Incident Summary
A twin-engine aircraft engaged in aero-magnetic survey operations was reported overdue after failing to return to Cloncurry as scheduled. The burnt-out wreckage was located early the next morning approximately 9 km north of the survey area. The pilot and an equipment operator were on board.
Sequence of Events
The aircraft was tasked with flying a series of north-south tie lines spaced 2 km apart at a height of 80 m above ground level and a speed of 140 knots, with each line occupying about 20 minutes of flight time. The survey area extended from approximately 40 km to 130 km south of Cloncurry. The flight was planned to depart Cloncurry between 0700 and 0730 Eastern Standard Time and return by 1230 to prepare collected data for transfer to the company’s head office.
An employee of the operating company observed the crew, consisting of the pilot and an equipment operator, preparing to leave the motel for the airport at about 0500. No person has been found who saw the crew at the aerodrome or who witnessed or heard the aircraft depart.
At approximately 1000, three witnesses at a mining site in the southern section of the survey area saw a twin-engine aircraft at low level heading in a northerly direction. About 1.5 hours later, one of these witnesses saw what he believed was the same aircraft flying in an easterly direction approximately 1 km from his position. Between 1000 and 1030, two witnesses at a mine site located about 9 km north of the survey area (and approximately 5 km west of the accident site) heard an aircraft flying in a north-south direction at low level.
When the aircraft had not returned to Cloncurry by 1230, a company employee at Cloncurry initiated various checks at Cloncurry and other aerodromes in the area, contacted Brisbane Flight Service, and later in the afternoon communicated with the company’s head office. At about 2030, the employee advised the company chief pilot that the aircraft was overdue. The chief pilot contacted the Civil Aviation Authority Search and Rescue organisation at approximately 2045, and search-and-rescue action was initiated.
The burnt-out wreckage of the aircraft was found early the following morning approximately 9 km north of the survey area.
Investigation and Probable Cause
Investigation determined that, for reasons which could not be conclusively established, the pilot shut off the fuel supply to the left engine and feathered the left propeller. Subsequently, for reasons which could not be conclusively established, the pilot lost control of the aircraft.