Separation in the Vicinity of Aerodromes
by Capt. Pankaj Pahil
📋 Table of Contents
- Procedures for Departing Aircraft — General, SID clearances
- Minimum Separation between Departing Aircraft — 1 min, 2 min, 5 min rules
- Separation: Departing from Arriving Aircraft — Instrument approach & straight-in
- Reduction in Separation Minima — Three conditions for reduction
- Information for Departing Aircraft — Met & visual/non-visual aids
- Procedures for Arriving Aircraft — STARs, visual approach, instrument approach
- Clearance to Maintain Own Separation in VMC
- Expected Approach Time (EAT) & Onward Clearance Time
- Information for Arriving Aircraft — Initial contact, final approach, during final
- DGCA Practice Questions & Answers — 10 MCQs with explanations
Procedures for Departing Aircraft
A departure clearance from ATC must specify the following (when necessary for separation):
- 1Direction of take-off and the turn after take-off
- 2Heading or track to be made good before taking up the cleared departure track
- 3Level to maintain before continuing the climb to the assigned level
- 4Time, point and/or rate at which a level change shall be made
- 5Any other manoeuvre consistent with safe operation of the aircraft
At aerodromes where Standard Instrument Departures (SIDs) have been established, departing aircraft should normally be cleared to follow the appropriate SID.
Minimum Separation between Departing Aircraft
Condition: Aircraft are to fly on tracks diverging by at least 45° immediately after take-off so that lateral separation is provided.
Applied minimum: 1 MINUTE between take-offs.
Condition: Preceding aircraft is 40 kt or MORE faster than the following aircraft, and both aircraft propose to follow the same track.
Applied minimum: 2 MINUTES between take-offs.
Condition: A departing aircraft will be flown through the level of a preceding departing aircraft AND both propose to follow the same track. Vertical separation does not exist during this period.
Applied minimum: 5 MINUTES between take-offs.
Additional obligation: Action must be taken to ensure that the 5-minute separation will be maintained or increased while vertical separation does not exist.
Separation: Departing Aircraft from Arriving Aircraft
The following separation shall be applied when take-off clearance is based on the position of an arriving aircraft.
A departing aircraft may take off:
In any direction until the arriving aircraft has started its procedure turn or base turn leading to final approach.
In a direction which is different by at least 45° from the reciprocal of the direction of approach — after the arriving aircraft has started procedure turn or base turn leading to final approach — provided that the take-off will be made at least 3 minutes before the arriving aircraft is estimated to be over the beginning of the instrument runway.
A departing aircraft may take off:
In any direction until 5 minutes before the arriving aircraft is estimated to be over the instrument runway.
In a direction which is different by at least 45° from the reciprocal of the direction of approach of the arriving aircraft:
- B(b)(i): Until 3 minutes before the arriving aircraft is estimated to be over the beginning of the instrument runway, OR
- B(b)(ii): Before the arriving aircraft crosses a designated fix on the approach track — the location of such fix to be determined by the appropriate ATS authority after consultation with the operators.
| Arriving Aircraft Situation | Departure Direction | Key Time/Condition |
|---|---|---|
| Complete Instrument Approach Before procedure/base turn started |
Any direction | Until procedure/base turn started |
| Complete Instrument Approach After procedure/base turn started |
≥ 45° from reciprocal of approach | At least 3 min before arriving a/c over instrument runway THR |
| Straight-In Approach | Any direction | Until 5 min before arriving a/c over instrument runway |
| Straight-In Approach | ≥ 45° from reciprocal of approach | Until 3 min before arriving a/c over instrument runway THR OR before crossing designated fix on approach track |
Reduction in Separation Minima Near Aerodromes
In the vicinity of aerodromes, the separation minima may be reduced if any of the following three conditions are satisfied:
Adequate separation can be provided by the aerodrome controller when each aircraft is continuously visible to this controller.
Each aircraft is continuously visible to flight crews of the other aircraft concerned, and the pilots thereof report that they can maintain their own separation.
In the case of one aircraft following another: The flight crew of the succeeding aircraft reports that the other aircraft is in sight and separation can be maintained.
Information for Departing Aircraft
Information regarding significant changes in meteorological conditions in the take-off or climb-out area, obtained by the unit providing approach control service after a departing aircraft has established communication, shall be transmitted without delay — except when it is known the aircraft already has the information.
