Categories for Aviation



Aircrafts throughout their journeys need to be in contact with air traffic controllers. Long haul ocean crossing flights are increasing steadily every year due to growing demands. The increasing air traffic over the ocean is a serious concern for the controllers where the aircrafts are beyond the eye of the radar and ground stations that track their motion in air. The present communication between the cockpit and the controller is a high frequency radio communication where the position of the aircraft is sent to the air traffic controller through a third party radio operator who acts as an intermediary between them. Relatively the half duplex nature of the system and the use of a single frequency channel add complexity to the problem.

Though the modern communications is going through an era where graphical interaction systems are being developed, the communication in an oceanic haul is still voice communication.

This project focuses to improve and analyze the performance of data communications in exchanging information between the pilot and the controller in oceanic haul long routes. The controller pilot data link communications is taken for analysis in its performance in oceanic routes.


Aviation has seen rapid developments. Modern airliners are now heavily computerized monsters. They now fly higher and faster. The role of an air traffic control is massive in the field of aviation. Since they provide information about other planes approaching nearer to them and maintain spacing between planes. Pilots usually communicate with the controllers using radio aids that allow them to use normal voice communications, which is the very existing problem in the industry of aviation.

Demand for air traffic has been increasing steadily in recent times. Increasing flights to the United States of America have led to the increase in air traffic over the oceans which have also intensified the job of the air controllers. With Nearly hundreds of carriers crossing the Atlantic every day, the responsibility of the air traffic control are huge, because they are the only point of reference to a pilot for navigating and knowing information about the traffic prevailing around him. The Traditional HF voice communication system has drawbacks which limits the points of communication between a pilot and an air traffic controller. Call sign confusion, interference and many more factors are hurdles to a good ground to air communications.

Effective communication management is primary concern in developing co-operative multi user interaction systems. Each individual agent must know what, when and how to communicate. Effective Utilization of shared communication resources also should also be taken in to account, when there is limited resource available. This needs more attention when the demand exceeds the capacity of the system, and a priority is required

This project focuses on how to improve communication between them, taking in to account various parameters that affect the transmission in a high frequency radio communication. Apart from, the attempt to replace traditional voice communication, to a text based communication using CPDLC (Controller Pilot Data Link Communication) in an oceanic haul is also developed,that would be a base to the future aviation researches .


The main idea is to achieve data link communication in a oceanic haul where there are no radar coverages and grond station contacts.This research was carried out in past ,over few years back.The CPDLC is a continuously on-going research project.Some of the old papers are still being researches to achieve text based information exchanges through datalink commnications.However due to the advent of growth in technology each and every day,advances in research also take a new shape than and there. This has motivated this project to evaluate the performance issues of applications in the aeronautical telecommunication networks ,which is the backbone network in aviation .

Aims and Objectives :

This thesis aims to :

To develop a robust and reliable communication model using adhoc systems

Research the various performance issues in using the ATN application CPDLC in long haul routes.

The main objectives of this project is to

Reduce the work load of the air traffic controllers by developing text data communications using adhoc networks

Reduce workload for pilots

Prevent congestion of air traffic

Preventing air accidents due to misinterpretation of communications from the controller

Research Methodology:

The background for this thesis includes a lot of introduction and information about how ground to air communications take place.In order to review the present standards of communication,to analyze their nature and also to understand its properties ,a very intense search has been made and during this phase ,references to various technical publications ,articles expert opinions were read and references from various international organizations like ICAO and Eurocontrol were taken up to write this thesis.After careful analysis, performance analyziz was made and implementing text based communication was studied.The next part of this project will discuss all necessary things needed to understand this thesis.

Literature survey :

The History of communications in aviation is vast .We would be discussing only the current developments in modern technology and reviewing some of the applications developed in relations to this thesis.

The standards in Aviation are monitored by certain governing bodies that are responsible for the safety and security of the air transport.The International Civil Aviation Organisation (ICAO) is the major governing body and specialized agengy of the United Nations for standard and recommended procedures in civil aviation.

Aeronautical telecommunication Network:

ICAO having endorsed a proposal for the future communications in aviation that uses digital datalinks to supplement voice communication to provide a good and reliable communication,has led to the development of Aeronautical telecommunication network.It is an international infrastructure that manages digital data transfer between the aircraft and the air traffic control.In fact it is a dedicated network for aviation to provide seamless ground to air as well as ground to ground communication for the aircrafts.It is designed to support the increasing air traffic due to increasing demands.

