General: ATS Surveillance Systems Flashcards
What do Surveillance Services comprise of?
- Separation of arriving, departing, and en-route traffic
- Vectoring
- Position info to assist in the navigation of aircraft
- Monitoring traffic to provide info to the procedural controller
- Assistance to aircraft crossing CAS
What shall an ATCO do before providing surveillance services to an aircraft?
- Identify the aircraft, using a method appropriate to the surveillance system in use;
- Have had the identity of the aircraft transferred from another ATCO.
The act of identifying an aircraft does not imply that a service is being given.
What may surveillance systems also be used for, whether an aircraft has been identified or not?
- Information on the position of aircraft likely to constitute a hazard
- Avoiding action
- Information about observed weather for pilots & other ATCOs
- Assistance to aircraft in emergency
How should surveillance services be provided?
- Surveillance services shall be provided to the maximum extent practicable to cover the operational requirement subject only to workload, communications, or equipment capability.
What surveillance services are available inside & outside CAS?
- CAS: Radar Control Service
- Outside CAS: Deconfliction Service / Traffic Service
When must a pilot be advised when a surveillance service commences, terminates, or changes?
- Outside CAS
- Entering CAS
- Leaving CAS - unless pilots are provided with advance notice.
When should ATCOs inform pilots with advanced notice of leaving CAS?
- The lateral / vertical point at which aircraft will leave CAS. (Provided between 5-10NM or 3,000-6,000ft prior to the boundary of CAS).
- The type of ATS that will subsequently be provided unless the aircraft is coordinated & transferred to another ATSU before crossing the boundary of CAS.
To whom may a Radar Control Service be provided?
Aircraft operating;
* IFR
* SVFR
* VFR in Class B-D airspace
When providing the service ATCOs issue instructions to which;
* Pilots of aircraft operating IFR are required to comply
* Pilots of aircraft operating SVFR/VFR will comply unless they advise ATCO otherwise.
What must an ATCO establish before an aircraft enters CAS?
Which flight rules the pilot will be operating under.
Describe the Turn Method for Primary aircraft identification
An aircraft may be identified by ascertaining its heading &, following a period of track observation, correlating the observed movement of a particular Position Indication with;
- The acknowledged execution of an instruction to alter heading by at least 30 degrees
- One / more changes of heading of at least 30 degrees as instructed by another ATCO
- One / more changes of heading of at least 30 degrees reported by the pilot
What should an ATCO take into consideration when using the Turn Method for identification?
- Terrain
- Other surveillance returns
- PSR coverage
- RoA Regulations
A turn for identification does not constitute the provision of a surveillance service.
Describe the Departing Aircraft Method
- Identification achieved by observing & correlating the Position Indication of a departing aircraft to a known airborne time.
- Identification is to be achieved within one mile of the end of the runway.
- Particular care should be taken to avoid confusion with aircraft overflying/making a missed approach/departing from an adjacnet runway/holding overhead
What shall an ATCO do when using the turn method?
- Verify the movements of not more than one Position Indicaiton correspond with those of the aircraft
- Exercise caution particularly when employing this method in areas where changes of aircraft heading are commonly made as a navigational routine
Describe the Position Report Method of identification
Identification achieved by;
Correlating a particular Position Indication with a report from the pilot that the aircraft is;
* Over an exact reporting point which is displayed on the situation display
* At a particular distance not exceeding 30NM on a particular radial from a co-located VOR/DME. The source must be displayed on the situation display
* Over a notified visual reference point / prominent geographical feature displayed on the situation display. (Provided the flight is operating with visual reference to the surface < 3,000ft above the surface.
When must the position report method be reinforced by alternative means?
When there is any doubt about identification because of;
* Close proximity of other returns
* Inaccurate reporting from aircraft at high level / distance from navigational facilities
When should pilots be informed they are identified?
- Pilots should be informed asap they have been identified.
- When operating inside CAS the pilot of an aircraft need only be informed if identified by the turn method.
How does an ATCO identify an aircraft using Mode A?
