Séparation non radar
A partir du grade 
et programme examen du grade 
et supérieurs
1. Introduction
Cette fiche est dédiée à la séparation non-radar. Dans certains espaces aériens français (La Réunion et Mayotte, Tahiti, Saint-Pierre et Miquelon, et en Nouvelle-Calédonie), dépourvus d'équipements radars, le contrôle est basée principalement sur des espacements en temps, et report de position.
2. Types de séparation
Dans les espaces aériens contrôlés, le contrôleur aérien sépare les aéronefs volant dans un espace donné en les maintenant à des distances suffisantes afin d'éviter les risques de collision.
On distingue 2 types de séparation :
- La séparation horizontale ;
- La séparation verticale.
2.1 Séparation verticale
La séparation verticale est la différence d’altitude minimale nécessaire entre deux appareils volant dans une zone donnée lorsque la distance horizontale est inférieur à celle préconisée. La séparation verticale est obtenue en autorisant les aéronefs à voler à des altitudes/niveaux différents.
En fonction de l’espace aérien au sein du quel l’aéronef évolue, et du régime de vol, la séparation verticale minimale pourra être de 1000 ft ou de 2000 ft.
En espace RVSM cette séparation est de :
- 1 000ft en dessous du FL410 ;
- 2 000ft au-dessus du FL410.
2.1 Séparation horizontale
Il existe deux types de séparation horizontale : latérale ou longitudinale.
La séparation horizontale est la distance minimale qui doit être maintenue entre deux aéronefs dont la séparation verticale n'est pas acquise. La séparation horizontale peut être obtenue en agissant sur les vitesses ou les estimés/HAP.
3. Critères de séparation
2 aéronefs sont considérés séparés si au moins un type de séparation est établi.
4. Perte de séparation
Un contrôleur aérien doit anticiper une éventuelle perte de séparation et donner des instructions à au moins 1 des aéronefs concernés afin de maintenir une séparation supérieure aux minimums.
En-dessous de ces minimum de séparation, on parle alors de perte de séparation.
Le terme "airprox", issu du réel (rapport d’une perte de séparation constatée par un pilote) est souvent employé.
Le contrôleur est responsable de la séparation des aéronefs en contact sous son contrôle vis-à-vis de tous les aéronefs dont il a connaissance (et même si ils ne sont pas tous sous son contrôle). C’est la base de la sécurité partagée par tous.
5. Séparation horizontale
5.1 Séparation latérale
L’espacement latéral doit être appliqué de telle sorte que la distance entre les portions des routes prévues pour lesquelles les aéronefs doivent être espacés latéralement ne soit jamais inférieure à une distance établie pour tenir compte d’inexactitudes de navigation plus une marge spécifiée.
Cette marge est déterminée par l’autorité compétente et inclus dans la séparation latérale.
La séparation latérale est obtenue en exigeant l’exploitation sur des routes différentes ou dans des emplacements géographiques différents.
Si l’aéronef suit la même procédure de vol ou la même route ATS, l’espacement à appliquer ne doit pas être une séparation latérale mais longitudinale. La séparation latérale s’applique lorsque les aéronefs sont sur des routes différentes.
5.1.1 Critères de séparation latérale
Les situations dans lesquelles une séparation latérale peut être appliquée sont :
- Par référence à des emplacements géographiques identiques ou différents (par rapport aux rapports de position qui indiquent bien que les aéronefs se trouvent dans des emplacements géographiques différents) :
- Par l’utilisation d'une aide à la navigation identique entre les aéronefs ou méthode (en exigeant que les aéronefs volent sur des voies spécifiées qui sont séparées par une distance minimale appropriée à l’aide à la navigation ou à la méthode utilisée)
La séparation latérale entre les aéronefs utilisant des aides à la navigation différentes, ou lorsqu’un aéronef utilise un équipement RNAV, doit être établie en veillant à ce que les espaces aériens protégés dérivés pour l’aide(s) à la navigation ou le RNP ne se chevauchent pas.
