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The large areas of military and naval
airspace in close proximity to Perth International Airport necessitates
complicated tracking arrangements for departing and arriving air traffic. In the mid-1990’s the rapidly growing civil traffic and the
major military and naval investments at RAAF Pearce and HMAS Stirling led to
a review of procedures and airspace management.
This review included representatives from Airservices Australia, the
RAAF, the RAN, and national and regional airlines and operators.
Restricted areas, which had been based on Pearce TACAN radials, were
redrawn to conform with the Perth VOR radials, new SIDs and STARs were
developed to, as much as possible, segregate inbound and outbound traffic,
and Letters of Agreement detailing responsibilities and coordination
protocols were agreed to with the RAAF and RAN.
The result is a traffic handling procedure known as the Perth
Traffic Management Plan.
The Perth Traffic Management Plan
The Perth Traffic
Management Plan applies segregated tracks between outbound and inbound
aircraft and minimises the civil transit of military airspace. Traffic handling
procedures, including level assignments, are standardised and coordination between adjacent sectors is
minimised. These procedures,
binding on controllers, are published in West Radar Local Operating
Instructions and, for pilots, in ERSA.
Two separate plans, or system
routes, apply determined by the runway in use:
Essentially, the inbound and
outbound system routes of one plan reverse direction and become the outbound
and inbound system routes of the other plan.
The Perth Traffic Management
Plan applies to all aircraft cleared:
-
Inbound to Perth, Jandakot or Pearce at FL140 and above;
-
Outbound from Perth, Jandakot or Pearce at FL130 and above.
Aircraft below these
levels are cleared via flight planned route and are subject to normal
coordination between controllers.
Outbound Clearances
Clearances for outbound
aircraft are based on:
-
The Perth Traffic Management Plan in use (ie. The Southwest
Plan or the Northeast Plan);
-
The intended route of the pilot from 160nm Perth (or the first
OCTA waypoint);
-
Noise abatement requirements.
Thus the clearance that the pilot receives,
such as a SID, will take the aircraft via the appropriate outbound system
route to intercept the pilot’s flight-planned route by 160nm Perth.
Aircraft from Jandakot and Pearce are not on a Perth SID, so fly the
SID waypoints or are vectored around the SID.
Military aircraft that require to track other
than via a system route, such as “special requirements” flights (i.e.
minimum fuel) and NAVEX aircraft, are subject to individual coordination.
Outbound Traffic Handling
PHD assigns outbound aircraft A060 and gives
“heads up” coordination of the departure to LCI.
Once this is done, PHD assigns the aircraft FL130 and hands it off to
LCI who may then assign up to FL180. A
higher level cannot be given until KNG assigns further climb.
KNG is responsible for separating departing traffic with the inbound
traffic, which is in Class A and E airspace above FL180, much of which is not yet radar identified.
(The base of Class E is A085 in LCI sector but steps up in KNG sector at
90NM Perth to FL180). This does not leave much time for the KNG
controller to formulate a procedural separation standard if one is required
because most jets and turboprop aircraft quickly reach FL180.
Procedural separation is applied, such as:
- restricting outbound aircraft to levels below the inbound
traffic until they’ve passed;
- requiring outbound aircraft to reach a level above inbound
traffic by 10 minutes prior to passing;
- establishing aircraft on a laterally separated routes
- vectoring aircraft outside of the tracking tolerances of inbound
aircraft until vertically separated, then vectoring them onto their
planned route.
In-trail Spacing
PHD provides LCI (and LCI provides KNG) with an orderly traffic flow as follows:
Before aircraft leave radar coverage
(at about 200nm from Perth for the higher flying types) and are handed off to the procedural sectors, a
procedural separation standard must exist.
Track Modification
Once an aircraft is airborne its track may be
modified to resolve a traffic confliction or to track shorten the flight.
LCI may coordinate a modified route to PHD, such as:
-
a heading,
-
direct tracking to a SID waypoint at 80nm Perth,
-
direct tracking to a 160nm waypoint (after advice from KNG).