- Surface wind direction or speed
- Visibility
- Runway Visual Range (RVR)
- Air temperature (for turbine-engine aircraft)
- Occurrence of thunderstorm or cumulonimbus
- Moderate or severe turbulence
- Wind shear
- Hail
- Moderate or severe icing
- Severe squall line
- Freezing precipitation
- Severe mountain waves
- Sand storm / Dust storm
- Blowing snow
- Tornado or Waterspout
Information regarding changes in the operational status of visual or non-visual aids essential for take-off and climb shall be transmitted without delay to a departing aircraft, except when it is known that the aircraft already has received the information.
Procedures for Arriving Aircraft
At aerodromes where Standard Instrument Arrivals (STARs) have been established, arriving aircraft should normally be cleared to follow the appropriate STAR.
The aircraft shall be informed of the type of approach to expect and runway-in-use as early as possible.
After coordination with the approach control unit, the ACC may clear the first arriving aircraft for approach rather than to a holding fix.
A visual approach is an approach by an IFR flight when either part or all of an instrument approach procedure is not completed and the approach is executed in visual reference to terrain.
- Clearance for visual approach may be requested by the pilot, or
- May be initiated by the controller.
The controller shall NOT initiate a visual approach when there is reason to believe that the flight crew is not familiar with the aerodrome and its surrounding terrain.
Controller should take into consideration prevailing traffic and meteorological conditions before initiating a visual approach.
Aircraft may be cleared for direct base leg / final, if there is reasonable assurance that visual approach and landing can be completed.
When clearance to execute visual approach has been issued, it shall be the responsibility of the pilot to maintain terrain clearance.
Separation shall be provided between an aircraft cleared for visual approach and other arriving and departing aircraft.
A flight crew may request visual approach if they have runway in sight and can maintain visual reference to terrain, subject to the following conditions:
| Condition | Requirement | Aircraft Category |
|---|---|---|
| (a) Ground Visibility | Not below higher of aerodrome operating minima of associated non-precision approach or minimum visibility/RVR | — |
| Min visibility/RVR = 2800 m | Category A/B aeroplanes | |
| Min visibility/RVR = 3200 m | Category C aeroplanes | |
| Min visibility/RVR = 3600 m | Category D aeroplanes | |
| Ground visibility ≥ 5 km if only a circling approach is available for that runway | All categories | |
| (b) Ceiling | Reported ceiling is at or above the level of the beginning of the initial approach segment | All |
| (c) Pilot's Own Report | Pilot reports at initial approach segment level or during instrument approach that conditions are such that visual approach and landing can be completed with reasonable assurance | All |
The pilot shall advise the controller immediately when:
- aWeather has deteriorated and unable to keep the terrain in sight
- bUnable to continue flight following the preceding aircraft
- cAdditional spacing is required from the preceding aircraft
The pilot at the time of requesting visual approach should also give a position report.
The approach control unit shall specify the instrument approach procedure to be used by arriving aircraft. A flight crew may request an alternative procedure and, if circumstances permit, should be cleared accordingly.
Clearance to Fly Maintaining Own Separation While in VMC
When so requested by an aircraft and provided it is agreed by the pilot of the other aircraft and so authorised by the appropriate ATS authority, an ATC unit may clear a controlled flight — including departing and arriving flights — operating in Airspace Classes D and E in VMC during the hours of daylight to fly subject to maintaining own separation to one other aircraft and remaining in VMC.
- Must be requested by the aircraft
- Must be agreed by the pilot of the other aircraft
- Must be authorised by the appropriate ATS authority
When a controlled flight is so cleared, the following shall apply:
The clearance shall be for a specified portion of the flight at or below 3050 m (10,000 ft), during climb or descent, and subject to further restrictions as and when prescribed on the basis of regional air navigation agreements.
If there is a possibility that flight under VMC may become impracticable, an IFR flight shall be provided with alternative instructions to be complied with in the event that flight in VMC cannot be maintained for the term of the clearance.
The pilot of an IFR flight, on observing that conditions are deteriorating and considering that operation in VMC will become impossible, shall inform ATC before entering IMC and shall proceed in accordance with the alternative instructions given.
Essential traffic information shall be given to controlled flights concerned whenever they constitute essential traffic to each other.
Expected Approach Time (EAT) & Onward Clearance Time
An Expected Approach Time (EAT) is the time at which ATC expects that an arriving aircraft, following a delay, will be cleared to commence its approach from the holding fix.
