Tehran ACC Operations Manual PDF

TEHRAN ACC OPERATIONS MANUAL CHAPTER 5 Procedural Separation Methods and Minima 5.1 Introduction Note 1. Chapter 5 contains procedures and procedural separation minima for use in the separation of aircraft in the en-route...

TEHRAN ACC OPERATIONS MANUAL CHAPTER 5 Procedural Separation Methods and Minima 5.1 Introduction Note 1. Chapter 5 contains procedures and procedural separation minima for use in the separation of aircraft in the en-route phase of flight. Procedures and separation minima applicable to the use of ATS surveillance systems are contained in Chapter 6. Note 2. No separation minima shall be applied by Tehran ACC, unless it is included in chapter 5 or 6 of the present operation manual. Note 3. Although the use of strategic lateral offset procedures (SLOP) is not described in I.R. Iran AIP, to avoid wake turbulence en-route, if an aircraft requests to proceed offset either to the left or right, up to 2 NM should be approved by the controller, if traffic permits. Note 4. The objectives ofArea Control Service as prescribed in 2.11.2 do not include prevention of collision between aircraft and obstructions. The procedures prescribed in this chapter do not relieve the pilots-in-command of their responsibility to ensure that any clearances issued by Tehran ACC are safe regarding terrain clearance. Note 5. There is no obstruction at FL220 or above within the boundaries of Tehran FIR. 5.2 General 5.2.1 Where information derived from an ATS surveillance system is not required for the provision of Area Control Service, the following types of procedural separation are to be provided by Tehran ACC: a) vertical separation b) horizontal separation l. longitudinal separation ll. lateral separation 5.2.2 Vertical or horizontal separation shall be provided: a) between all flights in Class A airspace; b) between IFR flights in Class C and D airspaces; c) between IFR flights and VFR flights in Class C airspace; 5.2.3 No clearance shall be given to execute any maneuvers that would reduce the spacing between two aircraft to less than the separation minimum applicable in the circumstances. 5.2.4 Larger separations than the specified minima should be applied whenever exceptional circumstances such as unlawful interference or navigational difficulties call for extra precautions. This should be done with due regard to all relevant factors so as to avoid impeding the flow of air traffic by the application of excessive separations. 5.2.5 Where the type of separation or minimum used to separate two aircraft cannot be maintained, another type of separation or another minimum shall be established prior to the time when the current separation minimum would be infringed. Second Edition, JAN. 2021 130  TEHRAN ACC OPERATIONS MANUAL 5.2.6 Whenever, as a result of failure or degradation of navigation, communications, altimetry, flight control or other systems, aircraft performance is degraded below the level required for the airspace in which it is operating, the flight crew shall advise the ATC unit concerned without delay. Where the failure or degradation affects the separation minimum currently being employed, the controller shall take action to establish another appropriate type of separation or separation minimum. 5.3 Vertical Separation 5.3.1 Vertical Separation Application 5.3.1.1 Vertical separation is obtained by requiring aircraft using prescribed altimeter setting procedures to operate at different levels expressed in terms of flight levels or altitudes in accordance with the provisions in Chapter 2, 2.36 and 2.37. 5.3.1.2 Geometric height shall not be used in level measurement for provision of vertical separation between aircraft, but only barometric levels in terms of flight level or altitude shall be taken advantage of in this regard. 5.3.1.3 In applying vertical separation, when two or more aircraft are simultaneously cleared to vertically separated levels, where horizontal separation is not applied, step climb or step descent method may be carried out. 5.3.1.3.1 step Climb To simultaneously climb aircraft to vertically separated levels, step climb technique may be applied by progressively assigning the lower aircraft levels which provide vertical separation with the level vacated by the higher climbing aircraft. 5.3.1.3.2 step Descent To simultaneously descend aircraft to vertically separated levels, step descend technique may be applied by progressively assigning the higher aircraft levels which provide vertical separation with the level vacated by the lower descending aircraft. 