Development Of ATN:

Air traffic management needed enhancements due to its rapid increase in traffic .as a result a single controller cannot handle such a large amount of traffic .Hence the concept of distributed traffic handling were followed by the controllers to handle the rising amount of traffic.Efforts were also taken to automate traffic handling.When critical analysis were made regarding the automation of traffic,it became apparent that air traffic automation requires more exchange of computer to computer data interchange that included transfers between aircraft and ground computers.Apart from that automation also required infrastructures that need to be integrated with aircraft and ground stations.The real automation of this air traffic could be possible only data computers rather than being independent processors were also a networking peers with their respective ground stations.These operational objectives when combined together led to a dedicated forming of a complete network exclusively for the field of aviation,that came to be known as the Aeronautical telecommunications network.

Data communications have been deployed both(air to ground and ground to ground ) for many years not only for air traffic management but also for administrative and ground operations.Besides the aeronautical telecommunications support a wide environment where tcket sales,crew duty rotas,weather forecasts are all done.Certain standards and protocols are used. The international air transport associationhave developed a set of OSI profiles called the aeronautical OSI profile,that can be used over the ATN.

Benefits of ATN over the traditional networks:

The ATN has scored over the traditional voice communications with a number of advantages that would make air travel more safe and secure.the following are some of the advantages over which

Are described below:

  1. ATN offers more clarity in communications.As a result retransmission rate is reduced much and interpretation errors are minimized in a long distance communication
  2. The Communication channel is made use more effieciently to transmit data between the computers rather than usage of channel in voice communication.
  3. It gives increased possibility to connect two end users without knowing their locations in a global data communication network environment.
  4. It minimizes work load for the pilots and controllers ,since a number of preformatted and short text messages are available .These standard message are very well known to the pilots.These standards are globally fixed and they mean the same everywhere in world.Hence communication becomes easy ,eliminating misinterpretation errors completey.
  5. The multitude for accommodation of various ground systems like ATSC,AOC,AAC,APC are easily done using ATN.
  6. ATN provides a unique solution to satisfy a wide range of data communications therby providing much ease and effiecient useage of the available resources.
  7. It provides a robust an reliable service to achieve higher availability and integrity that should be need for an improved operational capability.
  8. It provides for timely exchange of ATS information between ground facility improving security and productivity of the entire system

The above reasons justify that the ATN has unique features and its applications are widely important in both ground to air as well us ground to ground communications

The ATN environment:

Operating in a global environment is always a challenge for a network .The ATN is designed to operate in extreme environment considering rough weather and other circumstances.Apart from lot of constraints,the ATN has been designed to operate under four major situations .Each one is termed an element.The first element is to capability of the network to transfer data to an aircraft without the sender knowing where actually the aircraft is, in other words hidden identity.This network mobility is essentially the powerful feature of the Aeronautical telecommncation network.The next element is to use the available multiple links installed in aircraft simultaneously.In this case the specification of the cost,link and speed preferences are advised b the applications that ATN uses when forwarding the data to an air borne system.It is these preferences that determine which link to be chosen to send and receive data over the other available links.The third element is to accommodate all available low bandwidth links both grond and airlinks in this case.These links are normally used to compress the data to be sent.The last element is the standardization of the applications and all services used by the ATN so that they remain the same throughout the world and do not cause further confusion in supporting applications.

The ATN Mobility:

An important feature in network is that all the other end users must know the availability of the datalinks so that congestion can be reduced.Hence it is necessary in a network to let to know the end users about the links and the multiple paths that reach all the aircraft airborne.Broadcasts in a network can lead to a serious problem of flooding. Hence inorder to satisfy network mobility the ATN designers have stipulated a concept called the backbone routing technology.This effiecient technology restricts the broadcasting of information to avoid flooding but at the same time allows the ground system to send information about the availability of the links and other information to the nearest aircraft that are with ints reach. This simple figure would easily demonstrate the backbone routing implementation.

The router r0 is the aircraft router that is airborne.Now when it is necessary to communicate with the router R7 .the ground router has to update all the backbone routers that the aircraft is aavailable for contact.It is also noted that only the routers in home domain are updated and all the others remain unnoticed.Hence considering this situation R1 R2 R 3 are updated and the others are left unnoticed .. Hence routers not in home domain do not know what is happening. This helps to avoid flooding .

