Section 1, Chapter 6 - ATS Surveillance Systems

Question 1

What services are included in the provision of surveillance services?

Answer 1

Surveillance services comprise:

• Separation: Separation of arriving, departing, and en-route traffic.
• Vectoring: Providing directional guidance to aircraft.
• Position Information: Assisting in the navigation of aircraft by providing position information.
• Traffic Monitoring: Monitoring traffic to provide information to the procedural controller.
• Assistance: Assisting aircraft crossing controlled airspace.

Question 2

What must a controller do before providing surveillance services?

Answer 2

Before providing any surveillance services, a controller must either:

• Identify the Aircraft: Using a method appropriate to the surveillance system in use.
• Transfer of Identity: Have had the identity of the aircraft transferred from another controller.

Note: Identifying an aircraft does not imply that a service is being given

Question 3

What additional services can surveillance systems provide, regardless of whether the aircraft has been identified?

Answer 3

Surveillance systems may also provide the following services:

• Hazard Information: Information on the position of aircraft likely to constitute a hazard.
• Avoiding Action: Instructions or guidance to help aircraft avoid hazards.
• Weather Information: Observed weather information for pilots and other controllers.
• Emergency Assistance: Assistance to aircraft in emergency situations.

Question 4

Under what conditions should surveillance services be provided, and what actions can controllers take if they believe a risk of collision exists?

Answer 4

Provision Conditions: Surveillance services shall be provided to the maximum extent practicable to cover the operational requirement, subject to:

• Workload
• Communications
• Equipment capability

Controller Actions: Regardless of the type of airspace or the air traffic service being provided, controllers can take any action they consider appropriate if they believe a risk of collision exists.

Question 5

How does the type of airspace determine the type of surveillance service available?

Answer 5

Controlled Airspace: Radar Control Service
Outside Controlled Airspace:
* Deconfliction Service
* Traffic Service

Question 6

When must pilots be advised of the commencement, termination, or change of a service?

Answer 6

Pilots must be advised if a service commences, terminates, or changes under the following conditions:

• Outside Controlled Airspace
• Entering Controlled Airspace: Except when entering in connection with an IFR flight holding in Class E airspace.
• Changing Flight Rules: Changing from IFR to VFR or VFR to IFR within Class E airspace.
• VFR Flights:
  1. Entering Class B-D airspace from Class E airspace.
  2. Leaving Class B-D airspace to enter Class E airspace.
• Leaving Controlled Airspace:
  1. Unless provided with advance notice.
  2. Except when leaving in connection with an IFR flight holding in Class E airspace.

Question 7

When must IFR pilots be advised of a change in airspace classification, and under what conditions?

Answer 7

IFR pilots must be advised of the change in airspace classification when entering and leaving Class E airspace if:

• The flight is an unplanned diversion.
• No flight plan has been filed at the time a clearance to enter controlled airspace is requested.

Associated Phraseology: The phraseology for this is contained within CAP 413.

Question 8

What advance notice should controllers provide to pilots for flights leaving controlled airspace?

Answer 8

Controllers should provide pilots with advance notice of:

Exit Point:
* The lateral or vertical point at which the aircraft will leave controlled airspace.
* Notice should be given between 5-10 NM or 3,000-6,000 ft prior to the boundary of controlled airspace.

Subsequent ATS:
* The type of Air Traffic Service (ATS) that will be provided after leaving controlled airspace, unless the aircraft is coordinated and transferred to another ATS unit before crossing the boundary.

Question 9

What are the requirements for controllers when IFR airborne holding is not fully contained within Class E airspace?

Answer 9

• No Advisory Required: Controllers are not required to advise pilots of changes in ATS as they leave or enter Class E airspace during IFR airborne holding.
• Service Provided: Controllers must provide either a Deconfliction Service or a Procedural Service for the portion of the IFR flight in Class G airspace, depending on the availability of ATS surveillance.
• Advisory on Procedural Service: Controllers are required to advise pilots when a Procedural Service will be provided, as pilots will assume a Deconfliction Service will be provided unless otherwise advised.

Question 10

To which aircraft may a Radar Control Service be provided?

Answer 10

A Radar Control Service may be provided to aircraft operating:

• IFR (Instrument Flight Rules)
• Special VFR (Visual Flight Rules)
• VFR (Visual Flight Rules) in Class B-D airspace

Question 11

What are the compliance requirements for pilots when a Radar Control Service is provided?

Answer 11

When providing a Radar Control Service, controllers issue instructions that:

• IFR Pilots: Pilots of aircraft operating under IFR are required to comply with.
• Special VFR or VFR Pilots: Pilots of aircraft operating under Special VFR or VFR will comply with unless they advise the controller otherwise.

Note: The integration of VFR flights under Radar Control Service with IFR traffic flow in the vicinity of aerodromes is described in Section 3.

Question 12

What must a controller do before an aircraft enters controlled airspace?

Answer 12

Before an aircraft enters controlled airspace, the controller must establish which flight rules the pilot will be operating under (IFR, Special VFR, or VFR).

Question 13

What must be done before terminating a Radar Control Service to IFR flights?

Answer 13

Before terminating a Radar Control Service to IFR flights, procedural separation must be applied unless:

At ACCs, when an aircraft will be entering an adjacent sector and:
* A radar handover has been given; or
* The conditions of any standing agreement have been met.

Question 14

What type of service is provided to participating VFR flights in Class E airspace?

Answer 14

Participating VFR flights in Class E airspace shall not be provided with an Air Traffic Control Service but will receive one of the following types of UK Flight Information Services (FIS):

• Basic Service
• Traffic Service

Reference: CAP 774 – UK Flight Information Services.

Question 15

What are the responsibilities of independent units providing an ATS surveillance service for aircraft penetrating controlled airspace under another ATSU’s jurisdiction?

Answer 15

• CAA Specification: Certain units are permitted by the CAA to provide an ATS surveillance service for aircraft wishing to penetrate controlled airspace under another ATSU’s jurisdiction.
• Controller Responsibility: Controllers at these independent units are responsible for separating aircraft under their control from all other aircraft in that controlled airspace.

Question 16

What methods should be used for identifying aircraft with Primary Surveillance Radar (PSR), and how can direction finding equipment assist?

