M1, S1, C6 - ATS Surveillance Systems

Question 1

Surveillance services comprise:

Answer 1

1) separation of arriving, departing and en route traffic 2) vectoring 3) position information to assist in the navigation of aircraft 4) monitoring traffic to provide information to the procedural controller 5) assistance to aircraft crossing CAS

Question 2

Before a controller provides any surveillance services he shall either:

Answer 2

1) identify the aircraft, using a method appropriate to the surveillance system in use or 2) have had the identity of the aircraft transferred from another controller. The act of identifying an aircraft does not imply that a service is being given.

Question 3

Surveillance systems may also be used to provide the following, whether or not the aircraft had been identified:

Answer 3

1) information on the position of aircraft likely to constitute a hazard 2) avoiding action 3) information about observed weather for pilots and other controllers 4) assistance to aircraft in emergency

Question 4

Surveillance services shall be provided to the…

Answer 4

…maximum extent practicable to cover the operational requirement subject only to workload, communications or equipment capability.

Question 5

Regardless of the type of airspace, or the air traffic service being provided, nothing shall…

Answer 5

…prevent a controller from taking action he considers appropriate if he believes a risk of collision exists.

Question 6

The airspace within which the aircraft is flying determines the type of surveillance service available:

Answer 6

Inside CAS - radar control service Outside CAS - deconfliction service or traffic service

Question 7

Pilots must be advised if a service commences, terminates or changes when:

Answer 7

1) outside CAS 2) entering CAS, except when entering CAS in connection with an IFR flight holding in a Class E in accordance with P1B.4 below (IFR airborne holding) 3) changing from IFR to VFR or VFR to IFR within a Class E 4) VFR flights entering Class B-D from a Class E airspace, or VFR flights leaving Class B-D to enter Class E 5) leaving CAS: A) unless pilots are provided with advance notice IAW P1B.4 below B) except when leaving CAS in connection with an IFR flight holding in Class E IAW P1B.5

Question 8

Additionally, pilots of IFR flights must be advised of the change of airspace classification when entering and leaving Class E airspace when the flight is:

Answer 8

1) an unplanned diversion or 2) no flight plan has been filed at the time a clearance to enter CAS is requested The associated phraseology is in CAP 413

Question 9

1B.4 For flights leaving CAS controllers should provide pilots with advance notice of:

Answer 9

1) the lateral or vertical point at which the aircraft will leave CAS. Such notice should be provided between 5-10nm or 3000-6000ft prior to the boundary of CAS 2) the type of ATS that will subsequently be provided, unless the aircraft is coordinated and transferred to another ATS unit before crossing the boundary of a CAS

Question 10

1B.5 IFR airborne holding might not be fully contained within…

Answer 10

…the lateral boundaries of Class E airspace. Controllers are not required to advise pilots of such flights on the changes of ATS provided as they leave or enter Class E airspace. However, the controller shall provide either a DS, or procedural service, depending on the availability of ATS surveillance, for the portion of IFR flight in Class G airspace. Controllers are only required to advise pilots when a procedural service will be provided as pilots assume, unless otherwise advised, that the type of U.K. FIS they will receive will be a DS.

Question 11

A radar control service may be provided to aircraft operating:

Answer 11

1) IFR 2) SVFR 3) VFR in Class B-D airspace

Question 12

When providing a RCS controllers issue instructions to which:

Answer 12

1) pilots of aircraft operating IFR are required to comply 2) pilots of aircraft operating SVFR or VFR will comply unless they advise the controller otherwise

Question 13

Before an aircraft enters CAS the controller must establish…

Answer 13

…which flight rules the pilot will be operating under.

Question 14

Before a RCS to IFR flights is terminated…

Answer 14

procedural separation must be applied, except at ACCs when an aircraft will be entering an adjacent sector and: 1) a radar handover had been given or 2) the conditions of any standing agreement have been met

Question 15

Participating VFR flights in a Class E airspace shall not be provided with…

Answer 15

…an Air a Traffic Control Service, but one of the following types of U.K. FIS IAW CAP774: 1) Basic Service 2) Traffic Service

Question 16

Surveillance services provided within Class G airspace (DS and TS)…

Answer 16

…are detailed in CAP774 UK FIS

Question 17

The CAA has specified that certain units are permitted to provide an ATS surveillance service to aircraft wishing to…

Answer 17

…penetrate CAS which is under the jurisdiction of another ATSU. Controllers at these independent units are responsible for separating aircraft under their control from all other aircraft in that CAS.

Question 18

One of the following methods is to be employed when PSR is used to identify aircraft.

Answer 18

The Turn Method The Departing Aircraft Method The Position Report Method Direction a Finding equipment should be used to assist the identification provided it has been approved for such use.

