What happened
On 5 June 2025, a Piper Chieftain PA-31, registered VH-PGO, was performing a passenger transport flight from Carnarvon to Meekatharra, Western Australia. While approaching Meekatharra Airport, the pilot observed the right engine surging, accompanied by the illumination of the right low fuel flow and right fuel boost inoperative warning lights. The pilot performed the necessary memory item checks, feathered the right propeller, and successfully landed the aircraft without further incident.
The investigation
Post-flight inspections revealed fuel staining behind the right inboard fuel cap, suggesting fuel had leaked during the flight. A significant discrepancy in fuel levels was noted; the right inboard tank required 204 L to refill, while the left tank required only 67 L. This indicated that approximately 131 L of fuel had been lost through the cap.
Investigators found that the fuel cell had collapsed upwards toward the filler port. This collapse was caused by negative pressure as fuel was siphoned overboard by airflow. This movement of the fuel cell floor likely lifted the float-style sender unit, causing the cockpit gauge to provide an overreading of the actual fuel remaining. While the chief engineer could not replicate the incorrect installation, it was determined that the cap was likely not seated correctly, possibly due to the lanyard interfering with the seal.
Findings
- The right inboard fuel cap was almost certainly incorrectly secured, allowing fuel to siphon out during flight.
- The pilot failed to verify that the fuel caps were properly secured, as required by company and aircraft operating procedures.
- The fuel cell collapse caused the cockpit gauge to show an inaccurate, higher fuel quantity than was actually present.
- The pilot was unaware of the specific procedures required upon the illumination of the low fuel flow warning light, such as switching tanks or using crossfeed.
- Shine Aviation's training for the Piper Chieftain PA-31 did not sufficiently address the actions required by the pilot when the low fuel flow warning light illuminated.