The pilot of a twin-engine Islander aircraft was attempting to exit south-west Tasmania’s Western Arthur Range in low visibility conditions when it collided with a ridgeline, an Australian Transport Safety Bureau investigation details.
The Airlines of Tasmania-operated aircraft was conducting a positioning flight under visual flight rules on the morning of 8 December 2018 from Hobart’s Cambridge Airport to an airstrip at Bathurst Harbour in the Southwest National Park. A single pilot was on board.
Satellite-based ADS-B transponder data from the aircraft showed that the pilot had tracked from Cambridge Airport direct to Bathurst Harbour, passing through a gap (or saddle) in the Arthur Range known as ‘the portals’, a route used in low cloud conditions.
After passing through the saddle, flight data showed the aircraft manoeuvred in a valley, consistent with the pilot assessing different options for possible routes through to Bathurst Harbour, before tracking back towards the portals, the investigation’s final report details.
While in a turn under power and pilot control, the aircraft collided with a ridge on the Western Arthur Range, at an elevation of about 885 m (2,805 ft). The aircraft was destroyed in the accident and the pilot was fatally injured.
“The ATSB’s investigation found that the pilot was using a route through the Arthur Range due to low cloud and had continued over a saddle in the range at a lower altitude than previous flights along the same route,” said ATSB Director Transport Safety Dr Stuart Godley.
“During this, the pilot likely encountered reduced visual cues, and while attempting to exit the range, the aircraft collided with a ridge that formed part of the Western Arthur range,” he said.
“For pilots, this tragic accident highlights the hazards associated with flying in mountainous terrain and the need to have an escape route. It also shows the challenges of in-flight weather-related decision‑making.”
The investigation also found that Airlines of Tasmania’s guidance to its pilots for operations to Bathurst Harbour was primarily given verbally and was not well documented.
“This resulted in the operator’s pilots having varied understandings of the expectations regarding in-flight weather-related decision-making at the Arthur Range saddle,” Dr Godley said.
The ATSB’s investigation also found that, while not a contributing factor to the accident, the operator’s safety management processes had limited opportunities to proactively identify risks in all operational activities and to assess the effectiveness of risk controls.
“For operators, this investigation highlights the importance of using multiple sources to identify the hazards potentially affecting the safety of their operations, rather than relying on one key source. These can include safety occurrence reports, inspections, audits, flight data, and expert judgment,” Dr Godley said.
“Likewise, it is equally important that operators monitor and evaluate the ongoing effectiveness of existing risk controls to ensure that they remain appropriate.”
Subsequent to the accident, in January 2020, Airlines of Tasmania introduced specific guidance for its south‑west Tasmanian operations, introducing visibility requirements for pilots using the direct route through the Arthur Range saddle.
In addition, the operator added further information and guidance to its training syllabus, and introduced changes to its safety management system.
The investigation notes the operator has also committed significant resources into installing technologies to assist with flight planning and oversight of its operations. This included the installation of a new high definition 360° webcam at the Bathurst Harbour airstrip and the installation of ADS-B ground receivers at a number of locations, including within the Southwest National Park.
Another aspect of the ATSB’s investigation was an analysis of the Civil Aviation Safety Authority (CASA)’s oversight of Airlines of Tasmania, including surveillance activities. The investigation found that, while not a contributing factor to the accident, CASA’s process for acquitting repeat safety findings was not effective. While there were ongoing communications with the operator, CASA did not conduct any formal surveillance activities specifically related to the operator's safety management system.
Finally, the investigation notes that, while ADS-B transponder data provided important information to the ATSB’s investigation, the aircraft was not fitted with an onboard recording device (nor was it required to be).
“An on-board recorder would have provided valuable information to better understand the pilot’s in-flight weather-related decision-making and identify potential safety issues,” Dr Godley said.
“The use of lightweight recorders on smaller aircraft conducting commercial passenger operations can provide a relatively simple and cost-effective way of achieving of the benefits of traditional recorders fitted to large aircraft.”Last update 20 December 2021