Question 19

The Turn Method:

Answer 19

An aircraft may be identified by ascertaining its heading and, following a period of track observation, correlating the observed movement of a particular position indication with: 1) the acknowledged execution of an instruction to alter heading by at least 30deg 2) one or more changes of heading of at least 30deg, as instructed by another controller 3) one or more changes of heading of at least 30deg reported by the pilot A turn for identification does not constitute the provision of a surveillance service. However, controllers should take into consideration terrain, other surveillance returns, PSR coverage and the RoA before instructing an aircraft to alter heading. In using the turn method the controller shall: 1) verify that the movements of not more than one position indication correspond with those of the aircraft 2) exercise caution particularly when employing this method in areas where changes of aircraft heading are commonly made as a navigational routine

Question 20

The Departing Aircraft Method:

Answer 20

By observing and correlating the position indication of a departing aircraft to a known airborne time. Identification is to be achieved within 1nm of the end of the runway unless otherwise authorised by the CAA. Particular care should be taken to avoid confusion with aircraft overflying the aerodrome, making a missed approach, departing from an adjacent runway or holding overhead the aerodrome

Question 21

The Position Report Method:

Answer 21

By correlating a particular position indication with a report from the pilot that the aircraft is: 1) over an exact reporting point which is displayed on the situation display or 2) at a particular distance not exceeding 30nm on a particular radial from a co-located VOR/DME or TACAN (DME). the source facility must be displayed on the situation display. or 3) over a notified visual reference point or prominent geographical feature, in either case approved for the purpose and displayed on the situation display, provided that the flight is operating with visual reference to the surface and at a height of 3000ft or less above the surface. The identification must follow a period of track observation sufficient to enable the controller to compare the movement of the position indication with the pilot’s reported route. The reported position and level of the aircraft must indicate that it is within known PSR cover. This method must be reinforced by an alternative method if there is any doubt about the identification because of: 1) the close proximity of other returns or 2) inaccurate reporting from aircraft at high level or some distance from navigational facilities.

Question 22

A pilot is to be informed as soon as…

Answer 22

…his aircraft has been identified. When operating inside CAS, the pilot of an aircraft need only be so informed if the identification is achieved by the turn method.

Question 23

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

Answer 23

1) observing the pilots compliance with the instruction to select a discrete 4 digit code 2) recognising a validated 4 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 3) observing an IDENT feature when it has been requested Caution must be exercised when employing this method because simultaneous requests for SPI transmissions within the same area may result in misidentification. Aircraft displaying a conspicuity or special purpose code are not to be identified by this method.

Question 24

Controllers are to assign Mode A codes to aircraft according to the Code Assignment Plan, which comprises:

Answer 24

1) Discrete codes comprising: A) domestic codes which are assigned to aircraft flying within the areas of responsibility of a unit B) ORCAM codes which are assigned to international flights and will normally be retained beyond the area of responsibility of the assigning unit 2) Special purpose codes allocated internationally 3) Conspicuity codes, allocated nationally, or to specific users/units

Question 25

When providing a surveillance service to an aircraft, controllers operating at SSR equipped units should…

Answer 25

…allocate that flight with a discrete code IAW the SSR assignment plan. Unless otherwise directed by an ATCU, Mode C will be selected in conjunction with Mode A. Controllers must, therefore, verify the accuracy of the Mode C readout when assigning discrete codes to aircraft.

Question 26

A controller assigning any Mode A code must…

Answer 26

…validate the code by checking as soon as possible, either by direct reference to his display or with the assistance of another controlling agency, that the data displayed corresponds with the code which has been assigned. At units where code callsign conversion equipment is in use, procedures to ensure the correct correlation of the callsign with the assigned code are to be applied.

Question 27

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

Answer 27

1) instructing the aircraft to squawk the assigned code and observing that the correct numbers appear on the situation display 2) instructing the aircraft to squawk IDENT and simultaneously checking the code numbers associated with the SSR response 3) matching an already identified position indication with the assigned code for the flight

Question 28

If the Mode A code readout does not correspond to that assigned, the pilot is to be instructed to…

Answer 28

…reset the assigned code. Where this fails to achieve display of the assigned code then the pilot is to be instructed to select code 0000. If a corrupt code still exists the pilot should normally be instructed to switch off the transponder. However, the corrupt code may be retained to assist identification and tracking provided the Mode C has been verified. Associated ATCUs are to be informed of the retention of corrupt data.

Question 29

Controllers may deem Mode A codes to be validated when it can be ascertained from the Code Assignment Plan that…

Answer 29

…an observed Mode A code has been assigned by a unit capable of validating the code, unless: 1) the code is promulgated as being unvalidated or 2) the controller has been notified that the code is corrupt

Question 30

The Mode A code and associated Mode C data of special purpose codes must be…

Answer 30

…considered unvalidated and unverified.

Question 31

Controllers should be aware of the following special purpose codes:

Answer 31

1) emergency codes 7500, 7600, 7700 2) code 1000, to indicate an aircraft conducting IFR flight as GAT, where the downlinked aircraft identification is validated as matching the aircraft identification entered in the flight plan 3) code 2000, which is selected by pilots of aircraft entering the U.K. from an adjacent FIR where the operation of transponders has not been required NOTE: Code 2000 is also used for the purposes of IFR conspicuity 4) code 7007, which is selected by aircraft engaged on airborne observation flights under the terms of the treaty on Open Skies. Flight priority Cat B status has been granted for such flights and details will be published by NOTAM.

