C3 - Traffic Service

Question 1

A Traffic Service is a…

Answer 1

…surveillance based ATS, where in addition to the provisions of a Basic Service, the controller provides specific surveillance-derived traffic information to assist the pilot in avoiding other traffic.

Controllers may provide headings and/or levels for the purposes of positioning and/or sequencing; however, the controller is not required to achieve deconfliction minima, and the pilot remains responsible for collision avoidance.

Question 2

A Traffic Service shall only be provided by a controller with access to…

Answer 2

…an ATS surveillance system

Question 3

Traffic Service is available under…

Answer 3

…IFR outside controlled airspace in any meteorological conditions, or under VFR.

If a controller issues a heading and/or level that would require flight in IMC, a pilot who is not suitably qualified to fly in IMC shall inform the controller and request alternative instructions.

Pilots should be aware that a Traffic Service might not be appropriate for flight in IMC or where lookout is significantly constrained by other factors, when other ATSs are available.

Question 4

To provide a TS, the controller shall…

Answer 4

…identify the aircraft, inform the pilot that he is identified, and maintain identity.

If identity is lost the pilot shall be informed and the controller shall attempt to re-establish identity as soon as practicable

Question 5

The controller shall pass traffic information…

Answer 5

…on relevant traffic, and shall update the traffic information if it continues to constitute a definite hazard, or if requested by the pilot.

However, high controller workload and RTF loading may reduce the ability of the controller to pass traffic information, and the timeliness of such information

Question 6

Traffic is normally considered to be relevant when, in the judgement of the controller…

Answer 6

…the conflicting aircraft’s observed flight profile indicates that it will pass within 3 NM and, where level information is available, 3,000 ft of the aircraft in receipt of the Traffic Service or its level-band if manoeuvring within a level block.

Question 7

However, controllers may also use their judgment to decide on occasions when such traffic is not relevant, e.g….

Answer 7

…passing behind or within the parameters but diverging.

Question 8

Controllers shall aim to pass information on relevant traffic…

Answer 8

…before the conflicting aircraft is within 5 NM, in order to give the pilot sufficient time to meet his collision avoidance responsibilities and to allow for an update in traffic information if considered necessary.

Controller judgement is essential to ensure that traffic information is relevant and timely.

Controllers should take account of the aircraft’s relative speeds, lateral and vertical closure rates, and track histories.

Distances displayed on ATS surveillance systems can be at variance to the actual distances between aircraft due to the limitations in accuracy of surveillance systems. Furthermore, some aircraft may not be displayed at all by ATS surveillance systems.

Question 9

Deconfliction is not provided under a Traffic Service.

If a pilot requires deconfliction advice outside controlled airspace…

Answer 9

…Deconfliction Service shall be requested. (IFR only)

The controller shall make all reasonable endeavours to accommodate this request as soon as practicable.

Question 10

When providing headings/levels for the purpose of positioning and/or sequencing or as navigational assistance, the controller should take into account…

Answer 10

…traffic in the immediate vicinity based on the aircraft’s relative speeds and closure rates, so that a risk of collision is not knowingly introduced by the instructions passed.

However, the controller is not required to achieve defined deconfliction minima and pilots remain responsible for collision avoidance even when being provided with headings/levels by ATC.

Question 11

Subject to ATS surveillance system coverage, Traffic Service may be provided…

Answer 11

…below ATC unit terrain safe levels; however, pilots remain responsible for terrain clearance at all times.

Other than when following a notified instrument flight procedure, a pilot intending to descend below the ATC unit terrain safe level shall be reminded that he remains responsible for terrain clearance.

Question 12

A pilot may operate under his own navigation or…

Answer 12

…a controller may provide headings for the purpose of positioning, sequencing, or as navigational assistance.

Question 13

When operating under their own navigation, pilots may…

Answer 13

…alter course as required; however, unless safety is likely to be compromised, pilots shall not change their general route or manoeuvring area without first advising and obtaining a response from the controller

Question 14

When following an ATC heading, unless safety is likely to be compromised, a pilot shall not…

Answer 14

…change heading without first advising and obtaining a response from the controller, as the aircraft may be coordinated against other airspace users without recourse to the pilot.

If an ATC heading is unacceptable to the pilot he shall advise the controller immediately.

Pilots remain responsible for collision avoidance even when in receipt of ATC headings and shall advise the controller in the event that they need to deviate from a heading in order to comply with Rules of the Air with regard to collision avoidance.

Question 15

Controllers shall only instigate heading allocations when…

Answer 15

…the aircraft is at or above an ATC unit’s terrain safe level.

However, if pilots request a heading from the controller whilst operating below the ATC unit terrain safe level, this may be provided as long as the controller reminds the pilot that he remains responsible for terrain clearance

Question 16

Pilots may select their own operating levels or…

Answer 16

…may be provided with level allocations by the controller for the positioning and/or sequencing of traffic or for navigational assistance.

If a level is unacceptable to the pilot he shall advise the controller immediately.

Unless safety is likely to be compromised, a pilot shall not change level or level band without first advising and obtaining a response from the controller, as the aircraft may be co-ordinated against other airspace users without recourse to the pilot.

Pilots remain responsible for collision avoidance, even when flying at a level allocated by ATC and shall advise the controller in the event that they need to deviate from a level in order to comply with the Rules of the Air with regard to collision avoidance.

Question 17

Levels allocated by controllers shall be…

Answer 17

…terrain safe in accordance with the ATC unit terrain safe levels, unless an agreement is reached with the pilot, or such levels form part of VFR clearance for aerodrome arrival or to enter controlled airspace that by necessity require flight below the unit terrain safe levels; in such circumstances, the instruction shall be accompanied by a reminder that the pilot remains responsible for terrain clearance.

In order to reduce RT loading and increase flexibility, pilots who require to frequently change level whilst receiving a Traffic Service should request a level ‘block’ to operate within.