Recommendation

SUBJECT



The provision of timely traffic information to flight crew



OCCURRENCE SUMMARY



Occurrence 9702191



A De Havilland Dash 8 (Dash 8) was on climb to FL210 and was
tracking between Horn Island and Cairns. The crew was given traffic
information on an Embraer Brasilia (Brasilia) which was en-route
from Cairns to Bamaga. The crew of the Brasilia was cleared by air
traffic control (ATC) to leave controlled airspace on descent and
was then provided with traffic information on the Dash 8. Prior to
leaving controlled airspace, the crew of the Brasilia was unable to
establish communications on the area frequency with the crew of the
Dash 8. The pilot of the Dash 8 recalled that he saw the shadow of
the Brasilia as the aircraft passed each other.



Occurrence 9702426



A Shorts SH36 (Shorts) aircraft was maintaining 9,000 ft and was on
a flight from Williamtown to Brisbane. As it approached Taree, the
crew was given traffic information on a Dash 8 which was on a
flight from Sydney to Taree via Williamtown at FL150. The crew of
the Dash 8 was approved to leave controlled airspace on descent and
was instructed to transfer to the flight service frequency. Due to
frequency congestion, the crew was unable to seek traffic
information from flight service in order to assess the potential
for conflict with the Shorts. The relevant information was not
obtained until the Dash 8 was descending through 11,000 ft. The
crew discontinued the aircraft's descent at 10,000 ft and avoided
further conflict with the Shorts.



Occurrence 9704231



Two Boeing 737s (B737s) were at the same level and approaching
Parkes from the west on converging tracks. The sector controller
believed that he would be able to establish a 30-NM longitudinal
separation standard between the aircraft, before lateral separation
reduced to less than required. However, other aircraft in the
vicinity limited the controller's choice of levels for the B737s.
In addition, one of the B737s was unable to meet an amended level
requirement. As a result, the distance between the two aircraft
reduced to 18 NM before the controller was able to identify and
separate the two aircraft, by radar. The controller did not issue
traffic information to the B737 crews, nor were emergency
separation measures implemented.



SAFETY DEFICIENCY



Flight crews are not being provided with, or are unable to obtain,
traffic information in sufficient time to adequately assess the
potential for conflict with other aircraft.



ANALYSIS



The provision of traffic information by air traffic services (ATS),
or the facilitation by ATS for the gathering of traffic information
by flight crew, is integral to the continuing safe conduct of
flights. In 1997, there were 26 occurrences in which aspects of the
provision of traffic information was a factor. In seven of these
occurrences the timing of the provision of traffic information by
ATC was a factor. In two other occurrences the lack of provision of
traffic information, after separation had reduced to less than the
required minimum standard, was a factor.



ATS procedures



The timely establishment of communication with the flight crew of
other aircraft is necessary for flight crew whose aircraft is about
to leave controlled airspace or is operating in non-controlled
airspace. This communication enables them to determine the position
of other aircraft operating in their vicinity and then to avoid
those aircraft.



Generally, when flight service (FS) identify a need for the
provision of traffic information to the flight crew of an aircraft
intending to leave controlled airspace, they provide the traffic
information to ATC for relay to the crew. Alternatively, subject to
traffic and other requirements, ATC transfer the crew to FS in
order for that agency to provide the traffic information.



When ATC issue the traffic information, it is often passed either
just before, or after the crew has been instructed to leave
controlled airspace on descent. When FS issue the traffic
information, the crew are often instructed by ATC to contact FS at
"top of descent". Whilst the aircraft may still be within
controlled airspace, it may be close to the boundary between
controlled and non-controlled airspace. In both situations, the
crew usually have a high workload and may develop a mindset that
commits them to a course of action before being able to adequately
assess the traffic information or establish communications with
aircraft in non-controlled airspace.



Provision of traffic information by FS or ATC, or the establishment
of communication by the flight crew with other aircraft just prior
to entering non-controlled airspace, may have been appropriate for
earlier generations of aircraft. However, this practice is
incompatible with most modern regional airline and general aviation
aircraft due to the higher performance capabilities of these
aircraft. Many of these modern turbo-propeller or turbo-jet
aircraft are capable of considerably higher airspeeds and rates of
climb/descent than the older piston-powered aircraft. Consequently,
following the provision of traffic information by FS or ATC, there
is usually little time available for the crew to assess the
conflict potential with other aircraft and then to communicate with
the crews of those aircraft, prior to leaving the protection
afforded by controlled airspace.



The problem resulting from the higher performance of modern
aircraft is compounded by the inherent delay between when an
aircraft commences descent and when the crew actually report "on
descent" to ATS. This delay can be up to 1 minute after the
aircraft has vacated a previously maintained level. During this
period, a modern regional airline aircraft may have descended or
climbed up to 1,500 ft and travelled up to 5 NM. Again, aircraft
operating in close proximity to the boundary between controlled and
non-controlled airspace may conflict with other aircraft operating
in non-controlled airspace before the flight crew has received
traffic information.



Emergency provision of traffic information



When a separation standard does not exist and in a controller's
opinion, traffic proximity warrants, the controller is required to
issue traffic information to the crew of the aircraft concerned
(Manual of Air Traffic Services (MATS) 4-6-1 paragraph 6). Evidence
from investigations indicates that some ATS personnel are reluctant
to issue traffic information after separation has reduced to less
than the required standard. Consequently, flight crews have been
unable to assess the potential for conflict while aircraft have
been in close proximity. The failure to utilise flight crew to
assist in the resolution of a reduction in separation may
compromise aircraft safety.



Training



The investigations revealed that in some situations, this
reluctance by controllers to provide traffic information was due to
unfamiliarity with the process. While the provision of traffic
information is included in some ATC simulator exercises, the
timeliness of the advice to pilots does not appear to be an aspect
given much consideration. Additionally, the training scenarios
available to assist controllers to improve their delivery of
traffic information are limited. There is no specific requirement
for controllers to regularly practise the routine provision of
traffic information, or the provision of emergency traffic
information. Implementation of specific traffic information
scenarios and the regular use of these in a simulator would assist
controllers to improve the assessment, timing, and awareness of
those situations in which the provision of traffic information is
required.



Flight progress strip annotation



The guidance provided to personnel regarding the recording of the
provision of traffic information on flight progress strips (FPSs)
is in the MATS 10-1-4 paragraph 30. A controller or flight service
officer is required to both enter and tick the identification of
conflicting traffic after the information has been passed and
acknowledged. A better procedure may be to annotate the conflicting
traffic on the FPSs as soon as the conflict is recognised. In this
way the annotation can be a cue for further action. A tick should
then be placed beside the conflicting traffic annotation only after
it has been issued to, and acknowledged by, the relevant aircrew.
This aspect could be clearly stated in the MATS and the procedure
covered in specific traffic information training undertaken by ATS
personnel.



The provision of prompts to assist controllers, as described, is an
aspect that may require further consideration due to the pending
use of electronic FPSs with the introduction of The Australian
Advanced Air Traffic System (TAAATS).