Question 32

The Mode A code and associated Mode C of conspicuity codes must be…

Answer 32

…considered unvalidated and unverified.

Question 33

Pilots are required to squawk a VFR or IFR conspicuity code when…

Answer 33

…operating at and above FL100 and are advised to do so when below FL100 unless: 1) they have been assigned a discrete code 2) they are transponders on one of the special purpose codes, a frequency monitoring code or on one of the other specific conspicuity codes assigned IAW the Code Assignment Plan 3) they are flying below 3000ft in the aerodrome traffic pattern and have been instructed to select the aerodrome traffic pattern conspicuity code 7010 4) on grounds of safety the aircraft had been instructed to squawk standby. In view of the associated reduction in protection from ACAS, such circumstances are to be regarded as exceptional. ATSUs shall love the circumstances and duration of any such occurrences. Records are to be made available to the CAA on request.

Question 34

0024

Answer 34

Radar flight evaluation or calibration. Only to be used for the duration of the radar evaluation or calibration. The code shall not be used whilst transiting to/from the trial.

Question 35

0033

Answer 35

Paradropping. Unless a discrete Mode A code has already been assigned, pilots of transponder equipped aircraft should select Mode A code 0033, together with Mode C pressure altitude reporting mode of the transponder, 5. Invites before the drop commences until the drop is complete and parachutists or loads are estimated to be on the ground.

Question 36

7000

Answer 36

VFR Conspicuity code Used when operating in U.K. airspace VFR and have not received a specific instruction from an ATSU concerning the setting of the transponder

Question 37

2000

Answer 37

IFR Conspicuity code Used when operating in U.K. airspace IFR and have not received a specific instruction from an ATSU concerning the setting of the transponder

Question 38

7001

Answer 38

Military fixed wing low level conspicuity and climbout Used by military fixed wing aircraft operating in the U.K. low flying system. When an ATS is required on climb out from the low flying system, the aircraft will retain the code until an ATC unit passes alternative instructions

Question 39

7002

Answer 39

Danger areas general

Question 40

7003

Answer 40

Red arrows display/transit

Question 41

7004

Answer 41

Aerobatics and display Unless a discrete code has already been assigned, pilots of transponder equipped aircraft will select conspicuity code 7004 5mins before commencement of their aerobatic manoeuvres until they cease and resume normal operations.

Question 42

7005

Answer 42

High energy manoeuvres Unless a discrete code has already been assigned, outside CAS, below FL195 and outside U.K. low flying system, pilots of military fast jet aircraft will select Mode A code 7005 prior to engaging in sustained high energy manoeuvres

Question 43

7006

Answer 43

Autonomous ops within TRA and TRA(G)

Question 44

7010

Answer 44

Aerodrome traffic pattern conspicuity code The purpose of this code is to facilitate greater availability of the collision avoidance function provided by ACAS. It also allows a unit with appropriate equipment to filter or highlight the aircrafts position symbol as appropriate. May be allocated by ATSUs or selected. Y a pilot as local procedure may require, when the aircraft is operating in or within approx 2nm of the aerodrome traffic pattern.

Question 45

In order to both prevent and mitigate the consequences of airspace infringements, pilots operating close to the peripheries of certain CAS may select…

Answer 45

…local SSR conspicuity codes and monitor the promulgated frequency. Selection of such codes and associated frequency monitoring does not imply the provision of any form of ATS. Procedures for the use of monitoring codes and actions to be taken by controllers shall be detailed in MATS2.

Question 46

There are 2 levels of Mode S:

Answer 46

Elementary and Enhanced

Question 47

Elementary Mode S provides…

Answer 47

..selective interrogation of aircraft, and the aircraft ID down linked airborne parameter (DAP)

Question 48

Enhanced Mode S enables further DAPs from an aircrafts flight management system, which include:

Answer 48

1) selected altitude 2) IAS 3) ground speed 4) magnetic heading 5) rate of climb/descent

Question 49

In addition to traditional Mode A/C capabilities, Mode S transponder equipped aircraft engaged in international civil aviation also incorporate an…

Answer 49

…aircraft ID feature, sometimes referred to as Flight Identity or Flight ID. Flight crew of aircraft equipped with a Mode S aircraft ID feature will set the aircraft ID in the transponder. The aircraft ID feature should not be confused with the “aircraft address” which is a unique ICAO code relating directly to the airframe in which the Mode S transponder has been installed and over which crews have no control.

Question 50

Direct recognition of the aircraft ID feature on the situation display may be used to establish surveillance identification subject to either:

Answer 50

1) correlation of the aircraft ID feature with the aircraft ID entered I. The flight plan and displayed to controllers on FPS or 2JR correlation of the aircraft ID feature with the aircraft’s Callsign used in a directed RT transmission to the controller. However, controllers shall exercise particular caution when there are aircraft with similar callsign son frequency, and shall utilise an alternative method if they have any doubt about the surveillance identification.

Question 51

Whenever it is observed on the situation display that the down-linked aircraft ID feature is different from that expected from the aircraft…

Answer 51

…the pilot shall be requested to confirm and, if necessary, re-enter the aircraft ID feature.

