The plan was to fly VH-MDX from Proserpine to Bankstown with a single refuelling stop at Coolangatta. The flight was planned to the Visual Flight Rules (VFR) requiring the aircraft to be navigated clear of clouds. Night fell by the time VH-MDX was overhead Coffs Harbour.
The weather was forecast as and, was found to be, generally clear skies, a strong south-westerly wind, localised cloud around the western tops of mountains and mountain wave activity east of the ranges and coastal.
All appeared normal until Taree after which VH-MDX tracked in excess of 20 nautical miles off the planned track to the west. It is not known why this occurred.
Failure of the primary attitude and heading instruments and penetration of cloud was advised by the pilot to Sydney Flight Service effectively at the same time.
VH-MDX attempted to climb but failed to do so as a suspected result of ice accumulation and downdrafts. Sydney ATC identified VH-MDX and tracked the aircraft on radar until approximately thirty seconds prior to the final received radio call from the aircraft.
RAAF Williamtown ATC obtained a single confirmed radar fix approximately three and one half minutes prior to loss of radio contact.
Further ice was reported as being accumulated by the pilot minutes before radio contact was lost.
During the final few minutes of recorded communications, an ever-increasing rate of descent was indicated by the timing of the pilot’s altitude reports.
The last received radio call from the pilot was ‘five thousand’ indicating the altitude VH-MDX was passing at that moment.
Radar information reveals that VH-MDX almost circumnavigated the entire group of main ranges associated with Mount Barrington.
Final radar positions are not completely reliable and this coupled with the significant terrain and vegetation of the Barrington ranges has kept VH-MDX hidden for over thirty years.