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Separation Requirements


Content contained within this section was written by Charles Rizzi.

Radar Separation


In the real world there are many complex standards and guidelines for radar separation that depend on the type of equipment being used and other factors. Fortunately for our purpose in VATSIM things can be somewhat simplified. Also before you can apply radar separation you must be certain that you know which target on your screen is which aircraft. This will be discussed in much greater detail later in the Radar Identification section.

As an Approach controller you will usually be responsible for different classes of airspace as described earlier under "The National Airspace System". Most major airports are surrounded by the typical "inverted layer cake" of Class B airspace. Generally the airspace around the class B is class E airspace but often there are class C and class D areas associated with other nearby airports in and around the primary airport. There will also be areas of uncontrolled Class G airspace under the Class E airspace which generally starts at 1200 ft AGL. Although this may be more complex than the area you are training in if we take a quick look at the sectional chart depicting the area to the Southeast of Los Angeles we can see the jigsaw puzzle of airspaces in that area.



So what's your job in reference to separation in the various types of airspace?

Class B - Separate all a/c IFR and VFR using minima described below. The only situation in which you are not responsible for positive radar separation is between VFR helicopters.

Class C - Separate all IFR a/c from both VFR a/c and IFR a/c using minima described below. You are not required to provide separation between VFR aircraft - just traffic advisories and safety alerts. This includes VFR aircraft operating in the "outer area" of the Class C airspace which generally extends out to a 20 mi radius from the primary airport and up to the ceiling of the approach control's delegated airspace.

Class D - Separate all IFR a/c from other IFR aircraft as above. No radar separation services are provided to VFR aircraft. In VATUSA Class D airspace is usually operated under the guidelines of local SOP. If the local TWR is not considered "open" as defined by local coverage guidelines then it is common practice to consider the Class D to have reverted to Class E airspace (to the surface).

Class E - Separate all IFR a/c from other IFR aircraft as above. No radar separation services are required for VFR aircraft. Generally controllers will provide IFR aircraft with traffic information about and even positive guidance around observed VFR traffic.

Class G - Uncontrolled airspace - not your responsibility.

In summary the controller is always responsible for separating IFR traffic from other IFR traffic. The separation services provided to VFR aircraft vary with the class of airspace.

In VATUSA 3 miles separation between IFR aircraft has been the standard minimum for controllers working an approach position where their radar client is most likely zoomed such that the entire visible scope area is no more than 80-100 miles across. This is based on real world guidelines for the resolution of approach control radar systems. For center positions (where the scope is zoomed out further) we use 5 miles as the basic minimum IFR separation based on similar real world guidelines but subject to local letters of agreement (LOA). When transitioning IFR aircraft from an approach position to a center position the approach controller is responsible for insuring that at least 5 miles stable separation is established before the aircraft enter center airspace unless the aircraft are on diverging courses or the lead aircraft is faster such that the separation will increase to 5 miles without further instructions from either controller.

Approach Separation Standards


  1. Approach - 3 miles laterally or 1000 ft vertically.
  2. Transitioning for Approach to Center - 5 miles laterally. If less than on diverging courses or the lead aircraft faster such that the separation is increasing to 5 miles.
  3. VFR Separation in Class B and Class C airspace
  • Class B airspace - Separate any VFR aircraft from all other VFR or IFR aircraft weighing more than 19,000 lbs and all jets by 1.5 mi laterally, 500 ft vertically or by applying visual separation. Separate any VFR aircraft (weighing 19,000 lbs or less) from all other VFR or IFR aircraft weighing 19,000 lbs or less by target resolution laterally, 500 ft vertically or by applying visual separation.
  • Class C airspace - Separate VFR aircraft from all IFR aircraft by visual separation, target resolution (targets not allowed to overlap) or 500 ft vertically

(Although it is not of great practical importance in VATSIM, it should be noted that the separation requirements outlined above can be applied to the edge of a controller's airspace to ensure that two controllers working adjacent airspace don't have aircraft at the edge of their airspace in such a way that the basic underlying separation requirements between the two aircraft are not met. Thus for approach airspace 1.5 miles (half the 3 mile standard) is required between the aircraft and the edge of the airspace (2.5 miles - one half of 5 miles for Center))

Wake Turbulence Separation


In the following ATCast video, brought to you by SATCA (external link) and the University of North Dakota, you will learn more about Wake Turbulence and how to apply it in the Terminal Environment.