Question 52

If the discrepancy continues to exist following confirmation by the pilot that the correct aircraft ID has been set in the aircraft ID feature, the controller shall take the following minimum actions:

Answer 52

1) inform the pilot of the persistent discrepancy 2) assign a discrete Mode A code 3) notify the erroneous aircraft ID feature transmitted by the aircraft to the next control position or unit

Question 53

Transfer of ID using the Mode S aircraft ID feature relies on…

Answer 53

…both units having appropriate Mode S surveillance capability; therefore, it shall only be conducted IAW locally agreed arrangements and specified in M2.

Question 54

The selected altitude DAP is generated by…

Answer 54

…flight crew inputs into the aircrafts auto pilot system. Subject to appropriate surveillance system capability, the selected altitude DAP can be displayed to controllers on situational displays.

Question 55

Selected altitude data will be presented as either…

Answer 55

…a flight level or an altitude, depending on local surveillance system settings, which are to be detailed in M2. For ATC and RT purposes, the generic phrase ‘selected level’ is used to encompass data presented as either an altitude or a flight level.

Question 56

Selected levels display…

Answer 56

…intent-based information only and shall not be used for the purposes of separation.

Question 57

There are occasions where, whilst the flight crew have correctly interpreted the ATC instruction, the selected level will be at variance. These situations will vary according to aircraft type, aircraft operator, and mode of operation, but may include the following:

Answer 57

1) SID/STAR with vertical restrictions, where pilots may select the final cleared level and utilise the aircraft flight management system to achieve the vertical constraints 2) Final approach, at which point pilots may pre-select the missed approach procedure altitude 3) when the aircraft is being flown manually, in particular in response to vertical avoiding action manoeuvres

Question 58

Units equipped with enhanced mode S surveillance systems that enable DAPs should display…

Answer 58

…selected levels on the situation display as a means of mitigating the risk of level busts.

Question 59

The checking of selected levels shall not be used as…

Answer 59

…a substitute for RT read-back of level clearances

Question 60

Where the selected level is seen to be at variance with an ATC clearance, controllers shall not…

Answer 60

…state on RT the incorrect level as observed on the situation display. However, taking into account the limitations of selected levels, controllers may query the discrepancy using the following phraseology: “(Callsign), check selected level, cleared level is (correct cleared level)”

Question 61

Downlinked Mode S barometric pressure setting data has the potential to assist in the prevention of level busts. Where such data is available to a controller and a discrepancy is observed between the QNH passed and that selected by the pilot…

Answer 61

…a controller should query the discrepancy, using the following phraseology: “(Callsign), check altimeter setting QNH 1000” (where QNH 1000 is the correct value)

Question 62

TMZ is…

Answer 62

…airspace of defined dimensions within which aircraft are required to operate a transponder IAW promulgated procedures.

Question 63

A TMZ may be established for…

Answer 63

…overriding safety reasons, where the airspace classification would not ordinarily require aircraft to carry a transponder.

Question 64

The pilot of an aircraft that wishes to operate in a TMZ without such serviceable transponder equipment may…

Answer 64

…be granted access to the TMZ subject to specific ATC approval. Procedures pertinent to each TMZ shall be promulgated, which specify detailed access and notification requirements.

Question 65

Within a TMZ…

Answer 65

…standard ATC procedures and separation/deconfliction minima, appropriate to the airspace classification, are to be applied.

Question 66

If only PSR is available, a controller may transfer the identity of an aircraft to another controller by any of the following methods:

Answer 66

1) Direct designation (pointing) of the position indication where 2 situation displays are adjacent or a conference type of display is used. If the information on 2 situation displays is derived from separate PSR heads (or beams, if using a stack beam system) the transferring controller must ensure that the blips on both displays correlate before using this method. If parallax is likely to cause an error, an alternative method is to be used. 2) Designation of the position indication in terms of a direction and distance from a common reference point (geographical position or nav facility) accurately indicated on both displays. The position indication, as seen by the accepting controller, must be within 3nm of the position stated. The distance between the aircraft and the reference point must not exceed: A) 30nm, if the aircraft is flying along a published ATS route or direction is given as a bearing in degrees B) 15nm in other circumstances 3) Designation of the position indication by positioning an electronic marker or symbol so that only one position indication is thereby indicated and there is no possible doubt of correct identification

Question 67

A pilot shall be advised whenever identification is lost, except:

Answer 67

When using SSR, controllers may be temporarily unable to read the data blocks associated with aircraft due to overlapping or garbling eg in holding areas. Although this constitutes a loss of identification, the pilot need not be advised that identification has been lost if the controller anticipates that identification will be re-established immediately the overlapping or garbling ceases.

Question 68

When providing surveillance services OCAS, a pilot is to be informed…

Answer 68

…as soon as his aircraft has been identified. When operating inside CAS, the pilot of an aircraft need only be so informed if the identification is achieved by the turn method.