5.1.2 Minima de séparation latérale
Les minima d’espacement latéral par utilisation de la même aide à la navigation sont :
- VOR : les deux aéronefs sont positionnés sur des radiales qui s’écartent d’au moins 15° et au moins un aéronef se trouve à une distance de 28 km ou 15 NM ou plus de l’installation
- NDB : les deux aéronefs sont établis sur des voies en direction ou à partir du NDB qui divergent d’au moins 30° et au moins un aéronef se trouve à une distance de 28 km ou 15 NM ou plus de l’installation
- Compte à rebours : les deux aéronefs sont établis sur des voies qui divergent d’au moins 45° et au moins un aéronef se trouve à une distance de 28 km ou 15 NM ou plus du point d’intersection de la voie et les deux aéronefs sont établis en partance de l’intersection.
Lateral separation minima for departures and arrivals
Lateral separation of departing and/or arriving aircraft on published adjacent instrument flight procedures will exist under the following conditions:
- Where the distance between RNAV1, Basic RNP1, RNP APCH and/or RNP AR APCH is not less than 13km or 7NM
- Where the protected areas of tracks designed using obstacle clearance criteria do not overlap and provided operational error is considered.
If the aircraft take the same departure or arrival flight procedure, the separation to apply shall not be lateral separation but longitudinal separation.
Lateral separation of aircraft on parallel or non-intersecting tracks
Lateral separation of aircraft on parallel or non-intersecting tracks or ATS routes shall be established in accordance with the following:
- For a minimum spacing between tracks of 50NM or 93km when using a navigational performance of RNAV10 (RNP10) or RNP4
- For a minimum spacing between tracks of 30NM or 55.5km when using a navigational performance of RNP4
Longitudinal separation general
Longitudinal separation shall be applied so that the spacing between the estimated positions of the aircraft being separated is never less than a prescribed minimum.
Longitudinal separation between aircraft following the same or diverging tracks may be maintained by application of speed control, including Mach number technique.
When aircraft are expected to reach minimum separation, speed control shall be applied to ensure that the required separation minimum is maintained.
Definition: same, reciprocal and crossing tracks
Same tracks are same direction tracks or intersecting tracks when angular difference of these both tracks is less than 45° or more than 315°
Reciprocal tracks are opposite direction tracks and intersecting tracks when angular difference of these both tracks is more than 135° or less than 225°
Crossing tracks are intersecting tracks in other conditions than "same track" and "reciprocal track"
Longitudinal separation minima based on time
Aircraft maintaining same level on same track
| Situation | Default minimum separation | Default minimum separation if navigation aids permit frequent determination of position and speed | Default minimum separation in each case the preceding aircraft is maintaining a true airspeed of 37km/h (20kt) or more faster than the succeeding aircraft | Default minimum separation in each case the preceding aircraft is maintaining a true airspeed of 74km/h (40kt) or more faster than the succeeding aircraft |
| Aircraft on same track | 15 minutes | 10 minutes | 5 minutes | 3 minutes |
Aircraft maintaining same level on crossing track
| Situation | Default minimum separation | Default minimum separation if navigation aids permit frequent determination of position and speed |
| Aircraft on crossing track | 15 minutes | 10 minutes |
Aircraft climbing and descending on same track
| Situation | Default minimum separation | Default minimum separation if navigation aids or GNSS permit frequent determination of position and speed | Default minimum separation if level change is commenced within 10 minutes of the time of second aircraft has reported over common point (derived from ground based radio navigation aids or by GNSS) |
| Aircraft on same track | 15 minutes while vertical separation does not exist | 10 minutes while vertical separation does not exist | 5 minutes while vertical separation does not exist |
Note GNSS=GPS navigation
Both figure above: Default minimum separation
Both figures above: Default minimum separation if navigation aids or GNSS permit frequent determination of position and speed
Both figures above: Default minimum separation if level change is commenced within 10 minutes of the time of second aircraft has reported over common point
Aircraft climbing and descending on crossing track
| Situation | Default minimum separation | Default minimum separation if navigation aids permit frequent determination of position and speed |
| Aircraft on crossing track | 15 minutes while vertical separation does not exist | 10 minutes while vertical separation does not exist |
Both figures above: Default minimum separation
Both figures above: Default minimum separation if navigation aids permit frequent determination of position and speed
Aircraft on reciprocal track
When lateral separation is not provided, vertical separation shall be provided for at least 10 minutes prior to and after the time the aircraft are estimated to pass or are estimated to have passed.
