Investigation number
200404178
Occurrence date
Location
65 km SE Alice Springs, Aero.
State
Northern Territory
Report release date
Report status
Final
Investigation type
Occurrence Investigation
Investigation status
Completed
Aviation occurrence category
ACAS warning
Occurrence class
Incident
Highest injury level
None

The report presented was prepared principally from the information supplied to the Bureau.

Reported Information

On 21 October 2004, at about 1150 Central Standard Time, a Boeing Company 737-76N aircraft (737) registered VH-VBN was tracking to Alice Springs Airport on the 122 radial of the VHF omnidirectional radio range (VOR) navigation aid on descent to 9,000 ft. The crew reported that at about 35 NM from the airport, they received a traffic alert and collision avoidance system (TCAS) traffic advisory (TA) alert. Shortly after, the crew received a TCAS resolution advisory (RA) to reduce the aircraft's rate of descent. After changing to the Alice Springs aerodrome controller's (ADC) frequency, the crew was provided with traffic information on a Beech Aircraft Corporation 58 Baron aircraft (Baron), that was in the vicinity of the 737 at 9,500 ft and tracking in the opposite direction.

The ADC provided an air traffic service in the Class D control zone and the Class E control area steps surrounding the Alice Springs Airport, from ground level to 8,500 ft, within an area encompassed by a circle with a radius of 36 NM centred on Alice Springs Airport. Controllers were required, in Class D airspace, to separate instrument flight rules (IFR) flights from other IFR flights and to provide traffic information to pilots of IFR flights about any visual flight rules (VFR) flights. A similar level of service was required within Class E airspace for IFR flights with the exception that pilots of IFR flights would be provided with traffic information on VFR flights as far as practicable. The 737 was an IFR category flight and the Baron was a VFR category flight.

The ADC had flight details on both aircraft and it would have been prudent to provide traffic information to the crew of the 737 in sufficient time to enable them to assess the likelihood of a conflict in either class of airspace. At the time of the occurrence the ADC was busy with coordination tasks and managing other aircraft.

On 25 November 2004, as a result of National Airspace System (NAS) changes, the Class E airspace around Alice Springs was changed to Class C. In Class C airspace controllers are required to separate IFR flights from other IFR and VFR flights. Consequently, in future similar circumstances the ADC will be required to separate the aircraft.

Aircraft Details
Manufacturer
The Boeing Company
Model
737
Registration
VH-VBN
Operation type
Air Transport High Capacity
Sector
Jet
Departure point
Sydney NSW
Departure time
0927 CST
Destination
Alice Springs NT
Damage
Nil
Aircraft Details
Manufacturer
Beech Aircraft Corp
Model
58
Registration
VH-XSY
Operation type
Private
Sector
Piston
Departure point
Alice Springs NT
Departure time
1143 CST
Destination
Unknown
Damage
Nil