Question 69

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

Answer 69

1) following identification of the aircraft using the turn method 2) when the pilot requests the information 3) when the aircraft is flying off the correct track 4) when an aircraft estimate differs significantly from the controllers estimate based on ATS surveillance system observation 5) when the pilot is instructed to resume his own navigation following vectoring, if considered necessary by the controller Additionally, controllers may pass position info to aircraft whenever they consider it necessary

Question 70

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

Answer 70

1) a well known geographical position; bearing (using points of the compass) and distance from a known position 2) magnetic track and distance to a location displayed on the situation display that is a reporting point, an en route navaid, or an approach aid 3) latitude and longitude (by specific units only when authorised in M2) 4) distance from touchdown of the aircraft is on final approach

Question 71

Method of ID: SSR

Answer 71

Inside CAS: Inform identified? NO Pass position? NO Outside CAS: Inform identified? YES Pass position? NO

Question 72

Method of ID: TURN

Answer 72

Inside CAS: Inform identified? YES Pass position? YES Outside CAS: Inform identified? YES Pass position? YES

Question 73

Method of ID: DEPARTING AIRCRAFT

Answer 73

Inside CAS: Inform identified? NO Pass position? NO Outside CAS: Inform identified? YES Pass position? NO

Question 74

Method of ID: POSITION REPORT

Answer 74

Inside CAS: Inform identified? NO Pass position? NO Outside CAS: Inform identified? YES Pass position? NO

Question 75

When providing a BS, a controller may…

Answer 75

…identify an aircraft to facilitate co-ordination or to assist in the provision of generic nav assistance, but is not required to inform the pilot that identification has taken place or to pass a position report

Question 76

When SSR is used to assess vertical separation the Mode C responses are to be…

Answer 76

…continually monitored to ensure that the vertical distance is never less than the prescribed minimum

Question 77

Vertical separation using Mode C is not applied against…

Answer 77

…aircraft transponding A0000

Question 78

Minimum vertical separation may be applied between…

Answer 78

…verified Mode C transponding aircraft provided the intentions of both aircraft are known to a controller because either: 1) they are under his control 2) they have been co-ordinated 3) they are operating IAW established agreements

Question 79

Aircraft under radar control service ie inside CAS: If the intentions of verified Mode S altitude reporting or Mode C transponding aircraft are not known

Answer 79

1) the minimum separation for IFR flights in Class A, C-E airspace must be increased to 5000ft, or alternative approved minima within M2 and 2) VFR flights in Class C airspace, must be increased to 5000ft, or alternative approved minima within M2

Question 80

Aircraft under Deconfliction Service ie outside CAS: If the intentions of Mode C transponding aircraft are not known…

Answer 80

…the vertical deconfliction minima must be increased to 3000ft, and unless the SSR Mode A indicates that the Mode C data has been verified, the surveillance returns, however presented, should not merge.

Question 81

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

Answer 81

1) for IFR flights within Class A, C and D, and VFR flights within Class C airspace, a minimum vertical separation of 5000ft, or an alternative approved within M2, and surveillance returns however presented are not allowed to merge 2) for IFR in Class E airspace, except against aircraft displaying VFR conspicuity or a frequency monitoring code, a minimum vertical separation of 5000ft, or an alternative approved within M2, and surveillance returns however presented are not allowed to merge 3) for IFR in Class E airspace against aircraft displaying VFR conspicuity or a frequency monitoring code, whenever practicable, pass TI and if requested by the pilot or when deemed necessary by the controller, suggest traffic avoidance advice Note: the procedure in 2) and 3) only applies against the FMCs notified for the purposes of VFR in Class E airspace

Question 82

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:

Answer 82

1) information received indicates that an aircraft is lost or has experienced a radio failure or 2) the controller has approved such an aircraft to enter the TMZ airspace without identifying the aircraft using an appropriate method

Question 83

When suggesting traffic avoidance advice, controllers shall aim to…

Answer 83

…prevent surveillance returns from merging

Question 84

For aircraft receiving a Deconfliction Service is outside CAS for Mode C vertical separation…

Answer 84

…refer to CAP 774 UK FIS

Question 85

Controllers are to verify…

Answer 85

…the accuracy of Mode C data, once the aircraft has been identified and the Mode A validated, by checking that the readout indicates 200ft or less from the level reported by the pilot. If the aircraft is climbing or descending, the pilot is to be instructed to give a precise report as the aircraft passes through a level.

Question 86

Verification may be achieved with…

Answer 86

…the assistance of an ATSU with which the aircraft is in contact.

Question 87

A Mode C readout can be assumed to have been verified if…

Answer 87

…it is associated with a deemed validated Mode A code

Question 88

There is no requirement to monitor level readouts when…

Answer 88

…Mode C data is not being used to provide vertical separation.

Question 89

However, if a controller observes a Mode C discrepancy the pilot is to be asked to…

Answer 89

…confirm his altimeter setting and level. If the discrepancy remains, the pilot is to be instructed to switch off Mode C. If independent switching of Mode C is not possible, the pilot is to be instructed to select A0000.

