Sequence of events
At 0208 coordinated universal time (UTC) VH-FNB, a Fokker 50,
departed Carnarvon for Perth southbound via air route B469 and was
climbing to FL210. The two-way air route was a direct track between
Carnarvon and Geraldton . VH-FNA, also a Fokker 50, had departed
Geraldton for Learmonth and was tracking via the B469 northbound.
The crew of FNA had reported to Perth Flight Service at 0201 that
the aircraft was on descent to FL180 from FL200. At 0213, they
reported at position HAMEL and were estimating overhead Carnarvon
at 0246. HAMEL was a reporting point located 120 NM
south-south-east of Carnarvon. FNB's estimated time of arrival at
HAMEL was 0242.
About 65 NM south-south-east of Carnarvon and approaching FL180,
the co-pilot of FNB glanced down at the traffic alert and collision
avoidance system (TCAS) display and noticed a return in the
11-o'clock position at about 7 NM at the same level. The pilot in
command of FNB, aware that FNA was likely to be in the area,
communicated with the crew of FNA and requested their position. At
0226, as the pilot in command of FNA replied, the pilot in command
of FNB saw FNA pass approximately 400 ft below his aircraft on a
reciprocal track. FNA was not fitted with a TCAS and the crew of
FNA did not see FNB. Flight service had not directed traffic
information to either crew.
Flight Service procedures
Both aircraft were outside controlled airspace and operating in
a directed traffic information environment in which air traffic
control does not provide positive separation between air traffic.
However, flight service was required to provide aircraft operating
under instrument flight rules information on other possibly
conflicting military or instrument flight rule traffic. The
requirements and parameters for issuing traffic advice by flight
service are in the Manual of Air Traffic Services. The procedures
in the manual required the flight service officer to provide
traffic information to the crews of both FNA and FNB about each
other's flight routes because both aircraft were going to be within
15 NM of each other laterally and FNB was climbing through FNA's
level.
When aircraft are planned to depart non-controlled airspace and
enter controlled airspace, the flight service officer calculates a
release time, which is the time at which the flight service officer
expects the pilot of the aircraft to be communicating with air
traffic control. When air traffic control receives notification
from flight service that an aircraft will be entering controlled
airspace, the controller calculates a time of acceptance when the
aircraft is expected to be on frequency. Neither the release nor
acceptance times are coordinated between flight service and air
traffic control.
Flight Service Officer actions
The flight service officer was managing the combined sectors of
Flight Service 1 and 8 at the time of the incident. Flight service
team leaders were responsible for the administration of shifts.
They did not provide active supervision of flight service officers
at their work positions.
At the time of the incident, the flight service officer was
responsible for monitoring 13 VHF and 8 HF frequencies, and 15
aircraft. Of the 15 aircraft, approximately 10 were active and the
remainder were pending. Consequently, the flight service officer
and his supervisor reported that the workload was considered light
to moderate.
The flight service officer reported that he had assessed that
after departure it would take FNB 15 minutes to climb through FL200
into controlled airspace. He therefore calculated that FNB would be
in controlled airspace at about 0223 and he rounded up his expected
release time to 0225. Air traffic control reported that they added
a standard 15 minutes to the departure time advised unless the
aircraft was known to have a low performance climb, such as the
Fokker 50. In this case, 20 minutes was added. Therefore, the
expected on-frequency time for FNB would have been 0228 and in
accordance with standard practice, communications checks would have
commenced by 0231.
The flight service officer reported that he would have normally
passed traffic information to the pilots of both aircraft when FNB
taxied at Carnarvon. The flight service officer was unable to
explain why he did not believe the two aircraft were potentially
conflicting. Following the incident, the flight service officer
reported that he thought the Fokker 50 would have climbed at about
1,500 ft/min, a figure he reportedly derived from a previous
conversation with one of the operator's pilots. Advice from the
operator indicated that it was highly unlikely that a Fokker 50
could achieve such a rate-of-climb, particularly at the flight
levels at which FNB was operating. The local flight service
management reported that flight service did not advocate
calculations based on rate of climb as a traffic assessment
method.
The flight service officer reported that he filed the flight
strip for FNB soon after the release time of 0225, believing the
aircraft to be clear of non-controlled airspace.
Human factors
The flight service officer had received some air traffic control
training and reported that he had previously used air traffic
control techniques to determine whether traffic was in potential
conflict. The use of air traffic control techniques was not
required or advocated in flight service procedures. The flight
service officer had passed a performance check the day before, when
the checking officer noted him using some air traffic control
procedures to decide what traffic information should be provided.
The supervisor counselled him at the time not to use such
procedures. The flight service officer reported that he had been
using air traffic control techniques for some time to determine
what information needed to be passed to aircraft operating outside
controlled airspace in an attempt to reduce the amount of, what he
considered, unnecessary radio calls. Although the flight service
officer had used unapproved procedures in the past, he did not have
any history of providing inadequate or inappropriate traffic
information. During the investigation, it was reported that other
flight service officers who had undergone some air traffic control
training were also known to have applied air traffic control
procedures in the flight service environment.
The flight service officer reported that Airservices Australia
had managed his career within the previous 2 years in such a manner
that caused him concern because there was substantial uncertainty
related to his future employment. The flight service officer also
reported that as a result of this uncertainty, he was facing
significant personal issues and was probably pre-occupied by these
issues when he started the shift on the day of the incident. He had
approached his local management prior to the incident for leave and
the request was being processed at the time of the incident.
The flight service officer reported that he was uncertain about
his future employment and as a result of this uncertainty he had
only a small amount of sleep the night before his shift and was
feeling tired at the time of the incident. The flight service
officer's immediate supervisor reported that he was unaware that
the flight service officer may have been experiencing significant
personal stress or that the flight service officer was fatigued
when he commenced duty.
Traffic alert and collision avoidance
system
Both aircraft belonged to the same operator. The operator was
introducing TCAS as each aircraft underwent a major servicing. FNB
was the only aircraft in the operator's fleet that had been fitted
with TCAS and not all of the operator's pilots had been trained in
the use of TCAS. The operator's policy was that unless both pilots
in a crew were qualified to use TCAS, then the equipment was only
to be used in the traffic advisory (TA) mode. A TA is indicated on
the equipment display to the crew when the aircraft are within
about 48 seconds of their closest passing, based on projections
derived from current flight path and speed.
