Anschluss

Various organizations of the air traffic

To ensure these services, an organization (control tower, centers on the way…) is set up. There are several types. According to the type of traffic, various organizations ensure the air traffic control:

the Centres on the way of the aerial navigation CRNA) are charged to ensure the services of the air traffic for the benefit of the aircraft in cruising (except proximity of aerodrome). For example, there exist 5 regional control centers (also called centers on the way) in France which are distributed the supply of the monitoring service on all the French territory.
the control centers of approach (APP) are charged to ensure the services of the air traffic the accesses of an aerodrome, in a control field whose size is variable. The controllers are generally located in the watchtower of a tower of control, or in an especially arranged room radar.

the control centers of aerodrome (TWR for Tower or control tower) are charged to ensure the services of the air traffic in a restricted zone (about ten kilometers) around an aerodrome. Their principal attribution is the management of the landing strip. The service is rendered since the watchtower of a tower of control.

These organizations were differentiated because required competences, applicable rules, and average the techniques necessary are not the same ones. A control center on the way requires a Radar, while the principal tool in control of aerodrome is the sight. In approach, all the planes want to go to the same place: the track, one has a phenomenon " thus; of entonnoir". On the way, the planes have all of the sources and different destinations, the problems thus for much are scattered and random. These differences, and others, have conduit has this classification.

There also exists of other organizations which are called " contrôle" by abuses language, but which do not provide the monitoring service, just the services of information and alarm. These organizations are:

MADE: Flight Information Service. They are organizations Co-established with a control center on the way or an approach. They render the services of information of flight and alarm in a space not controlled.

AFIS : Aerodrome Flight Information Service (service of information of flight on aerodrome), which replaces the control of aerodrome in an aerodrome not controlled by ensuring the services of information and alarm. Agent AFIS has, contrary to an air traffic controller, no responsibility and cannot give any instruction to the pilots. The latter are entirely responsible for their safety.

Existence of control in a given zone

Air control is always related to an airspace or an aerodrome, which can have the statute of " contrôlé" or " not contrôlé".

In an airspace

All the airspace is by defect not controlled. In this airspace, one created then where it is necessary controlled airspace. The more there is commercial traffic and the more constraining the class of the airspace controlled is.

Thus the existence of an organization of control is related to the existence of an airspace, and vice versa. Control does not exist that if there is a space, and the competence of the organization of control is limited to this space. In the same way, an airspace exists only in the schedules of permanence of the organization which of it is charged. Certain aerodromes for example close of night, in these cases there their space is generally of class G (not controlled) for this period.

This is valid for all the spaces managed by any organization (regional, approach) or controls aerodrome (TWR).

On an aerodrome

An aerodrome is just described as " contrôlé" or " not contrôlé". There are no nuances in not returned monitoring service as in spaces.

An organization of control of aerodrome can exist only on one controlled aerodrome. Apart from permanences of the organization of control, the aerodrome becomes not controlled. The zone of competence of control recovers the ground, the landing strip, and the immediately adjacent airspace with the track.

On an aerodrome not controlled, two cases can arise. Either a service AFIS is assured, in which case an agent AFIS in the tower of control ensures the services of information and alarm (an agent AFIS does not make control with the lawful direction of the term), or no permanence is ensured, in which case the pilots make car information, or on a frequency allotted to the aerodrome, or on the " frequency club" 123,5 MHz. In such a case, the pilots discuss between them on the frequency to agree on the orders of passage, and to get informed mutually about their respective positions.

See Control of aerodrome for more details

Tools of the controller

One finds certain elements in all the control centers, whatever the returned service type.

Radiotelefony

The Radiotelefony, usually called " fréquence" or " micro" , is the principal tool of the controllers. Air control uses mainly radiocommunications VHF, but also sometimes, in particular for oceanic control, of the frequencies HF which have a longer range. The soldiers use also the frequencies UHF. The waveband VHF reserved for the voice communication in Aéronautique extends from 118 MHz with 136.975 MHz (as comparison, radio operator FM is emitted between 87.5 and 107.95 MHz, and the Radionavigation Aéronautique uses, inter alia, the band of 108 with 117.975 MHz).

The frequency is the tool which the controller traditionally uses for:

To receive information on behalf of the pilots.
To deliver clearance S (instructions) with the aircraft.

The practical characteristic of the radiotelefony of the civil aviation is to be a unilateral communication: only one station can emit at a given time. If two stations emit at the same time, the frequency is scrambled, and none the speakers are understood.

