C4 - Deconfliction Service

Question 1

A Deconfliction Service is…

Answer 1

…a surveillance based ATS where, in addition to the provisions of a Basic Service, the controller provides specific surveillance-derived traffic information and issues headings and/or levels aimed at achieving planned deconfliction minima, or for positioning and/ or sequencing.

However, the avoidance of other traffic is ultimately the pilot’s responsibility.

Question 2

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

Answer 2

…an ATS surveillance system.

Question 3

A Deconfliction Service shall only be provided to…

Answer 3

…flights under IFR outside controlled airspace, irrespective of meteorological conditions.

The controller will expect the pilot to accept headings and/or levels that may require flight in IMC.

A pilot who is not suitably qualified to fly in IMC shall not request a Deconfliction Service unless compliance permits the flight to be continued in VMC.

Pilots that do not require ATC deconfliction advice or deconfliction minima to be applied should not request a Deconfliction Service.

Question 4

Pilots operating VFR and requiring an ATS shall request…

Answer 4

…a Basic Service or a Traffic Service as appropriate to the phase or conditions of flight.

Question 5

To provide a DS the controller shall…

Answer 5

…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 6

The controller may, subject to workload, pass…

Answer 6

…traffic information on deconflicted traffic in order to improve the pilot’s situational awareness.

Question 7

A controller shall provide traffic information, accompanied with a heading and/or level aimed at achieving a planned deconfliction minima against all observed aircraft in:

Answer 7

• Class G airspace;
• active Temporary Reserved Areas (TRA);
• active Military Training Areas (MTA).

Question 8

Controllers are not required to provide deconfliction advice on…

Answer 8

…aircraft within adjacent controlled airspace (excepting active TRA/MTA) unless surveillance-derived or other information indicates that such aircraft are leaving controlled airspace; however, controllers may pass traffic information.

Question 9

Military controllers providing radar to visual recoveries are not required to apply…

Answer 9

…deconfliction minima against aircraft conducting instrument approaches when within a MATZ, subject to the conditions specified in the Manual of Military ATM.

Although active TRA and MTA are controlled airspace, autonomous flight is permitted and UK FIS are provided.

Question 10

The deconfliction minima against unco-ordinated traffic are:

Answer 10

• 5 NM laterally (subject to surveillance capability and regulatory approval); or
• 3,000 ft vertically and, unless the SSR code indicates that the Mode C data has been verified, the surveillance returns, however presented, should not merge.

(Note: Mode C can be assumed to have been verified if it is associated with a deemed validated Mode A code. The Mode C data of aircraft transponding code 0000 is not to be utilised in assessing deconfliction minima).

Question 11

The deconfliction minima against aircraft that are being provided with an ATS by the same controller, or that have been subject to co-ordination, are:

Answer 11

• 3 NM laterally (subject to surveillance capability and regulatory approval); or
• 1,000 ft vertically; (2,000 ft within active MDA/MTA above FL410, and above FL290 where both aircraft are not RVSM approved); or
• 500 ft vertically (subject to regulatory approval).

Question 12

High controller workload or RTF loading may reduce the ability of the controller to…

Answer 12

…pass deconfliction advice and the timeliness of such information. Furthermore, unknown aircraft may make unpredictable or high-energy manoeuvres.

Consequently, it is recognised that controllers cannot guarantee to achieve these deconfliction minima; however, they shall apply all reasonable endeavours.

In areas of high traffic density, a Deconfliction Service may still be provided, despite the controller considering it unlikely that deconfliction minima will be able to be achieved.

In such circumstances controllers should provide an associated notification to the pilot of reduced traffic information and deconfliction advice should be given.

Question 13

The pilot shall inform the controller if he…

Answer 13

…elects not to act on the controller’s deconfliction advice.

The pilot then accepts responsibility for initiating any subsequent collision avoidance against that particular conflicting aircraft.

