Th Sydney Air Traffic Controllers were faced with many challenges involving VH-MDX.
Given the location of VH-MDX, the only radar display program able to present the aircraft’s radar returns was a Mosaic type display of around 290 nautical mile maximum display range.
Now consider the following combined with the large 290 nautical mile display:
– Secondary radar return symbols were around 5 nautical miles in size
– VH-MDX travelled only about 25 nautical miles whilst being radar observed by Sydney Air Traffic Control (ATC)
– VH-MDX tracked in a curved path (hard to assess where the aircraft was specifically tracking)
– Weather associated radar clutter was likely where VH-MDX was tracking (‘washing out’ VH-MDX’s radar returns).
From these points, one can see that attempting to determine VH-MDX’s track and intentions was challenging.
Consider the image presented below. It presents an overlay of the relevant Sydney ATC radar display with topographical charts.
The relatively small distance VH-MDX travelled on the Sydney radar display is obvious.
The Barrington ranges consist of severe terrain and significant vegetation. Remembering this, consider the zoom image below.
It can readily be seen that small changes in radar observed position on the large mosaic display results in significant changes of position in the Barrington ranges. Think about the radar paint sizes of around 5 nautical miles in relation to the geography.
It must also be remembered that:
– VH-MDX did not declare a urgency or emergency situation
– VH-MDX was located outside controlled airspace.
RAAF Williamtown was faced with similar challenges to Sydney. VH-MDX was located outside controlled airspace on the limits of the Williamtown radar display in significant terrain and weather clutter.
There was no requirement to have the radar on at Williamtown as procedural control was being conducted. Fortunately and in a prudent move, the Air Traffic Controller chose to have the radar on for extra situational awareness. This move provided a more refined position of VH-MDX to investigators.
Controller workload was high and VH-MDX was introduced to Williamtown ATC within the final few minutes of flight. Remember, VH-MDX was not the only aircraft of interest: other aircraft had to be controlled or liaison performed for at both Sydney and Williamtown ATC.
The image below presents an overlay photo of a Williamtown radar display on top of a topographical chart. The photo effectively represents the display in use and the radar clutter apparent during the accident.
Amongst the terrain clutter aligning with the Barrington ranges is where VH-MDX was radar observed.
It can be seen both Sydney and Williamtown ATC were faced with a challenging situation.