Incident Overview
The pilot of an aircraft planned a direct flight from Cockatoo Island to Derby at an altitude of 5,500 feet above sea level. However, during the departure call, the pilot amended the cruising altitude to below 5,000 feet. No further radio communications were received from the aircraft.
Observations
A workboat from Cockatoo Island was located 56 kilometres north-north-west of Derby and approximately 20 kilometres west of the direct track between Cockatoo Island and Derby. The crew of the boat observed an aircraft approaching at a very low altitude. The aircraft passed directly over the boat at an estimated height of 5 to 7 metres above the deck. Immediately after passing over, the aircraft entered a right-hand turn. During the turn, the right wing tip struck the water, causing the aircraft to cartwheel and crash approximately 400 metres from the boat.
Rescue
The fuselage broke open upon impact with the water. The occupants of the aircraft were subsequently rescued by the crew of the workboat.
Probable Cause and Relevant Factors
According to the official investigation, the pilot declined to provide any information that might have clarified the circumstances of the accident. However, available information indicates that the pilot carried out an unauthorized low pass over the boat. During the subsequent turn, the pilot misjudged the aircraft's height, resulting in the right wing tip striking the water. The investigation considered the following factors relevant to the development of the accident: the pilot was neither trained nor authorized to conduct low-level operations; the pilot exercised poor judgment by operating at an unnecessarily low height; and the pilot misjudged the aircraft's height above the water.