The squares in the figure represent applications used by the ATN. The CPDLC application of the ATN is discussed in the later chapters as how messages are transferred.Here application H1 when needs to communicate with aircraft airborne,has the router R8 in the home.R 8 does not know any information about the aircraft,so it forwards to the nearsest backbone router R2.R2 knows the information about the aircraft hence it sends the data to R7 through R1. Thus data traverses.In similar case, application H2 needing to communicate sends the data to R16,From there the backbone router R5 takes over.But R5 does not have any information about the aircraft hence instead of forwarding the packet to R5 it sends to R4 and then the same process takes place. Both the aircraft and the ground routers at the ground station communicate using a protocol called inter domain routing protocol which forms the basis of this inter domain routing.This is the protocol that redistributes data over the entire network without causing flooding and thereby enabling all the communication .

Now there is yet another to note in this backbone routing. Preference based routing is necessary to allow multiple paths in a network to be available simultaneously.Some applications may require quality of service for cost and safety for performance isues.In such cases it is required to route over the other available in this considered case,aircraft router has both VHF and satellite conection .In case if the VHF is not available then a satellite connection is used to transfer data . accordingly the aircraft router R9 will take its turn to send information through the router R4 which is in ground .all entries are stored in packets by the routers they pass through.By this the packets can be examined by the other router for the shortest path to be taken to the destined aircraft it should be sent.Thus the mobility of the ATN works,adding more reliability to the communication system .


As specifeied earlier the design of ATN is designated to accommodate the low bandwidth froundlinks to the network.Accordingly,the throughput for the groundlnks to operate in ATN is expected to operate in a low bandwidth than the available system today.Hence a compression methodology has to be used for thi purpose.The present VDL2 comunication used in aeronautical communication a channel that can transfer 32 k bits / second is shared by multiple aircraft using the carrier sense multiple access method.It is a notable feature that ATN has let also multiple compressions to occur in its routers .The rate of compression is not a fixed one.It is determined when an aircraft enters the region of an ATN router .An open system interconnection network connectionless protocol is used for this kind of purposes.It reduces hundred bytes of header information to six btes.Another technique used to compress the header is the deflate technique.A deflate algorithm uses the similar kind of mechanisms used by the ZIP used in compressing text files.It compresses both the header and the data units available to the aircraft .this way by compressing the data units,low bandwidth channels are made use by the ATN effieciently.


The standardization of ATN by the international civl aviation organisatio has led to the development of four applications.These four applications are of more significance in the aviation industry since they help in navigation of aircrafts when air borne .These applications are

  1. Context Management
  2. Automatic dependent surveillance system
  3. Controler pilot data link communications
  4. Digital-Inflight information system

The digital inflight information system is used to get updates from the ground sation required for the flight such as weather udates and other traffic conditions in terminal area ehich is essential during landing

The controller pilot data communications is a essential development and this thesis would deal mainly with this application that exactly replaces the voice communications with the data messages to the extent it could do .

The automatic dependent surveillance system is highky essential for the transmission of digital information regarding the position of the aircraft to the radar at the ground station so that automated networks and systems can maintain adequate separation of aircrafts in air.The separation of aircrafts depending up on their size and type is an important consequence in the field of Aviation where it constitutes to the safety of the planes going at higher altitudes .

Context management is another directional service,where specific features could be provided to the aircraft on logging in to that particular air traffic system,associated with the network address of the server at the ground station.Thus aircraft being guided till the terminal control are where the approach controller would take care after with the secondary radars being used for assistance .

These applications would surely contribute to the effective communication between the controllers and the pilots who are air borne.

The functionality of The Aeronautical Telecommunication Network :

The functionality of an aeronautical network seems to be little when compared to that of voice transmission networks,but it offers more robust connectivity and more integrity in communication between two end systems that are either fixed or mobile or even adhoc,taking in to consideration for transition paths and end to end delays.

ATN Components:

Notably ATN supports many Full dupliex communication system. These are some of the supportable forms of the communications

  1. Airline systems and ATS systems
  2. Airline and aircraft systems
  3. ATS and aircraft systems
  4. ATS systems interconnected
  5. Airline syatems inter connected together

Airline systems refer to the maintainence syatems that the airlines deploy such as dispatch deliveries and others whereas aircraft systems refer to the systems actually in aircraft that help to navigate the syatems

The above figure shows the typical environment of an ATN

Subnetworks,Routers and the Endsyatems are the major components that constitute to the building of an ATN.