5.3.2 Vertical Separation Minima 5.3.2.1 RVSM is being applied in Tehran FIR and the vertical separation minimum shall be a nominal 1000 feet below FL410 and a nominal 2000 ft at or above this level (see figure 21). Figure 21. Vertical Separation Minima Second Edition, JAN. 2021 131  TEHRAN ACC OPERATIONS MANUAL 5.3.2.2 When due to any reason, e.g. severe turbulence, RVSM is announced to be suspended, the vertical separation minimum shall be a nominal 1000 feet below FL290 and a nominal 2000 feet at or above this level. Note. Guidance material relating to RVSM is contained in 2.31. 5.3.2.3 Level Assignment 5.3.2.3.1 An aircraft maybe assigned a level previously occupied by another aircraft after the latter has reported vacating it. 5.3.2.3.2 The provision of 5.3.2.3.1 shall be withheld until the aircraft vacating the level has reported at another level separated by the required minima, where: a) severe turbulence is known to exist, or b) the difference in aircraft performance is such that less than the applicable separation minimum may result. Note. Cruise climb shall not be applied in Tehran FIR. 5.3.2.3.3 The cruising levels to be assigned to controlled flights shall be selected from table of cruising levels, provided in 2.37. 5.3.2.3.4 An aircraft at a cruising level shall normally have priority over other aircraft requesting that cruising level. When two or more aircraft are at the same cruising level, the preceding aircraft shall normally have priority. 5.3.2.3.5 In so far as practicable, cruising levels of aircraft flying to the same destination shall be assigned in a manner that will be correct for an approach sequence at destination. 5.3.2.3.6 An aircraft may be cleared to change cruising level at a specified time, place or rate. 5.3.2.3.7 Where a level change is required at the boundary of two sectors, e.g. due to track direction change, the level change shall be completed before the aircraft reaches the boundary point. Close coordination is required between two sectors to avoid any possible confliction of traffic communicating on different frequency channels. 5.4 Horizontal Separation Horizontal separation is achieved by providing: a) longitudinal separation; or b) lateral separation. 5.4.1 Longitudinal Separation 5.4.1.1 Longitudinal Separation Application 5.4.1.1.1 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 the Mach number technique. Second Edition, JAN. 2021 132  TEHRAN ACC OPERATIONS MANUAL 5.4.1.1.2 In applying a time- or distance-based longitudinal separation minimum between aircraft following the same track, care shall be exercised to ensure that the separation minimum will not be infringed whenever the following aircraft is maintaining a higher airspeed than the preceding aircraft. When aircraft are expected to reach minimum separation, speed control shall be applied to ensure that the required separation minimum is maintained. 5.4.1.1.3 Longitudinal separation may be established by requiring aircraft to: a) depart at a specified time (i.e. issuance of clearance expiry time or time before which the aircraft is not released to depart), b) arrive over a geographical location at a specified time (by speed adjustments as applied by the flight crew), or c) hold over a geographical location until a specified time (preferably over a point at which holding has been established (see 3.2.15.11). 5.4.1.1.4 For the purpose of application of longitudinal separation, the terms same track, reciprocal tracks and crossing tracks shall have the following meanings: a) Same track (see figures 22 and 25): same direction tracks and intersecting tracks or portions thereof, the angular difference of which is less than 45 degrees or more than 315 degrees, and whose protected airspaces overlap. Figure 22. Same track b) Reciprocal tracks (see Figure see figures 23 and 25): opposite tracks and intersecting tracks or portions thereof, the angular difference of which is more than 135 degrees but less than 225 degrees, and whose protected airspaces overlap. Second Edition, JAN. 2021 133  TEHRAN ACC OPERATIONS MANUAL Figure 23. Reciprocal tracks c) Crossing tracks (see figures 24 and 25): intersecting tracks or portions thereof other than those specified in a) and b) above. Figure 24. Crossing tracks Note. Regarding protected airspaces, see 2.33.1.1. Figure 25. Same, Crossing and Reciprocal Tracks Second Edition, JAN. 2021 134  TEHRAN ACC OPERATIONS MANUAL 5.4.1.2 Longitudinal Separation Minima 5.4.1.2.1 Longitudinal separation minima are defined based on: a) time, and b) distance. 