Answer 16

• Methods for PSR Identification: One of the approved methods must be used to identify aircraft when using PSR.
• Direction Finding Equipment: Should be used to assist with identification if it has been approved for such use.

Question 17

How can an aircraft be identified using the Turn Method with PSR?

Answer 17

An aircraft can be identified by ascertaining its heading and correlating the observed movement with:

• The acknowledged execution of an instruction to alter heading by at least 30°.
• One or more changes of heading of at least 30° as instructed by another controller.
• One or more changes of heading of at least 30° reported by the pilot.

Question 18

What must controllers consider before instructing an aircraft to alter heading for identification using the Turn Method with PSR?

Answer 18

• Terrain: Awareness of terrain to ensure safety.
• Other Surveillance Returns: Consideration of other aircraft and their positions.
• PSR Coverage: Ensuring the area has adequate PSR coverage.
• RoA Regulations: Compliance with the Rules of the Air Regulations.

Note: A turn for identification does not constitute the provision of a surveillance service.

Question 19

What procedures must a controller follow when using the Turn Method for PSR identification?

Answer 19

• Verify Movement: Ensure that the movements of no more than one Position Indication correspond with those of the aircraft.
• Exercise Caution: Be particularly cautious when employing this method in areas where changes of aircraft heading are commonly made as a navigational routine.

Question 20

How can an aircraft be identified using the Departing Aircraft Method with PSR, and what precautions should be taken?

Answer 20

Identification Process:

• Observe and correlate the Position Indication of a departing aircraft to a known airborne time.
• Identification must be achieved within one mile of the end of the runway unless otherwise authorized by the CAA.

Precautions:

• Avoid confusion with aircraft overflying the aerodrome.
• Be cautious of aircraft making a missed approach.
• Consider aircraft departing from an adjacent runway.
• Be aware of aircraft holding overhead the aerodrome.

Question 21

ow can an aircraft be identified using the Position Report Method with PSR?

Answer 21

An aircraft can be identified by correlating a particular Position Indication with a report from the pilot that the aircraft is:

• Over an exact reporting point displayed on the situation display.
• At a particular distance not exceeding 30 NM on a particular radial from a co-located VOR/DME or TACAN (DME), with the source facility displayed on the situation display.
• Over a notified visual reference point or prominent geographical feature, approved for the purpose and displayed on the situation display, provided the flight is operating with visual reference to the surface and at a height of 3,000 ft or less above the surface.

Question 22

What additional steps must a controller take when using the Position Report Method for PSR identification?

Answer 22

• Track Observation: The identification must follow a period of track observation sufficient to compare the movement of the Position Indication with the pilot’s reported route.
• Position and Level: Ensure that the reported position and level of the aircraft indicate it is within known PSR coverage.

Question 23

When must the Position Report Method for PSR identification be reinforced by an alternative method?

Answer 23

This method must be reinforced by an alternative method if there is any doubt about the identification due to:

• The close proximity of other returns.
• Inaccurate reporting from aircraft at high levels or some distance from navigational facilities.

Question 24

When should a pilot be informed that their aircraft has been identified using PSR, and what is the exception?

Answer 24

• General Rule: A pilot should be informed as soon as their aircraft has been identified.
• Exception: When operating inside controlled airspace, the pilot needs to be informed only if the identification is achieved by the Turn Method.

Question 25

What methods can be used to identify aircraft using SSR Mode A?

Answer 25

When using Mode A to identify aircraft, one of the following methods should be employed:

• Discrete Code Selection: Observing the pilot’s compliance with the instruction to select a discrete four-digit code.
• Recognising Validated Code: Recognising a validated four-digit code previously assigned to an aircraft callsign. When code/callsign conversion procedures are in use and the code/callsign pairing can be confirmed, the callsign displayed in the data block may be used to establish and maintain identity.
• IDENT Feature: Observing an IDENT feature when it has been requested.

Question 26

What caution must be exercised when using the IDENT feature for SSR Mode A identification, and what restriction applies?

Answer 26

• Caution: Simultaneous requests for SPI (Special Position Identification) transmissions within the same area may result in misidentification.
• Restriction: Aircraft displaying a conspicuity or special purpose code are not to be identified using the IDENT feature, unless specified otherwise in MATS Pt 2.

Question 27

How should controllers assign Mode A codes to aircraft according to the Code Assignment Plan?

Answer 27

Controllers should assign Mode A codes according to the following categories within the Code Assignment Plan:

Discrete Codes:

• Domestic Codes: Assigned to aircraft flying within the areas of responsibility of a unit.
• ORCAM Codes: Assigned to international flights and normally retained beyond the area of responsibility of the assigning unit.

Special Purpose Codes: Allocated internationally.

Conspicuity Codes: Allocated nationally or to specific users/units.

Question 28

What should controllers do when providing a surveillance service to an aircraft with SSR, and what must they verify?

Answer 28

• Allocate Discrete Code: Controllers at SSR-equipped units should allocate a discrete code to the flight in accordance with the SSR assignment plan.
• Mode C Selection: Unless otherwise directed by an ATC unit, Mode C should be selected in conjunction with Mode A.
• Verify Mode C: Controllers must verify the accuracy of the Mode C readout when assigning discrete codes to aircraft.

Question 29

How must controllers validate Mode A codes after assigning them to an aircraft?

Answer 29

Controllers must validate Mode A codes by:

• Checking: As soon as possible, either by direct reference to their display or with assistance from another controlling agency, to ensure the data displayed corresponds with the assigned code.
• Procedures: At units with code callsign conversion equipment, procedures must be applied to ensure the correct correlation of the callsign with the assigned code.

Question 30

What methods can be used to check and validate a Mode A code after it has been assigned to an aircraft?

Answer 30

The code must be checked by one of the following methods:

Squawk Observation:
* Instructing the aircraft to squawk the assigned code and observing that the correct numbers appear on the situation display.

Squawk IDENT:
* Instructing the aircraft to “squawk IDENT” and simultaneously checking the code numbers associated with the SSR response.

Matching Position Indication:
* Matching an already identified Position Indication with the assigned code for the flight.

Question 31

What steps should be taken if the Mode A code readout does not correspond to the assigned code?