- Observing the pilot’s compliance with the instruction to select a 4 digit discrete code.
- Recognising a validated 4-digit code previously assigned to an aircraft callsign.
- When code/callsign conversion procedures are in use & the code/callsign pairing can be confirmed, the callsign displayed in the data bloack may be used to establish & maintain identity
- Observing an IDENT featurn when it has been requested.
What is the Code Assignment Plan?
ATCOs are to assign Mode A codes to aircraft according to the Code Assignment Plan comprising;
* Discrete codes - domestic, which are assigned to aircraft flying within the areas of responsibility of a unit. ORCAM, which are assigned to international flights & will be retained beyond area of responsibility of assigning unit.
* Special purpose codes allocated internationally
* Conspicuity codes, allocated nationally or to specific users/units
What is Validation of Mode A Codes?
An ATCO assigning any Mode A code must validate the code asap by checking;
* by direct reference to their display / 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.
What methods are used to Validate Mode A codes?
- Instructing the aircraft to squawk the assigned code & observing that the correct numbers appear on the situation display.
- Instructing the aircraft to “squawk IDENT” & simultaneously checking the code numbers associated with the SSR response.
- Matching an already identified Position Indication with the assigned code for the flight.
What should an ATCO do when the Mode A code readout does not correspond to that assigned?
- The pilot is to be instructed to reset the assigned code.
- Where this fails to achieve display of the assigned code, the pilot should be instructed to select code A0000.
- 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 & tracking provided the Mode C has been verified. Associated ATCUs are to be informed of the retention of corrupt data).
When can ATCOs Deem a Mode A Code to be Validated?
ATCOs may deem Mode A codes to be validated whe 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 or;
* The ATCO has been notified that the code is corrupt.
How should ATCOs treat Mode A Special Purpose Codes?
- The Mode A & associated Mode C data of special purpose codes must be considered unvalidated & unverified.
What basic Special Purpose Codes should ATCOs be aware of?
- Emergency codes 7500, 7600, & 7700
- Code 1000, to indicate an aircraft conducting IFR flight as GAT, where the downlinked aircraft ID is validated as matching the identification entered in the flight plan.
- Code 2000 which is selected by pilots of aircraft entering the UK from an adjacent FIR where the operation of transponders has not been required (also IFR conspicuity)
- Code 7007, selected by aircraft enganged in airborne observation flights under the terms of the Treaty on Open Skies. (CAT B)
How should ATCOs treat Conspicuity Codes & when should pilots squawk these?
The Mode A & Mode C data of conspicuity codes must be considered uncalidated & unverified.
Pilots are required to squawk a VFR / IFR conspicuty when operating at & above FL100 & are advised to do so when below FL100 unless;
* They have been assigned a discrete code
* They are transponding on one of the special pirpose codes, frequency monitoring code, on one of the other specific conspicuity codes assigned in accordance with the Code Assignment PLan
* They are flying below 3,000ft in the aerodrome traffic pattern & have been instructed to squawk 7010
* On grounds of safety the aircraft has been instructed to squawk standby (In view of the associated reduction in protection from TCAS, such circumstances are to be regarded as exceptional. ATCUs shall log these).
Code 0024?
Calibrator - only during calibration, not while transiting.
Code 0033?
Para Dropping
Code 2000?
IFR Conspicuity
Code 7000?
VFR Conspicuity
Code 7001?
Military Fixed Wing Low Level Conspicuity
Used by military fixed wing in UK Low Level Flying System
Code 7002?
Danger Areas General
Code 7003?
Red Arrows Display / Transit
Code 7004?
Aerobatics & Display
Code 7005?
High Energy Manoeuvres
Code 7006?
Autonomous Operations within TRA
Code 7010?
Aerodrome Traffic Pattern Conspicuity.
Facilitates greater availability of the collision avoidance provided by TCAS.
Allows a unit with appropriate equipment to filter / highlight the aircrat’s position symbol.
What are frequency monitoring codes?
