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Separation procedures in case of control traffic.

There are three kinds of separation based on distance:

Vertical separation (FL or altitude) has to be provided according to the direction – eastern or western.

Vertical separation is obtained by requiring aircraft using prescribed altimeter setting procedures to operate at different levels expressed in terms of flight levels or altitude. Vertical separation between aircraft flying in opposite direction below FL 290 is 1 000ft and above FL 290- 2 000ft. Between FL 290 and FL 410 (RVSM airspace) vertical separation between aircraft following opposite direction is 1 000ft and above FL 410-

2 000 ft.

In case of climbing/ descending of an aircraft, a controller has to maintain separation between aircraft using vertical rate of climb/ descent.

Lateral separation of aircraft is obtained by requiring operation on different routes or in different geographical locations as determined by visual operation, by use of navigation aids or by use of area navigation equipment/

Lateral separation 20 km has to be provided when an aircraft has to cross FL (altitude) which is occupied by another aircraft in opposite direction and 10 km – occupied by an aircraft at the same direction.

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.

No clearance should be given to execute any manoeuvre that reduces spacing between two aircraft to less than prescribed separation minimum.

Large separation shall be applied whenever exceptional circumstances such as unlawful interference or navigational difficulties need extra precautions.

- What is the content of routine air-reports? – 4.12.2 (4444)

Routine air-reports include the following information:

Section 1. Position information:

aircraft identification



FL or altitude

next position and time over

ensuing significant point

Section 2. Operational information:

7. estimated time of arrival

8. endurance

Section 3. Meteorological information:

9. air temperature

10. wind direction

11. wind speed

12. turbulence

13. aircraft icing

14. humidity (if available).

10. - General provision in case of controlled traffic. – 5.2.1 (4444)

Vertical or horizontal separation shall be provided:

Between all flights in Class A and B airspaces;

Between IFR flights in Class C, D and E airspaces, except during the hours of daylight when flights, climbing or descending, maintain own separation and remain in VMC;

Between IFR flights and VFR flights in Class C airspace;

Between IFR flights and special VFR flights;

Between special VFR flights, when so prescribed by the appropriate ATS authority.

No clearance shall be given to execute any manoeuvre that would reduce the spacing between two aircraft to less than the separation minimum applicable in the circumstances.

Larger separation than the specified minima should be applied in exceptional circumstances, such as unlawful interference or navigational difficulties. This should be done taking into account all relevant factors to avoid obstructing the flow of traffic by the application of excessive separation.

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 (νΰπσψενϋ).


- What weather conditions effect the work of an ATCO?

Weather is a major factor in traffic capacity. Rain or ice and snow on the runway cause landing aircraft to take longer to slow and exit, thus reducing the safe arrival rate and requiring more space between landing aircraft. Fog also requires a decrease in the landing rate. These, in turn, increase airborne delay for holding aircraft.

In Area Control Centers, a major weather problem is thunderstorms, which present a variety of hazards to aircraft. Aircraft will deviate around storms, reducing the capacity of the en-route system by requiring more space per aircraft, or causing congestion as many aircraft try to move through a single hole in a line of thunderstorms. Occasionally weather considerations cause delays to aircraft prior to their departure as routes are closed by thunderstorms.


11.- Separation between aircraft using single (the same) RW. –7.9.1 (2) (4444)

A landing aircraft will not normally be permitted to cross the runway threshold on its final approach until the departing aircraft has crossed the end of the runway-in-use, or has started a turn, or until all preceding landing aircraft are clear of the runway-in-use.

There are three kinds of separation between aircraft using the same RW:

between arriving aircraft and between arriving and departing aircraft longitudinal separation is applied:

H –H – 8km

M - H & L - M – 10 km

L – H - 12 km

L – L – 6 km

In all other cases – 6 km.

between departing aircraft time separation is used:

H – H – 1 min

M - H & L - M – 2 min

L – H – 3 min

L – L – 1 min

M (going to depart not from the beginning of the runway) – H – 3 min.

