SSR Identification

Question 1

What is Radar Contact?

Answer 1

When the position indication of a particular aircraft is seen and identified on a situation display.

Question 2

What is Identification?

Answer 2

The act of correlating a particular position indication with a specific aircraft target by means of laid down procedures.

Question 3

What is Validation?

Answer 3

Validation is the task of checking that the correct transponder code has been selected by the pilot and is shown on the situation display.

Question 4

How is Validation achieved?

Answer 4

Instruct aircraft to squawk assigned code and observe that the correct numbers appear on the situation display

Instructing the aircraft to “squawk ident” and simultaneously checking that the code numbers associated with the radar return.

Matching a previously identified primary radar
return with the assigned code for the flight.

Question 5

When is a transponder code deemed validated?

Answer 5

When the code set can be recognised by the Code Assignment Plan to have been assigned by an ATC unit capable of validating the code, providing the code has not been notified as being corrupt.

Question 6

What is Verification?

Answer 6

Once a transponder code is validated, verification is a a check to confirm that the aircrafts Mode C (altitude) read out is accurate within agreed parameters.

Question 7

What is Correlation?

Answer 7

By means of a radar processor, Mode A data may be correlated with stored flight plan data enabling a code-callsign conversion to take place.

Question 8

Can Mode A data be used to identify aircraft?

Answer 8

Yes

Question 9

When should a pilot be informed that their aircraft is identified?

Answer 9

Outside of controlled airspace

Question 10

What are the ways that aircraft can be identified using SSR/MLAT?

Answer 10

Recognition of aircraft identification in a Mode A label.

Direct recognition of the aircraft identification from a Mode S label.

By transfer of identification from another ATCO.

Observation of compliance with an instruction to set a
specific code.

Observation of compliance with an instruction to squawk IDENT.

Question 11

If you allocate a squawk, what must an ATCO do?

Answer 11

The ATCO must validate and verify it.

Question 12

When is Mode C deemed to be verified?

Answer 12

Mode C can be assumed to have been verified if associated with a validated Mode A code.

Verification may be achieved, if necessary, with the assistance of another ATSU.

Question 13

What are the actions if transponder is showing a Mode C error?

Answer 13

If in error, Request the pilot to “check altimeter setting and confirm level”

If still an error:
“Stop Squawk Altitude”
“Stop squawk Altitude, wrong
indication”
“Squawk 0000”

Question 14

How is an aircraft assessed to be maintaining an assigned level?

Answer 14

When Mode C readout indicates ± 60m (± 200ft) from that level in RVSM (FL290 - 410).

or ± 90m (± 300ft) in other airspace, unless the ATS authority specify a smaller criterion, no less than RVSM.

Question 15

How is an aircraft assessed to have vacated a level?

Answer 15

When Mode C readout shows a change of more than 90m (300ft) from its previously occupied level and is continuing in the anticipated direction.

Question 16

How is an aircraft assessed to be passing a level when climbing or descending?

Answer 16

When Mode C readout indicates that the aircraft has passed the level in the required direction by more than 90 m (300 ft).

Question 17

How is an aircraft assessed to have reached an assigned level?

Answer 17

An aircraft is considered to have reached the assigned level when the elapsed time of three display updates, three sensor updates or 15 seconds, whichever is the greater, has passed since the Mode C information has indicated that it is within the appropriate tolerances of the assigned level.

Question 18

How can SSR Identification be achieved without the ATCO personally verifying and validating?

Answer 18

Transfer of Identification Method

Question 19

What are the Transfer of Identification methods?

Answer 19

a) Automated transfer, provided there is no possible doubt of correctly identifying only one position indication.

b) Notification of the aircrafts SSR code.

c) Notification that the aircraft is Mode S equipped where coverage is available.

d) Notification that the aircraft is ADS-B equipped where coverage is available.

e) “Direct Designation” of the position indication by another ATCO. (pointing with finger)

f) Designation of the position indication by reference to bearing and distance from a geographical position or nav facility.

g) Instructing an aircraft to change SSR code by the transferring controller and the observation of the change by the accepting controller.

h) Issuance of an instruction to the aircraft by the transferring controller to ‘squawk IDENT’ and observation of this response by the accepting controller.

Question 20

When should an aircraft be informed of its position?

Answer 20

a) Upon identification, except when based on pilots report of position, transfer of identification or from Mode S.

b) When the pilot requests this information.

c) When a pilots estimate differs significantly from the controllers estimate based on the observed position.

d) When the pilot is instructed to resume own navigation if the previous vectoring had diverted the aircraft from its assigned route.

e) Immediately before termination of ATS surveillance service if the aircraft is observed to deviate from its intended route.

Question 21

How should position information be passed to aircraft?

Answer 21

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

a) As a well-known geographical position

b) Magnetic track and distance to a significant point, an en-route navigation aid, or an approach aid

c) Direction (using points of the compass) and distance from a known position

d) Distance to touchdown, if the aircraft is on final approach

e) Distance and direction from the centre line of an ATS route