- In order to prevent & mitigate the consequences of airspace infringements, pilots operating close to the peripheries of certain CAS may select local SSR conspicuity codes & monitor the promulgated frequency.
- Selection of such codes & frequency monitoring does not imply the provision of any form of ATS. See MATS2
What are the two levels of Mode S & what do they include?
- Elementary & Enhanced.
- Elementary: Provides selective interrogation of aircraft & aircraft identification DAP.
- Enhanced: Enables further DAPs including; selected altitude, IAS, ground speed, magnetic heading, RoC/RoD
How are aircraft identified using Mode S?
Direct recognition of the Aircraft Identification Feature on the situation display may be used to establish surveillance identification subject to;
* Correlation of the Aircraft Identification Feature with the aircraft identification entered in the flight plan & displayed to ATCOs on flight progress strips
* Correlation of the Aircraft Identification Feature with the aircraft’s callsign used in a directed RTF transmission to the ATCO. (However, ATCOs shall exercise particular caution when there are aircraft with similar callsigns on the frequency & shall utilise an alternative method if they have any doubt about the surveillance identification.)
What should ATCOs do when it is oberved on the situation display that the downlinked aircraft identification feature is different from that expected?
- The pilot shall be asked to confirm & re-enter the aircraft ID feature
- If the discrepancy continues, the ATCO shall take the following minimum actions;
- Inform the pilot of the persistent discrepancy
- Assign a discrete Mode A code
- Notify the erroneous Aircraft Identification Feature transmitted by the aircraft to the next control position / unit
How is the Selected Altitude DAP used?
- The Selected Altitude DAP is generated by flight crew inputs into the aircraft’s auto pilot system. (Can be displayed on the situation display)
- Selected Altitude data will be presented as either a flight level / an altitude. (For RTF the phrase “Selected Level” is used)
- Selected levels shall not be used for purposes of separation.
Why should units with Enhanced Mode S surveillance systems show Selected Levels on the situation display?
- To mitigate the risk of level busts
- Selected Levels shall not be used as a substitude for RT readback of level clearances
In what situations will the selected level be at a variance with ATC instruction?
- SID/STARs with vertical restrictions, where pilots may select the final cleared level
- Final Approach, at which point pilots may pre-select the missed approach procedure altitude
- When the aircraft is being flown manually, particularly in response to vertical avoiding action manoeuvres
What is the phraseology used when the Selected Level is seen to be at variance with an ATC clearance?
- “(Callsign), check selected level. Cleared level is (correct cleared level)”.
- ATCOs shall not state on the RT the incorrect level observed on the situation display.
What are Transponder Mandatory Zones? (TMZ)
A TMZ is airspace of defined dimensions within which aircraft are required to carry & operate a Mode S SSR transponder.
A TMZ is established for safety reasons when the airspace would not normally require the carriage of a transponder but where a change to a more restrictive classification of CAS is not warranted.
A TMZ creates a “recognised air traffic environment” within which ATS, where provided, are more able to provide enhanced levels of safety.
How does an ATCO transfer the identity of an aircraft to another ATCO when only PSR is available?
- Direct designation (pointing) of the Position Indication where two situation displays are adjacent.
- Designation of the Position Indication in terms of a direction & distance from a common reference point (geographical position / navigational facility) accurately indicated on both displays. The Position Indication, as seen by the accepting ATCO, must be within 3 NM of the position stated.
- The distance between the aircraft and the reference point must not exceed;
- 30 NM if the aircraft is flying along an ATS route or direction is given as a bearing in degrees
- 15 NM in other circumstances
When should pilots be advised identification has been lost?
Pilots shall be advised whenever identificaiton is lost execept for; garbling, holding areas, overlapping SSR if the ATCO anticipates that identification will be re-established immediately after the overlapping/garbling ceases.
When shall pilots be informed their aircraft has been identified?
- A pilot is to be informed as soon as their aircraft has been identified.
- When operating inside CAS, the pilot need only be informed if the identification is achieved by the turn method.
When should pilots be informed of their position?
