The ATSB has provided a substantive update on progress made, and noted several areas of ongoing focus, in its investigation of a floatplane accident off Rottnest Island, WA, with the publication of an interim report.
The report details that the Cessna 208 Caravan floatplane, operated by Swan River Seaplanes, hit swell and became airborne, then collided with water, during an attempted take-off from Thomson Bay, on Rottnest's north-east, on 7 January 2025. The pilot and two passengers were fatally injured.
ATSB Chief Commissioner Angus Mitchell said the interim report follows the publication of a preliminary report in March and adds further detail around the occurrence itself, and contextual information developed so far in the investigation.
"Analysis of the wreckage, witness statements, text messages, recorded onboard data and video footage has provided a more detailed understanding of the accident sequence," Mr Mitchell began.
"Due to strong winds, the pilot had surveyed the operator's normal take-off area in the middle of Thomson Bay twice on the afternoon of the accident.
"Considering the conditions to be unsuitable along the normal southerly track, the pilot instead opted for an easterly take-off, closer to shore where they perceived the swell was not as bad."
After the six passengers were conveyed by boat to the pontoon in Thomson Bay where the aircraft was stationed, the pilot taxied the aircraft to the north-west before turning and commencing the take-off to the east.
"The aircraft accelerated along the water in a strong crosswind and a light tailwind, and as it passed Phillip Rock, it encountered sea swell and chop," Mr Mitchell said.
With an indicated airspeed of 57 kt, the aircraft struck swell and became airborne. Its nose attitude increased significantly and, after reaching a maximum altitude of 16 ft, it rolled to the left.
The left wing impacted the water, followed by the fuselage and the rest of the aircraft, and the wreckage came to rest on its nose on the seafloor, partially submerged.
Four of the passengers were able to exit the wreckage; two with serious injuries and one with minor injuries. The pilot and two remaining passengers were fatally injured, however.
A pathologist's report for the WA Coroner identified the causes of death as drowning for the pilot, and one passenger in the first row of seats. The cause of death for the other passenger, in the second row, was drowning with head injury.
"The identification of factors contributing to the survivability of the aircraft's occupants is an important area of focus," Mr Mitchell said.
This is aligned with the ATSB's ongoing SafetyWatch priority of reducing the severity of injuries in accidents involving small aircraft.
"Examination of the wreckage identified the wings hinged backwards at impact, and the trailing edge of each wing penetrated the cabin in the area of the second row of passenger seating," Mr Mitchell said.
"The investigation is considering the crashworthiness of the Cessna Caravan aircraft and the suitability of the manufacturer and operator's emergency equipment and procedures for accidents involving immersion in water."
The ongoing investigation will also review the pilot's assessment of conditions on the day of the accident, including the decision to conduct an eastwards take-off. The influence of the tailwind, crosswind and other environmental conditions on the aircraft performance, and the aircraft handling in those conditions, will be examined.
"While the investigation is interested to understand the role of the pilot's actions and decision-making on the accident, the procedures and other risk controls used by Swan River Seaplanes for operations in the Thomson Bay area are also an area of focus," Mr Mitchell said.
"The investigation will also consider the operator's identification and assessment of Thomson Bay for floatplane operations, and its operational oversight practices."
Also under examination is the Cessna Caravan's stall warning system, noting passenger video did not capture any stall warning sounds during the take-off run, and the stall warning circuit breaker was found in the disconnected position after the accident.
"While the Cessna Caravan's handbook instructs pilots to have all circuit breakers in before commencing flight, experienced Caravan amphibian pilots have reported false alarms from the stall warning system during water take-offs, which can cause a loud distraction and concern to passengers," Mr Mitchell explained.
"This has led to a reported practice within the industry of disconnecting the stall warning system circuit breaker prior to take-off, the implications of which the investigation will consider."
The interim report also contains information gathered into the aircraft's maintenance history, extended periods of inactivity, and return to service actions taken after the aircraft was leased by Swan River Seaplanes in late 2024.
Mr Mitchell emphasised that the investigation was still underway.
"The areas of ongoing focus detailed in today's interim report should not be interpreted as likely findings in the investigation, given they are still undergoing detailed analysis," he said.
That analysis, and the findings that they lead to, will be detailed in the ATSB investigation's final report, currently anticipated for public release in the second half of 2026.
"Until then, if any critical safety issues are identified, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken," he concluded.
You can find here the interim report: Loss of control and collision with water involving Cessna 208 Caravan amphibian, VH-WTY, Rottnest Island, Western Australia, on 7 January 2025