However, the controller is not prevented from passing further information in relation to the conflicting traffic, if in his opinion it continues to constitute a definite hazard.

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.

Consequently, lateral deconfliction minimum may have to be greater than those specified above, as detailed in a unit’s regulatory approval. Furthermore, some aircraft may not be displayed at all by ATS surveillance systems.

Question 14

A Deconfliction Service shall only be provided to aircraft operating…

Answer 14

…at or above the ATC unit’s terrain safe level, other than when a controller at an Approach Control unit provides an ATS to aircraft on departure from an aerodrome and climbing to the ATC unit’s terrain safe level, or to aircraft following notified instrument approach procedures.

Question 15

In all other circumstances, if a pilot requests descent below ATC unit terrain safe levels…

Answer 15

…controllers shall no longer provide a Deconfliction Service but should instead, subject to surveillance and RTF coverage, apply a Traffic Service and inform the pilot.

Question 16

If an approach controller detects a confliction when an aircraft is below the ATC unit terrain safe level whilst departing from an aerodrome and climbing to the ATC unit terrain safe level, or when following notified instrument approach procedures, traffic information without deconfliction advice shall be passed.

However, if the pilot requests deconfliction advice, or the controller considers that a definite risk of collision exists, the controller shall immediately offer such advice as follows:

Answer 16

• For aircraft on departure, controllers shall provide avoiding action advice and a terrain warning.
• For aircraft conducting pilot interpreted instrument approaches, controllers shall provide avoiding action advice and an associated terrain safe level to climb to or fly at. It is assumed that conformity with such advice will necessitate repositioning.
• For aircraft being provided with Ground Controlled and Surveillance Radar Approaches:
• If the terrain safe area for the procedure is known to the controller or indicated on the surveillance display, avoiding action may be passed without an associated climb instruction, as long as the controller ensures that the aircraft remains within the terrain safe area, and the turn instruction is such that the controller considers that the approach can be continued without the need for repositioning.
• If the controller anticipates that the avoiding action turn will result in flight outside the terrain safe area or the approach not being able to be completed, a terrain safe level to fly at will also be provided, and repositioning will be necessary.

Question 17

When aircraft are in the initial stages of departure or on final approach, due to limited aircraft manoeuvrability, controllers need to balance…

Answer 17

…the safety impact of passing deconfliction advice at these critical stages of flight against the risk of collision presented by conflicting aircraft.

Consequently, deconfliction minima do not apply in these constrained circumstances and avoiding action is instead aimed at preventing collision.

Furthermore, controllers need to be aware of the high flight deck workload that is likely to be present in the event of avoiding action which is at variance to the published missed approach procedure being followed.

Question 18

The procedures regarding deconfliction advice to aircraft on initial departure and final approach are designed to cater for…

Answer 18

…‘pop up’ conflictions over which the controller has no advance warning due to the uncontrolled nature of Class G airspace.

Controllers should attempt to co-ordinate and deconflict observed traffic prior to allowing either the departure of an aircraft that is expected to require Deconfliction Service, or the final approach of an aircraft that is already receiving a Deconfliction Service.

Where aircraft are transferred to the Aerodrome Controller once established on final instrument approach, ATC units should use internal ATC liaison processes to ensure that warnings of conflicting traffic are passed in a timely fashion to the pilot.

Question 19

A pilot may operate under his own navigation or a controller may…

Answer 19

…provide headings for the purpose of positioning, sequencing, navigational assistance, or to achieve deconfliction minima.

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

Unless safety is likely to be compromised, a pilot shall not alter course without first obtaining approval from the controller, as the flight profile may have been co-ordinated against other airspace users without recourse to the pilot.

Question 20

Controllers will normally provide level allocations for…

Answer 20

…positioning, sequencing, navigational assistance, or to achieve deconfliction minima.

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 without first obtaining approval from the controller, as an aircraft’s flight profile may be co-ordinated against other airspace users without recourse to the pilot.