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  • VATPAC Tutorials: Separation Standards

    Separation Standards - IFR

    In Australia, aircraft flying under instrument flight rules (IFR) in controlled airspace up to 29 000 ft must be separated by 1000 ft vertically unless they are separated horizontally. This is standard practice for all aircraft within VATPAC airspace. Aircraft eastbound would usually fly at an odd altitude, eg 5000ft with westbound aircraft flying at even levels like 6000ft. 

    Separation diagramVFR and IFR Cruising Altitudes - Vertical Separation

    (Source: Airservices Australia)

    In terminal area airspace, the minimum separation is 3 nm horizontal distance. In controlled en-route airspace, the horizontal separation standard between aircraft at the same level is 5 nm. Within the confines of an airport control zone, the separation can be as close as practicable as long as the aircraft remains separated, in pratice this is done through visual seperation from Tower. In airspace where aircraft are not being identified and monitored by radar or other satellite-based navigation services, aircraft separation is achieved by the use of numerous procedural rules including time estimates. 

    Separation Standards - Ground & Runway 

    ATC responsibility for collision avoidance covers the parts of the aerodrome used for the take-off, landing and taxiing of aircraft, excluding aprons and parking areas. This is known as the manoeuvring area and is defined in AIP GEN 2.2. ATC is not responsible for aircraft operations on aprons, parking areas or any other area that is outside the manoeuvring area. Therefore, contrary to popular belief an ATC clearance is not required to operate in these areas.

    ColliisionAvoidanceApron.jpg.7b5d3a61c8005e4dcab47cda24e95067.jpg

    On the manoeuvring area, it is a joint pilot-controller responsibility to avoid a collision. Beyond the manoeuvring area (i.e. on aprons & parking areas), it is the responsibility of the pilot and assisting ground personnel. ATC helps by providing traffic information about other aircraft entering or leaving the same apron or parking area. (AIP ENR 1.1.4.3.6 and 1.1.17.8) The following diagram of a section of Adelaide airport (YPAD) illustrates these two areas and highlights the responsibility for collision avoidance.

    Runway Operations

    Do not clear an aircraft for take off until the preceding departure is airborne and has:

    • passed the upwind threshold of the runway;
    • commenced a turn; 
    • reached a point at least 1800M (6000FT) along the runway (subject to wake turbulence and enroute sequencing considerations).

    Do not clear an aircraft for take off until the preceding arrival has vacated the runway and don't clear an aircraft to take off or land until a departing aircraft on the crossing runway has crossed the intersection, or an arriving aircraft has either crossed the intersection or landed and stopped short of the intersection.

    Separation Standards - RVSM 

    Above 29 000 ft (FL290), the vertical separation increases to 2000 ft, except in airspace where Reduced Vertical Separation Minima (RVSM) is applied. This allows greater flexibility and density within the airspace without compromising safety. Between FL290 and FL410 aircraft equipped with the minimum equipment required for RVSM can apply only 1000ft vertical separation.

    The minimum equipment required to apply RVSM separation standards are:

    1. Two independent altitude measurement systems. 
    2. One secondary surveillance radar altitude reporting transponder. 
    3. An altitude alert system
    4. An automatic altitude control system

    In VATPAC it is usually applied that most IFR capable aircraft are generally able to apply these RVSM separation standards. Aircraft flying above FL410 will see 2000ft vertical separation instead of 1000ft. 

    Separation Standards - Wake Turbulence

    Behind every aircraft exists a region of turbulent air known as "wake turbulence".  Wake turbulence has a serious potential to disrupt the stability of other aircraft following or passing too close behind a preceding aircraft.  This potential and the severity of the disruption increases as the size of the preceding aircraft increases. While TWR is responsible for applying wake turbulence between departures, APP/CTR is responsible for maintaining wake turbulence for arrivals (and all other aircraft movements). Here is the wake turbulence table summarising the distance required between aircraft.

    Lead aircraft

    Following aircraft

    Distance (NM)

    SUPER
    (A380)

    SUPER
    HEAVY
    MEDIUM
    LIGHT

    -
    6
    7
    8

    HEAVY

    HEAVY
    MEDIUM
    LIGHT

    4
    5
    6

    MEDIUM

    HEAVY
    MEDIUM
    LIGHT

    -
    -
    5

     

    Lead aircraft

    Following aircraft

    Time (Min)

    SUPER
    (A380)

    SUPER
    HEAVY
    MEDIUM
    LIGHT

    -
    2
    3
    3

    HEAVY

    HEAVY
    MEDIUM
    LIGHT

    -
    2
    2

    MEDIUM

    HEAVY
    MEDIUM
    LIGHT

    -
    -
    2

    Separation Standards - VFR

    VFR separation depends on the type of aircraft and flight occurring. An example would be Broome sightseeing helicopters apply the use of the ‘see and avoid’ principles where pilots maintain their own visual separation. For VFR aircraft outside of the controlled area, separation can be as close as 500 ft vertically and 500 ft horizontally. Within class C VFR will receive separation from IFR aircraft and traffic information on other VFR aircraft. VFR aircraft are entitled to a Radar Information Service (RIS) in Class G airspace - on request and subject to controller workload. VFR aircraft receiving a RIS must be provided with traffic information, and, if requested, position and navigation advice. The service commences upon identification of the aircraft.

    Loss of Separation Standards

    A loss of separation assurance (LOSA) occurs when no clear application of separation standards have occurred. When two aircraft experience an infringement of the minimum separation distance, which depends on airspace and flight rules, is referred to as a loss of separation (LOS). A loss of separation does not mean that the aircraft was at any risk of colliding or having a near miss, it simply means that separation standards were not maintained.

     

    Adapted from CAAP 181A-1(2), TMA & TWR Moodles 

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