EXECUTIVE SUMMARY
This report follows a previous report published by the
Australian Transport Safety Bureau (ATSB) in 2003 on
airspace-related occurrences titled Airspace-Related
Occurrences Involving Regular Public Transport and Charter Aircraft
within Mandatory Broadcast Zones. The 2003 report provided a
detailed examination of the ATSB's accident and incident data for
airspace-related occurrences in Mandatory Broadcast Zones (MBZs),
between 1994 and 2001. In recognition of changes in traffic levels,
occurrence reporting rates and the classification of incidents
following the enactment of the Transport Safety Investigation
Act in 2003 (ATSB, 2003b), an update of the analyses was
considered necessary.
The purpose of the current report was to examine occurrences
associated with MBZs in Australia. Specifically, the objectives of
the report were to:
- examine the number of occurrences involving General Aviation
(GA) aircraft in addition to occurrences involving Regular Public
Transport (RPT) aircraft that occurred in MBZ airspace from 2001 to
2004; and - examine the number of occurrences involving GA aircraft and RPT
aircraft that were associated with intentional and unintentional
non-compliance with MBZ procedures from 2001 to 2004.
MBZ occurrences were identified using the ATSB aviation
occurrence database and subsequently validated by two ATSB Senior
Transport Safety Investigators. The occurrences were then examined
according to three different criteria. The first criterion
encompassed all airspace-related occurrences within MBZs. The
second criterion related to only those occurrences where the pilot
intentionally mis-complied with MBZ procedures. In contrast, the
third criterion related to only those occurrences where the pilot
unintentionally mis-complied with MBZ procedures.
In total, 257 airspace-related occurrences in MBZ airspace
involving GA aircraft and RPT aircraft for 2001 - 2004 were
identified. The highest number of occurrences took place in 2001
and were classified as a Category 5. The number of airspace-related
occurrences declined from 3.9 in 2001 to 3.1 per 100,000 hours
flown by GA and RPT aircraft in 2002 and remained at 3.1 for 2003
and 2004. These findings suggest that the number of MBZ
airspace-related occurrences declined slightly over the four-year
period. The findings contrast with those presented in the 2003
report (Figure 1, page 9), which showed an increase in
airspace-related occurrences between 1994 and 2001 (ATSB,
2003a).
Of the airspace-related occurrences identified, 145 involved
intentional non-compliance with MBZ procedures and 25 involved
unintentional non-compliance with MBZ procedures. Most of the
non-compliance occurrences were in 2001 and were classified as a
Category 5. The number of intentional non-compliance occurrences
decreased from 2.6 per 100,000 hours flown by GA and RPT aircraft
in 2001 to 1.4 in 2004. This finding suggests that the number of
occurrences involving non-compliance generally declined over the
2001 - 2004 period. In contrast, the rate for unintentional
occurrences remained below 1 per 100,000 hours flown and did not
appear to vary across the four-year period.
Overall, the findings suggest that the number of MBZ
airspace-related occurrences in Australia between 2001 and 2004,
including those specifically relating to non-compliance with MBZ
procedures, was relatively low. Furthermore, the findings suggest
that the rate of MBZ-related occurrences did not rise during this
period. It may therefore be deduced that the risk due to
MBZ-related occurrences did not increase. Importantly though, due
to recent changes and potential inconsistencies in the reporting
and recording of occurrences, the findings on which these
conclusions are based need to be interpreted with caution.