What happened
On June 25, 2008, a Diamond Aircraft Industries DV 20 Katana, registration HB-SCL, was performing a private VFR flight from Hausen am Albis toward Birrfeld. The flight included a passenger. During the cruise phase at approximately 3,500 feet, the pilot noticed the fuel pressure warning light illuminate. While activating the electric fuel pump temporarily restored pressure, the warning light soon reappeared, and the engine began to sputter.
Recognizing the impending engine failure, the pilot initiated a descent to maintain airspeed and executed emergency checklists. After being unable to restore engine power, the pilot searched for a suitable landing site near Wohlen and notified Birrfeld airport of the intended emergency landing. The aircraft attempted to land in a field, but instead struck a potato field just short of the intended meadow. The rough terrain caused the aircraft to decelerate so violently that the nose gear collapsed and the aircraft nearly overturned. There were no injuries to the two occupants.
The investigation
SUST examined the fuel system components and maintenance records of the aircraft. The investigation focused on the mechanical and electric fuel pumps and the history of fuel pressure warnings. Investigators also reviewed the maintenance logs, which revealed that the fuel pressure warning had been noted in the aircraft's logs on May 10, 2008, and June 21, 2008, just four days before the accident.
Findings
- The engine failure was caused by a failure of the mechanical fuel pump due to a manufacturing defect in its inlet check valve, which allowed loose internal parts to obstruct fuel flow.
- The effectiveness of the electric fuel pump was also compromised because its outlet check valve was partially restricted, creating additional flow resistance.
- The combination of the defective mechanical pump and the restricted electric pump resulted in insufficient fuel pressure to the carburetions.
- A significant contributing factor was the failure to perform a thorough investigation or corrective maintenance after the fuel pressure warnings had appeared twice in the preceding weeks.
Safety action
No specific safety recommendations were recorded in the provided report text.