Answer 31

• Reset Assigned Code: Instruct the pilot to reset the assigned code (SERA.13005(c)(1)).
• Select Code 0000: If resetting fails to display the assigned code, instruct the pilot to select code 0000.
• Switch Off Transponder: If a corrupt code still exists, normally instruct the pilot to switch off the transponder (SERA.13005(c)(2)).
• Retention of Corrupt Code: The corrupt code may be retained to assist identification and tracking, provided Mode C has been verified. Inform associated ATC units of the retention of corrupt data.

Question 32

When can controllers deem Mode A codes to be validated, and what are the exceptions?

Answer 32

Controllers may deem Mode A codes to be validated when it can be ascertained from the Code Assignment Plan that an observed Mode A code has been assigned by a unit capable of validating the code, unless:

• The code is promulgated as being unvalidated.
• The controller has been notified that the code is corrupt.

Question 33

What should controllers consider regarding the Mode A code and associated Mode C data of special purpose codes, and what are some examples of these codes?

Answer 33

Considerations: The Mode A code and associated Mode C data of special purpose codes must be considered unvalidated and unverified.

Special Purpose Codes:

• Emergency Codes: 7500 (Hijack), 7600 (Radio failure), 7700 (General emergency).
• Code 1000: Indicates an aircraft conducting IFR flight as General Air Traffic (GAT), where the downlinked aircraft identification matches the flight plan.
• Code 2000: Selected by pilots of aircraft entering the UK from an adjacent FIR where transponder operation has not been required; also used for IFR conspicuity.
• Code 7007: Selected by aircraft engaged in airborne observation flights under the Treaty on Open Skies. These flights have Flight Priority Category B status and details are published by NOTAM.

Question 34

What are the considerations and requirements for Mode A code and Mode C data of conspicuity codes, and when are pilots required to squawk a conspicuity code?

Answer 34

Considerations: The Mode A code and associated Mode C data of conspicuity codes must be considered unvalidated and unverified.

Requirements for Pilots: Pilots are required to squawk a VFR or IFR conspicuity code when operating at and above FL100 and are advised to do so when below FL100, unless:

• They have been assigned a discrete code.
• They are transponding on one of the special purpose codes, a frequency monitoring code, or one of the other specific conspicuity codes assigned according to the Code Assignment Plan.
• They are flying below 3,000 ft in the aerodrome traffic pattern and have been instructed to select the aerodrome traffic pattern conspicuity code (7010).
• On grounds of safety, the aircraft has been instructed to squawk standby. This is considered exceptional due to the associated reduction in protection from ACAS. ATSUs must log the circumstances and duration of such occurrences and make records available to the CAA on request.

Question 35

What are some specific UK conspicuity codes and their uses?

Answer 35

The SSR Code Assignment Plan provides a complete set of UK conspicuity codes, including those used at specific units or locations. Some of these codes are:

• 0024: Radar Flight Evaluation or Calibration. Used only for the duration of the radar evaluation or calibration. Not used while transiting to/from the trial.
• 0033: Para Dropping. Selected by transponder-equipped aircraft five minutes before the drop commences until parachutists or loads are estimated to be on the ground.
• 2000: IFR Conspicuity. Used when operating within UK airspace in accordance with IFR and have not received a specific instruction from ATS.
• 7000: VFR Conspicuity. Used when operating within UK airspace in accordance with VFR and have not received a specific instruction from ATS.
• 7001: Military Fixed Wing Low Level Conspicuity and Climbout. Used by military fixed-wing aircraft in the UK Low Flying System. Retained until an ATC unit gives alternative instructions.
• 7002: Danger Areas General
• 7003: Red Arrows Display/Transit. Used by the Red Arrows for display and transit.
• 7004: Aerobatics and Display. Selected five minutes before aerobatic manoeuvres commence until normal operations resume.
• 7005: High Energy Manoeuvres. Used by military fast-jet aircraft before engaging in sustained high-energy manoeuvres outside controlled airspace below FL 195 and outside the UK low-flying system.
• 7006: Autonomous Operations within TRA and TRA (G)
• 7010: Aerodrome Traffic Pattern Conspicuity Code. Facilitates ACAS collision avoidance. Selected when operating in or within approximately 2 NM of the aerodrome traffic pattern.

Question 36

What is the purpose of Frequency Monitoring Codes and what should pilots and controllers be aware of?

Answer 36

• Purpose: To prevent and mitigate the consequences of airspace infringements.
• Pilot Actions: Pilots operating close to the peripheries of certain controlled airspace may select local SSR conspicuity codes and monitor the promulgated frequency.
• Implication: Selection of these codes and frequency monitoring does not imply the provision of any form of ATS.
• Controller Procedures: Detailed procedures for the use of monitoring codes and actions to be taken by controllers are specified in MATS Part 2.

Question 37

What are the two levels of Mode S, and what additional Down-Linked Airborne Parameters (DAPs) does Enhanced Mode S provide?

Answer 37

Levels of Mode S:

Elementary Mode S:

• Provides selective interrogation of aircraft.
• Includes aircraft identification Down-Linked Airborne Parameter (DAP).

Enhanced Mode S:

• Enables further DAPs from an aircraft’s flight management system.

Additional DAPs in Enhanced Mode S:

• Selected altitude
• Indicated Airspeed (IAS)
• Ground speed
• Magnetic heading
• Rate of climb/descent

Question 38

What additional capability do Mode S transponder-equipped aircraft engaged in international civil aviation have, and how does it differ from the aircraft address?

Answer 38

• Additional Capability: Mode S transponder-equipped aircraft have an Aircraft Identification Feature (Flight Identity or Flight ID).
• Flight Crew Action: The flight crew sets the aircraft identification in the transponder.
• Difference from Aircraft Address:
  1. Aircraft Identification Feature: Set by the flight crew and relates to the flight’s identity.
  2. Aircraft Address: A unique ICAO code specific to the airframe, over which crews have no control.

Question 39

How can direct recognition of the Aircraft Identification Feature on the situation display be used to establish surveillance identification?

Answer 39

Direct recognition of the Aircraft Identification Feature on the situation display can be used to establish surveillance identification, subject to:

• Correlation with Flight Plan: Correlating the Aircraft Identification Feature with the aircraft identification entered in the flight plan and displayed to controllers on flight progress strips.
• Correlation with Callsign: Correlating the Aircraft Identification Feature with the aircraft’s callsign used in a directed RTF transmission to the controller.

