Incident Overview
On 9 August 2020, an AT-3 R100 aircraft, registration SP-TPF, was in flight when the pilot observed a fuel pressure drop on the gauge, indicated in the red range. The pilot informed AFIS Babice, and the aircraft landed with the assistance of airport services without any consequences.
Investigation and Cause
The Polish State Commission on Aircraft Accident Investigation (PKBWL) examined the incident. The aircraft was under warranty, and the manufacturer was notified, recommending replacement of the fuel pump. After replacement, fuel pressure during engine testing remained within normal limits. The manufacturer informed the operator that similar pressure drops had occurred in the past and had been clearly defined. The pressure drops were caused by unstable operation of the fuel pump, but despite the temporary pressure drop, engine stoppage never occurred. In each case, activating the electric fuel pump restored fuel pressure to nominal values.
The probable cause of the incident was unstable operation of the fuel pump causing fuel pressure drops. No contributing circumstances were determined.
Preventive Actions
The manufacturer implemented preventive measures. The fuel system was modified by adding a pressure pulsation damper. The aircraft with this modification accumulated several flight hours without any fuel pressure drop. An approval process for the proposed change by EASA was initiated. Additionally, the manufacturer proposed replacing rubber hoses with steel-braided Teflon hoses and installing a second electric fuel pump.
No safety recommendations were issued.