In all other cases – 1 min.

(Wake turbulence categories and longitudinal separation minima shall be taken into consideration)


- What shall a controller do in case of failure or irregularity of systems and equipment? –4.14 (4444)

ATC units shall immediately report in accordance with local instructions any failure or irregularity of communication, navigation and surveillance systems or any other safety-significant systems or equipment which can effect the safety of efficiency of flight operations and / or provision of air traffic control service.

An air traffic controller has to ensure what really has failed and do everything possible to maintain safety.

In case of a compass-system failure air traffic controller gives heading, and if CB radar failure – a controller gives vectors to avoid CB.


12.- Minima separation when Aerodrome service provided. – 5.6, 5.7, 5.8 (4444)

Minimum separation between departing aircraft:

- 1 minute separation is required if aircraft are to fly on tracks diverging by at least 45 degrees immediately after take-off so that lateral separation is provided;

- 2 minutes are required between take-offs when the preceding aircraft is 70 km/h (40 kt) or faster than the following aircraft and both aircraft will follow the same track.

- 5 minute separation is required while vertical separation does not exist if a departing aircraft will be flown through the level of a preceding departing aircraft and both aircraft will follow the same track.

Separation of the departing aircraft from arriving aircraft shall be applied when take-off clearance is based on the position of an arriving aircraft

The following wake turbulence radar separation minimum shall be applied to aircraft in the approach and departure phases of flight:

HEAVY aircraft behind HEAVY aircraft – 8 km;

MEDIUM aircraft behind HEAVY aircraft – 10 km;

LIGHT aircraft behind HEAVY aircraft – 12 km;

LIGHT aircraft behind MEDIUM aircraft – 10 km.

In all other cases wake turbulence separation minimum shall be 6 km.


- How dangerous is fire on board?

One of the most dangerous accidents on board the plane is fire. It usually takes 2 minutes from the beginning of the fire till non-survivable conditions. The higher level at which it occurs, the more serious the situation is. The controller should not call the crew until they get a survivable level. In case when fire is not put out the plane descends to make a forced landing. After forced landing passengers and crew must be evacuated without delay. The most common causes of fire are short circuit, transportation of dangerous goods, smoking, fuel leak, bomb explosion. Engine on fire results in abandoned take-off engine failure, smoke or fire in the cockpit and emergency landing.

13.- Procedure of issuing ATC clearance for departure and appropriate coordination when issuing suchclearance. –7.8.1 / 6.3.1,, (4444)

Clearances for departing aircraft shall specify, when necessary for the separation of aircraft, direction of take-off, heading or track to be made good before taking up the cleared departure track; level to be maintained before continuing climb to assigned level; time, point and/ or rate of which a level change should be made; and any other necessary manoeuvre consistent with which safe operation of the aircraft.

At aerodromes where SIDs have been established, departing aircraft should normally be cleared to follow the appropriate SID.

The appropriate ATS authority should, wherever possible, establish standardized procedures for transfer the control between the ATC units concerned.

Where standard clearances for departing aircraft have been agreed to between the units concerned, the aerodrome control tower will normally issue the appropriate standard clearance without prior coordination with or approval from the approach control unit or ACC.

Prior coordination of clearances should be required only in the event that a variation to the standard clearance or the standardized transfer of control procedures is necessary or desirable for operational reasons.

Standard clearances for departing aircraft should contain the following items:

- aircraft identification;

- clearance limit, normally destination aerodrome;

- designator of the assigned SID, if applicable;

- initial level, except when this element is included in the SID description;

- allocated SSR code;

- any other necessary instruction or information not contained in the SID description, e.g. instructions relating to change of frequency.

