Accident Overview
On 14 January 1994 at 0114, an Aero Commander 690 aircraft, registration VH-BSS, struck the sea while being radar vectored to intercept the Instrument Landing System approach to runway 34 at Sydney (Kingsford-Smith) Airport, New South Wales. The aircraft was operating as a cargo charter flight from Canberra to Sydney under Instrument Flight Rules. The last recorded position was approximately 10 miles southeast of the airport.
Pilot and Aircraft
The pilot, the sole occupant, held a valid pilot licence endorsed for the Aero Commander 690 and a valid multi-engine command instrument rating. No evidence indicated that the pilot's performance was adversely affected by physiological or psychological conditions. The aircraft was airworthy for the intended flight, despite minor anomalies in maintenance and serviceability of systems. Fuel was sufficient, and weight and balance were within normal limits.
Wreckage Recovery and Examination
The pilot's body was never recovered. Shortly after the accident, wreckage identified as part of the aircraft was located on the seabed, but salvage was not initially undertaken due to cost-benefit considerations. About 18 months later, fishermen recovered the wing and tail sections. A detailed examination was conducted to assess the original analysis that airworthiness was unlikely a factor. No evidence of defects affecting normal operation was found.
Investigation Findings
Recorded radio communications were normal, and ground-based navigation aids were serviceable. The aircraft was capable of normal flight at impact. It was fitted with an altitude alerting system but not a ground proximity warning system. The transponder provided altitude information on ATC radar, but the secondary surveillance radar updated altitude only every sixth sweep. The aircraft descended below the altitude cleared by air traffic control. The circumstances were consistent with controlled flight into the sea.
Significant Factors
Investigation identified several significant factors: the pilot's relative inexperience in single-pilot IFR operations on this type; descent over the sea in dark-night conditions; increased workload from a steep descent profile at high speed requiring multiple tasks; radio communications with another company aircraft during the critical phase; distraction leading to loss of vertical awareness; inadvertent descent below the authorized altitude; and the radar altitude readout update limitation. The approach controller did not notice a gross altitude change shortly after a normal radio communication.