5.4.1.2.1.1 Longitudinal Separation Minima Based on Time 5.4.1.2.1.1.1 Same Track Aircraft at the Same Cruising Level, Climbing or Descending 5.4.1.2.1.1.1.1 At least 10 minutes separation shall be applied between same track aircraft at the same cruising level, climbing or descending (while vertical separation does not exist), Second Edition, JAN. 2021 135  TEHRAN ACC OPERATIONS MANUAL provided that navigation aids permit frequent determination of position and speed. When frequent determination of position and speed cannot be achieved due to failure of navigation aids, a minimum of 15 minutes shall be applied. (see figure 26). 10 Minutes Figure 26. Same Track Aircraft at the Same Cruising Level, Climbing or Descending 5.4.1.2.1.1.1.2 At least 5 minutes separation shall be applied between same track aircraft at the same cruising level, when the preceding aircraft is maintaining a true airspeed (TAS) of 20 Knots or more faster than the succeeding aircraft and 3 minutes if this TAS differential is 40 Knots or more, in the following cases: a) Between aircraft that have departed from same aerodrome; or b) Between en-route aircraft that have reported over the same exact reporting point; or c) Between departing and en-route aircraft after the en-route aircraft has reported over a fix that is so located in relation to departure point as to ensure that five or three minutes separation can be established at the point the departing aircraft will join the air route (see figure 27). 5 Minutes 20 kt or more faster -O 3 Minutes Aerodrome or 40 kt or more faster Reporting point Second Edition, JAN. 2021 136  TEHRAN ACC OPERATIONS MANUAL Figure 27. Same Track Aircraft at the Same Cruising Level with Speed Differentials 5.4.1.2.1.1.1.3 At least 5 minutes separation shall be applied between same track aircraft climbing or descending, while vertical separation does not exist, provided that the level change is commenced within 10 minutes of the time the second aircraft has reported over a common point which must be derived from ground-based navigation aids or by GNSS (see figure 28). Figure 28. Same Track Aircraft Climbing or Descending Near NA VAID or Point 5.4.1.2.1.1.2 Aircraft on Crossing Tracks at the Same Cruising Level, Climbing or Descending At least 10 minutes separation shall be applied between aircraft on crossing tracks at the same cruising level, climbing or descending (while vertical separation does not exist), provided that navigation aids permit frequent determination of position and speed. When frequent determination of position and speed cannot be achieved due to failure of navigation aids, a minimum of 15 minutes shall be applied. (see figures 29, 30 and 31). Figure 29. Aircraft on Crossing Tracks at the Same Cruising Level Second Edition, JAN. 2021 137  TEHRAN ACC OPERATIONS MANUAL Figure 30. Aircraft on Crossing Tracks Climbing Figure 31. Aircraft on Crossing Tracks Descending 5.4.1.2.1.1.3 Aircraft climbing or descending on reciprocal tracks 5.4.1.2.1.1.3.1 Where 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 (see figures 32, 33 and 34). 5.4.1.2.1.1.3.2 Provided it has been determined that the aircraft have passed each other, with the consideration of type and wake turbulence category, the minimum specified in 5.4.1.2.1.1.3.1 need not apply. This determination shall be obtained by: a) one minute passing the time both aircraft report crossing the same significant point; or b) during daylight, both aircraft seeing each other and confirming that they are well clear. Note 1. TCAS or AMD shall not be used for establishment of this determination. Note 2. This shall not be applied in class A airspace. Second Edition, JAN. 2021 138  TEHRAN ACC OPERATIONS MANUAL Figure 32. Aircraft climbing or descending on reciprocal tracks Estimated time of passing Figure 33. 10 min before estimated time of passing Bl may descend or B2 may climb. Estimated time of passing Figure 34. 10 min after estimated time of passing Bl may descend or B2 may climb. 5.4.1.2.1.1.4 Longitudinal Separation Minima with Mach Number Technique Based on Time Note. See 3.3.1.5. 5.4.1.2.1.1.4.1 Aircraft subject to Mach number technique shall adhere to the true Mach number as instructed by Tehran ACC and shall request ATC approval before making any changes thereto. If it is essential to make an immediate temporary change in the Mach number (e.g. due to turbulence), Tehran ACC shall be notified as soon as possible that such a change has been made. Second Edition, JAN. 2021 139  TEHRAN ACC OPERATIONS MANUAL 5.4.1.2.1.1.4.2 If it is not feasible, due to aircraft performance, to maintain the last assigned Mach number during en-route climbs and descents, pilots of aircraft concerned shall advise Tehran ACC at the time of the climb/descent request. 