The pilot of an Aero Commander had to land the aircraft in a field after fuel siphoned overboard due to an incorrectly installed fuel cap, an ATSB investigation has concluded.
On 8 March 2024, the twin-engine Aero Commander 500-S was conducting a return freight flight from Bankstown to Parkes, with multiple stops each way.
Upon landing after the first sector of the day, the pilot found the aircraft's fuel cap was off and secured only by a retention chain.
The pilot re-secured the cap, but found the cap off again after the second sector, after landing in Parkes.
"For the two sectors from Bankstown to Parkes, the fuel cap had been incorrectly installed with the retention chain lodged in the fuel tank's anti-siphon valve, resulting in the cap dislodging in flight, and fuel being siphoned overboard," ATSB Director Transport Safety Stuart Macleod explained.
An inspection and rectification conducted at Parkes by a maintenance engineer fixed the issue.
"However, the pilot identified an unexplained discrepancy between expected fuel remaining and gauge quantity indication, but did not refuel to a known quantity, or amend the flight log," Mr Macleod noted.
"This meant the aircraft left Parkes without enough fuel to complete the remaining sectors on its return trip back to Bankstown."
After departing Parkes, the pilot likely did not monitor the fuel gauge, continued fuel calculations based on an incorrect fuel quantity, and did not refuel the aircraft to a known quantity when they landed at their final interim location, Bathurst.
Subsequently, shortly after take-off for the final sector to Bankstown, both engines lost power due to fuel exhaustion, and the pilot conducted a forced landing in a field. Fortunately, the aircraft was undamaged, and the pilot uninjured.
"A missing or unsecured fuel cap should be treated as an emergency, and if detected pilots should immediately divert to the nearest suitable aerodrome," Mr Macleod said.
Since the incident, the operator, GAM Air, published a notice to pilots reinforcing fuel management procedures. It also commenced periodic auditing of pilot fuel calculations.
Additionally, in response to an ATSB finding that its Quick Turn Around - Pre-Start checklist did not include a fuel quantity check before start, the operator has announced the intention to discontinue using this specific checklist.
"Pre-flight fuel quantity checks should use at least two different verification methods to determine the amount of fuel on board," Mr Macleod said.
"When using computed fuel on board and comparing against gauge readings, it is important that calculations are accurate. If any discrepancy is detected between the two methods, another method such as filling to a known quantity is required."
You can find here the final report: Fuel exhaustion involving Aero Commander 500-S, VH-MEH, 6 km east of Bathurst Airport, New South Wales, on 8 March 2024
