What happened
During preflight inspections for the first planned flight, the pilot in command used the aircraft’s dipstick to measure the fuel quantity. However, the dipstick was not correctly calibrated for the specific aircraft, leading to a measurement that significantly overestimated the actual fuel available. The crew remained unaware of this calibration error, resulting in an incorrect understanding of the fuel reserves necessary to complete the planned flights.
The investigation
The Australian Transport Safety Bureau (ATSB) examined how the pilots determined and verified their fuel on board (FOB). It was found that while operator policy required regular fuel checks, the pilots did not cross-reference the dipstick measurements with the aircraft’s fuel indicators either before or during the flights. This reliance on a single verification method meant the crew missed a significant discrepancy.
Evidence indicated that had the pilots compared the dipped measurement against the fuel indicators prior to departure from Tyabb Airport, a perceptible difference would have been evident. The actual fuel on board was approximately half of the expected amount based on consumption planning and recorded flight times. The ATSB noted that the aircraft’s fuel indicators had been calibrated in 2023, meaning any significant variance between the two methods should have flagged an error in one of them.
Findings
The investigation identified several contributing factors to the occurrence:
- The dipstick used to determine fuel on board was not calibrated for the aircraft, causing incorrect fuel quantity readings.
- Both pilots relied solely on the pre-flight dipstick measurement and failed to use the fuel indicators to crosscheck the amount of fuel on board prior to or during either flight.
- The Peninsula Aero Club’s recording form for fuel measurements only included one verification method. This administrative limitation prevented pilots and operators from readily crosschecking different verification methods to identify discrepancies in fuel on board.