The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority provide specific guidance to pilots as to
an appropriate buffer when approaching controlled airspace and
requesting a clearance.
This recommendation resulted from a study carried out in to
violations of controlled airspace.
Analysis
When pilots were asked when to request a clearance, either in time
or distance, answers ranged from 30 minutes down to 2 minutes or 1
NM. At 1 NM, the pilot of an aircraft travelling at 120 kts has
only 30 seconds to request a clearance, be identified if in a radar
environment, and receive the clearance. At 5 NM, the same pilot has
only 2.5 minutes to request and receive a clearance. At anything
less than 5 minutes, the call needs to be successful the first
time. Any unanticipated problems with the radio can quickly lead to
a situation where the pilot arrives at the boundary without a
clearance.
AIP OPS 20.2.1 provides general guidance as to when a pilot should
request an airways clearance. The section states in part:
In determining how far from the boundary to make the request, the
pilot should allow for aircraft performance, and also the
possibility of frequency congestion should the airspace be known to
be busy.
The publication does not provide specific guidance or suggested
distances or times at which to request a clearance.
The Bureau believes that pilots must allow sufficient time to
obtain a clearance when approaching controlled airspace or be
prepared to hold outside controlled airspace. The Civil Aviation
Safety Authority should provide more specific guidance to pilots as
to an appropriate time and/or distance at which to request a
clearance when approaching controlled airspace.
The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority provide specific guidance to pilots as to
an appropriate buffer when approaching controlled airspace and
requesting a clearance.
The following is in response to recommendations R970083 and
R970084 contained in BASI Special Study 96254.
R970083
In the past, AIP OPS contained a specific distance by which
pilots were to have initiated an airways clearance for entry into
controlled airspace. With the continuing unacceptably high number
of violations of controlled airspace (VCAs), the then Civil
Aviation Authority (CAA) came to the view that the nominated
distance was being used by a cross section of pilots as the point
at which a clearance request should be initiated. With the wide
range of aircraft performance involved and differing traffic
situations, the CAA considered that the nomination of a distance
was not the most appropriate means of identifying the requirement.
The present wording at AIP OPS 21.1.6, which requires pilots to
consider aircraft performance and possible frequency congestion
when determining where the clearance request will be made, results
from the Air Traffic Service/Flying Operations Branch review of
that situation.
The Civil Aviation Safety Authority is still of the view that
with the wide performance range of aircraft involved, it is
inappropriate for a specific distance to be specified for the
initiation of clearance request and that the present AI P OPS
reference provides the best advice to pilots to determine an
appropriate point at which to initiate a request. However, the
issue is under review as part of the procedures associated with the
proposed airspace model (Airspace 2000) which may require that a
time be specified to satisfy Air Traffic Control requirement.