5.4.1.2.1.1.4.3 When the Mach number technique is applied and provided that: a) the aircraft concerned have reported over the same common point and follow the same track or continuously diverging tracks until some other form of separation is provided; or b) if the aircraft have not reported over the same common point and it is possible to ensure, by radar (or AMD) that the appropriate time interval will exist at the common point from which they either follow the same track or continuously diverging tracks; minimum longitudinal separation between aircraft on the same track, whether in level, climbing or descending flight shall be: 1) 10 minutes; or 2) between 9 and 5 minutes inclusive, provided that: the preceding aircraft is maintaining a true Mach number greater than the following aircraft in accordance with the following: — 9 minutes, if the preceding aircraft is Mach 0.02 faster than the following aircraft; — 8 minutes, if the preceding aircraft is Mach 0.03 faster than the following aircraft; 7 minutes, if the preceding aircraft is Mach 0.04 faster than the following aircraft; — 6 minutes, if the preceding aircraft is Mach 0.05 faster than the following aircraft; — 5 minutes, if the preceding aircraft is Mach 0.06 faster than the following aircraft. 5.4.1.2.1.1.4.4 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 that maintained by the following aircraft. 5.4.1.2.1.2 Longitudinal Separation Minima Based on Distance 5.4.1.2.1.2.1 Longitudinal Separation Minima with Mach Number Technique Based on Distance Using RNAV Note 1. Guidance material on RNAV operations is contained in the Performance-based Navigation (PBN) Manual (Doc 9613). Note 2. See 2.14.4 and 2.33.1.4. Note 3. When the 50 NM longitudinal separation minimum with Mach number technique is being applied, the preceding aircraft shall maintain a Mach number equal to or greater than that maintained by the following aircraft. 5.4.1.2.1.2.1.1 RNAV distance-based separation minima shall not be applied after Tehran ACC has received pilot advice indicating navigation equipment deterioration or failure. 5.4.1.2.1.2.1.2 Separation shall be established by maintaining not less than 50 NM between aircraft positions as reported by reference to RNAV equipment. Direct controller-pilot communications shall be maintained, while such separation is used (see figure 35). Second Edition, JAN. 2021 140  TEHRAN ACC OPERATIONS MANUAL Figure 35.50 NMRNAV separation at the same level 5.4.1.2.1.2.1.3 When aircraft are at, or are expected to reduce to, the minimum separation specified in 5.4.1.2.1.2.1.2, speed control technique of Mach number assignment, shall be applied to ensure that the minimum distance exists throughout the period of application of the minima. Second Edition, JAN. 2021 141  TEHRAN ACC OPERATIONS MANUAL 5.4.1.2.1.2.1.4 To assist pilots to readily provide the required RNAV distance information, such position reports should, wherever possible, be referenced to a common waypoint ahead of both aircraft. 5.4.1.2.1.2.1.5 RNAV distance-based separation may be applied between RNAV- equipped aircraft when operating above FL285 or on designated RNAV routes. 5.4.1.2.1.2.1.6 Separation between aircraft at the same level shall be checked by obtaining simultaneous RNAV distance readings from the aircraft involved, at least every 24 minutes to ensure that the minimum will not be infringed. 5.4.1.2.1.2.1.7 When applied between climbing and descending aircraft, one aircraft shall maintain a level while vertical separation does not exist and the separation shall be established by obtaining simultaneous RNAV distance readings from the aircraft involved see Figure 36. 50 NM RNA V separation climbing/descending. Aircraft B maintains level while Al/C1 descends, or A2/C2 climbs. 5.4.1.2.1.2.1.8 During the application of the 50NM separation, when an aircraft fails to report its position, the controller shall take action within 3 minutes to establish communication. If communication has not been established within 8 minutes of the time the report should have been received, the controller shall take action to apply an alternative form of separation. 5.4.1.2.1.2.1.9 Within non-radar environment, RNAV5 ATS routes, the centerlines of which is 18.5 NM apart are procedurally separate. 5.4.1.2.1.2.2 Longitudinal Separation Minima Based on Distance Using Distance Measuring Equipment (DME) and /or GNSS Note 1. Aircraft selecting to use GNSS shall insert in item 10 of their flight plan the letter G and in item 18 in section "NAV/..." GNSS augmentation, with a space between two or more methods of augmentation, e.g. NAV/GBAS SBAS. Note 2. Where the term "on track" is used in the provisions relating to the application of longitudinal separation minima using DME and/or GNSS, it means that the aircraft is flying either directly inbound to or directly outbound from the station/waypoint. Second Edition, JAN. 2021 142  TEHRAN ACC OPERATIONS MANUAL 5.4.1.2.1.2.2.1 Separation shall be established by maintaining not less than specified distance(s) between aircraft positions as reported by reference to DME in conjunction with other appropriate navigation aids and/or GNSS. 