What happened
On August 22, 2009, a Cessna 172N, registration OK-JKF, was conducting a VFR flight from Brno-Tuřany Airport with a pilot and two passengers. The flight path took the aircraft over South Moravia, including areas such as Buchlov and the Lednicko-Valtický area. During a 180-degree right turn over the town of Rajhrad, the engine stopped running.
The pilot attempted to restart the engine three times, switching the fuel selector between the 'Both' and 'Right' positions, but was unsuccessful. The pilot then transitioned the aircraft into a glide, leveled the wings, and performed an emergency landing in a field near the village of Měnín. The aircraft sustained no damage, and there were no injuries to the pilot or the two passengers.
The investigation
An investigation by the ÚZPLN examined the aircraft's fuel system, maintenance history, and the fuel levels at the time of the incident. The investigation noted that the aircraft had previously experienced engine issues in July 2009, which the operator suspected were due to fuel contamination with sugar; however, laboratory tests of the fuel samples taken after this incident showed no evidence of sugar.
The investigators analyzed the fuel levels in the tanks. Before takeoff, the pilot had estimated the left tank was approximately one-third full and the right tank was approximately one-half full. Post-landing measurements showed that the total remaining fuel was approximately 26 liters. The investigation also looked into the aircraft's fuel system design, noting that the system relies on gravity feed rather than a pump.
Findings
- The flight began with asymmetrical fuel levels in the tanks.
- The fuel selector was left in the 'Both' position throughout the flight, which, combined with the aircraft's design and the pilot's maneuvers, led to the asymmetrical emptying of the tanks.
- During the 180-degree turn, the fuel level dropped to a point where the supply to the engine was interrupted.
- The pilot did not follow the instructions in the flight manual or operating manual, which recommend selecting either the 'Left' or 'Right' tank to ensure even distribution and prevent cross-feeding.
- There was no evidence of fuel contamination or mechanical failure of the engine or fuel system components.