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.
On 4 June 2020, a Cessna 210M departed Darwin for a charter flight to Maningrida, Northern Territory. There was a pilot and three passengers on board.
After take-off, the aircraft was cleared to climb to 7,500 ft and track direct to Maningrida. During cruise, the pilot switched from the left to the right fuel tank. Approximately 26 minutes after the tank switch, the pilot observed the exhaust gas temperature rising and the fuel flow gauge fluctuating. The pilot then turned on the fuel pump and observed that the fuel flow gauge ceased to fluctuate. Once the fuel pump was turned off again, the fuel flow fluctuations increased in severity, the engine’s performance was diminished and the RPM dropped. The engine subsequently stopped.
The pilot immediately turned on the fuel pump, reduced the mixture lever to half way, switched the fuel tank from right back to left and successfully restarted the engine. With no suitable landing areas identified, the pilot closely monitored the engine’s performance and maintained 6,000 ft until overhead Maningrida. The aircraft joined the circuit and landed without further incident.
Post-flight, the pilot checked that the fuel caps were secured correctly and conducted a fuel drain to check for contamination, of which there was none.
Engineers conducted a thorough inspection of the fuel system and discovered mud wasp nests in both fuel vent lines.
As a result of this incident, the operator and maintenance organisation advised the ATSB that they have taken the following safety action:
- A full fleet inspection was conducted where all fuel vent lines were examined for blockages.
- Fuel cap venting will be checked during 100 hourly aircraft inspections.
The ATSB has investigated a number of incidents involving insect activity disrupting aircraft systems and causing blockages that have been particularly difficult to identify. Mud wasps in particular, can build nests in aircraft that are stationary for very short periods of time. This incident serves as a reminder to operators that extra caution should always be taken in locations where known environmental hazards exist.
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.