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

may have been due to action errors by one of the pilots (such as not tuning the radio
to the correct Common Traffic Advisory Frequency (CTAF) being used in the vicinity
of that aerodrome). Situations where a pilot reported their location differently from
their actual position were also coded as communication-related errors. This occurred
in 13 cases.
Source: photo courtesy of Alex Gagiero (Temora Aerodrome, NSW)
Situational awareness-related information errors (almost one-third of cases) were
related to situations where one or more pilots had a less than adequate awareness of
nearby traffic. For example, a situation where a pilot taxied across an active runway
without broadcasting and it was known that he did not look to see if any aircraft were
on approach or takeoff was coded as a situational awareness error. Situational
awareness errors also included pilots landing on an incorrect runway.
Position/proximity assessment-related information errors (one-fifth of cases) occurred
when a pilot incorrectly assessed the position or intentions of the pilot of another
aircraft that they were aware of (leading to a reduced safety margin between those
two aircraft), or came too close to another aircraft that they were aware of on
approach or operating in a circuit. In 47 occurrences, the pilots were maintaining
separation with the assistance of radio alerting (or in some cases, the flight crew of
one aircraft were maintaining visual separation with a non-broadcasting aircraft);
however, the assessment of separation was found to be incorrect (due to a Traffic
Collision Avoidance System (TCAS) traffic advisory (TA) 25 , or because of a
manoeuvre by one of the aircraft).
25 A traffic alert (TA) is the first level of warning provided by a TCAS/ACAS to pilots and flight crews
that the margin of separation between two aircraft is reduced, and that the aircraft are coming into
conflict. TAs are intended to assist the pilot to visually acquire the conflicting aircraft, and prepare
the pilot for a potential resolution advisory (RA) if the TCAS/ACAS determines that there is a risk of
a collision. TCAS/ACAS operates on relatively short time scales. The maximum generation time for
a TA is 48 seconds before the point of collision. For an RA, the time is 35 seconds. The time scales
are shorter at lower altitudes (where aircraft typically fly slower). Unexpected or rapid aircraft
manoeuvres may cause an RA to be generated with much less lead time. It is possible that an RA
will not be preceded by a TA if a threat of collision is imminent (EUROCONTROL, 2010).
- 37 -