Subnetworks which form a part of the comuication network. A subnetwok forms the major transferring medium between the sytems in the ATN.They are infact a major component of ATN .Usually packet switching netwrks are the subnetworks used in ATN. A lot of grond as well as air borne systems are equipped with capability of supporting this features in ATN.

Subnetworks can be of two types.

  1. Ground to Ground (Fixed)
  2. Air to Ground (Mobile)

Ground to Ground subnetworks are usually local are networks connecte with in subsytems .It can be the local airport network connected with the ATC to share weather and other advisory informations where there is no controllers employed for certain routes.

Local area networks employed with token ring ,Ethernet FDDIare nowadays used as ground subnetworks

Air to Ground networks are usually wide are networks .They are used when the air craft is air borne and hence communicates with the ATC controllers.Based up on the type of Network the ATN routers adapts itself to transfer the data packets between the adjacent subnetworks.

The various air to ground subnetworks include

  • Very High Frequency Subnetwork
  • Satellite communication
  • Mode S subnetwork
  • HF subnetworks

The HF and MODE S subnetworks are mostly used in short range communications.Mostly short haul flights that travel in the European continents are equipped with instruments that make use of the Mode S Subnetworks.Both the communications and the automatic dependent surveillance for spacing can be achieved with Mode S which is relatively cheap when compared others.

HF Networks are much more similar networks but are used in relatively average haul flights which are in continuous contact with grund stations throughout their journeys with out any oceanic travel.

Satellite communication and VHF networks are the physical transfer mediums used in Long haul oceanic flights .RElativekly costlier for communication but still used in modern days.


The ATN routers play a major role in routing the packets to different subnetworks thus maintaining the integrity of the network.Since the air crafts change their course during their course of flight,the path taken in a network to reach that aircraft must be determined accordingly.It is the routers that decide the traversing of packets at any stage in network.The routing is performed on the basis of class of service the packets request and the availability of the links in the network.

Dynamic routing is also supported by ATN ,allowing each router to update ,due to the changing courses taken overby flight and other failures occurring unexpectedly where an alternate path is chosen.Routers operate at the third layer of the OSI layer according to a set of predefined protocols.The necessary information to route the packet are present in the header of the encapsulated packet that a router that deals with.

Routers in ATN can be broadly classified in to two types .

  1. Intra domain routers (static or dynamic)
  2. Inter domain routers

The intra domain routers are local routers that are used in local domains and are not to global international standards.But the inter domain routers are all set to global international standards and can handle more traffic than inter domain routers .

The ATN routers differ from the Normal routers by certai features that distinguish them.those are listed.

  1. In a ATN router there is a possibility of applying specific policies that enable the supporting of mobile communication providing effiecient air to ground routing
  2. The enhanced security system that ATN adheres to protect the tampering of data.
  3. Use of compression methods to accommodate low bandwidths in air to fround links and other data networks.
  4. Termination procedures and initialization of a new route when an aircraft enters the system or leaves is a major advantage in an ATN

End syatem:

These system integrate the host system with the network.all the application level services are coordinated to the host by these end systems to establish communications with the peer to peer system in network.

They have the capacity to communicate with another subnetworks end systes in order to provide end to end communications to the ATN applictons that handle operations. It is for this purpose they have a seven ;ayered protocol stack that hosts appropriate communication services in support to the applications of the ATN.

The above figure relates the constituent elements of the aeronautical telecommunication networks with the OSI layer protocol stack structures ,that helps in establishing peer to peer commuications with end systems.

ATN domains :

Unlike other networks ATN has also domains that are essential for routing purposes.Each domain may have inter domain router and end systems. To make the routing process simplified the administrations of the adjacent domains may combine together to form a single domain sharing a policy and hence making it single.

Administrative domains are part of ATN where they are managed by a single authority.This administrative domains are either the Civil Aviation Authority ,an Air traffic controller or an international aeronautical communication service provider (IACSP)

A routing domain may have the following characteristics.

  1. All informations regarding the connectivity and quality of the service related with the internal systems are are exchanged without any restrictions.
  2. With in a domain ,selected routes(the common routes to the other systems lying outside the domains ) may be advertised by a BIS router.
  3. These routes advertised by the BIS routers to the other routers that lie outside the domains are controlled by a policy that enforced by the advertising BIS router .