The exchanges in radiotelefony are codified. All the current messages have a canonical form which must be used. One calls that the Phraséologie. She is studied so that the messages are:

Concise
Clear
Without ambiguity

As example, the new figure decides in English " niner" (with a sound " r" at the end). In French, the figure is expressed " unité" for more clearness. Contrary to the generally accepted ideas, the expression " affirmatif" is prohibited, to avoid confusions. It is replaced by " affirme".

The three most frequent expressions for the assertion are: - Roger : ok, included/understood well - wilco : ( will comply ), I will make what was required - affirm : yes (in answer to a question) It should be noted that these three expressions are common to all the languages.

The Alphabet radio operator international is of application, it allows a better comprehension of each letter by means of comprehensible and pronounceable words the four corners of the sphere.

Lastly, the document collating (readback) is obligatory for the majority of the instructions: it is a question of repeating the instruction (or at least the elements principal) to confirm good comprehension. In certain cases, the controller must still confirm with the word " correct". For example, to authorize a plane on takeoff, the controller will communicate the instruction " to him; cleared for take off" or " authorized with the décollage" , will give the direction and the speed of the wind and the number of the track. The pilot must repeat the instruction and, if necessary, the track in service.

The communications are recorded and preserved during in general a month. It is strictly interdict to communicate on a frequency of aviation without being holder of a license of restricted radiotelefony (allotted, inter alia, with the air-traffic controllers, the pilots and the ground personnel which is brought to move on the Taxiway S and tracks).

Very often, in order to obtain the radio license, the candidate must lend oath never not to make share with the outside world of the communications heard on the frequencies. However certain countries legalize the sale and the use of scanners (apparatuses allowing the listening of the frequencies), therefore the secret character of the communications is not guaranteed more.

Notice on the use of the transmitters: many people think that it is not possible to identify a person emitting on a frequency of aviation. However the principal airports are very often equipped with Radiogoniomètre S (also called gonio or homer), which allow at the end of a few seconds of emission, to have information on the source of the signal. This means is useful, inter alia, to locate a lost plane (especially in the absence of radar) and to give him information (QDM) on the relative position of the aerodrome.

Strips

The strips are small “bands of progression” ( strip in English) out of paper on which the relative informations with the flights dealt with by air control are registered.

To each flight thus corresponds of the strips, where the known details of the flight are printed: call sign in radio telephony, road, source, destination, type of aircraft, level of flight or altitude.

The controller uses then this strip to register there the instructions which it gives to the aircraft: changes of course, of altitude or of speed, authorizations of landing or takeoff, schedules of passage of certain points…

Thereafter, the strip is filed and used as proof to invoice the air monitoring service with the airline company.

Certain modern systems replace the paper strips by “electronic strips” posted with the screen.

The radar

As opposed to what one could think, the Radar does not exist in all the control centers. The majority of the small aerodromes are deprived of display screens radar.

Two types of radar are used in the civil aviation:

the primary education Radar, which still is very much used for military air control, because it detects the planes having or not a Transpondeur. In the civilian, it fell in disuse to the profit from the secondary. It is still used on the great approaches, where it is in lining with the secondary radar by safety, and for the radars grounds on the large airports like the Aéroport Roissy-Charles-of-Gaulle, or it is used to follow the displacement of the aircraft and vehicles on the ground.
the secondary Radar is used the most in the civil aviation, which benefits from the identification of the tracks and the visualization only of the relevant flights. This type of radars locates only the planes having a Transpondeur.

The controller uses the radar to render three services, called " services radar" :

Assistance radar: provides to the aircraft relative informations with their position and to the variations compared to their road.
Monitoring radar: use the radar for better knowing the position of the aircraft.
Guidance radar: give courses to the aircraft in order to make them follow a specified trajectory.

These services radar can be assured only with identified aircraft radar. Moreover, certain organizations can ensure only part of the services radar, because of the performances of the systems or the configuration of their airspace. For example, guidance radar is not recommended in class E. In this case, only the monitoring and the assistance radar is provided.

For more information on the use of the radar in practice, to see regional Control and Control of approach

Services of the air traffic

As we saw higher, air control renders several services. We will see these services in detail more.

Monitoring service

The monitoring service is ensured with following aims:

To prevent:

boardings between aircraft
collisions between aircraft and the obstacles

To accelerate and order the air traffic

The most important remainder thus the safety of the flights. The best description of a controller is an guardian angel. It makes sure that nothing will arrive at the aircraft during its flight by external causes (another plane, obstacle), and that it will arrive its destination has as quickly as possible.