Longitudinal separation minima based on distance using DME and/or GNSS
Separation shall be established by maintaining not less than specified distance between aircraft positions as reported by reference to DME in conjunction with other appropriate navigation aids and/or GNSS (GPS).
This type of separation shall be applied between two aircraft using DME, or two aircraft using GNSS, or one aircraft using DME and one aircraft using GNSS. (This is applicable for all sub-chapters hereunder).
Separation is checked by obtaining simultaneous DME and/or GNSS reading from the aircraft at frequent intervals to ensure that the minimum will not be infringed.
Aircraft maintaining same level on same track
| Situation | Default minimum separation | Default minimum separation in each case the preceding aircraft is maintaining a true airspeed of 37km/h (20kt) or more faster than the succeeding aircraft |
| Aircraft on same track | 20 NM\ 37 km | 10 NM\ 19 km |
Aircraft maintaining same level on crossing track
| Situation | Default minimum separation | Default minimum separation in each case the preceding aircraft is maintaining a true airspeed of 37km/h (20kt) or more faster than the succeeding aircraft |
| Aircraft on crossing track | 20 NM\ 37 km | 10 NM\ 19 km |
This longitudinal separation shall also apply at the crossing point of the tracks and when the relative angle between the tracks is less than 90 degrees.
Aircraft climbing and descending on the same track
| Situation | Default minimum separation |
| Aircraft on same track | 19 km or 10 NM while vertical separation does not exist |
Aircraft on reciprocal tracks
Aircraft may be cleared to climb or descend through the levels occupied by other aircraft when it has been positively established that the aircraft have passed each other and are at least 10 NM apart.
Longitudinal separation minima with Mach number technique based on time
When the Mach number separation technique is applied and when aircraft follow the same track or continuously diverging tracks (until some other form of separation is provided):
- Minimum longitudinal separation between turbojet (whether in level, climbing, descending) is 10 minutes or
- Minimum longitudinal separation between turbojet (whether in level, climbing, descending) is between 5 and 9 minutes depending of speed of preceding aircraft given in the table below.
| Preceding aircraft is maintaining a true Mach number greater than the following aircraft | Minimum longitudinal separation using Mach separation technique |
|---|---|
| Preceding aircraft is Mach 0.02 faster than following aircraft | 9 Minutes |
| Preceding aircraft is Mach 0.03 faster than following aircraft | 8 Minutes |
| Preceding aircraft is Mach 0.04 faster than following aircraft | 7 Minutes |
| Preceding aircraft is Mach 0.05 faster than following aircraft | 6 Minutes |
| Preceding aircraft is Mach 0.06 faster than following aircraft | 5 Minutes |
When the 10 minute longitudinal separation minimum with Mach number technique is applied, the preceding aircraft shall maintain a true Mach number equal to or greater than the following aircraft.
Longitudinal separation minima with Mach number technique based on distance RNAV
An 80NM or 150km RNAV distance-based separation minimum with Mach number technique may be used on the same direction track in preplacement of a 10 minutes longitudinal separation with Mach number technique with:
- Each aircraft reports its distance to or from the same common point located on the track
- Separation between aircraft at the same level is checked by obtaining simultaneous RNAV distance readings from the aircraft at frequent intervals to ensure that the minimum will be not infringed
*Separation between aircraft climbing or descending is checked by obtaining simultaneous RNAV distance readings from the aircraft
*In the case of one aircraft climbing or descending, one aircraft maintains level while vertical separation does not exist
In order to require RNAV distance information, position reports should be referenced to a common point ahead of both aircraft.
RNAV distance based separation minima shall not be applied after ATC has received pilot advice indicating navigation equipment deterioration or failure.
When the 80 NM or 150km RNAV longitudinal separation minimum with Mach number technique is applied, the preceding aircraft shall maintain a true Mach number equal to or greater than the following aircraft.
Longitudinal separation minima based on distance using RNAV where RNP is specified
Direct controller-pilot communication shall be maintained while applying distance-based separation minima. Direct controller-pilot communication shall be voice or CPDLC (text mode).