Discover Simple, Private Sharing at Drop.io


Separate aircraft operating directly behind, or directly behind and less than 1,000 feet below, or following an aircraft conducting an instrument approach by:
  • Heavy behind heavy- 4 miles.
  • Large/heavy behind B757- 4 miles.
  • Small behind B757- 5 miles.
  • Small/large behind heavy - 5 miles.
(When applying wake turbulence separation criteria, directly behind means an aircraft is operating within 2500 feet of the flight path of the leading aircraft over the surface of the earth. Consider parallel runways less than 2,500 feet apart as a single runway because of the possible effects of wake turbulence.)

Separate an aircraft landing behind another aircraft on the same runway, or one making a touch-and-go, stop-and-go, or low approach by ensuring the following minima will exist at the time the preceding aircraft is over the landing threshold. (Consider parallel runways less than 2,500 feet apart as a single runway because of the possible effects of wake turbulence.)
  • Small behind large- 4 miles.
  • Small behind B757- 5 miles.
  • Small behind heavy- 6 miles.

Separation requirements for Airbus A-380


Procedures. Standard air traffic control procedures contained in FAA Order JO 7110.65 and facility letters of agreement must be applied in support of the A388 with the following additions/changes:

a. EN ROUTE
  • Small/large/heavy behind an A388 – 5 miles.
  • When transitioning to terminal airspace - provide a minimum of 10 miles spacing.
  • Include the expression “SUPER” immediately after the aircraft call sign in communications with a terminal facility about A388 operations, and when issuing traffic advisories regarding an A388.
  • Visual separation rules specified in FAA Order JO 7110.65, chapter 7, section 2, must not be applied with respect to the A388.

b. TERMINAL
1. Separate aircraft operating directly behind or directly behind and less than 1,000 feet below by:
  • Heavy behind A388 – 6 miles.
  • Large behind A388 – 8 miles.
  • Small behind A388 – 10 miles.

NOTE-
Consider parallel runways less than 2,500 feet apart as a single runway because of the possible effects of wake turbulence.


Visual Separation


Visual separation means separating aircraft (IFR and VFR) by means of pilots seeing and avoiding other aircraft or by means of a tower controller directly observing and separating aircraft visually. Given the technical realities of the VATSIM network and simulator visibility this is not necessarily as easy or applicable as it might be in the real world but it is still extremely useful for VATSIM controllers. Visual separation does not apply in Class A airspace (FL180 and above). From the 7110.65:

Aircraft may be separated by visual means, as provided in this paragraph, when other approved separation is assured before and after the application of visual separation. To ensure that other separation will exist, consider aircraft performance, wake turbulence, closure rate, routes of flight, and known weather conditions. Reported weather conditions must allow the aircraft to remain within sight until other separation exists. Do not apply visual separation between successive departures when departure routes and/or aircraft performance preclude maintaining separation.

And for TWR:

The aircraft are visually observed by the tower and visual separation is maintained between the aircraft by the tower. The tower shall not provide visual separation between aircraft when wake turbulence separation is required or when the lead aircraft is a B757.


If a pilot can see another (multiplayer) aircraft you can instruct the pilot to maintain visual separation from the other aircraft as follows:
  1. Tell the pilot about the other aircraft including position, direction and, unless it is obvious, the other aircraft's intention.
  2. Obtain acknowledgment from the pilot that the other aircraft is in sight.
  3. Instruct the pilot to maintain visual separation from that aircraft.
  4. Advise the pilot if the radar targets appear likely to converge.
  5. If the aircraft are on converging courses, inform the other aircraft of the traffic and that visual separation is being applied.
  6. Advise the pilots if either aircraft is a heavy.
  7. Issue wake turbulence cautionary advisories and the position, altitude if known, and direction of flight of the heavy jet or B757 to VFR aircraft not being radar vectored but that are behind heavy jets or B757s and IFR aircraft that accept a visual approach or visual separation
  8. If the pilot advises he/she has the traffic in sight and will maintain visual separation from it (the pilot must use that entire phrase), the controller need only approve the operation instead of restating the instructions.

PHRASEOLOGY-

TRAFFIC, (clock position and distance), (direction)-BOUND, (type of aircraft), (intentions and other relevant information).

If applicable,

ON CONVERGING COURSE.

DO YOU HAVE IT IN SIGHT?

If the answer is in the affirmative,

MAINTAIN VISUAL SEPARATION.

If the pilot advises he/she has the traffic in sight and will maintain visual separation from it (pilot must use that entire phrase):

APPROVED.

If aircraft are on converging courses, advise the other aircraft:

TRAFFIC, (clock position and distance), (direction)-BOUND, (type of aircraft), HAS YOU IN SIGHT AND WILL MAINTAIN VISUAL SEPARATION.

NEXT: Merging Target Procedures and Safety Alerts

PREVIOUS: Positions and Responsibilities













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