For that, control delivers clearance S. It acts of instructions and authorizations to circulate under specific conditions. These instructions can be comparable with orders. The commander of an aircraft can however decide to derogate from it but must justify his decision by a real question of security or of capacity (a too tight turn for its apparatus for example). The non-observance of an instruction of air control can lead to the final suspension of the license of the pilot.

In spite of that, air control is before a whole service with the pilots and very often makes it possible to help of the pilots in difficulty or the young pilots who lost themselves. Generally, the pilots also try to adapt to the traffic and the circumstances (by accepting immediate takeoffs for example), to help the controller to manage flow.

The means which the controller uses to prevent the boardings are the Espacement and the Information of traffic.

spacing consists in sparing between two aircraft a minimal distance, guaranteeing the safety of these two planes.

the information of traffic is accurate information on the position of another aircraft which can approach dangerously. The pilot can not see that a plane approaches, the information of traffic the assistance to be seen, in order to allow the pilot to avoid the conflict aircraft.

The means used to prevent the boardings depends on the Régime of flight and the class of space considered.

The methods used to ensure spacing and to deliver the information of traffic depend on the organizations.

In addition to air control, the airline pilots as well have often an instrument called TCAS (Traffic Collision Avoidance System), kind of embarked radar indicating the relative position of the planes, but also suggesting operations of avoidance by means of a voice of synthesis.

The private planes, them, generally fly in VFR (rules of flight at sight) and must be able to locate the traffic visually.

Small anecdote: the priority on the right exists in the plane! When two planes in flight at sight meet without air control of separation, that coming from right-hand side will pass the first (what justifies the light red on the left wing and green on the right wing). The goings beyond and crossings also exist them, but in rules different from those which one usually knows.

Service of information

The service of information of flight is ensured on all the French territory. In controlled airspace, it is ensured by the monitoring service. In the not controlled airspace, it is ensured by an organization SIV in flight, or AFIS on an aerodrome.

It consists has to deliver with the aircraft the information and opinions necessary to the sure and effective execution of the vol. This information can be (nonexhaustive list):

Weather: conditions weather on a ground, presences of storms…
Information on the traffic (not to be confused with the Information of traffic): information on a known or unknown traffic, according to the elements available, being able to interfere with an aircraft.
State of the assistances to navigation
State of the equipment ground of ground
Amendments of Flight plan
Information on the position, helps with the lost pilots
Others…

Nonaeronautical information can be sometimes delivered, but that remains with the discretion of the controller in place.

Information ON the traffic within the framework of the service of information of flight should not be confused with the information OF traffic within the framework of the monitoring service. The first can be vague and incomplete, according to the elements available. Second is precise and complete, and must be repeated until one of the two aircraft states to see the other. Within the framework of the service of information of flight, this information is a service whose controller discharges if it has time. Second is obligatory.

Service of alarm

The service of alarm is as vast as natural. It consists in meeting all the needs for the planes which are said in distress, or which one can think that they are in distress. This service recovers very varied fields:

If a plane deposited a Flight plan, and that control on arrival received confirmation which it took off well, it must supervise that the plane arrives well at destination at the neighborhoods of the hour envisaged, and throw of research if it is not the case.

If a plane does not answer the radio any more and disappears from the radar, the controller must check if the aircraft had a problem and if it were crushed or posed in urgency. It then starts the helps to seek the wreck and to help the occupants.

If an aircraft is crushed on the track or near the aerodrome, it starts the helps immediately and coordinates their action until the arrival of the reinforcements.

If a pilot announces to have problems with his aircraft likely to block the good progress of the flight, the controller can give him an absolute priority to the landing by drawing aside all the other aircraft.

If the controller knows or suspects that an aircraft is diverted, he prevents the competent authorities and brings to them all the help necessary.

Generally, this service is a legal authorization to carry help by all the means to a pilot in difficulty. Any human being would do it, but the service of alarm gives to the controller a legal justification to delay or divert certain aircraft in order to carry help to another.

Evolution of the tools of the controller

Electronic strips

The limits of the system of strip paper started to appear with the complexification of the display systems radar, in particular the appearance of the net of safeguard. It is about a function which makes it possible to predict the trajectory of the aircraft, and to post an alarm if the system provides that the aircraft will approach dangerously in the next minutes. The controller takes a corrective measure then.

This system is a progress enormous, but present limits. Calculations of trajectories are based only on information radar, and do not take into account the clearances given by the controller. Sometimes, an alarm starts whereas the controller already took measurements to correct it. In this case, in addition to the stress generated by alarm, the controller loses confidence in the system, and is likely to be unaware of alarm later at a time or it was justified. This limit of the system is thus a risk factor, and a study was undertaken to seek the possible solutions. One of these solutions is the electronic strip.