In the following circumstances;
* Following identification of the aircraft using the turn method.
* When the pilot requests the info
* When the aircraft is flying off the correct track
* When an aircraft estimate differs significantly from the ATCOs estimated based on ATS surveillance system observation
* When the pilot is instructed to resume their own navigation following vectoring if considered necessary.
What format should position information be passed in?
- A well-known geographical position
- Bearing (using points of compass) & distance from a known position
- Magnetic track & distrance to a location displayed on the situation display that is a reporting point, nav aid, approach aid
- Lat & Long (only when authorised in MATS2)
- Distance from touchdown if aircraft is on final
What should ATCOs do when SSR is used to assess vertical separation using Mode C?
The Mode C responses should be continually monitored to ensure that the vertical distance is never less than the prescribed minimum.
Can you use Mode C to vertically separate aircraft squawking A000?
No.
When can minimum vertical separation be applied?
Between Verified Mode C transponding aircraft provided the intentions of both aircraft are know to an ATCO because either;
* They are under their control
* They have been coordinated
* They are operating in accordance with the established agreements.
For IFR flihgts in Class A-E Airspace, what is the minimum vertical separation increased to against Mode C of aircraft with unknown intentions?
- 5,000ft / alternative approved minima within MATS2
See MATS2
When can Unverified Mode S / Mode C data be used for separation within CAS?
- For IFR flights in Class A - D airspace, a minimum vertical separation of 5,000ft / alternative approved minimum in MATS2 AND surveillance returns are not allowed to merge
When do ATCOs have to verify Mode C & how do they do this?
- Once the aircraft has been identified & validated.
- Checking the readout indicates 200ft or less from the level reported by the pilot.
- A Mode C readout can be assumed to have been verified if it is associated with a deemed validated Mode A code
What are the criteria when assessing the vertical position of a Mode C transponding aircraft?
- At a level provided Mode C indicates 200ft or less
- Left a level when Mode C is 400ft or more from that level & continuing
- Passed through a level when Mode C indicates level has been passed by 400ft or more & continuing
- Reached a level when 3 successive Mode C readouts indicate 200ft or less from that level
What conditions need to be in place for a Radar Handover?
- Satisfactory 2-way speech comms between ATCOs
- The identity has been transferred to / has been established by the accepting ATCO
- The accepting ATCO is informed of any level/speed/vectoring instructions applicable to the aircraft at stage of transfer
If route not know ATCO is to pass observed track
What is an ATCOs responsiblity with regards to vectoring?
- An ATCO may instruct an aircraft to turn in any direction as dictated by cirumstances - when avoiding unknown aircraft the RoA Regulations should be observed if practicable.
- Aircraft flying outside CAS are not oblighed to follow instructions given by ATC (when pilot accepts TS/DS the ATCO can expect their instructions will be followed)
When can aircraft be vectored outside CAS?
Unless an aircraft has planned to leave CAS, it is not to be vectored outside the horizontal / vertical limited except;
* When an emergency situation arises
* When avoiding severe weather (the circumstances must be explained to the pilot before the aircraft leaves CAS)
* When requested by the pilot
How far should aircraft be kept inside CAS?
- Flights inside CAS are deemed separated from unknown aircraft flying in adjoining uncontrolled airspace, however;
- ATCOs should aim to keep the aircraft at least 2NM within CAS.
- ATCOs should monitor the operation of aircraft in adjacent uncontrolled airspace.
What should ATCOs ensure for levels given to IFR flights?
ATCOs are to ensure that levels assigned to IFR flights in receipt of a Radar Control Service provide adequiate terrain clearance for the phase of flight as shown below.
What responsibility do ATCOs have with regards to terrain clearance for SVFR & VFR aircraft?
- ATCOs have no responsibility for the terrain clearance of & shall not assign levels to (S)VFR within CAS which accept vectors
What is the Minimum Terrain Clearance within the defined final approach area?
- Achieved if levels are assigned in accordance with a procedure approved by the CAA
What is the Minimum Terrain Clearance within the Surveillance Minimum Altitude Area?
