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

Airproxes and other separation issues (air-air and air-ground)
Airproxes 1 and other situations where a separation issue occurred between two
aircraft were also very common. Conflicts between aircraft and other aircraft or
vehicles occurred in 71 per cent of occurrences. Most conflicts were due to reduced
separation between aircraft in the circuit, conflicts between aircraft on base, final
approach, or runway incursions. Airproxes accounted for almost all serious
incidents (55 of 60) in the vicinity of non-towered aerodromes. Separation issues
generally occurred between general aviation (GA) aircraft, or involved a GA
aircraft and a passenger transport aircraft. There were very few conflicts involving
two passenger transport aircraft. Most runway incursions involved a backtracking
aircraft coming into conflict with an aircraft on landing or final approach to the
same runway.
See-and-avoid conflicts
See-and-avoid conflicts where situational awareness errors were involved (also
contributed to by inadequate or no communications in some cases) made up about
one-seventh of all occurrences. These types of conflicts led to almost all of the six
accidents recorded in the vicinity of non-towered aerodromes between 2003 and
2008, four of which were mid-air collisions, and two of which were runway
incursions leading to a collision on the ground. Furthermore, there were 60 serious
incidents in which an accident almost occurred. Once again, these were mostly due
to a lack of communication between pilots or an insufficient awareness of nearby
traffic, leading to an airprox. In 87 occurrences, a Traffic Collision Avoidance
System (TCAS) alert occurred due to a potential separation issue. In over half of
these cases however, the TCAS alert was the only indication that pilots of an
aircraft had of the other traffic.
In approximately 20 per cent of all conflicts, the pilot of one or more aircraft took
avoiding action to prevent a collision or an airprox. In a further 17 per cent, one
aircraft made a precautionary diversion from its intended flight path in order to
maintain safe separation with another aircraft that was not communicating or aware
of other nearby aircraft.
Inadequate communication between aircraft
Insufficient communication and broadcasts between pilots, radio failures or
misunderstandings were the biggest contributors to occurrences in the vicinity of
non-towered aerodromes between 2003 and 2008 (388 of 709 occurrences).
Communication issues accounted for 38 per cent of all information errors and 31
per cent of all action errors for these occurrences.
Good communication between pilots on the CTAF is critical to creating a safe
operating environment in uncontrolled airspace, especially in higher traffic density
locations such as at non-towered aerodromes. Despite this, in almost a third of all
occurrences, it was known (or likely) that the pilot was operating within the vicinity
1 An airprox is defined in the Transport Safety Investigation Regulations 2003 as an occurrence in
which two or more aircraft come into such close proximity that a threat to the safety of those
aircraft exists or may exist, in airspace where the aircraft are not subject to an air traffic separation
standard or where separation is a pilot responsibility.
- xii -