Note: Controllers should exercise particular caution when there are aircraft with similar callsigns on the frequency and should use an alternative method if there is any doubt about the surveillance identification.

Question 40

What should a controller do if the down-linked Aircraft Identification Feature is different from what is expected?

Answer 40

• Action Required: The controller shall request the pilot to confirm the Aircraft Identification Feature.
• Correction: If necessary, the pilot should re-enter the correct Aircraft Identification Feature.

Question 41

What minimum actions should a controller take if the Aircraft Identification Feature discrepancy continues after pilot confirmation?

Answer 41

• Inform the Pilot: Notify the pilot of the persistent discrepancy.
• Assign Discrete Mode A Code: Assign the aircraft a discrete Mode A code.
• Notify Next Control Position: Inform the next control position or unit of the erroneous Aircraft Identification Feature transmitted by the aircraft.

Question 42

Under what conditions can the transfer of identification using the Mode S Aircraft Identification Feature be conducted?

Answer 42

• Requirement: Both units must have appropriate Mode S surveillance capability.
• Condition: Transfer of identification using the Mode S Aircraft Identification Feature shall only be conducted in accordance with locally agreed arrangements.
• Specification: Procedures must be specified in MATS Part 2.

Question 43

What is the Selected Altitude DAP, and how should it be used by controllers?

Answer 43

• Generation: The Selected Altitude DAP is generated by flight crew inputs into the aircraft’s autopilot system.
• Display Capability: Subject to appropriate surveillance system capability, the Selected Altitude DAP can be displayed to controllers on situational displays.
• Presentation: Selected Altitude data will be presented as either a flight level or an altitude, depending on local surveillance system settings, detailed in MATS Part 2.
• Terminology: For ATC and RTF purposes, the generic phrase ‘Selected Level’ is used to encompass data presented as either an altitude or a flight level.
• Usage Limitation: Selected Levels display intent-based information only and shall not be used for the purposes of separation.

Question 44

When might the Selected Level be at variance with the actual flight level, despite correct ATC instruction interpretation by the flight crew?

Answer 44

Situations where the Selected Level may be at variance with the actual flight level include:

SID/STARs with Vertical Restrictions:

• Pilots may select the final cleared level and use the aircraft flight management system to achieve vertical constraints.

Final Approach:

• Pilots may pre-select the missed approach procedure altitude.

Manual Flight:

• Particularly in response to vertical avoiding action manoeuvres, when the aircraft is being flown manually.

Question 45

How should units equipped with Enhanced Mode S surveillance systems use Selected Levels to mitigate level busts?

Answer 45

Units equipped with Enhanced Mode S surveillance systems that enable DAPs should display Selected Levels on the situation display to mitigate the risk of level busts.

Important Note: Checking of Selected Levels shall not be used as a substitute for RT readback of level clearances.

Question 46

How should controllers address discrepancies between the Selected Level and an ATC clearance?

Answer 46

• Do Not State Incorrect Level: Controllers shall not state on RT the incorrect level as observed on the situation display.
• Query the Discrepancy: Controllers may query the discrepancy using the following phraseology:

“(Callsign), check selected level. Cleared level is (correct cleared level).”

Question 47

How should controllers address discrepancies between the altimeter setting passed and the setting selected by the pilot using Mode S Barometric Pressure Setting data?

Answer 47

• Query the Discrepancy: If a discrepancy is observed between the altimeter setting passed and that selected by the pilot, a controller should query the discrepancy using the following phraseology, as appropriate:

“(Callsign), check altimeter setting QNH 1000” (where QNH 1000 hPa is the correct value).

“(Callsign), check altimeter setting, confirm standard pressure is set?” (where 1013.25 hPa is the correct value).

Question 48

What is a Transponder Mandatory Zone (TMZ) and what are the requirements for aircraft operating within it?

Answer 48

• Definition: A TMZ is airspace of defined dimensions within which aircraft are required to carry and operate a Mode S SSR transponder.
• Alternative Provisions: Aircraft must comply with alternative provisions prescribed for that particular airspace by the ANSP, as referred to in SERA.6005(b).

Question 49

Why is a Transponder Mandatory Zone (TMZ) established and what is its purpose?

Answer 49

Establishment Reason: A TMZ is established for overriding safety reasons where the airspace classification would not normally require the carriage of a transponder, but changing to a more restrictive classification of controlled airspace is not warranted.

Purpose:
* Creates a ‘recognised air traffic environment’.
* Enhances the ability of ATS to provide safety.
* Enables the operation of airborne and ground-based safety nets.

Question 50

What are the conditions for an aircraft unable to comply with TMZ requirements to access the TMZ, and what procedures are applied within a TMZ?

Answer 50

Access to TMZ:

• Pilots of aircraft unable to comply with TMZ requirements may be granted access subject to specific approval by the ANSP.
• Approval conditions depend on:
• Types and density of air traffic operating or planned within the TMZ.
• Actual or forecast meteorological conditions.

Procedures within TMZ:

• Standard ATS procedures and separation/deconfliction minima appropriate to the airspace classification are applied.
• The existence of a TMZ does not confer or suggest any particular airspace classification.

Question 51

What methods can a controller use to transfer the identity of an aircraft to another controller when only PSR is available?

Answer 51

When only PSR is available, a controller can transfer the identity of an aircraft to another controller by the following methods:

Direct Designation (Pointing):

• Pointing at the Position Indication where two situation displays are adjacent or a conference-type display is used.
• Ensure blips on both displays correlate if the information is derived from separate PSR heads or beams.
• Use an alternative method if parallax is likely to cause an error.
• Direction and Distance from a Common

Reference Point:

• Designate the Position Indication in terms of direction and distance from a common reference point (geographical position or navigational facility) accurately indicated on both displays.
• The Position Indication as seen by the accepting controller must be within 3 NM of the position stated.
• The distance between the aircraft and the reference point must not exceed:
  1. 30 NM if the aircraft is flying along a published ATS route or direction is given as a bearing in degrees.
  2. 15 NM in other circumstances.