The figure gives an example of an ATN domain

Thus the very basic essentials of a data network that is used to exchange informations was discussed. In next chapters VHF which is used as a physical transfer medium is discussed .

Aircraft Performance and Aviation Management

Briefly discuss about the main objectives of Air Traffic Services?

This information is supported by (,2014) says the objectives of the air traffic services shall be to:

  • Prevent collisions between aircraft
  • Prevent collisions between aircraft on the manoeuvring area and obstructions on that area
  • Expedite and maintain an orderly flow of air traffic;
  • Provide advice and information useful for the safe and efficient conduct of flights
  • Notify appropriate organizations regarding aircraft in need of search and rescue aid, and assist such organizations as required.

Explain how these objectives affect the aircraft movements and ground movements.

This data is supported by (,2014) says Ground controllers must exchange information as necessary for the safe and efficient use of airport runways and movement areas. This may be accomplished via verbal means, flight progress strips, other written information, or automation displays. As a minimum, provide aircraft identification and applicable runway/intersection/taxiway information as follows:

  • Ground control must notify local control when a departing aircraft has been taxied to a runway other than one previously designated as active.
  • Ground control must notify local control of any aircraft taxied to an intersection for takeoff. This notification may be accomplished by verbal means or by flight progress strips.
  • When the runways in use for landing/departing aircraft are not visible from the tower or the aircraft using them are not visible on radar, advise the local/ground controller of the aircraft’s location before releasing the aircraft to the other controller.

Aircraft movements

This information was mentioned in (flyingwithoutfear,2014)

  • When an aircraft starts its journey it first has to get permission to start its engines from a ground controller, then it will have to get permission to push back from its stand from another ground controller.
  • Prior to taxi-ing it will be given instructions to take a particular route to the active runway according to its parking gate position and any other aircraft which are using the same runway.
  • This permission will be given by yet another ground controller. Before the aircraft is given clearance to take off it will have to speak to the controller whose sole job is to give permission to aircraft to take off or land.
  • When airborne, the pilots will change to another frequency and speak to a departure controller who will give permission for the aircraft to climb to a higher altitude.
  • Once clear of other departing and arriving traffic the aircraft will transfer to an airways controller who will give permission for the aircraft to climb to its cruising height.
  • The crew have to ask for permission to leave its cruising height before descending towards its destination. As the aircraft approaches the destination airport, various controllers will be responsible for its safe passage until it lands and parks at its arrival gate.

Analyse the physical appearance of the control tower and its contribution to achieve these objectives and explain about the communication failure procedures.

This data is mentioned in (,n.d) says In the past, Airport Traffic Control Tower (ATCT) siting decisions have been significantly influenced by the upper height limits imposed by terminal procedures (TERPS) and controller opinions. Because tower siting (height and location) affects airport safety and construction costs, the FAA had no means to measure quantitatively the improvement in air traffic controller visibility that can be gained by changing the tower height and location on the airport surface, and there was no required minimum criterion for tower height.

This information is supported by (experimentalaircraft,2014)

Preflight -During preflight make sure that you have the correct frequencies with you: check the AIP, NOTAMs, approach and/or enroute charts. Preflight also means that you need to check communications availability for the airports and the route you plan to use. If not sure then a phone call with your destination will solve that problem, also ask if they accept NORDO (No Radio) aircraft.

Garmin SL40 Aircraft Radio – Radio’s can become complex equipment when they are integrated into Garmin G1000 systems like EFIS. Standalone Icom, Bendix King or Apollo/Garmin radio’s are really easy to control. Having the pilots quick reference manual in your flight bag or with the aircraft documentation or manual can be a big help. It will save the day should you become confused about any function of the radio.

ATC light gun -Some aviation charts depict them: ATC light gun signals. Make sure you know them by heart or carry a copy of their meaning with you. Practice these signals every once in a while.

Frequency change -If contact can not be established after a frequency change, go back to the previous frequency or channel and verify with the controller that you have the correct frequency. This is first thing you must do in this case.

Second radio -If you suspect that your radio has failed and you have a second one, set that frequency in the other radio and try again. When I fly an aircraft with multiple radio’s I plan to use all of them, and during a handover I set the next frequency into the other radio and use that one. This way I always have both radio’s checked and functional. Should I need to switch back, its done within a blink of an eye on the intercom panel.