Question 90

The following criteria apply when assessing the vertical position of a Mode C transponding aircraft:

Answer 90

1) an aircraft may be considered to be at an assigned level provided that the Mode C readout indicates 200ft or less from that level 2) An aircraft which is known to have been instructed to climb or descend may be considered to have left a level when the Mode C readout indicates a change of 400ft or more from that level and is continuing in the anticipated direction 3) 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 400ft or more and continuing in the required direction 4) An aircraft may be considered to have reached an assigned level when 3 successive Mode C readouts indicate 200ft or less from that level

Question 91

Mode C information is normally displayed as…

Answer 91

…a Flight Level, but on some ground equipment the vertical position of an aircraft flying below a pre-determined datum is displayed as an altitude.

Question 92

Radar Handover: The transfer of responsibility for a aircraft from one controller to another may be effected provided that:

Answer 92

1) satisfactory 2 way speech communication is available between them 2) the identity has been transferred to the accepting controller, or has been established by him and 3) the accepting controller is informed of any level or vectoring instructions applicable to the aircraft at the stage of transfer If the route of the aircraft is not known the offering controller is to pass the observed track or reported aircraft heading to the accepting controller

Question 93

Radar Release: Control of arriving aircraft may be transferred to approach radar control, when other aircraft would otherwise delay the released aircrafts progress, in accordance with the following conditions:

Answer 93

1) the transfer of control message is prefixed “radar release” 2) details of all conflicting aircraft are passed to the approach radar controller 3) conflicting aircraft are either transferred to approach radar control or identified according to the accepting controllers decision 4) neither the track nor the level of the conflicting aircraft is altered without co-ordination

Question 94

A controller may instruct an aircraft to turn…

Answer 94

…in any direction as dictated by circumstances but when avoiding unknown aircraft the R of A Regulations should be observed if practicable.

Question 95

Aircraft flying outside controlled airspace and aircraft flying VFR within Class E airspace are not obliged to…

Answer 95

…follow instructions given by ATC, but where the pilot of an aircraft accepts a Traffic Service or Deconfliction Service, the controller can expect that his instructions will be followed.

Question 96

Unless an aircraft has planned to leave controlled airspace, it is not to be vectored outside the horizontal or vertical limits, except:

Answer 96

(1) when an emergency situation arises requiring the aircraft to be vectored outside controlled airspace; (2) when avoiding severe weather; the circumstances must be explained to the pilot before the aircraft leaves controlled airspace; (3) when specifically requested by the pilot.

Question 97

Although IFR flights within class A-D airspace, and VFR flights within B/C airspace, are deemed to be separated from unknown aircraft flying in adjoining uncontrolled airspace, controllers should aim to…

Answer 97

…keep the aircraft under their control at least two miles within the boundary. Controllers should monitor the operation of aircraft in adjacent uncontrolled airspace, particularly if circumstances have made it necessary to vector an aircraft to be less than two miles from the boundary. In such circumstances, consideration should be given to co-ordinating with the appropriate controlling agency if applicable. However, regardless of airspace divisions and classifications, controllers should take appropriate action with respect to the safety of aircraft if unknown aircraft appear to present a risk of collision.

Question 98

When vectoring is complete, pilots will be instructed to…

Answer 98

…resume their own navigation. Where a direct route is required, the controller shall specify this in the instruction.

Question 99

When an aircraft inbound to a VOR/DME holding pattern is vectored away from a standard VOR radial, the controller must either…

Answer 99

…provide magnetic track and distance information on instructing the aircraft to resume own navigation or issue vectoring instructions to intercept the appropriate radial to the holding or routeing fix.

Question 100

Controllers are to ensure that levels assigned to IFR flights in receipt of a Radar Control Service provide…

Answer 100

…adequate terrain clearance for the phase of flight as shown below.

Question 101

Controllers have no responsibility for the terrain clearance of, and shall not assign levels to…

Answer 101

Controllers have no responsibility for the terrain clearance of, and shall not assign levels to, aircraft operating Special VFR or VFR within controlled airspace which accept vectors

Question 102

Within Class G airspace, regardless of the service being provided, pilots are ultimately responsible for…

Answer 102

…terrain clearance. However, terrain requirements pertaining to level allocations and the provision of vectors are specified within the conditions of the services as detailed within CAP 774 – UK Flight Information Services.

Question 103

A position symbol which cannot be associated with an aircraft known by the controller to be operating within the airspace concerned shall be…

Answer 103

A position symbol which 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 104

The action to be taken by controllers when they observe an unknown aircraft, which they consider to be in unsafe proximity to traffic receiving an ATS varies according to the airspace classification in which the event takes place as follows:

Answer 104

Question 105

When providing traffic avoiding advice, controllers shall remind pilots of…

Answer 105

When providing traffic avoiding advice, controllers shall remind pilots of their responsibility to remain clear of cloud with the surface in sight.

Question 106

When the controller considers that more immediate action is required by the pilot…

Answer 106

When the controller considers that more immediate action is required by the pilot, traffic avoidance advice may be passed by ATC before traffic information.

Question 107

Whenever the flight rules employed by pilots of unknown aircraft cannot be determined…

Answer 107

Whenever the flight rules employed by pilots of unknown aircraft cannot be determined the procedure detailed in section 1, chapter 6, paragraph 10A.5(2) shall be applied.