Electronic Marker or Symbol:

• Designate the Position Indication by positioning an electronic marker or symbol so that only one Position Indication is indicated and there is no possible doubt of correct identification.

Question 52

When must a pilot be advised of lost identification, and what is the exception?

Answer 52

General Rule: A pilot must be advised whenever identification is lost.

Exception:
* When using SSR, controllers may temporarily lose the ability to read data blocks due to overlapping or garbling (e.g., in holding areas).
* If the controller anticipates that identification will be re-established immediately after the overlapping or garbling ceases, the pilot need not be advised of the lost identification.

Question 53

When should a pilot be informed that their aircraft has been identified?

Answer 53

• Outside Controlled Airspace: A pilot should be informed as soon as their aircraft has been identified.
• Inside Controlled Airspace: The pilot needs to be informed only if the identification is achieved by the turn method.

Question 54

When should pilots be informed of their position?

Answer 54

Pilots should be informed of their position in the following circumstances:

• Following identification of the aircraft using the turn method.
• When the pilot requests the information.
• When the aircraft is flying off the correct track.
• When an aircraft estimate differs significantly from the controller’s estimate based on ATS surveillance system observation.
• When the pilot is instructed to resume their own navigation following vectoring, if considered necessary by the controller.

Question 55

When should controllers inform pilots of identification and pass position information based on the method of identification and airspace?

Answer 55

Table of Identification and Position Information:

• Additional Note: When providing a Basic Service, a controller may identify an aircraft to facilitate coordination or to assist in the provision of generic navigational assistance. However, the controller is not required to inform the pilot that identification has taken place or to pass a position report.
• General Rule: Controllers may pass position information to aircraft whenever they consider it necessary.

Question 56

In what forms should position information be passed to pilots?

Answer 56

Position information should be passed in one of the following forms:

• A well-known geographical position.
• Bearing (using points of the compass) and distance from a known position.
• Magnetic track and distance to a location displayed on the situation display that is a reporting point, an en-route navigational aid, or an approach aid.
• Latitude and Longitude (by specific units only when authorized in MATS Part 2).
• Distance from touchdown if the aircraft is on final approach.

Question 57

What should controllers do when using Mode C responses to assess vertical separation?

Answer 57

When using Mode C responses to assess vertical separation, controllers must continually monitor the Mode C responses to ensure that the vertical distance is never less than the prescribed minimum.

Question 58

Can vertical separation be applied using Mode C against aircraft transponding A0000?

Answer 58

No, vertical separation using Mode C is not applied against aircraft transponding A0000.

Question 59

Under what conditions can minimum vertical separation be applied between verified Mode C transponding aircraft?

Answer 59

Minimum vertical separation may be applied between verified Mode C transponding aircraft if the intentions of both aircraft are known to a controller because:

• They are under the controller’s control.
• They have been coordinated.
• They are operating in accordance with established agreements.

Question 60

What is the required minimum vertical separation for aircraft under Radar Control Service if the intentions of verified Mode S altitude reporting or Mode C transponding aircraft are not known?

Answer 60

If the intentions are not known, the minimum separation is:

IFR Flights within Class A, C-E Airspace:

• Increased to 5,000 ft, or alternative approved minima within MATS Part 2.

VFR Flights within Class C Airspace:

• Increased to 5,000 ft, or alternative approved minima within MATS Part 2.

Question 61

How can unverified Mode S altitude reporting or Mode C data be used for separation purposes within controlled airspace?

Answer 61

Unverified Mode S altitude reporting or Mode C data may be used for separation within controlled airspace as follows:

IFR Flights within Class A, C, and D Airspace, and VFR Flights within Class C Airspace:

• A minimum vertical separation of 5,000 ft, or an alternative approved minimum within MATS Part 2.
• Surveillance returns, however presented, are not allowed to merge.

IFR Flights within Class E Airspace (Except Against Aircraft Displaying VFR Conspicuity or a Frequency Monitoring Code):

• A minimum vertical separation of 5,000 ft, or an alternative approved minimum within MATS Part 2.
• Surveillance returns, however presented, are not allowed to merge.

IFR Flights within Class E Airspace (Against Aircraft Displaying VFR Conspicuity or a Frequency Monitoring Code):

• Whenever practicable, pass traffic information.
• If requested by the pilot or deemed necessary by the controller, suggest traffic avoidance advice.

Note: The procedure in points (2) and (3) only applies to Frequency Monitoring codes notified for the purposes of VFR within Class E airspace.

Question 62

When can aircraft that do not meet the published operating requirements for a TMZ be deemed to be operating outside that TMZ?

Answer 62

Aircraft that do not meet the published operating requirements for a particular volume of TMZ may be deemed to be operating outside that TMZ unless:

• Information received indicates that an aircraft is lost or has experienced a radio failure.
• The controller has approved such an aircraft to enter TMZ airspace without identifying the aircraft using an appropriate method

Question 63

What should controllers aim to do when suggesting traffic avoidance advice, and where can information on Deconfliction Service be found?

Answer 63

• Traffic Avoidance Advice: Controllers shall aim to prevent surveillance returns from merging when suggesting traffic avoidance advice.
• Deconfliction Service: Refer to CAP 774, Chapter 4, Paragraph 4.10 for information on Deconfliction Service.

Question 64

How should controllers verify the accuracy of Mode C data, and what should be done if the aircraft is climbing or descending?

Answer 64

Verification Process:

• Once the aircraft has been identified and the Mode A validated, verify that the Mode C readout indicates 200 ft or less from the level reported by the pilot.
• If the aircraft is climbing or descending, instruct the pilot to give a precise report as the aircraft passes through a level.

Assistance:

• Verification may be achieved with the assistance of an ATSU with which the aircraft is in contact.

Question 65

When can a Mode C readout be assumed to have been verified?

Answer 65

A Mode C readout can be assumed to have been verified if it is associated with a deemed validated Mode A code (SERA.13010(b)).

Question 66

What actions should a controller take if a Mode C discrepancy is observed, but Mode C information is not being used to provide vertical separation?

Answer 66

• Confirm Altimeter Setting and Level: Ask the pilot to confirm their altimeter setting and level.
• Persistent Discrepancy: If the discrepancy remains:
  1. Instruct the pilot to switch off Mode C.
  2. If independent switching of Mode C is not possible, instruct the pilot to select A0000.