Departures shall normally be cleared in the order in which they are ready for take- off, except that deviations may be made from this order of priority to facilitate the maximum number of departures with the least average delay. Factors which should be considered in relation to the departure sequence include:

- types of aircraft and their relative performance;

- routes to be followed after take-off;

- any specified minimum departure interval between take-offs;

- need to apply wake turbulence separation minima;

- aircraft which should be afforded priority; and

- aircraft subject to ATFM requirements.

For aircraft subject to ATFM requirements, it is the responsibility of the pilot and the operator to ensure that the aircraft is ready to taxi in time to meet any required departure time, bearing in mind that once a departure sequence is established on the taxiway system, it can be difficult, and sometimes impossible, to change the order.

- How should a hijacked aircraft inform ATC about it?

An aircraft known or believed to be in a state of emergency, including being subjected to unlawful interference, shall be given maximum consideration, assistance and priority over other aircraft as may be necessities by the circumstances.

To indicate that it is in a state of emergency, an aircraft equipped with an SSR transponder might operate the equipment as follows:

a) on Mode A, Code 7500, to indicate specifically that it is being subjected to unlawful interference; or b) on Mode A, Code 7700.

When an occurrence of unlawful interference with an aircraft takes place or is suspected, ATS units shall attend promptly to request by the aircraft. Information pertinent to the safe conduct of the flight shall continue to be transmitted and necessary action shall be taken to expedite the conduct of all phases of the flight, especially the safe landing of the aircraft.


14.- Issuance clearance procedure for start-up engines. – (4444), 4.2 (9432)

Start-up procedures should be performed where necessary to avoid congestion and excessive delays on the maneuvering area of when warranted by ATFM regulations.

Start-up time procedures should be contained in local instructions, and should specify the criteria and conditions for determining when and how start-up times shall be calculated and issued to departing flights.

- When an aircraft is subject to ATFM regulations, it should be advised to start-up in accordance with its allocated slot time.

- When delay for a departing aircraft is expected to be less than a time period specified by the appropriate ATS authority, an aircraft should be cleared to start-up at its own discretion.

- When delay for a departing aircraft is expected to be more than a time period specified by the appropriate ATS authority, an aircraft should be issued an expected start-up time.

A start-up clearance shall only be withheld under conditions specified by the appropriate ATS authority and the aircraft crew shall be advised of the reason.

- Lateral separation criteria and minima.– (4444)

Means by which lateral separation may be applied are the following:

- By reference to the same or different geographical locations (by positions reports which positively indicate the aircraft locations as determined visually or by reference to a navigation aid).

- By use of the same navigation aid or method (by requiring the aircraft to fly on special tracks which are separated by a minimum amount appropriate to the navigation aid or method used). Lateral separation between two aircraft exists when:

VOR: both aircraft are established on radials diverging at least 15 degrees and at least one aircraft is at a distance of 28 km (15 NM) or more from the facility;

NDB: both aircraft 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;

dead reckoning (DR): both aircraft are established on tracks diverging by at least 45 degrees and at least one aircraft is at a distance of 28 km (15 NM) or more from the point of intersection of the tracks;

RNAV operations: both aircraft are established on tracks which diverge by at least 15 degrees and the protected airspace associated with the track of one aircraft does not overlap with the protected airspace associated with the other aircraft.

- By use of different navigation aid and method (shall be established by ensuring that the protected airspaces for the navigation aid(s) or RNP do not overlap).

- RNAV operations where RNP is specified on parallel tracks or ATS routes (may be applied by requiring the aircraft to be established on the centre lines of parallel tracks or ATS routes spaced at a distance which ensures that the protected airspace does not overlap).

- RNAV operations where RNP is specified on intersecting tracks or ATS routes. The use of this separation is limited to intersecting tracks that converge to or diverge from a common point of angles between 15 and 135 degrees. The distance of the lateral separation points from the track intersection shall be determined by collision risk analysis and will depend on complex factors such as the navigational accuracy of the aircraft, traffic density, and occupancy.

Lateral separation exists between two aircraft when at least one aircraft is outside the area of conflict.


Date: 2014-12-29; view: 224

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