Squelch setting -A squelch is used to suppress the white noise when no station is transmitting, turn the knob clockwise until the noise just about disappears (on radio’s with an automatic squelch you need to pull or push the volume knob). Sometimes after switching and verifying that you have the correct frequency and that the radio is operating correctly it might be that you are just to far away (or flying too low) for the next station. Its signal strength is just too weak to open the squelch you will hear nothing.

First thing I do is to open up the squelch manually (pull/push the volume knob) and listen to the noise/static and other aircraft and retransmit when able. Chances are that you hear them calling you just above the noise level. By the time you get closer, the signal strength will have improved enough so that you can use the squelch again.

Radio Failure -It will not happen that often but radio’s can fail and having a second on standby will save the day. Should it happen, try pulling the fuse wait a couple of minutes and push it in again. This might reset the radio. Should this fail then and you have only one radio, set 7600 on the transponder and determine if you need to divert to an airport where NORAD aircraft are allowed. It is advisable to call ATC after landing to explain the situation.

Altitude -VHF communications rely on antenna’s to be in line of sight of each other to be able to receive their signals. Should you not hear the other station then climb, if possible, a couple of thousand feet. This will improve the range in which you can contact stations.HF communications rely on radio wave propagation by the Earth’s Ionosphere and line of sight is not so much of an issue here.

Relaying-At times you may find that other, possibly higher flying aircraft, are willing to relay your message to the ground station. Sometimes even without asking, because they can hear you and the ground station and its obvious to them that you can not reach or hear ATC.


Aircraft Transponder – The transponder code for lost communications is 7600 in any mode (A/C/S). Setting this code will ring bells in ATC facilities and you will most definately get their attention! Again, make sure to explain the situation after landing.

Diversion – If all else fails and your destination is a controlled airport where radio communications are mandatory, then by all means divert to an airport where you can land without a radio and have your radio checked by a radio shop before you continue on to your final destination. Overflying the signal area before entering the circuit/pattern is a wise decision at that time.

Describe about the visual signals and their use, colours and effects of the markings. Also identify other markings in the manoeuvring area and their use.

This information was mentioned in (,2012) says A series of green flashes directed at an aircraft means respectively


in flight

on the ground


cleared to land;

cleared to taxi.


return for landing;

cleared for take-off.


return for landing;

cleared to taxi.


cleared to land;

cleared for take-off.

A steady red light directed at an aircraft means


in flight

on the ground


give way to other aircraft and continue circling;



give way to other aircraft and continue circling;

taxi clear of landing area in use.


airport unsafe do not land;

taxi clear of landing area in use.


airport unsafe do not land;


A series of red flashes directed at an aircraft means respectively


in flight

on the ground


airport unsafe, do not land;

taxi clear of landing area in use.


give way to other aircraft and continue circling;



do not land for time being;

return to starting point on airport.


you are in prohibited area, alter course;


A steady green light directed at an aircraft means respectively


in flight

on the ground


cleared to land;

cleared to taxi.


return for landing;

cleared to taxi.


return for landing;

cleared for take-off.


cleared to land;

cleared for take-off.

A flashing white light directed at an aircraft on the manoeuvring area of an airportmeans

  1. stop.
  2. return to starting point on the airport.
  3. cleared to taxi.
  4. taxi clear of landing area in use.

Blinking runway lights advises vehicles and pedestrians to

  1. return to the apron.
  2. vacate the runways immediately.
  3. be aware that an emergency is in progress; continue with caution.
  4. be aware that an emergency is in progress; hold your position.

This information is mentioned in (airservicesaustralia,2013)


  • Runway markings are white(although yellow taxiway centrelines may lead on,lead off, or cross the runway).
  • Taxiway markings are yellow.
  • Markings on aprons and in ramp areas may include other colours(e.g. it is common to mark vehicle roadways in white).

Taxiway marking patterns

ƒIf a marking pattern consists of two or more lines—some of which are solid and

some of which are dashed—these are runway holding position markings.

  • It is always permissible to cross from the dashed side to the solid side.
  • ATC permission is always required to cross from the solid side to the dashed side at an aerodrome with an operating control tower.
  • When instructed to ‘hold short’ always stop before the first solid line of the runway holding point marking as depicted below.