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. Direct controller-pilot VHF voice communication shall be maintained while such separation is used. 5.4.1.2.1.2.2.2 When applying these separation minima between any aircraft with area navigation capability, controllers shall specifically request GNSS-derived distance. For this purpose, the following phraseologies shall be used: REPORT (distance) MILES (GNSS or DME) FROM (name of DME station) (or significant point); REPORT (GNSS or DME) DISTANCE FROM (significant point) or (name of DME station). 5.4.1.2.1.2.2.3 This separation shall not be used between aircraft at the same cruising level, either on the same or crossing tracks, unless in specific circumstances that the General Director of ATM approves the provision of 20 NM separation between aircraft at the same cruising level on the same track with the fulfilment of the following conditions: a) each aircraft utilizes: the same "on-track" DME station when both aircraft are utilizing DME; or ii. an "on-track" DME station and a collocated waypoint when one aircraft is utilizing DME and the other is utilizing GNSS; or iii. iii) the same waypoint when both aircraft are utilizing GNSS; and b) separation is checked by obtaining simultaneous DME and/or GNSS readings from the aircraft at frequent intervals to ensure that the minimum will not be infringed. 5.4.1.2.1.2.2.4 Aircraft Climbing or Descending on the Same Track At least 10 NM separation shall be applied while vertical separation does not exist provided: a) each aircraft utilizes: the same "on-track" DME station when both aircraft are utilizing DME; or ll. an "on-track" DME station and a collocated waypoint when one aircraft is utilizing DME and the other is utilizing GNSS; or Ill. the same waypoint when both aircraft are utilizing GNSS; and b) one aircraft maintains a level while vertical separation does not exist; and c) separation is established by obtaining simultaneous DME and/or GNSS readings from the aircraft (see figure 37). Second Edition, JAN. 2021 143  TEHRAN ACC OPERATIONS MANUAL Figure 37. Aircraft B maintains level while Al/C1 descend, or A2/C2 climb. Note. To facilitate application of the procedure where a considerable change of level is involved, a descending aircraft may be cleared to some convenient level above the lower aircraft, or a climbing aircraft to some convenient level below the higher aircraft, to permit a further check on the separation that will be obtained while vertical separation does not exist. 5.4.1.2.1.2.2.5 Aircraft on Reciprocal Tracks Aircraft utilizing on-track DME and/or collocated waypoint or same waypoint may be cleared to climb or descend through the levels occupied by other aircraft utilizing on- track DME and/or collocated waypoint or same waypoint, provided that it has been positively established that the aircraft have passed each other and are at least 10 NM apart (see figure 38). 1 ONM DME/GNSS  TEHRAN ACC OPERATIONS MANUAL Figure 38. Aircraft on reciprocal tracks 5.4.2 Lateral Separation 5.4.2.1 Lateral Separation Application 5.4.2.1.1 Lateral separation shall be applied so that the distance between those portions of the intended routes for which the aircraft are to be laterally separated is never less than an established distance to account for navigational inaccuracies plus a specified buffer. This buffer is included in the lateral separation minima as an integral part thereof. 5.4.2.1.2 Lateral separation of aircraft is obtained by requiring operation on different routes or in different geographical locations as determined by visual observation, by the use of navigation aids or by the use of area navigation (RNAV) equipment. 5.4.2.1.3 When information is received indicating navigation equipment failure or deterioration below the navigation performance requirements, Tehran ACC shall then, as required, apply alternative separation methods or minima. 