit stays in the low state until there is a trigger
input. This type of circuit is ideal for use in a "push to operate" system we can push a button to
start a model's mechanism moving, and the mechanism will automatically switch off after a set
time. 

The delay period, the time that the output is high, in seconds is given by:
T = 1.1 x C1 x R
Where R is in Mega ohm and

32
C is in microfarads.
In our project we assume that the delay period (the time that the escalators take to rotate half
circle) is twenty seconds and resistance R is 1.6 Mega ohm. Starting from our assumption the
capacitor C1 can be calculated that:
C1 = 20 sec = 11.6 microfarads.
1.1x1.6 Mohm
So the capacitor C1 and resistance R are used to control the timing interval. In most 555 circuits,
control pin is simply connected to ground usually through a small capacitor. Therefore we
connect this pin to ground through capacitor C2 which equal to 0.01microfarads. The purpose of
this capacitor is to level out any fluctuations in the supply voltage that might affect the
operation of the timer.
Vcc

U1
8

4 3
VCC

R Q

DC
7 R
1.6 Mohm
5
CV
GND

2 6
TR TH

C1
C2
1

555 11.6 microF

0.01 microF Timer

Fig 12- designed 555 timers

Photoelectric sensor: A photoelectric sensor, or photo eye, is a device used to detect the
distance, absence, or presence of an object by using a light transmitter, often infrared, and
a photoelectric receiver. There are three different functional types: opposed (through beam),
retro-reflective, and proximity-sensing (diffused).

33
A retroreflective arrangement places the transmitter and receiver at the same location and uses a
reflector to bounce the light beam back from the transmitter to the receiver. An object is sensed
when the beam is interrupted and fails to reach the receiver.A proximity-sensing (diffused)
arrangement is one in which the transmitted radiation must reflect off the object in order to reach
the receiver. In this mode, an object is detected when the receiver sees the transmitted source
rather than when it fails to see it.
The one used in this project is an opposed (through beam) arrangement which consists of a
receiver located within the line-of-sight of the transmitter. In this mode, an object is detected
when the light beam is blocked from getting to the receiver from the transmitter. There this
sensor detects the passengers when they inter between transmitter and receiver which located at
left and right side of the way to the escalator. Then its output is sent to the motor to start at
expected speed.

3.4 Working principle

The project we think is just to overcome the problem of wasting energy of escalator without
use.In this company there are around six escalators. Those escalators are operate (run) 24
hours without consideration of presence of users (passengers). So we think that the escalators
must be operate or run only when there is users to pass from floor to floor of the building. In
our project we use photo sensors to start the escalators and timers to stop the system.
Additionally there is emergency button to stop the overall system at emergency time.
There are two photo sensors to start the system. The first photo sensor detect the passengers
from specific distance and send comands to the motor to start at sleep mode with specific
speed. After the passengers pass the first photo sensor, the second photo sensor detect the
passengers and send the command to the motor to start at run mode that means the motors
start runing at normal speed. In our project we think that the escalator takes twenty seconds to
take passengrs from floor to floor. Therefore the timer start counting sudenly after the second
photo senser detect the passengers and stop the motors after twenty seconds. So the system
will stay in stop up to the sensors detect the image. The first photo sensor (the sensor used to
start the system at sleep mode) is used only at starting. That means after the sytem start
operating, the detection of the first photo sensor is not chnges the condition of the system. But
every and each detection of the second photo sensor (the sensor used to start system at
normal speed) will change the delay time by twenty seconds. This will make the system to stay
in running for additional twenty seconds for each detection of the sensor. So the system stay in
runing for additional twenty seconds when the other passenger board on the escalators before
the first passenger will not leave the escalators.

34
 Power supply

Cyclo-converter

Motor start at sleep mode Motor start at run

Photo sensor 1 Photo sensor 2
mode Motor stop

555 timer

Fig 13- block diagram of the system

3.5 Control system

The control circuit of our system is as follows. We use contactors, control buttons and others to
control the system. When the first sensor detects the passengers, sleep mode starter (SMS) will
become closed and contactor C1 becomes closed. But contactor C2 remain open. Therefore the
power supplied will reach the motor by passing through Cyclo-converter which allow the motor
to run at sleep mode by varying supply frequency. When the second sensor detects the
passenger, run mode starter (RMS) will become closed which means contactor C 2 become
closed. This cause that the supplied power is reaches the motor directly without variation in
frequency. So at this moment the motor is run at normal speed.

35
Fig 14-control circuit of the system

3.6. Discussion

This project modify some parts and operation mechanism of the exist system. The system exist
runs 24 hours a day without considering the presence and absence of the users. Therefore it
run without use around four o’clock daily which result in high power wastage. Additionally, the
operation of system is start and stops manually without at emergency and fault time in which
the system stops automatically. But in modified system, its operation is start and stop
automatically depending on presence and absence of the users. And also this system can
minimize power wastage. Therefore the modified system can reduce the power that the system
exists used by around 16 percent in average with in 24 hour.