The problem comes owing to the fact that the computer does not have sufficient information to calculate the trajectories in a precise way, on an time interval several minutes. Information that the controller notes on his strips would be very useful for the system to refine its predictions. It is thus necessary that the controller informs his strips, either on paper, but on a computer, there so that the net of safeguard can go to draw information which it needs. The first projects consisted of a horizontal screen where strips are drawn that the controller can fill using a keyboard and of a mouse. Another project is a visualization radar with pull-down menus making it possible to change the course, speed, the altitude of the planes.

However among the controllers, this subject causes mistrust. Indeed the strip paper is regarded as the last recourse when the other tools break down. If visualization radar and the electronic system of strip break down at the same time, the controller loses all his information, and is unable to do his work. Also from a more psychological point of view, the strip was always the tool and the symbol of the controllers, and to be detached some is not easy.

In the control centers where a system without strip exists (Maastricht, Geneva, Roma, Padova, etc.) initial mistrust made place with a good acceptance of the stripless. Information which was available on the strip is easily introduced into the system. Thus the system can update the situation and give alarms if necessary. The division of information between sector is possible contrary to the strip paper which is readable only by the controllers in the vicinity

Link Dated

Created initially to help with the control of the traffic to the top of oceanic spaces, this system is on the way to become a new tool able to replace or assist the radar and to supplement the voice communications. Thanks to special equipment aboard plane, the data of the calculators of edge (position, altitude, speed, weather) are collected, then transmitted to regular intervals by satellite - with the top of the oceans - towards the equipment on the ground. An graphical interface makes it possible to visualize these elements and their update on a screen. The images obtained can even be integrated on the radar screens of last generation (graphic monitor). It is also a question of using an email for the dialogs between pilots and controllers.

Rendered services:

ADS ( Dependant Automatic Monitoring ): Automatic monitoring of the real position of the plane. For the moment one uses mainly the ADS-C (for Contrat). Contracts are drawn up automatically between the ground and the flights so that the data are sent to regular intervals towards air control (e.g.: every 20 minutes). If the plane deviates of its profile of authorized flight (road…), it passes in a tighter mode of monitoring which makes it possible to correct its position quickly. It is not despite everything step a replacement of a traditional radar, mainly because of the time between the updates. This system is in service currently in many oceanic areas, for example with the top of the Pacifique between the FIR of the New Zealand, of Tahiti and that of Oakland to the the United States.

The future, it is the ADS-B (Broadcast: diffusion). There, the times of sending of information by the flights will be very short and will allow an heightened surveillance, identical to that of a traditional radar. This system is in the course of homologation by ICAO. The Australia already jointly tests it with a radar system to be able to use it with the top of the semi-desert zones where the installation of radars is either too expensive or impossible. The France soon will equip the zone with the Meeting and could then extend this system to all the zones impossible to equip out of radar (Polynesian archipelagoes, Guyana, etc).

CPDLC ( Control-Pile Dated Link Communications ): In addition to automatic the monitoring part reserved for the ADS, the second contribution of DATED LINK is the possibility of communication between the pilots and the controllers by a mail system. The improvement is spectacular particularly in the transoceanic zones, where only HF is usable. These dialogs are codified for safety reasons: messages préformatés with passage of parameters (ex: authorization to go up or go down to such or such level from flight), with procedures of looping to make sure that information indeed was sent, received and followed.

Still let us quote the " monitoring enrichie" or CAPE ( Controller Access Parameters ) which is " implemented in continental Europe using radars known as " S" mode;. The systems edge will automatically send precise information of monitoring such as: the magnetic course, the rate of rise, speed indicated… This information becoming available for the air-traffic controllers, the monitoring of the flights becomes finer and the communication official reduced between pilots and controllers.

See too

Internal bonds

Airspace
Phraseology
Management of the air traffic
Control system automated of the air traffic
Regulation of the Air traffic
Head office of the civil aviation
ICAO
EUROCONTROL
air Monitoring services in the world: VOR Federal Canada, Aviation Administration (the United States)

Sources

RCA 1 - Definitions
RCA 2 - Services of the air traffic

External bonds

rudiments of air control
site made by an air-traffic controller
French military air traffic
Site of the professional association of the French air-traffic controllers
Site of the European organization for the air safety (EUROCONTROL)
Site of the public limit company skyguide: air control in Switzerland

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