Incident Overview
On November 29, 2006, at 14:37 UTC, a Diamond DA20-A1-100 "Katana" with registration F-GNDG was conducting an instructional local flight at Montpellier Méditerranée aerodrome. The aircraft was operated by a club and carried two occupants: a 29-year-old instructor and a 40-year-old student pilot on their third dual-controlled flight. No injuries were reported.
Sequence of Events
During the final approach to runway 31L, the engine vibrated and stopped at approximately 400 feet altitude. The electric fuel pump and carburetor heat were both engaged. After manipulating the power control, the engine restarted, but the aircraft was above the final approach path. The instructor elected to land with reduced power.
Technical Findings
Post-incident inspection revealed a blue trace of fuel leakage at the mechanical fuel pump. The original BING pump (P/N 892.236) was replaced. Subsequent operations revealed that replacement pumps (P/N 892.545) also exhibited leaks or low-pressure warnings, leading to the aircraft's immobilization after a fourth pump failed.
Analysis of Cause
The investigation identified that when the electric fuel pump is active, it delivers pressure up to 1 bar, exceeding the specifications for the mechanical BING pumps (0.3–0.4 bar). This excessive pressure can damage the flexible membrane inside the mechanical pump, causing fuel to leak into the pump case and escape through the vent. Additionally, high pressure can enrich the fuel-air mixture excessively, potentially leading to engine misfires or stoppage, particularly when carburetor heat is applied.