For aircraft cruising, climbing or descending on the same track, the following separation minimum may be used:
- 50 NM or 93km separation minimum and,
- RNP 10 and,
- Direct controller-pilot communication and,
- Procedural position reports and,
- Verification of position at least every 24 minutes
During application of this separation, when an aircraft fails to report its position, the controller shall take action to establish communication. If communication has not been established within 8 minutes, the controller shall take action to apply an alternative form of separation.
Longitudinal separation minima based on distance using RNP RNAV using ADS-C
This chapter is not applicable for the IVAO network as ADS-C is not implemented in our tools.
Consult ICAO 4444 documentation §5.4.2.6.4.1.
Separation of aircraft holding in flight
Except when lateral separation exits in this area, vertical separation shall be applied between aircraft holding in flight and other aircraft (whether arriving, departing and en-route) whenever the other aircraft concerned are within five minutes flying time of the holding area.
Minimum separation between departing aircraft
The following separations are complementary to the longitudinal separation minima specified in this documentation.
1 minute is required if aircraft are to fly on tracks diverging by at least 45° immediately after take-off.
Note that this minimum may be reduced when aircraft are using parallel runways or diverging runways which do not cross approved by local air traffic regulation or parallel runway regulation.
2 minutes are required between take-offs when the preceding aircraft is 40kt or 74km/h (or more) faster than the following aircraft and both aircraft will follow the same track.
5 minutes separation is required while vertical separation does not exist if a departing aircraft will be flown through the level of a preceding departing aircraft and both aircraft will follow the same track
Separation of departing aircraft from arriving aircraft
The following separation shall be applied when take-off clearance is based on the position of an arriving aircraft:
⠀- If an arriving aircraft is making a complete instrument approach, a departing aircraft may take off:
⠀⠀⠀- In any direction until an arriving aircraft has started its procedure turn or base turn leading to final approach
⠀⠀⠀- In a direction which is different by at least 45° from the reciprocal of the direction of approach after the arriving aircraft has started its procedure turn or base turn leading to final approach, provided that the take-off will be made at least 3 minutes before the arriving aircraft is estimated to be over the beginning of the instrument runway.
⠀- If an arriving aircraft is making a straight-in approach, a departing aircraft may take off :
⠀⠀⠀- In any direction until 5 minutes before the arriving aircraft is estimated to be over the instrument runway
⠀⠀⠀- In a direction which is different by at least 45° from the reciprocal of the direction of approach after the arriving aircraft:
⠀- Until 3 minutes before the arriving aircraft is estimated to be over the beginning of the instrument runway, or *Before the arriving aircraft crosses a designated fix on the approach track. (the location of such fix is determined by air traffic control authority).
Wake turbulence separation longitudinal separation
Please consult "wake turbulence separation minima" article.
Clearances to fly maintaining own separation while in VMC
The provision of vertical and/or horizontal separation by an air traffic control unit is not applicable in respect of any specified portion of a flight cleared subject to maintaining own separation and remaining in visual meteorological conditions (VMC).
Note that a VFR flight must remain in visual meteorological conditions at all times. Accordingly, the issuance of a clearance to a VFR flight to fly subject to maintaining own separation and remaining in visual meteorological conditions has no other object than to signify that, for the duration of the clearance, separation from other aircraft by air traffic control is not provided.
An air traffic controller may clear a controlled flight, including departing and arriving flight, operating in airspaces classes D and E in visual meteorological conditions (VMC) during the hours of daylight to fly subject to maintaining own separation to one other aircraft and remaining in visual meteorological conditions.
The following conditions shall apply:
- The clearance shall be for a specified portion of the flight at or below 10000ft or 3050m, during
climb or descent and subject to further restriction prescribed by regional air navigation regulation.
- The pilot shall inform ATC before entering instrument meteorological conditions (IMC) and shall
proceed in accordance with the alternative instruction given. An IFR flight shall be provided with alternative instructions.
The objectives of the air traffic control service do not include prevention of collision with terrain. The procedures prescribed in this document do not relieve pilots of their responsibility to ensure that any clearances issued by air traffic control units are safe in this respect.