This position appears to have been recorded during the post accident search in August 1981 and was included in the 1st September 1981 Air Safety Investigation Report. The position is clearly labeled as a radar fade position indicating where VH-MDX disappeared from RAAF Williamtown ATC radar at 0940UTC (1940EST).
It appears this position was determined by RAAF Williamtown vectoring a helicopter to the ‘last’ observed Williamtown radar position of VH-MDX. This position was used as one of the focal points for the initial post accident search as well as many following searches.
Our detailed investigations suggest that this position is unlikely to be a radar fade position but more likely the position of VH-MDX at 0936UTC (approximately 3.5 minutes prior to the final received transmission from VH-MDX) so, an intermediate radar position.
This means that VH-MDX in our current view is unlikely to be located in very close proximity to this position. But one can never completely rule this position out as a radar fade position.