Flight Planning
The pilot, on holiday leave, hired the aircraft from his employer for a private flight. The journey began at Moorabbin on 25 August, with stopovers at Coolangatta and Proserpine, arriving at Cairns around midday on 30 August. After three days of leisure in the Cairns area, the pilot attended the Cairns Briefing Office on the day of the accident to obtain weather forecasts and file a flight plan. The flight plan indicated Instrument Flight Rules (IFR) but contained a deficiency: no details were provided for the first route segment from Cairns to Biboohra. The pilot had not noticed that the enroute chart showed tracks west of Cairns emanating from Biboohra, not Cairns, and no track line connected the two points. This error was not detected when the plan was submitted.
Departure
When issued an airways clearance, the pilot initially did not understand its terms, which specified Biboohra as the initial tracking point. After the location was explained, he accepted the clearance. He chose a visual departure over the published Standard Instrument Departure (SID) profile. A visual departure from the runway in use allowed earlier intercept of the track toward Biboohra. Takeoff instructions included clearance for a right turn after departure. Witnesses observed the aircraft turn right, heading southwest before turning northwest and entering cloud, which had a base estimated between 2000 and 2500 feet above mean sea level (amsl). No further communications were received; a search began that afternoon but was hampered by weather. Wreckage was located the following afternoon.
Accident and Investigation
Inspection of the wreckage revealed that the aircraft struck the top of a ridge line, 250 metres southwest of the highest point of the Mt Williams area. At impact, the aircraft was on a west-north-westerly heading, flying wings level and climbing at about five degrees. No fault was found with the aircraft that could have contributed to the occurrence. The investigation determined that upon entering cloud, the pilot should have reverted to IFR procedures, which require ensuring adequate terrain clearance during climb to the lowest safe altitude. For the Cairns-to-Biboohra route segment, the relevant lowest safe altitude is 4500 feet amsl. The aircraft impacted at about 3250 feet amsl while apparently under control, indicating the pilot likely overlooked the lowest safe altitude requirements.