| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
On 20 January 2018, a remotely piloted aircraft (RPA) was being operated on a training exercise over water off Wategos Beach near Byron Bay, New South Wales.
At about 1318 Eastern Daylight-saving Time (EDT),[1] while maintaining 100 ft above ground level, the crew detected a propeller malfunction on one of the RPA’s six propellers. The crew elected to conduct a precautionary landing of the RPA into the water about 200 m offshore. The RPA operator indicated that this was in accordance with their emergency procedures for a propeller malfunction in order to reduce the risk to the beach-going public.
The RPA was recovered from the water and inspected by the operator. The initial inspection indicated that bolts fastening the propeller to the motor unit had failed. Figure 1 shows the failed bolts (left) along with a picture of a non-damaged propeller assembly (right). The RPA has been sent back to the manufacturer for further examination.
Figure 1: Failed bolts that secure the RPA propeller to motor (left) and example of an undamaged propeller and motor assembly (right)
Source: RPA operator, modified by the ATSB
Safety message
The ATSB’s research report A safety analysis of remotely piloted aircraft systems 2012 to 2016: A rapid growth and safety implications for traditional aviation found that, there has been rapid growth in the number of RPA systems in Australia. This incident highlights the importance of contingency planning for RPA operations. While the manufacturer indicated that, for this RPA configuration, control could be maintained in the event of a single propeller failure, a loss of a control surface would result in a degradation of performance. In this case, the crew identified the reduced performance and acted accordingly by landing the RPA offshore, thereby reducing the risk to third parties.
The Civil Aviation Safety Authority has published guidance on the operation of RPA’s in the advisory circular, Remotely piloted aircraft systems – licencing and operations. Section 4.6 specifically states that, procedures to be followed in the event of an engine/propeller failure should be in place and included in the RPA system mission plan.
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.
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