Question 108

When traffic avoidance advice is issued to an IFR aircraft under a Radar Control Service, controllers must seek to achieve…

Answer 108

When traffic avoidance advice is issued to an IFR aircraft under a Radar Control Service, controllers must seek to achieve the required minima and pilots must comply with the instructions given. However when avoiding action is issued to an IFR aircraft under a Radar Control Service in Class D or E airspace, and the pilot reports that he has the unknown aircraft in sight and has positively stated that he will maintain his own separation from it, further controller action may then be limited to passing traffic information. It is recognised that it may not always be possible for controllers to achieve the required separation minima against unknown traffic infringing controlled airspace due to the potential for their sudden appearance and/or unpredictable manoeuvres; however, controllers shall apply all reasonable endeavours (SERA.7002(a)).

Question 109

However when avoiding action is issued to an IFR aircraft under a Radar Control Service in Class D or E airspace, and the pilot reports that he has the unknown aircraft in sight and has positively stated that he will maintain his own separation from it, further controller action may then be limited to…

Answer 109

…passing traffic information.

It is recognised that it may not always be possible for controllers to achieve the required separation minima against unknown traffic infringing controlled airspace due to the potential for their sudden appearance and/or unpredictable manoeuvres; however, controllers shall apply all reasonable endeavours.

Question 110

When traffic avoidance advice is issued on request to VFR/SVFR aircraft under Radar Control Service, controllers are not required to…

Answer 110

…achieve separation minima. Such avoiding action instructions shall be aimed at ensuring that the risk of collision is reduced as far a

Question 111

Controllers shall advise pilots when…

Answer 111

Controllers shall advise pilots when the conflict no longer exists

Question 112

Controllers who observe that an aircraft using an assigned SSR code is, or is about to, make an unauthorized infringement of their airspace should…

Answer 112

…attempt to contact the relevant agency to identify the aircraft and agree a course of action

Question 113

In the case of aircraft using A1177, controllers should contact…

Answer 113

In the case of aircraft using A1177, controllers should contact the appropriate London FISO who will assist in identification. For example, by relaying instructions to “Squawk Ident”, and instructions, as necessary, for the aircraft to be transferred to the controller’s frequency:

“G-ABCD, at (unit) request - contact (unit) (frequency) immediately”

Question 114

Controllers should note that simple transfers of communication form part of the London FISOs’ standard operating procedures.

However, FISOs are not permitted to…

Answer 114

Controllers should note that simple transfers of communication form part of the London FISOs’ standard operating procedures. However, FISOs are not permitted to issue any 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 so that the controller can resolve the situation.

Question 115

Traffic information to aircraft shall include the following:

Answer 115

(1) Bearing from the aircraft in terms of the 12-hour clock (when the aircraft is turning, direction of the unknown aircraft by compass points);
(2) Distance from the aircraft in miles;
(3) Direction in which the unknown aircraft is proceeding, e.g. “traffic is opposite direction/crossing left to right”, etc.
(4) Height information when available, this may include the unverified Mode C of unknown aircraft.

Under some circumstances, controllers may consider it prudent to inform a pilot of other traffic which is separated from his aircraft. In such cases, to prevent any possible confusion, no reference should be made to the actual level of the other aircraft. If necessary, the pilot should be informed that the other aircraft is “(number) thousand feet above/below”.

Question 116

A controller may be alerted to the presence of adverse weather by a variety of sources including;

Answer 116

A controller may be alerted to the presence of adverse weather by a variety of sources including; radar observations, reports from pilots or adjacent ATSUs, Meteorological Office reports and unit briefings

Question 117

When weather is observed on the situation display, or is known to be present, pilots should be advised of…

Answer 117

When weather is observed on the situation display, or is known to be present, pilots should be advised of the weather’s location and, if known, intensity and direction of movement.

Question 118

When a pilot requests an alternative heading or route for weather avoidance, controllers shall…

Answer 118

When a pilot requests an alternative heading or route for weather avoidance, controllers shall accommodate such requests, taking into account the prevailing traffic situation. When a pilot’s request cannot be accommodated, controllers shall offer an alternative weather avoidance clearance or explain to the pilot why his request cannot be met

Question 119

When weather avoidance will take an aircraft outside controlled airspace…

Answer 119

When weather avoidance will take an aircraft outside controlled airspace the pilot must be informed of this and offered an appropriate service. Pilots routeing outside controlled airspace for weather avoidance should be issued a clearance to rejoin as required

Question 120

If a pilot is cleared to follow his own navigation, or accepts a heading, in order to avoid weather, he should be requested to…

Answer 120

…report when able to accept vectors back on-track.

Question 121

There are many potential causes of spurious primary returns (‘clutter’), including:

Answer 121

There are many potential causes of spurious primary returns (‘clutter’), including: weather; anomalous propagation; ground/sea returns; birds; wind turbine effects; and radar countermeasures such as chaff. Whilst it may be possible for some forms of clutter to be distinguishable from aircraft surveillance returns, this may not always be possible, especially where processed surveillance systems are employed.