36
3.7 Conclusion

Generally, the escalator that starts and stops automatically with considering the users is
suitable and good system to save power. This system is controlled by the working principle of
the controller components used in design. When the passengers come, the first photo sensor
unit sensing the passenger and sends its output to motor to start it in sleep mode. Then as soon
as the passenger reach at second sensor unit it sense and send its output to the 555 timer and
motor at the same time. At this moment the motor start running at full speed and the timers
start counting. After the time adjusted end the system will stop automatically. Therefore the
motor is controlled to start and stop the system depend on the presence and absence of the
users which minimize power wastage.

37
 CHAPTER FOUR

BENEFITS WE HAVE GAINED FROM INTERNSHIP EXPERIENCE

From internship many experiences are gained when what theoretically learned is brought to
practical one. Therefore intern ship enables students comparing theoretical knowledge with
practical world. Generally benefits gained from internship can be in terms of:
 Improving practical skills
 Upgrading theoretical knowledge
 Improving interpersonal communication skills
 Improving team playing skills
 Improving leader ship skills
 Understanding the work ethics
 Improving entrepreneur ship skills.

4.1. Improving Practical skills

We have got a lot of practical experience while we were trying to troubleshoot and in
maintaining during systems come across problem. Also we have got an opportunity to work on
equipments which we only know theoretically those special electronics components, electrical
machinery and some other equipment which we were not able to see and work on them in our
regular laboratory session.

4.2. Upgrading Theoretical knowledge

While assignment is given to us from our supervisor and other staff in the factory, we look
around for some materials and manuals as reference which gave us the opportunity to study

38
different books and other materials. Additionally what we got from technicians in the company
by asking them about different electrical equipment is also upgrade our theoretical knowledge.

4.3. Improving interpersonal communication

We have got different ways of communicating with different people according to their way they
like to communicate with others

Since factory staffs are responsible for what happens to the system during operation or during
maintenance, we need to convince them what we are going to do before doing anything. So
this makes us to get into trying to communicate them that help us to improve us our
communication skill.

4.4. Improving Team playing skills

We usually work in a team with at least one responsible person assigned by our supervisor
which forced us to spend much time in a team.

Most of the time while we are trying to troubleshoot we discuss in team to provide solution to
a give problem that also contribute to us to work in team and also increase our interpersonal
communication skill. So team work gave us the opportunity to share what we know with each
other and also gave us opportunity to gain a lot of theoretical and practical knowledge from
staffs on the factory and also from students from another university.

4.5. Improving Leadership skill

Our ability to lead is Improved as we sometimes given an opportunity to lead troubleshooting a
given problem with each other and sometimes with electricians. So our leadership skill is
improved which forced us to act responsibly.

4.6. Understanding work ethics

Internship program helped us to understanding work ethics such as;

 Strictly following rule and regulation of the factory.

 Availing ourselves on time.
 Give all cares for the staff while communicating.
 Handling all equipments in right way not to damage the nature of the equipments and
miss-management of resources.

39
4.7. Improving entrepreneur ship skills
Internship practice can be also improving entrepreneur ship skills. So our skill is improved in terms of
taking risk for all our works.

In addition to those mentioned benefits, internship is used to cause people from different
places know one another and share their experiences.

CHAPTER FIVE
CONCLUSION AND RECOMMENDATION

5.1 Conclusion
Generally in doing our internship we observe different objects those are facilitating in airport.
We see how they operate, for which purpose they use and their components with their
features. And also we observe the process over take in this transportation system from entering
to the building up to boarding to the air craft. This process is the step that the passengers and
their baggage are passing through to reach to the aircraft. Additionally we observe the facilities
and process on the run way for the pilot in order to take off and landing of aircraft safely.

40
5.2 Recommendation
In doing our internship from starting day up to now we gate different knowledge and also we
face different failure (problems). So let as recommend them.

 As we try to mention above in the company there are many machines those have an old
manual and also those have no manual. So it is difficult to understand the circuit and
operation of the system. It is also difficult to maintain the system because of the
absence of the manual.We recommend the company to put all machines with their
manual which can give full information about that machine.
 The company has no detector system when a plane takes off or land on Runway that
affect plane safety as well as a man pass the Runway during takeoff or landing plane. So
we recommend the company to use different detection system such as traffic light
which has connection with air traffic control (ATC) system and others.
 Insulation testing system by using megger is very boring and also takes long time to gate
the place of problem. So we recommended that to change the system.

41
  Escalators in the company are run 24 hours even if there are no passengers. Therefore
this is the great power wastages. We recommended the interested body to change this
system.

References
[1] “EDX-2is sys manual” by Smiths Heiman
[2] “Maintenance manual of escalator and elevator” by KONE GmbH, printed in Germany
[3] “TIP management operator’s manual” by an OSI systems company, second revision, February
2005
[4] “Operator manual OP77 HMI S7” by Nederland B.V., Vanderlande Industries
[5] www.google.com
[6] www.eae.gov.et
[7] www.wikepedia.gov.com/wiki/

42
Appendix
AABIA- Addis Ababa Bole International Airport
AGL- Airfield ground lighting
ATC- Airfield traffic controller
CCTV- Closed circuit television
EAE- Ethiopian Airport Enterprise
EDS - Explosive detection system

43
EDX- Explosive detection x-ray
MIS- Message information system
PCB- Power control board
PLC- Programmable logic control
UPS- Uninterrupted power supply

44