Flight and Weather Conditions
The aircraft, registration VH-HOX, was operating a scheduled passenger service from Brisbane to Port Macquarie with planned intermediate stops at Coolangatta and Coffs Harbour. Weather conditions over the route were influenced by a widespread unstable airmass. The terminal forecast for Coffs Harbour indicated surface wind 360/15, visibility over 10 km, 5 octas stratus at 1000 ft, 5 octas cumulus at 2000 ft, with thunderstorms temporarily reducing visibility to 2000 metres. Actual weather was generally consistent with the forecast. Runway 03 was in use.
Navigation Aids and Facilities
Coffs Harbour was equipped with NDB, VOR, and domestic DME. A VOR/DME approach was published for Runway 03; aircraft without DME could use VOR or NDB approaches. Runway 03 had a 6-stage T-VASIS and 3-stage runway lighting. All facilities were functioning normally except the VOR, which experienced intermittent power failures due to heavy rain; it could be reset manually from the control tower. The tower was scheduled to be unmanned before the flight's arrival, but the duty air traffic controller elected to remain on duty until the aircraft landed and called a technician to attend to the VOR.
Approach and Accident Sequence
The aircraft was equipped with dual ILS/VOR and ADF receivers plus International DME, but not domestic DME as required by ANO 20.8. After descending in the VOR/NDB holding pattern, the aircraft was cleared for an instrument approach. The pilot was informed of the VOR's intermittent operation and indicated he would use the NDB. Weather fluctuated about circling minima of 950 feet (QNH) and 5 km visibility. The controller advised of a heavy shower south of the field. The aircraft completed the approach and the pilot reported "visual". The controller observed the aircraft's lights in a position consistent with a right downwind leg for Runway 03 and cleared it to land. Shortly after, the lights disappeared briefly, consistent with passing through a rain/cloud area, then reappeared as if turning onto finals before disappearing again, followed by a short series of clicks on the tower frequency. No further communications were received.
Accident Site
The accident site was located about 1070 metres short of the runway threshold and 750 metres to the right of the extended centreline. The aircraft initially struck a nine-metre-high tree in a nose-low attitude, steeply banked to the right, on a track of 050 degrees. After striking the tree with the outboard section of the right wing, it hit other trees before hitting the ground and overturning. A fire broke out shortly after the aircraft came to rest. Because the controller remained on duty, he was able to immediately notify emergency services, facilitating rescue of survivors.
Investigation Findings
A subsequent examination of the aircraft structure, systems, and components found no evidence of any pre-existing defect or malfunction. The pilot was properly licensed and qualified. Evidence indicated the pilot had flown approximately 930 hours in the previous 365 days, exceeding the ANO 48 limitation of 900 hours. Other breaches of Flight and Duty Limitations had occurred during the previous 12 months, but in the three months prior no significant breaches were found. Specialist medical advice considered the 30-hour exceedance not significant. Low-level windshear or microburst was considered but not determined to be a factor. A Coroners' Inquest examined allegations of irregular operating practices over several years, but no new evidence related to the accident flight.
Probable Cause
The investigation concluded that the aircraft was turning onto a short right base leg when it entered a localized area of rain and low cloud. The pilot was required to look out the right cockpit window to maintain visual reference with the runway. It is considered probable that the pilot briefly diverted attention from the flight instruments while attempting to maintain visual reference as the aircraft passed through reduced visibility. During that period, the aircraft continued to roll to the right, resulting in inadvertent loss of height. The pilot was unable to effect a recovery before striking trees. Factors considered relevant included: low cloudbase with rain squalls and reduced visibility, a low-level right-hand night circling approach, the pilot losing visual reference at a critical stage, failure to initiate a missed approach, and probable diversion of attention from flight instruments.