ATS Surveillance Systems 2 Flashcards
As stated in MATS 1, fully describe the methods of identification using SSR and when such methods are to be used. Include any precautions to be taken.
When using Mode A to identify aircraft, one of the following methods is to be employed:
1) Observing the pilots compliance with the instruction to select a discrete four digit code
2) 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.
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 the conspicuity code 7000 are not to be identified by this method.
As stated in MATS 1, describe the different types of Mode-A codes that controllers are to assign to aircraft, as detailed in the Code Assignment Plan. Include in your answer the actions of controllers at SSR equipped units when allocating such a code.
Controllers are to assign Mode-A codes to aircraft according to the Code Assignment Plan, which comprises:
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 to specific users/units.
When providing a surveillance service to aircraft, controllers operating at SSR equipped units should allocate that flight with a discrete code in accordance with the SSR assignment plan. Unless otherwise instructed by an ATC Unit, 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.
As stated in the MATS 1, describe the procedure and methods for the validation of Mode-A codes. Include in your answer the procedure to be carried out when validation is not possible.
A controller assigning any Mode A code must 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.
The code must be checked by one of the following methods:
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.
If the 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 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 ATC units are to be informed of the retention of corrupt data.
According to MATS 1, under what circumstances may a controller consider a Mode A code to be deemed validated?
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:
1) The code is promulgated as being unverified or,
2) The controller has been notified that the code is corrupt
a) What considerations must be taken into account in respect of Mode-A and Mode-C of conspicuity codes?
b) When are pilots required to, and advised to squawk conspicuity code 7000? List the occasions when suitably equipped aircraft would squawk a different code.
a) The Mode A code and associated Mode C data of conspicuity codes must be considered unvalidated and unverified.
b) Pilots are required to squawk conspicuity code 7000 when 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 transponding on one of the special purpose codes or on one of the other specific conspicuity codes assigned in accordance with the Code Assignment Plan
3) They are flying below 3,000 feet in the aerodrome traffic pattern and have been instructed to select the aerodrome traffic pattern conspicuity code (7010) or
4) On grounds of safety the aircraft has 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 log the circumstances and duration of any such occurrences. Records are to be made available to the CAA on request.
