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.
|Date:||16 July 2000||Investigation status:||Completed|
|Time:||1623 hours EST|
|Location:||13 km NNW Sydney, Aero.|
|State:||New South Wales|
|Release date:||24 October 2001||Occurrence category:||Incident|
|Report status:||Final||Highest injury level:||None|
|Aircraft manufacturer||S.A.A.B. Aircraft Co|
|Type of operation||Air Transport Low Capacity|
|Damage to aircraft||Nil|
|Departure point||Canberra, ACT|