On 17 November 2005, at 1327 Central Standard Time, a Boeing
Company 717-200 (717) aircraft, registered VH-NXE, was inbound to
Alice Springs, NT, on the 055 degree radial of the very high
frequency omni-directional radio range (VOR) ground-based
navigation aid, on a scheduled flight from Cairns, Qld. The 717
crew reported to the Alice Springs aerodrome controller that they
passed almost overhead and within about 1,500 ft of a Cessna
Aircraft Company C310R (C310) that was outbound from Alice
Springs.
The C310, registered VH-JOI, was being operated on a pilot
instrument rating renewal flight and, after becoming airborne off
runway 12, was being tracked via a GAFER ONE standard
instrument departure (SID), on climb to operate in a training area
located to the east of Alice Springs (Figure 1), not above 6,000
ft. A SID is a published instrument flight rules departure
comprising obstacle clearance data to the minimum safe altitude and
tracking data until the aircraft reaches a specified point on its
air traffic control cleared route. The GAFER ONE SID provided
altitude requirements and heading instructions that enabled the
pilot to intercept the 055 degree radial from the VOR.
Figure 1: Alice Springs visual terminal
chart showing the 055 degree radial, the approximate track of the
GAFER ONE standard instrument departure and the Eastern Training
Area
The approved testing officer, who was also the pilot in command
on board the C310, later reported that when the aircraft was at
about 15 NM from Alice Springs, the pilot being tested turned the
aircraft right, off the 055 degree radial of the VOR, and tracked
towards the training area.
The Alice Springs airspace was not serviced by radar and as such
the Alice Springs aerodrome controller was required to apply
non-radar (procedural) control, in accordance with published
procedures. The aerodrome controller was responsible for
controlling aircraft operating within the Alice Springs control
zone and control area up to 8,500 ft. Procedural control is
achieved by the use of information from sources other than radar.
The aerodrome controller intended to establish a lateral separation
standard between the C310 and the inbound 717 once the C310 was
established in the training area.
The aerodrome controller initially applied a vertical separation
standard of 1,000 ft between the C310 and the 717. At 1326, the
pilot of the C310 reported, to the aerodrome controller, that the
C310 was established in the training area to the east of Alice
Springs. That training area was procedurally separated, using a
lateral separation standard, from the 055 degree radial from the
Alice Springs VOR. Once the pilot of the C310 reported established
in that training area, the C310 was laterally separated from the
717. The aerodrome controller then cleared the crew of the 717 to
descend below the altitude of the C310.
About a minute later, the crew of the 717 reported that they had
the C310 in sight about 1,500 ft below their aircraft. The pilot in
command of the C310 later reported that he heard that broadcast
made by the crew of the 717, but despite conducting a search for
the 717, did not see the aircraft.