5.4.2.1.4 All waypoints within Tehran FIR are fly-by waypoints. In case it is required for an aircraft to flyover a waypoint (e.g. for slight track extensions), a separation other than the normally prescribed lateral separation shall be applied for that portion of the flight between the flyover waypoint where the turn is executed and the next waypoint (see figures 39 and 40). Second Edition, JAN. 2021 145 Second Edition, JAN. 2021 142  TEHRAN ACC OPERATIONS MANUAL Figure 39. Turn overflyover waypoint Figure 40. Turn atfly-by waypoint 5.4.2.2 Lateral Separation Criteria and Minima 5.4.2.2.1 Means by which lateral separation may be applied include the following:  TEHRAN ACC OPERATIONS MANUAL 5.4.2.2.1.1 By reference to the same or different geographic locations. By position reports which positively indicate the aircraft are over different geographic locations as determined by reference to a navigation aid (see figure 41). Figure 41. Using same or different geographic locations 5.4.2.2.1.1.1 In defining locations which are geographically separate, the presence of navigation aids is mandatory and it shall be established that the distance between aircraft involved will never be less than 20 NM. 5.4.2.2.1.1.2 The following significant points in Tehran FIR are geographically separate, provided that both aircraft are in-bound the station. At the time the first aircraft is crossing the navigation aid, another type of separation shall have already been applied. a) (from BOXIX to) SNJ and (from ILM to) KMS; b) (from DNH to) SHR and (from DNZ to) GGN. c) (from TULAX to) MAH and (from ROTOX to) AJR; d) Eastbound, (From UMH and TBZ to) ZAJ and (From MAGRI and SIBVU to) RST; e) Eastbound, ARB and (From LALDA to) RST; f) Eastbound; DAR and KER; g) Westbound, (From DI-IN and DE-MBA to) NSR and DNZ; h) Westbound, DNZ and GGN (not on W156 and N636); i) Westbound, SAV and RUS; j) Westbound, TBZ and (From TUBAR to) UMH; k) Westbound, TBZ and KHY; Second Edition, JAN. 2021 143  TEHRAN ACC OPERATIONS MANUAL l) Westbound; DAR and KER; and m) Westbound; RAF and SRJ. 5.4.2.2.1.2 By use of NDB, VOR or GNSS on intersecting tracks or ATS routes. By requiring aircraft to fly on specified tracks which are separated by a minimum amount appropriate to the navigation aid employed. Lateral separation between two aircraft exists when: a) VOR: both aircraft have passed the VOR and are established on radials diverging by at least 20 degrees and at least one aircraft is at a distance of 20 NM or more from the facility (see figure 42); Figure 42. Separation using the same VOR b) NDB: both aircraft have passed the NDB and are established on tracks to or from the NDB which are diverging by at least 30 degrees and at least one aircraft is at a distance of 28 km (15 NM) or more from the facility (see figure 43); NDB 15NM Figure 43. Separation using the same NDB c) GNSS/GNSS: each aircraft is confirmed to be established on a track with zero offset between two waypoints and at least one aircraft is at a minimum distance from a common point as specified in Table 7; or Second Edition, JAN. 2021 144  TEHRAN ACC OPERATIONS MANUAL d) VOR/GNSS: the aircraft using VOR is established on a radial to or from the VOR and the other aircraft using GNSS is confirmed to be established on a track with zero offset between two waypoints and at least one aircraft is at a minimum distance from a common point as specified in Table 7. Aircraft 1: VOR or GNSS Aircraft 2: GNSS Angular difference FLOIO - FL190 FL200 - FL600 between tracks Distance from a common Distance from a common measured at the point point common point (degrees) 15 - 90 15 NM 23 NM The distances in the table are ground distances and, in their determination, the distance (slant range) from the source of a DME signal to the receiving antenna when DME is being utilized to provide range information is taken into account. Table 7. Lateral separation for aircraft flying VOR and GNSS 5.4.2.2.1.2.1 Before applying GNSS-based track separation, the controller shall confirm that the aircraft are navigating using GNSS and neither of them are applying lateral offset. 5.4.2.2.1.2.2 GNSS-based track separation shall not be applied in cases of pilot- reported receiver autonomous integrity monitoring (RAIM) outages. 5.5 Clearances to Fly Maintaining Own Separation while in Visual Meteorological Conditions Note 1. As indicated in this Section, the provision of vertical 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. It is for the flight so cleared to ensure, for the duration of the clearance, that it is not operated in such proximity to other flights as to create a collision hazard. Note 2. It is axiomatic 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. Note 3. The objectives of the air traffic control service as prescribed in Annex 11 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. 5.5.1 When so requested by an aircraft and provided it is agreed by the pilot of the other aircraft, Tehran ACC may clear a controlled flight, including departing and arriving flights, operating in airspace Class D in visual meteorological conditions during the Second Edition, JAN. 2021 145  TEHRAN ACC OPERATIONS MANUAL hours of daylight to fly subject to maintaining own separation to one other aircraft and remaining in visual meteorological conditions. 