What happened
On 7 May 2024, a Cessna 208 amphibian was operating a round-trip sightseeing flight from a floating pontoon facility in Talbot Bay, Western Australia with a pilot in command under supervision, a supervising pilot and 6 passengers on board. The facility had the capacity for up to 4 seaplanes to launch and dock side by side. The aircraft was moored on dock 1, the forward‑most dock.
A strong pushing on[1] tide existed on the day with an easterly 8 kt wind. Two dockhands on the pontoon assisted the flight crew with the launch of the aircraft while the flight crew began the engine start sequence.
The environmental conditions had a greater effect on the aircraft than the crew anticipated, and the tide pivoted the front of the aircraft left around the corner of the dock, while the wind pushed the tail of the aircraft away from the pontoon. Once the aircraft was out of reach of the dock crew, the tidal movement pushed the aircraft through the water towards a houseboat at the front of the pontoon’s configuration.
The crew continued with the engine start and the aircraft started to move forward under its own power. The supervising pilot took over control, increasing engine power and bringing the propeller out of the feathered[2] position. However, the wind continued to rotate the aircraft to the left, and the flight crew was unable to achieve sufficient forward speed through the water before the aircraft collided with the houseboat.
The aircraft’s left wing impacted first, swinging the aircraft into the bow of the houseboat, resulting in a further propellor impact (Figure 1). The aircraft came to rest entangled in the pontoon’s mooring lines. There were no injuries to the flight crew or passengers.
Figure 1: Propeller damage
Source: Operator, annotated by the ATSB
Operator’s procedures
The operator provided a pontoon operating manual which outlined the standard operating procedures and limitations. The manual identified pushing on tides as one potentially hazardous scenario when it could be difficult for dockhands to maintain control of the aircraft. To mitigate the risk in such conditions, a wind limit of 10 kt was stipulated when the prevailing winds were blowing opposite to the tidal flow, and further limitations were to be observed when operating from dock 1 in pushing tides.
The procedures for launching from dock 1 required dockhands to push the aircraft from the pontoon while maintaining control of the aircraft from the rear and pulling on ropes attached to the wing. By positioning the nose downwind of the launch, this procedure allowed the aircraft to be swung into its position while the flight crew conducted the engine start. Once in the correct position, the dockhands would call ‘clear’, notifying the pilot in command that the aircraft was safe to dispatch and launch. The pilot in command would then announce ‘launching’ and commence the engine start and subsequent launch from the pontoon.
The operator’s manual stated that if at any time the dockhands observed anything abnormal related to the dispatch sequence not complying with the standard operating procedures, they were to notify the crew using hand signals or radio contact.
Operator’s comments
The operator advised that mechanical or steering malfunctions that would have precluded the normal operation of the aircraft were ruled out as contributing factors.
The operator determined that the crew’s decision to not abort the launch, while attempting to recover the aircraft, exacerbated the situation by swinging the aircraft back towards the dock.
Safety message
During times of significant workload, effective communication is important when relaying safety critical information. This incident highlights the importance of adhering to operational limitations and defined operating procedures, especially in marginal conditions. It is also a reminder of the importance of conducting regular risk assessments to ensure the safe operation of the aircraft and its crew and passengers.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
[1] Pushing on tide: The term ‘Pushing On’ comes from the effect of the tidal currents pushing the aircraft onto the pontoon.
[2] A practice employed by operators where the propeller blades are rotated to an edge-on angle to the airflow to assist in securing the propeller while the aircraft is docked. This reduces the risk of injury and damage to the engine caused by the internal components rotating without a supply of oil.