Levels allocated must be in accordance with the information published on the SMAC
What is the Minimum Terrain Clearance within 30NM of the radar antenna associated with the unit providing the service?
1,000ft above any fixed obstacle within;
* 5NM of the aircraft
* 15NM ahead & 20 degrees either side of the aircraft’s track
When the aircraft is within 15NM of the antenna, & provided a SMAC or approved provedure has been notified, the 5NM & 15NM may be reduced to 3 & 10 NM respectively.
What is the Minimum Terrain Clearance outside the above phases?
1,000ft above any fixed obstacle;
* Which lies within 15NM of the centreline of the ATS route
* Within 30NM 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 1,500ft terrain clearance.
Who is responsible for terrain clearance outside CAS?
- Within Class G airspace, regardless of the service being provided, pilots are responsible for terrain clearance.
- However, terrain requirements pertaining to level allocations & the provision of vectors are specified within the conditions in CAP774 UKFIS
Define an Unknown Aircraft
A position symbol which cannot be associated with an aircraft known by the ATCO to be operating within the airspace concerned shall be considered to represent an unknown aircraft.
What action should an ATCO take when an Unknown Aircraft penetrates Class D airspace?
If surveillance derived / other info indicates an a/c is making an unauthorised penetration of the airspace;
* IFR flihgts shall be given traffic avoidance advice & TI shall be passed
* VFR & SVFR flights shall be given TI & if requested or necessary, avoidance advice
Remind VFR/SVFR to remain COCSIS
What action should an ATCO take against unknown aircraft in unsafe proximity to traffic in Class G?
- Flights receiving DS shall be given traffic info & deconfliciton advice in accordance with UKFIS CAP774
- Flights receiving TS/BS shall be given traffic info in accordance with UKFIS CAP774
What shall ATCOs do when conflict against unknown traffic no longer exists?
ATCOs shall advise the pilots
What is the London FIS code?
A1177
What shall Traffic Information to Aircraft include? (format)
- Bearing from the aircraft in terms of 12-hour clock (or cardinal points)
- Distance in NM
- Direction unknown a/c is proceeding e.g. opposite direction/crossing left to right
- Height info
What should an ATCO do when weather is observed on the situation display / known to be present?
ATCOs should advise pilots of the weather’s location, intensity, and direction of movement (if known).
What shall ATCOs do when a pilot requests an alterative heading / route for weather avoidance?
- ATCOs shall accommodate such requests, taking into account the traffic situation.
- When a request cannot be accommodated, ATCOs shall offer an alternative / explain why
What should ATCOs do when weather avoidance will take an aircraft outside CAS?
- PIlots must be informed of this & offered an appropriate service.
- Pilots routeing outside CAS for weather avoidance should be issued a clearance to rejoin as reqd.
What should an ATCO do when a pilot is cleared to follow their own nav / accepts a heading to avoid weather?
ATCOs should ask the pilot to report when able to accept vectors back on track.
What are potential causes of clutter on the situation display?
- Anoprop
- Ground/sea returns
- Birds
- Wind turbine effects
- Chaff
In what way may clutter on the situation display disrupt ATS provision?
- Increased risk of the ATCO not detecting conflicting traffic
- Aircraft position symbols, track histores, data blocks may be hidden / obscured
- Spurious tracks may be generated which may be indistinguishable form genuine aircraft returns
- There may be a delay in aircraft being identified & placed under an ATS
- Increased ATCO workload
The existence of clutter may necessitate aircratf being rerouted / ATS being reduced
Clutter Inside vs Outside CAS
- DS/TS, advise pilot extent of clutter & offer a reroute.
- TS, reduce traffic info
- RCS, shall not be terminated, vector around clutter if able
What emergency separation is used in the event of a Surveillance System Failure?
- Inform aircraft under control of the failure & apply local contingency procedures (MATS2)
- Reduced vertical separation of half the applicable vertical separation (e.g. 500ft where an ATCO would normally apply 1,000ft) ((inform pilots))
