LONGITUDINAL DISTANCE BASED SEPARATION MINIMA

5.4.2.6.4 IN AN RNPRNAV ENVIRONMENT USING ADS-C

5.4.2.6.4.1 Separation based on the use of ADS-C shall be applied so that the distance between the calculated positions of the aircraft is never less than the prescribed minimum. This distance shall be obtained by one of the following methods:

a) when the aircraft are on the same identical track, the distance may be measured between the calculated positions of the aircraft or may be calculated by measuring the distances to a common point on the track (see Figures 5-28 and 5-29);

Note.— Same identical tracks are a special case of same track defined in 5.4.2.1.5 a) where the angular difference is zero degrees or reciprocal tracks defined in 5.4.2.1.5 b) where the angular difference is 180 degrees.

b) when the aircraft are on same or reciprocal non-parallel tracks other than in a) above, the distance shall be calculated by measuring the distances to the common point of intersection of the tracks or projected track (see Figures 5-30 to 5-32); and

c) when the aircraft are on parallel tracks whose protection areas overlap, the distance shall be measured along the track of one of the aircraft as in a) above using its calculated position and the point abeam the calculated position of the other aircraft (see Figure 5-33).

Note.— In all cases presented in Figures 5-28 to 5-33, “d” is calculated by subtracting the distance of the closer aircraft from the common point from the distance of the more distant aircraft from the common point, except in Figure 5-32 where the two distances are added and the order of the aircraft is not important in the calculation.

5.4.2.6.4.2 When aircraft are at, or are expected to reduce to, the minimum separation applicable, speed control techniques, including assigning Mach number, shall be applied to ensure that the minimum distance exists throughout the period of application of the minima.

5.4.2.6.4.3 For aircraft cruising, climbing or descending on the same track, the following separation minima may be used:

Separation minima RNP type

Maximum ADS-C periodic reporting interval

93 km (50 NM) 10 27 minutes

4 32 minutes

55.5 km (30 NM) 4 14 minutes

Note 1.— Detailed information on the analysis used to determine these separation minima and on performing safety assessments, including examples of communication media and operational assumptions that can satisfy the intervention requirements, are contained in the Manual on Airspace Planning Methodology for the Determination of Separation

Minima (Doc 9689). The indicated periodic reporting intervals are specific to the use of ADS-C and are derived from

performed safety assessments. As a result, these intervals may differ from those required for use with other procedural RNAV longitudinal separation minima.

Note 2.— The separation minima shown in the above table require specific RNP values and are based on collision risk modelling which determines communications and surveillance requirements. However, this modelling does not include all operational and technical aspects and is dependent upon parameter values that may vary depending on the particular airspace where the minimum will be applied. Therefore, prior to implementation, a system verification of sufficient duration and integrity must be performed to assess such parameters and conditions including weather deviations or other contingency events for the airspace concerned and to demonstrate that operational and technical requirements are met.

5.4.2.6.4.3.1 Operational and technical requirements for the provision of ADS-C services shall comply with the provisions in Chapter 13.

Note.— Before implementation, particular attention should be given to the requirements in Chapter 13, 13.4.3 and 13.4.3.4.6.

5.4.2.6.4.3.2 The communication system provided to enable the application of the separation minima in 5.4.2.6.4.3 shall allow a controller, within 4 minutes, to intervene and resolve a potential conflict by contacting an aircraft using the normal means of communication. An alternative means shall be available to allow the controller to intervene and resolve the conflict within a total time of 10½ minutes, should the normal means of communication fail.

Figure 5-28. Calculation of longitudinal distance between aircraft — identical track, same direction (see 5.4.2.6.4.1 a))

Figure 5-29. Calculation of longitudinal distance between aircraft — identical track, opposite direction (see 5.4.2.6.4.1 a))

d d2 d1 d = d – d2 1 Common point d₁ d₂ d d = d – d_{2 1} Common point

Figure 5-30. Calculation of longitudinal distance between aircraft — same track, but not identical (see 5.4.2.6.4.1 b))

Figure 5-31. Calculation of longitudinal distance between aircraft — same track projected, but not identical (see 5.4.2.6.4.1 b))

d2 d1 Common point d = d – d2 1 d2 d1 Common point d = d – d2 1

Figure 5-32. Calculation of longitudinal distance between aircraft — opposite sides of the common point (see 5.4.2.6.4.1 b))

Figure 5-33. Calculation of longitudinal distance between aircraft — parallel tracks (see 5.4.2.6.4.1 c))

d2 _d 1 Common point d = d + d2 1 d₁ d₂ d d = d – d_{2 1} Common point Abeam point

5.4.2.6.4.3.3 When an ADS-C periodic or waypoint change event report is not received within 3 minutes of the time it should have been sent, the report is considered overdue and the controller shall take action to obtain the report as quickly as possible, normally by ADS-C or CPDLC. If a report is not received within 6 minutes of the time the original report should have been sent, and there is a possibility of loss of separation with other aircraft, the controller shall take action to resolve any potential conflict(s) as soon as possible. The communication means provided shall be such that the conflict is resolved within a further 7½ minutes.

5.4.2.6.4.4 Opposite-direction aircraft on reciprocal tracks may be cleared to climb or descend to or through the levels occupied by another aircraft provided that the aircraft have passed each other by the applicable separation minimum, calculated in accordance with 5.4.2.6.4.1.