EAT should be transmitted to the aircraft as soon as practicable and preferably not later than at the commencement of its initial descent from cruising level.
A revised EAT shall be transmitted to the aircraft without delay whenever it differs from that previously transmitted by 5 minutes or more, or such lesser period of time as agreed between the ATS units concerned.
The holding fix to which an EAT relates shall be identified together with the EAT whenever circumstances are such that this would not otherwise be evident to the pilot.
"Onward clearance time" is the time at which an aircraft can expect to leave the fix at which it is being held.
In the event an aircraft is held en route or at a location or aid other than the initial approach fix, the aircraft concerned shall, as soon as practicable, be given an expected onward clearance time from the holding fix. The aircraft shall also be advised if further holding at subsequent holding fixes is expected.
Information for Arriving Aircraft
As early as practicable after an aircraft has established communication with the unit providing approach control service, the following elements of information, in the order listed, shall be transmitted to the aircraft (except what the aircraft is already known to have received):
- aType of approach and runway-in-use
- bMeteorological information, as follows:
- cCurrent runway surface conditions, in case of precipitants or other temporary hazards
- dChanges in the operational status of visual and non-visual aids essential for approach and landing
If it becomes necessary or operationally desirable that an arriving aircraft follow an instrument approach procedure or use a runway other than that initially stated, the flight crew shall be advised without delay.
The following information shall be transmitted to aircraft at the commencement of final approach:
- aSignificant changes in the mean surface wind direction and speed
- bLatest information, if any, on wind shear and/or turbulence in the final approach area
- cCurrent visibility representative of the direction of approach and landing, or the current RVR value(s) and trend (supplemented by slant visual range, if provided)
| Wind Component | Significant Change Threshold |
|---|---|
| Mean Head-wind component | 10 kt |
| Mean Tail-wind component | 2 kt |
| Mean Cross-wind component | 5 kt |
During final approach, the following information shall be transmitted without delay:
- aThe sudden occurrence of hazards (e.g., unauthorized traffic on the runway)
- bSignificant variations in the current surface wind, expressed in terms of minimum and maximum values
- cSignificant changes in runway surface conditions
- dChanges in the operational status of required visual or non-visual aids
- eChanges in observed RVR value(s) in accordance with the reported scale in use, or changes in the visibility representative of the direction of approach and landing
DGCA Practice Questions & Answers
1-A 2-B 3-C 4-A 5-C 6-B 7-B 8-C 9-A 10-C
Quick-Reference Summary — Key Numbers
| Rule / Scenario | Separation / Value | Condition |
|---|---|---|
| Departing a/c — diverging tracks | 1 minute | Tracks diverge ≥ 45° immediately after T/O |
| Departing a/c — same track, speed diff | 2 minutes | Preceding a/c ≥ 40 kt faster, same track |
| Departing a/c — level crossing | 5 minutes | Second a/c flies through level of first, same track |
| Dep vs Arr — any direction (instrument approach) | Before procedure turn | Until arriving a/c starts procedure/base turn |
| Dep vs Arr — ≥45° off reciprocal (instrument approach) | 3 min before THR | After arriving a/c starts procedure turn |
| Dep vs Arr — any direction (straight-in) | 5 min before THR | Until 5 min before arriving a/c over instrument runway |
| Dep vs Arr — ≥45° off reciprocal (straight-in) | 3 min before THR or designated fix | Straight-in approach, specific direction |
| VMC own-separation clearance — max altitude | 3050 m / 10,000 ft | Classes D & E, daylight only |
| EAT — delay trigger | 10 min delay | EAT to be determined and transmitted |
| EAT — revision trigger | Differs by ≥ 5 min | Revised EAT transmitted without delay |
| EAT — expeditious transmission trigger | ≥ 30 min hold | By most expeditious means |
| Wind — significant headwind change | 10 kt | Final approach, component form |
| Wind — significant tailwind change | 2 kt | Final approach, component form |
| Wind — significant crosswind change | 5 kt | Final approach, component form |
| Visual approach min visibility — Cat A/B | 2800 m | Minimum visibility/RVR |
| Visual approach min visibility — Cat C | 3200 m | Minimum visibility/RVR |
| Visual approach min visibility — Cat D | 3600 m | Minimum visibility/RVR |
| Visual approach — circling-only runway | 5 km | Ground visibility must not be less than 5 km |
Reinforce Chapter 6: Separation in the Vicinity of Aerodromes
Test your knowledge and practice actual exam questions for Air Regulations.