What happened
On 26 June 2017, an aircraft departed Burketown for Normanton with an undocumented fuel deficit. Although the aircraft's fuel log indicated 248 L of fuel remained on board, the actual quantity was approximately 48 L. This discrepancy originated on 15 June 2017, when a refueling error occurred; while only 200 L of fuel was actually delivered, 400 L was recorded on the delivery receipt. The pilot failed to identify this error and updated the fuel log with the incorrect volume.
As the aircraft approached Normanton, the fuel in the right main tank was depleted, causing the right engine to begin failing. The pilot attempted to maintain engine operation by utilizing the cross-feed function to draw from the left main tank. However, the left tank was also nearly empty, and the remaining fuel was quickly exhausted, resulting in the failure of both engines.
The investigation
The investigation focused on the period between the initial refueling error and the engine failure. It was determined that the refueling procedures in place lacked a mandatory cross-check to verify the volume of fuel provided against the amount recorded. While the refueller eventually noticed the error at the end of the day on 15 June, this information was never communicated to the pilot or the aircraft operator.
Furthermore, the investigation examined the pilot's verification process. Prior to the flight, the pilot checked the fuel gauges, which showed the tanks at roughly one quarter full. Because the aircraft's fuel calibration card suggested that a one-quarter reading should correspond to 170 L—a figure much closer to the log's 248 L than the actual 48 L—the pilot's belief that the log was accurate was likely reinforced.
Findings
- A refueling error occurred where 200 L was delivered but 400 L was documented.
- The lack of a cross-check procedure during refueling allowed the error to go undetected by the refueller and the pilot.
- The error regarding the fuel discrepancy was not communicated to the pilot or the operator.
- The discrepancy remained undetected through multiple flights over an 11-day period.
- The aircraft's fuel calibration card provided a reading that supported the incorrect log entry, misleading the pilot during pre-flight checks.
- The engines failed due to fuel exhaustion.