Question 67

What criteria apply when assessing the vertical position of a Mode C transponding aircraft?

Answer 67

• At Assigned Level: An aircraft may be considered to be at an assigned level if the Mode C readout indicates 200 ft or less from that level.
• Leaving a Level: An aircraft instructed to climb or descend may be considered to have left a level when the Mode C readout indicates a change of 400 ft or more from that level and is continuing in the anticipated direction.
• Passing Through a Level: An aircraft climbing or descending may be considered to have passed through a level when the Mode C readout indicates that the level has been passed by 400 ft or more and is continuing in the required direction.
• Reaching an Assigned Level: An aircraft may be considered to have reached an assigned level when three successive Mode C readouts indicate 200 ft or less from that level.

Question 68

How is Mode C information typically displayed, and what is the exception?

Answer 68

• Normal Display: Mode C information is typically displayed as a Flight Level.
• Exception: On some ground equipment, the vertical position of an aircraft flying below a pre-determined datum is displayed as an altitude.

Question 69

What conditions must be met for the transfer of responsibility for an aircraft from one controller to another, and what additional information is required if the aircraft’s route is unknown?

Answer 69

Conditions for Transfer:

• Satisfactory two-way speech communication is available between the controllers.
• The identity of the aircraft has been transferred to, or established by, the accepting controller.
• The accepting controller is informed of any level, speed, or vectoring instructions applicable to the aircraft at the stage of transfer.

Additional Information:

• If the route of the aircraft is not known, the offering controller must pass the observed track or reported aircraft heading to the accepting controller.

Question 70

Under what conditions can control of arriving aircraft be transferred to Approach Radar Control to avoid delays caused by other aircraft?

Answer 70

Control of arriving aircraft may be transferred to Approach Radar Control under the following conditions:

• The transfer of control message is prefixed with “radar release.”
• Details of all conflicting aircraft are passed to the approach radar controller.
• Conflicting aircraft are either transferred to Approach Radar Control or identified according to the accepting controller’s decision.
• Neither the track nor the level of the conflicting aircraft is altered without coordination.

Question 71

What is the responsibility of a controller when instructing an aircraft to turn, especially when avoiding unknown aircraft?

Answer 71

• Controller Authority: A controller may instruct an aircraft to turn in any direction as dictated by circumstances.
• Avoidance of Unknown Aircraft: When avoiding unknown aircraft, the Rules of the Air (RoA) Regulations should be observed if practicable.

Question 72

Under what conditions can an aircraft be vectored outside the horizontal or vertical limits of controlled airspace?

Answer 72

An aircraft can be vectored outside the horizontal or vertical limits of controlled airspace under the following conditions:

• Emergency Situation: When an emergency situation arises requiring the aircraft to be vectored outside controlled airspace.
• Severe Weather: When avoiding severe weather; the circumstances must be explained to the pilot before the aircraft leaves controlled airspace.
• Pilot Request: When specifically requested by the pilot.

Question 72

What is the obligation of aircraft flying outside controlled airspace and VFR within Class E airspace regarding ATC instructions, and what can a controller expect if a Traffic Service or Deconfliction Service is accepted?

Answer 72

• Outside Controlled Airspace and VFR within Class E Airspace: Aircraft are not obliged to follow instructions given by ATC.
• Traffic Service or Deconfliction Service: If the pilot accepts a Traffic Service or Deconfliction Service, the controller can expect that their instructions will be followed.

Question 73

What should controllers aim to do regarding aircraft under their control and unknown aircraft in adjoining uncontrolled airspace, and what actions should be taken if an aircraft is vectored close to the boundary?

Answer 73

• Separation Goal: Controllers should aim to keep the aircraft under their control at least 2 NM within the boundary of controlled airspace.
• Monitoring: Controllers should monitor the operation of aircraft in adjacent uncontrolled airspace, especially if circumstances necessitate vectoring an aircraft to be less than 2 NM from the boundary.
• Coordination: Consider coordinating with the appropriate controlling agency if applicable.
• Safety Action: Regardless of airspace divisions and classifications, controllers should take appropriate action for the safety of aircraft if unknown aircraft appear to present a risk of collision.

Question 74

What should controllers do when vectoring is complete, and how should they specify a direct route if needed?

Answer 74

• Instruction to Resume Navigation: When vectoring is complete, pilots will be instructed to resume their own navigation.
• Direct Route: If a direct route is required, the controller shall specify this in the instruction.

Question 75

What must a controller provide when an aircraft inbound to a VOR/DME holding pattern is vectored away from a standard VOR radial?

Answer 75

The controller must either:

• Provide Magnetic Track and Distance Information: When instructing the aircraft to resume own navigation.
• Issue Vectoring Instructions: To intercept the appropriate radial to the holding or routing fix.

Question 76

What must controllers ensure regarding levels assigned to IFR flights in receipt of a Radar Control Service within controlled airspace?

Answer 76

Controllers must ensure that levels assigned to IFR flights in receipt of a Radar Control Service provide adequate terrain clearance for the phase of flight.

Question 77

What is the controller’s responsibility for terrain clearance within controlled airspace, and what are the minimum terrain clearances for different phases of flight?

Answer 77

Controller Responsibilities:

• Controllers ensure levels assigned to IFR flights in receipt of a Radar Control Service provide adequate terrain clearance.
• Controllers have no responsibility for terrain clearance of, and shall not assign levels to, aircraft operating Special VFR or VFR within controlled airspace which accept vectors.

Minimum Terrain Clearances:

Within the defined final approach area:

• Achieved if levels are assigned in accordance with a procedure approved by the CAA.

Within the Surveillance Minimum Altitude Area:

• Levels allocated must be in accordance with the information published on the SMAC.

Within 30 NM of the radar antenna associated with the unit providing the service:

• 1,000 ft above any fixed obstacle within:

1. 5 NM of the aircraft.
2. 15 NM ahead and 20° either side of the aircraft’s track.

• When the aircraft is within 15 NM of the antenna, provided a SMAC or approved procedure has been notified, the 5 NM and 15 NM distances may be reduced to 3 NM and 10 NM, respectively.

