Investigation number
200003091
Occurrence date
Location
13 km NNW Sydney, Aero.
State
New South Wales
Report release date
Report status
Final
Investigation type
Occurrence Investigation
Investigation status
Completed
Occurrence class
Incident
Highest injury level
None

The crew of a Saab 340 were arriving at Sydney from the north-west and had been cleared by air traffic control to make a visual approach to runway 16R. The controlled airspace steps in that sector required the crew to maintain an altitude of 2,500ft until 12 NM, when further descent would be available. As they were passing through 2,400ft, they observed an airship immediately in front and below. The aircraft's traffic alert and collision-avoidance system (TCAS) issued a Resolution Advisory alert, and the crew reduced the rate of descent until they had passed the airship.

The airship had been tracking outside controlled airspace at a planned altitude of 1,500ft and was being navigated along the boundary of that airspace which, at that point, was a 12 NM arc based on Sydney airport. The crew was required to remain north-west of that boundary.

Analysis of the recorded data indicated that the airship had marginally infringed controlled airspace and was 11.9 NM from Sydney. The Saab 340 had descended marginally through the 2,500ft limit and was approximately 2,300ft when it passed the airship.

The TCAS actuated based on the reducing altitude differential and provided the crew with timely information on the airship below it.

Aircraft Details
Manufacturer
Saab Aircraft Co.
Model
340
Registration
VH-KDQ
Serial number
340B-325
Operation type
Air Transport Low Capacity
Sector
Turboprop
Departure point
Canberra, ACT
Destination
Sydney, NSW
Damage
Nil