Question 122

Clutter on the situation display has the potential to impact on ATS provision in the following ways:

Question 123

The impacts listed above (wx clutter) are likely to affect the degree, accuracy and timeliness of the instructions, advice, and information that controllers are able to provide to pilots, with consequent impacts on safety and expedition. Additionally, the existence of clutter may necessitate…

Answer 123

…aircraft being rerouted, or air traffic services reduced below the level requested by the pilot. Specific tactical procedures to be applied by controllers in response to clutter observed on the situation display are provided below.

Question 124

In addition to observable clutter, wind turbines have the potential to generate…

Answer 124

a variety of other negative effects on ATS systems and these should be considered by ATS providers when participating in the wind turbine application planning process. CAP764 (CAA Policy and Guidelines on Wind Turbines) provides specific information

Question 125

Where clutter of a long term or permanent nature is generated in a particular area, in addition to the procedures…

Answer 125

…the potential impacts and mitigations should be assessed locally and procedures documented in MATS Part 2.

Question 126

Outside CAS:

In the event of clutter being present on the situational display controllers should consider the nature and extent of the clutter and if necessary take the following actions:

Answer 126

(1) For aircraft in receipt of a Deconfliction Service or Traffic Service, controllers should inform the pilot of the extent of the clutter and where practicable offer a reroute. However, this may not be possible due to traffic density, airspace availability and/or the requirement to follow specific arrival or departure tracks. The extent of such a reroute should where possible aim to achieve the planned lateral deconfliction minima from the observed clutter. However, it may still be necessary to reduce traffic information, and if applicable deconfliction advice, from the direction of the clutter as detailed within CAP 774 – UK Flight Information Services.
(2) For aircraft in receipt of a Traffic Service, and those aircraft under a Deconfliction Service that are not rerouted as above, controllers shall inform pilots of a reduction in traffic information/deconfliction advice as detailed within CAP 774 – UK Flight Information Services. If the controller cannot maintain aircraft identity, the service shall be terminated.
(3) For all surveillance services, in order to maintain track identity of aircraft being vectored to final approach, if re-routing around the clutter is not practicable for the reasons specified above, an alternative type of approach may need to be conducted.

Question 127

Inside CAS:

In the event of clutter being present on the situational display Radar Control Service shall not be terminated, nor the air traffic service terminated. Controllers should consider the extent of the clutter and if necessary take the following actions:

Answer 127

(1) The controller may vector the aircraft around the clutter; however, this might not be practicable due to traffic density, airspace availability and/or the requirement to follow specific arrival or departure tracks.
(2) If the intensity of the clutter is such that the controller is not able to clearly see the aircraft’s PSR or SSR position symbol, radar separation shall not be used to separate it and other controlled aircraft.
(3) The controller may provide IFR traffic in Class E airspace with reduced traffic information.

Question 128

In the event of clutter being present on the situational display, VFR flights receiving a Traffic Service within Class E airspace shall be managed…

Answer 128

In the event of clutter being present on the situational display, VFR flights receiving a Traffic Service within Class E airspace shall be managed in accordance with 18B.1(1) and 18B.1(2) above.

Question 129

The controller remains responsible for providing advice and information on aircraft that are considered to be…

Answer 129

The controller remains responsible for providing advice and information on aircraft that are considered to be infringing controlled airspace. Therefore, the controller should consider the nature and consistency of the clutter including any observed movement, relative speed and track, and take appropriate action if it is considered to be an unknown aircraft

Question 130

In addition to the procedures above, in all classes of airspace, for aircraft intending to make a radar approach, the controller shall assess the nature and extent of the clutter and decide whether:

Answer 130

(1) a radar approach is not possible owing to clutter, in which case the controller shall inform the aircraft; or
(2) a radar approach could be carried out, but there may be a possibility of radar contact being lost. In this case the controller shall inform the aircraft as early as possible that clutter is affecting his display and that missed approach instructions will be passed in good time if it becomes necessary to abandon the approach.

Question 131

In the event of surveillance system failure, the controller shall…

Answer 131

…inform aircraft under control of the failure and apply local contingency procedures, which shall be detailed in MATS Part 2.

Reduced vertical separation of half the applicable vertical separation (e.g. 500 feet where a controller would normally apply 1000 feet vertical separation and 1000 feet where a controller would normally apply 2000 feet vertical separation) may be employed temporarily if standard separation cannot be provided immediately.

When reduced vertical separation is employed, pilots shall be informed and essential traffic information passed as necessary

Question 132

When a previously failed surveillance system is notified as being serviceable, before any ATS surveillance service is provided the controller shall…

Answer 132

…re-identify all aircraft by an approved method in accordance with the procedures described in this Chapter.

Question 133

In the event an STCA is generated in respect of controlled flights, the controller shall without delay…

Answer 133

…assess the situation and, if necessary, take action to ensure that the applicable separation minimum will not be infringed.

Specific local STCA procedures shall be detailed in MATS Part 2. Comprehensive requirements for STCA can be found in CAP 670 (ATS Safety Requirements).