Outside the above phases:

• 1,000 ft above any fixed obstacle:

1. Within 15 NM of the centerline of the ATS route.
2. Within 30 NM of the aircraft (for all other flights).

• In sections of control areas where the base is defined as a flight level, the lowest useable level normally provides not less than 1,500 ft terrain clearance.

Question 78

What is the responsibility for terrain clearance within Class G airspace, and where can the specific terrain requirements for level allocations and vector provision be found?

Answer 78

• Pilot Responsibility: Within Class G airspace, regardless of the service being provided, pilots are ultimately responsible for terrain clearance.
• Specific Terrain Requirements: Terrain requirements pertaining to level allocations and the provision of vectors are specified within the conditions of the services as detailed in CAP 774 – UK Flight Information Services.

Question 79

How should a controller identify an unknown aircraft?

Answer 79

Unknown Aircraft: A position symbol that cannot be associated with an aircraft known by the controller to be operating within the airspace concerned shall be considered to represent an unknown aircraft.

Question 80

What actions should controllers take when observing an unknown aircraft in unsafe proximity to traffic receiving an ATS, based on airspace classification?

Answer 80

Class A:

• If the aircraft is making an unauthorized penetration, is lost, or has experienced radio failure:
• Provide traffic avoidance advice.
• Pass traffic information.

Class C:

• If the aircraft is making an unauthorized penetration, is lost, or has experienced radio failure:
• IFR flights: Provide traffic avoidance advice and pass traffic information.
• VFR flights: Pass traffic information and suggest traffic avoidance advice if requested by the pilot or deemed necessary by the controller.

Class D:

• If the aircraft is making an unauthorized penetration, is lost, or has experienced radio failure:
• IFR flights: Provide traffic avoidance advice and pass traffic information.
• VFR and SVFR flights: Pass traffic information and suggest traffic avoidance advice if requested by the pilot or deemed necessary by the controller (remind pilots to remain clear of cloud with the surface in sight).

Class E:

• Pass traffic information unless sequencing and separating IFR flights is compromised.
• IFR flights:
• Provide traffic avoidance advice if the aircraft is lost, has experienced radio failure, or infringes Class E airspace.
• Pass traffic information whenever practicable and suggest traffic avoidance advice if requested by the pilot or deemed necessary by the controller.
• Participating VFR flights: Pass traffic information according to CAP 774 – UK Flight Information Services.

Class G:

• Flights receiving Deconfliction Service or Procedural Service: Pass traffic information and deconfliction advice according to CAP 774 – UK Flight Information Services.
• Flights receiving Traffic Service or Basic Service: Pass traffic information according to CAP 774 – UK Flight Information Services.
• If more immediate action is required, pass traffic avoidance advice before traffic information.

Notes:
* When providing traffic avoidance advice, remind pilots of their responsibility to remain clear of cloud with the surface in sight.
* If more immediate action is required, traffic avoidance advice may be passed before traffic information.
* If the flight rules of unknown aircraft cannot be determined, apply the procedure in Section 1, Chapter 6, Paragraph 10A.5(2).

Question 81

What should controllers and pilots do when traffic avoidance advice is issued to an IFR aircraft under a Radar Control Service, and what are the exceptions in Class D or E airspace?

Answer 81

General Rule:

• Controllers must seek to achieve the required minima.
• Pilots must comply with the instructions given.

Exception in Class D or E Airspace:

• If the pilot reports having the unknown aircraft in sight and positively states that they will maintain their own separation from it:
• Further controller action may be limited to passing traffic information.

Consideration:

• It may not always be possible to achieve the required separation minima against unknown traffic infringing controlled airspace due to their sudden appearance and/or unpredictable maneuvers.
• Controllers shall apply all reasonable endeavors to achieve separation (SERA.7002(a)).

Question 82

What are the requirements and limitations when traffic avoidance advice is issued to VFR/SVFR aircraft under a Radar Control Service?

Answer 82

• Separation Minima: Controllers are not required to achieve separation minima.
• Avoiding Action Instructions:
• Aimed at reducing the risk of collision as far as possible.
• Must consider aircraft proximity and constraints.
• Pilot Compliance: Subject to prevailing meteorological conditions (SERA.7002(a)).

Question 83

What should controllers do when the conflict no longer exists?

Answer 83

Controllers shall advise pilots when the conflict no longer exists (SERA.7002(b)).

Question 84

What should controllers do if they observe an aircraft using an assigned SSR code making or about to make an unauthorized airspace infringement?

Answer 84

Controllers should attempt to contact the relevant agency to identify the aircraft and agree on a course of action.

Question 85

What actions should controllers take when dealing with aircraft using A1177, the London FIS code?

Answer 85

Contact London FISO:

• Controllers should contact the appropriate London FISO for assistance in identifying the aircraft.
• Example instruction: “G-ABCD, at (unit) request - contact (unit) (frequency) immediately.”

Achieve Identification:

• Once the subject aircraft is on the controller’s frequency, ensure that identification of the aircraft is achieved.

Relay Instructions:

• Simple transfers of communication are part of the London FISOs’ standard operating procedures.
• FISOs are not permitted to issue control instructions to aircraft.
• Controllers must not request FISOs to relay any instructions other than for the aircraft to transfer directly to their control frequency.

Royal Flights:
* Procedures for Royal Flights in fixed-wing aircraft are detailed in Chapter 9.

Question 86

What elements should be included in traffic information provided to aircraft?

Answer 86

Traffic information to aircraft shall include the following elements:

Bearing from the Aircraft:

• Given in terms of the 12-hour clock.
• If the aircraft is turning, direction is given by compass points.

Distance from the Aircraft:

• Provided in nautical miles.

Direction of the Unknown Aircraft:

• Described as, for example, “traffic is opposite direction/crossing left to right,” etc.

Height Information:

• When available, includes the unverified Mode C of the unknown aircraft.

Question 87

What should controllers do when informing a pilot about other traffic that is separated from their aircraft to prevent confusion?

Answer 87

• Controllers should avoid referencing the actual level of the other aircraft.
• If necessary, inform the pilot that the other aircraft is “(number) thousand feet above/below.”

Question 89

What are the key considerations and procedures for controllers regarding solar radiation and space weather?