Intermediate Holding Positions

Intermediate holding position markings show a holding position between taxiways. Youwill need to hold at these if ATC direct you to hold short of a particular taxiway.

Aerodrome signs – how to get from here to there safely

Along with aerodrome markings and lights, aerodrome signs are designed to assist you in navigating around an aerodrome.It is essential that you understand the colour coding and meaning of these five types of signs when taxiing on an aerodrome:

1. Location sign:

Identifies the taxiway you are currently located on. It has a yellow inscription on a black background


Mandatory instruction sign:

Identifies the entrance to a runway or critical area, and areas prohibited for use by aircraft. It has a white inscription on a red background. You must obtain a clearance from ATC prior to proceeding past this point


Direction sign:identifies the designations of taxiways leading out of an intersection along with an arrow indicating the approximate direction of turn needed to align the aircraft on that taxiway. They are located before the intersection, normally on the left side and normally with a location sign. It has a black inscription on a yellow background

Destination sign:Identifies with arrows the directions to specific destinations on the airfield (e.g. runways, terminals or airport services). It also has a black inscription on a yellow background

Sign arrays:Grouping of direction signs. Signs are orientated clockwise from left to right. Left turn signs are on the left of the location sign and right turn signs are on the right of the location sign.


Aerodrome lighting

There are many different lighting combinations that may exist on some aerodromes, especially where aircraft operations are conducted in the lower visibility ranges. For taxiing operations around airfields, you should remember:

  • edge lights are white (although on runways fitted with high intensity lighting, the runway edge lights within 600 m from the end of the runway will beyellow.)


  • taxiway edge lights or reflectors are blue


  • taxiway centreline lights or reflectors are green


  • guard lights are flashing yellow lights (either in the pavement or located on the side of the taxiway) and highlight a runway holding point


  • intensity approach lighting (HIAL) is red and white


Communication capabilities of the users and the role of tower controller

This information is supported by (,2014) sat the FAA’s air traffic controllers ensure the safe and efficient flight for about two million aviation passengers per day – or almost one billion people per year. Air traffic controllers safely manage more than 60 million aircraft annually to their destinations.

The U.S. air traffic controller workforce consists of approximately 15,000 dedicated and well-trained men and women working in air traffic control towers, terminal radar approach control centers, and en route control centers managing 30.2 million square miles of airspace.

Air Traffic Control Tower Controllers Work in the glassed-in towers you see at airports. They manage traffic from the airport to a radius of 3 to 30 miles out. They give pilots taxiing and take off instructions, air traffic clearance, and advice based on their own observations and experience. They provide separation between landing and departing aircraft, transfer control of aircraft to the en route center controllers when the aircraft leave their airspace, and receive control of aircraft on flights coming into their airspace.

Terminal Radar Approach Controllers Work in radar rooms, using terminal radar sensors to assist the aircraft until it reaches the edge of the facility’s airspace, usually about 20 to 50 miles from the airport and up to about 17,000 feet, before handing it off to the En Route Center Controllers

En Route Center Controllers Work in 21 centers across the country, in a location away from the airport. You will never see them during the course of your flight, but they will normally direct your aircraft for the bulk of your ride. Controlling traffic usually at or above 17,000 feet, the typical center has responsibility for more than 100,000 square miles of airspace generally extending over a number of states. These controllers give aircraft instructions, air traffic clearances and advice using radar or manual procedures they keep track of the thousands of planes in the sky at any one time. Due to the radar equipment, they work in semi-darkness and guide aircraft on the scope

Reference, (2014) Chapter 3- Airport Traffic Control- Terminal. [Online] Available at: <> Accessed on 2nd July 2014 Page, (2014) Air traffic services. [Online] Available at: <>Accessed on 2nd July 2014 Page

flyingwithoutfear, (2014) air traffic control. [Online] Available at: <>Accessed on 2nd July 2014 Page

experimentalaircraft, (2014) Loss of communication. [Online] Available at: <>Accessed on 2nd July 2014 Page (2012) 2.0 Visual Signals. [Online] Available at:<>Accessed on 2nd July 2014 Page

airservicesaustralia, (2013) 6. Aerodrome markings, signs and lights. [Online] Available at:<>Accessed on 3rd July 2014 Page, (2014) Roles and Responsibilities of Air Traffic Control Facilities. [Online] Available at:<>Accessed on 3rd July 2014 Page