5.5.2 When a controlled flight is so cleared, the following shall apply: a) the clearance shall be for a specified portion of the flight at or below 10000 feet, during climb or descent; b) if there is a possibility that flight under visual meteorological conditions may become impracticable, an IFR flight shall be provided with alternative instructions to be complied with in the event that flight in visual meteorological conditions (VMC) cannot be maintained for the term of the clearance;  TEHRAN ACC OPERATIONS MANUAL c) the pilot of an IFR flight, on observing that conditions are deteriorating and considering that operation in VMC will become impossible, shall inform Tehran ACC before entering instrument meteorological conditions (IMC) and shall proceed in accordance with the alternative instructions given; d) essential traffic information shall be provided to the flights concerned. 5.6 Essential Traffic Information 5.6.1 Essential traffic is that controlled traffic to which the provision of separation by ATC is applicable, but which, in relation to a particular controlled flight is not, or will not be, separated from other controlled traffic by the appropriate separation minimum. Note. Pursuant to Section 5.2, but subject to certain exceptions stated therein, Tehran ACC is required to provide separation between IFR flights in airspace Classes A and D. Tehran ACC is not required to provide separation between VFR flights. Therefore, as for Tehran ACC, only IFR flights may constitute essential traffic to IFR traffic. 5.6.2 Essential traffic information shall be given to controlled flights concerned whenever they constitute essential traffic to each other. Note. This information will inevitably relate to controlledflights cleared subject to maintaining own separation and remaining in visual meteorological conditions and also whenever the intended separation minimum has been infringed. 5.6.3 Essential traffic information shall include: a) direction of flight of aircraft concerned; b) type and wake turbulence category (if relevant) of aircraft concerned; c) cruising level of aircraft concerned; and estimated time over the reporting point nearest to where the level will be crossed; or ii. relative bearing of the aircraft concerned in terms of the 12-hour clock as well as distance from the conflicting traffic; or iii. actual or estimated position of the aircraft concerned. d) any other information with a view to enhancing air safety in accordance with the objectives of ATS as defined in Chapter 2 of Annex 11. 5.7 Increasing Separation Minima The separation minima specified above should be increased in the following circumstances: a) VIP flights, indicating STS/HEAD in item 18 if the flight plan; b) Pilot reporting severe turbulence or the aircraft is known to be entering an area of severe turbulence; c) Failure of a navigational aid or communication equipment that reduces the capacity for frequent determination of position and speed; d) Aircraft performance is degraded below the level required for the airspace, as a result of failure or degradation of navigation, communications, altimetry, flight control or other systems; Second Edition, JAN. 2021 146  TEHRAN ACC OPERATIONS MANUAL e) An aircraft experiencing emergency; and  TEHRAN ACC OPERATIONS MANUAL f) An aircraft is being subjected to unlawful interference. 5.8 Air Move Display (AMD) Note. Provision of Radar Information Service, specified in 8.21, shall not be confused with provision of procedural control service using AMD. 5.8.1 In Tehran ACC sectors or part thereof in which ATS Surveillance Service is not provided, the situation displays are called Air Move Display (AMD). 5.8.2 Information derived from AMDs shall not be used as the basis for provision of procedural vertical or horizontal separations, but pilot reports remain the sole basis for this provision. 5.8.3 AMD is only considered to provide the controller with improved information regarding conflict detection, deviation recognition and issuance of traffic information. 5.8.4 In case of observing deviations mentioned in 6.22, controllers may inform the pilot by using the following or similar phrases: IT SEEMS YOU ARE RIGHT (LEFT) OF COURSE. IT SEEMS YOU ARE MAKING RIGHT (LEFT) ARC. IT SEEMS YOU ARE BELOW (ABOVE) CLEARED LEVEL. IT SEEMS YOU ARE BELOW MNM SAFE LEVEL. 5.8.5 Normally there is no need to inform pilot that the aircraft is shown on the AMD or not. 5.8.6 The progress of an aircraft in emergency should be followed on the AMD as far as practicable. 5.8.7 The final confirmation for ascertaining the position, level, etc. of the aircraft, remains with the pilots. Second Edition, JAN. 2021 147