Answer 89

Space Weather Overview:

• The Earth is subjected to electromagnetic and high-energy particle radiation from galactic sources and the Sun, known as space weather.
• Most space weather variability is of solar origin, with minor events being more common than major ones.
• Several times in each 11-year solar cycle, space weather can have an operational impact.

Effects of Severe Space Weather:

• Increased solar radiation is typically detected at higher altitudes.
• Severe space weather events can affect both aircraft at altitude and ground level.
• These events can degrade or cause loss of satellite-based and/or ground-based navigation and communications systems.
• Aircraft occupants, especially those in high-level flight, can be exposed to increased levels of solar radiation.

Space Weather Forecasts and Alerts:

• Available from the Met Office and ICAO.
• Aircraft operators should consider space weather impacts when filing a flight plan.
• Severe space weather can occur without warning, and flights above 49,000 ft AMSL must carry equipment to monitor radiation dose rates.

Pilot Requests and Emergency Procedures:

• Pilots may request a descent to a lower level during severe space weather events.
• Controllers should accommodate such requests whenever possible.
• Pilots may initiate an emergency descent without clearance, using transponder code A7700 and informing ATC as soon as possible.
• During an emergency descent, pilots are responsible for separation and collision avoidance.

Question 90

What are the potential causes of spurious primary returns (clutter) on the situation display?

Answer 90

Potential causes of spurious primary returns (clutter) include:
* Weather: Adverse weather conditions affecting radar returns.
* Anomalous Propagation: Unusual atmospheric conditions causing false returns.
* Ground/Sea Returns: Reflections from the ground or sea surface.
* Birds: Birds causing radar returns.
* Wind Turbine Effects: Interference from wind turbines.
* Radar Countermeasures: Use of chaff or other countermeasures.

Note: Distinguishing clutter from actual aircraft surveillance returns may be difficult, especially with processed surveillance systems.

Question 91

How can clutter on the situation display impact ATS provision?

Answer 91

Clutter on the situation display can impact ATS provision in the following ways:

• Increased Risk: The controller may not detect conflicting traffic.
• Obscured Information: Aircraft position symbols, track histories, and data blocks may be hidden or obscured.
• Spurious Tracks: Spurious tracks may be generated, which can be indistinguishable from genuine aircraft returns.
• Identification Delays: There may be a delay in identifying aircraft and placing them under an ATS.
• Increased Workload: Controller workload may increase.

Question 92

What are the potential effects of clutter on the degree, accuracy, and timeliness of ATS provision, and what might be necessary as a result?

Answer 92

Potential Effects of Clutter:

• Reduced degree, accuracy, and timeliness of instructions, advice, and information provided by controllers.
• Impacts on safety and expedition of flight operations.

Possible Necessities Due to Clutter:

• Aircraft may need to be rerouted.
• Air traffic services may be reduced below the level requested by the pilot.

Procedures:

• Specific tactical procedures to be applied by controllers in response to observed clutter are provided below (in the document).

Question 93

What should ATS providers consider regarding wind turbines according to CAP 764?

Answer 93

Wind turbines can generate various negative effects on ATS systems, which should be considered during the wind turbine application planning process. CAP 764 provides specific information on these impacts. Long-term or permanent clutter impacts should be assessed locally, with procedures documented in MATS Part 2.

Question 94

What actions should controllers take if clutter is present on the situational display outside controlled airspace?

Answer 94

Controllers should consider the nature and extent of the clutter and take the following actions:

• Inform pilots under Deconfliction Service or Traffic Service about the clutter extent and offer a reroute if possible.
• Inform pilots about the reduction in traffic information/deconfliction advice if rerouting is not feasible, as detailed in CAP 774.
• For all surveillance services, maintain aircraft identity; if rerouting is impracticable, consider an alternative type of approach. If identity cannot be maintained, terminate the service.

Question 95

What actions should controllers take if clutter is present on the situational display inside controlled airspace?

Answer 95

Controllers should consider the extent of the clutter and take the following actions:

• Vector the aircraft around the clutter, if practicable.
• If clutter intensity obscures the aircraft’s PSR or SSR position symbol, avoid using radar separation for that aircraft.
• Provide IFR traffic in Class E airspace with reduced traffic information if necessary. Radar Control Service and air traffic service shall not be terminated.

Question 96

How should controllers manage VFR flights receiving a Traffic Service within Class E airspace when clutter is present on the situational display?

Answer 96

Controllers should manage VFR flights receiving a Traffic Service within Class E airspace by following the procedures in 18B.1(1) and 18B.1(2):

• Inform pilots about the extent of the clutter and offer a reroute if possible.
• Inform pilots about the reduction in traffic information if rerouting is not feasible.

Additionally, controllers remain responsible for providing advice on aircraft infringing controlled airspace and should consider the clutter’s nature, consistency, observed movement, relative speed, and track to identify unknown aircraft.

Question 97

What should controllers consider for aircraft intending to make a radar approach when clutter is present on the situational display in all classes of airspace?

Answer 97

Controllers should assess the nature and extent of the clutter and decide whether:

• A radar approach is not possible due to clutter and inform the aircraft.
• A radar approach could be carried out, but radar contact may be lost. Inform the aircraft early about the clutter and provide missed approach instructions in advance if necessary.

Question 98

What actions should controllers take during a surveillance system failure?

Answer 98

During a surveillance system failure, controllers should:

• Inform aircraft under control of the failure.
• Apply local contingency procedures detailed in MATS Part 2.
• Employ reduced vertical separation temporarily (e.g., 500 ft instead of 1,000 ft or 1,000 ft instead of 2,000 ft) if standard separation cannot be provided immediately. Inform pilots and pass essential traffic information as necessary.
• When the surveillance system is notified as serviceable again, re-identify all aircraft by an approved method before providing any ATS surveillance service.
• Follow MATS Part 2 procedures that obviate the need for notification of the system’s return to serviceable state, if approved by the CAA.

Question 99

What should a controller do when a Short-Term Conflict Alert (STCA) is generated for controlled flights?

Answer 99

When an STCA is generated, the controller should:

• Immediately assess the situation.
• Take necessary action to ensure that the applicable separation minimum is not infringed.
• Follow specific local STCA procedures detailed in MATS Part 2.
• Refer to CAP 670 for STCA requirements.