A controller will use a heading to vector
aircraft out of conflict, such as where inbound and outbound tracks cross,
permitting outbound traffic to continue climbing and inbound aircraft to
continue descending. Departing
aircraft may be vectored 5nm laterally from the SID to allow a faster
following aircraft to fly the SID, thus establishing two independent and
separate departure trails. Individual
aircraft may be track shortened to separate them with other departing
aircraft or to clear an inbound traffic sequence.
Inbound Clearances
Inbound aircraft, above FL140, are cleared by the
appropriate inbound system route, which is determined by:
-
the Perth Management Plan in use;
-
the aircraft’s inbound route;
-
noise abatement requirements.
Thus the STAR that the pilot receives will take
the aircraft off its flight-planned route at the 160nm Perth waypoint, and
reroute it by the appropriate inbound system route to Perth. Aircraft planned via non-published routes must be cleared by
the nearest suitable system route. Aircraft
to Jandakot and Pearce fly the STAR waypoints or are vectored around the
STAR.
Aircraft cleared at FL135 and below are
coordinated directly with Perth TMA for a cleared route (usually direct to
Perth). They may opt for a STAR.
Inbound Traffic Handling
KNG assigns inbound aircraft FL190 for descent and hands them off to
LCI. As they near the terminal area, LCI assigns them FL140 for
aircraft that will cross PHD airspace, and A090 for those entering PHA
airspace directly. These are the standard levels for handoff and keep
the inbound aircraft in Class E airspace and above the uncontrolled Class G
airspace.
Any other assigned levels, due to crossing traffic for example, must be coordinated.
No coordination is necessary for aircraft on STARs, who are assigned
standard handoff levels.
Separation Standards
Aircraft are said to be in conflict when a separation standard does not,
or will not, exist between them. There are, perhaps, more than 100
separation standards, designed by ICAO, involving the three spatial
dimensions - lateral separation, longitudinal separation and vertical
separation - and time. The actual magnitudes of the separation
standards do not apply universally in all airspace sectors but are
dependent on the nature and quality of the navigational information
available to the pilots and controllers.
For aircraft to be separated, a controller needs only
one standard
to apply. A breakdown of separation occurs when no standard
exists between two aircraft. This is not the same as a near miss.
It is important to realise that a
separation standard guarantees just 1 mile of separation between two
aircraft when all possible equipment errors and tolerances are taken into
account. Thus a 5 mile radar standard, a 20 mile DME standard, a 30
mile RNAV standard and a 10 minute time standard usually mean that aircraft
are many miles from each other. But in a worse case scenario they
might only be 1 mile apart.
The art of controlling is to be able to move smoothly and seamlessly
between standards as aircraft climb, cruise and descend through other
traffic so that, in most instances, pilots aren't even aware that differing
standards are being applied to separate them from other aircraft in the
airspace (nor are they normally aware of which aircraft they are in
conflict). This requires the air traffic controller to project each
flight ahead and work on future conflicts while maintaining situational
awareness of the current traffic disposition.
Vectoring and Speed Control
In enroute radar airspace, the most commonly used
separation standards are radar separation of 5nm and vertical separation of
1000ft. The fine weather around Perth often permits visual separation,
so that a pilot might be instructed to "sight and follow" another
aircraft. When aircraft tracks come into conflict, one or both may be
vectored (placed on a heading) until they're out of conflict then instructed
to "resume own navigation". Vectoring is also used to permit
unrestricted climb or descent of aircraft. The mix of aircraft types
means that often a faster jet will overtake a slower turboprop on the climb
out of Perth or on descent into Perth, so one must be vectored off track
until the faster aircraft has overtaken the slower. For similar types of aircraft on
the same route, speed control may be used to maintain radar separation on
the climb out of Perth until they reach less congested airspace. Then
one can be vectored and the speed control removed. An
aircraft with a slow rate of climb may be "step-climbed" under one with
a faster rate of climb.
Aircraft departing Perth tend to spread out but as aircraft approach Perth they begin converging
with other traffic. An orderly sequence of traffic must be organized,
not only because common sense tells us that only one aircraft can land at a
time, but a mandated separation standard must exist between them, too. This is covered on the next page, Flow Control and
Sequencing.
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