What happened
On August 9, 2020, while operating an AT-3 R100 aircraft, registration SP-TPF, the pilot observed a drop in fuel pressure into the red zone on the cockpit instruments. The pilot immediately notified the Babice AFIS (Aerodrome Flight Information Service) regarding the technical issue. The aircraft subsequently performed a landing at Warsaw (EPBC) under the assistance of airport emergency services. The landing was completed without further incident or damage.
The investigation
The investigation focused on the mechanical cause of the pressure fluctuation. Because the aircraft was still under warranty, the manufacturer was notified and involved in the technical assessment. Following the event, the fuel pump was replaced. Subsequent engine tests demonstrated that fuel pressure remained within normal parameters after the replacement. The manufacturer further clarified that similar pressure drops had occurred previously and were linked to specific mechanical behavior of the fuel pump, noting that while pressure fluctuated, engine flameout had never occurred because activating the electric fuel pump restored nominal pressure.
Findings
The investigation established that the unstable operation of the fuel pump was the direct cause of the fuel pressure drop.
Safety action
The manufacturer has implemented several preventive measures to address the instability. The fuel system was modernized by adding a pressure pulsation damper to the system. Additionally, the manufacturer proposed replacing rubber hoses with steel-braided Teflon lines and installing a second electric fuel pump. The process for EASA approval of the modified fuel system installation is currently underway.