Safety in the vicinity of non-towered aerodromes - Australian ...

Airproxes classified as a high collision risk generally involved both reduced lateral
and vertical separation. In high collision risk airproxes, the separation between the
conflicting aircraft at the time of the occurrence was an average of 200 m laterally and
55 ft vertically. In some of the occurrences at non-towered aerodromes, the separation
was significantly less.
Occurrence number 200803375
The Jabiru aircraft was conducting circuits on runway 32 at West Sale Aerodrome, Vic. All
the appropriate radio broadcasts were made. A Victa Airtourer aircraft was inbound from the
southwest, but did not make a 5 NM inbound broadcast. On the downwind leg of the circuit,
the Victa was observed less than 150 m away and slightly above the Jabiru. There was no
time to take avoiding action, and the aircraft passed each other with 6 m lateral and 15 ft
vertical separation. The other pilot then gave a joining crosswind broadcast for runway 09,
but they did not seem to receive any radio broadcasts from the Jabiru.
In low collision risk airproxes, separation was usually reduced only in one axis (either
reduced horizontal or vertical separation).
When operation types were considered, occurrences involving a passenger transport
aircraft (regular public transport or charter operations) were involved in fewer
airproxes where the risk of collision was deemed to be high (Figure 15). This was
likely due in part to the effectiveness of TCAS and ACAS systems, and to a greater
awareness by passenger transport pilots of the relatively high performance of their
aircraft compared with others operating in the vicinity of non-towered aerodromes.
Figure 15: Collision risk assessments by operation type, airproxes in the
vicinity of non-towered aerodromes, 2003 to 2008
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