95 / 476
85
PrimaryRadar
isasystemwhere thegroundbasedantenna transmitsa radar
pulse then listens for thesmall amountof returnenergy that is reflected froman
aircraft. The timedelaybetween the transmissionof thepulseand the receiptof
the reflected return isameasureof the range.
SecondaryRadar
requiresanairborne transponderwhich responds to the receipt
of apulse fromagroundbasedantennaby transmittinga returnsignal.Because
the transponder transmitsamuchstronger signal than thatwhich is reflectedoff an
aircraft inprimary radar systems, greater rangeand reliabilitycanbeachievedwith
secondary radar andcheaper andmoreefficientgroundequipment canbeused.
Additionally, informationsuchasaltitudeandacodecanbeadded to the returned
signal from the transponderwhich is thendisplayedon theoperator’sscreen.
A
TrafficAlertandCollisionAvoidanceSystem (TCAS)
isanairbornesystem
which iscapableof interpreting the transponder returnsofnearbyaircraft and
displaying thepositionsof theseaircraftonacockpitdisplay. TCAScanwarn the
crewof impendingcollisionsandadviseavoidingmanoeuvresprovided it receives
thealtitude information fromnearbyaircraft. For this reason,modeC (theALT
selectionona typical transponder) shouldalwaysbeselectedbyall aircraftoutside
controlledairspace.
TCAS isfitted tomost commuter aircraft thatoperate inClassD,EandGairspace.
It is therefore ineverybody’s interest for all VFR transponderequippedaircraft in
ClassEorG tosquawkcode1200withALTselected.
ADS-BAPPROVALANDOPERATIONS
AutomaticDependent Surveillance - Broadcast (ADS-B) is ameans bywhich
aircraft, aerodrome vehicles and other objects can automatically transmit
or receive data such as identification, position and additional data, as
appropriate, in a broadcastmode via a data link. To receive anADS-Bderived
ATS surveillance service inAustralian airspace, aircraft operatorsmustmake
application toAirservicesAustralia. Only aircraftmeeting the criteria for
ADS-B operations inAustralia as specified inCASACAOs shall be eligible to
receiveADS-B derived services. ADS-Bdata from ineligible aircraftwill not be
displayed toATC.
VFR FLIGHTS INCLASSEORGAIRSPACESQUAWK1200MODEC (ALT)
primary and secondary radar
T
S
E
T
T
L
A
N
O
Y
B
T
S
F
F
O
IDENT
1 2 00
VFROCTA
1 — radar transponders
radar transponders