A seaplane crash on the Hawkesbury River in 2017 which killed six people was likely caused by engine fumes that leaked into the cabin, a coroner has found.
The Sydney Seaplanes DHC-2 Beaver nosedived into water at Jerusalem Bay on December 31, during a sightseeing trip.
The crash claimed the lives of pilot Gareth Morgan and five passengers — the chief executive of catering giant Compass, Richard Cousins, his two adult sons Edward and William, his fiancé Emma and her 11-year-old daughter Heather.
NSW Deputy State Coroner Derek Lee today found cracks in the aircraft's exhaust collector ring allowed gases with high carbon monoxide concentrations to pass into the cabin.
He said while the reason for the ingress couldn't be precisely determined, it was most likely that holes in access panels left open by three missing bolts provided the route.
"Exposure to carbon monoxide in the cabin resulted in an elevated carboxyhemoglobin level in the pilot, which impaired the pilot's ability to operate the aircraft safely, especially given the complexity of this task," Magistrate Lee said.
The findings follow a report published by the Australian Transport Safety Bureau (ATSB) in 2021, which put together the aircraft's final movements through a series of photographs taken by the front-seat passenger.
Initially there was no evidence of an in-flight break-up, bird strike, flight control failure or fuel contamination, but toxicological testing revealed all passengers had elevated levels of carboxyhemoglobin.
This finding led crash investigators to discover several small cracks in the exhaust collector ring within the wreckage, which likely released the exhaust gas.
Delays in testing
The inquest heard carbon monoxide detection was not performed as part of routine toxicological tests in post-mortem examinations.
While the absence of this test was stipulated in reports sent to NSW Police and the ATSB, both agencies mistakenly assumed it had been done.
Magistrate Lee found this was "not unreasonable" as an assumption, but it was "regrettable" no action was taken to advance the issue in 2018.
It wasn't until some 12 months later arrangements were made for the tests.
Magistrate Lee said this delay meant further investigative steps were required, and the emotional wellbeing of grieving relatives was impacted.
One of his recommendations was that carbon monoxide testing be routinely conducted for all deaths resulting from airplane crashes.
The deputy state coroner acknowledged relatives who joined the hearing remotely, and thanked them for their continued engagement with the coronial process.
