10.7.1 Vertical Buffers between Aircraft Inside and Outside Controlled Airspace
10.7.1.1 Levels assigned to VFR aircraft must provide a buffer of at least 500 FT with the base of CTA.
10.7.1.2 If the base of CTA is a VFR level, levels assigned to IFR aircraft must provide a buffer of at least 500 ft with the base of CTA. If it is known that an IFR aircraft is operating less than 500 ft below the CTA base, levels assigned must provide a buffer of at least 1 000 ft with the base of CTA.
10.7.1.3 Where the base of CTA is an IFR level, levels assigned to IFR aircraft must provide a buffer of at least 1,000 FT with the base of CTA, unless it is known that no IFR traffic is operating at the base of CTA. In this instance a buffer of at least 500 FT must be applied.
10.7.2 Vertical Separation Below High Altitude Balloons
10.7.2.1 Unless visual separation is applied, aircraft in CTR/CTA must not be permitted to transit vertically below the 15 NM radius of the balloons position while the balloon is ascending until the balloon has passed FL600.
10.7.3 Step Climbs and Descents
10.7.3.1 The Step Climb Procedure may be used to simultaneously climb aircraft to vertically separated levels provided that the lower aircraft is progressively assigned levels that provide vertical separation with the higher aircraft.
10.7.3.2 When applying the step climb or step descent procedures, pilots must be advised that they are subject to a step climb or descent.
10.7.4 Specifying Rates of Climb
10.7.4.1 Except for international aircraft, a rate of climb or descent must be described in each level clearance when a specified rate is required to ensure the vertical separation is maintained.
10.7.4.2 When it is necessary to specify a rate of climb or descent to an international aircraft, the rate must always be specified in feet per minute, not ‘standard rate’.
10.7.4.3 ATC must endeavour to avoid prescribing rate of climb or descent if it is believed that an aircraft is:
(a) operating in close vertical proximity to the control area lower limit; or
(b) descending VISUAL or VFR to an assigned level and maintaining clearance from terrain or cloud.
10.7.4.4 A rate of descent must not be specified to any aircraft instructed to make a ‘VISUAL APPROACH” or “DME ARRIVAL”, or to an aircraft on that part of an instrument approach below the lowest holding altitude.
10.7.5 Rate in Step Climb/Descent
10.7.5.1 During a Step Climb or Step Descent where a rate of climb or descent has been specified, the rate must apply to all level clearances issued in the course of the climb or descent. The rate must be specified in the initial clearance using the phrase: “... STEP CLIMB (or STEP DESCENT) - STANDARD RATE (or at FEET PER MINUTE)”.
Section (a) operating in close vertical proximit - Manual of Standards Part 172—Air Traffic Services - (a) operating in close vertical proximity to the control area lower limit; or | Zoe
10.7.6 Assigning Vacated Levels
10.7.6.1 A level vacated by one aircraft may be assigned immediately to a second aircraft provided that:
(a) the required vertical separation has not been increased because of the possibility of turbulence;
(b) the first aircraft has been assigned a level requiring a level change of at least the minimum being applied; and
(c) both aircraft have been instructed to change level at a specified rate which will ensure that the applicable vertical separation standard is not infringed.
10.7.6.2 The lowest holding altitude may be assigned to a second aircraft when the first aircraft has reported, “ON FINAL - LEFT (final approach altitude)”, provided that the following aircraft is instructed to descend at “STANDARD RATE” (or at 500 FT per minute).
10.7.7 Vertical Separation Using ADS-C
10.7.7.1 A tolerance of ± 200 ft must be applied to ADS-C level information.
10.7.7.2 ADS-C level information may be used for the application of vertical separation if:
(a) the reported ADS-C level is FL 130 or above; and
(b) displayed ADS-C level information is within the specified tolerance of the expected or cleared flight level.
10.7.7.3 An aircraft cleared to leave a level is taken to have commenced its manoeuvre and vacated the previously occupied level when the ADS-C-derived level information indicates a change of 400 ft or more in the anticipated direction from its previously assigned level.
10.7.7.4 If displayed ADS-C level information for an aircraft maintaining a level does not conform to the required tolerance, the controller must send a demand contract request to update the level displayed.
10.7.7.5 If, following the update, the level is still beyond the required tolerances, the pilot must be advised accordingly and requested to confirm the aircraft’s level. If, following confirmation of the level, the displayed ADS-C level information is still beyond the required tolerance, another method of separation or another method of determining level information must be applied.
10.7.8 Transition Layer, Altitude and Level
10.7.8.1 The system of altimetry used in Australia makes use of a Transition Layer between the Transition Altitude of 10,000 FT and the Transition Level of FL110, to separate aircraft using QNH from those using 1013 Hpa. Cruising in the transition layer must not be permitted.
10.7.9 Common Altimeter Settings
10.7.9.1 In the application of vertical separation at or below the transition altitude, aircraft using terminal QNH and aircraft using Area QNH may be considered to be using common settings.
10.7.10 Levels Unavailable when QNH less than 1013
10.7.10.1 Whenever the QNH/Area QNH is less than 1013 HPa, certain flight levels at or above the transition level are precluded from use in accordance with Table 10.7-1: