What happened
On November 30, 2019, a Jodel D 117, registration HB-SPO, was conducting a training flight for a private pilot license. The flight departed from Speck-Fehraltorf airfield, intended to perform simulated circuit patterns near Grüningen. During the flight, the instructor noticed the engine began to sputter. Upon attempting to maneuver for a landing, the engine failed completely and the propeller stopped spinning.
The pilot attempted to restart the engine by switching to the rear fuel tank and engaging the starter, but the engine would not fire. The instructor declared a "Mayday" and requested emergency assistance. The aircraft performed a forced landing in a field approximately 1 km south of Gossau. The impact was hard, resulting in heavy damage to the aircraft, including collapsed main landing gear and a broken wing spar. Both the instructor and the student escaped the wreckage without injury.
The investigation
SUST examined the aircraft's fuel system and maintenance records. The investigation revealed that while the crew believed they were using the front tank, the fuel selector valve had been incorrectly installed, effectively reversing the "FRONT" and "REAR" positions. Consequently, the crew was actually drawing from the rear tank, which was empty.
Furthermore, the investigation found that the electrical fuel gauge had been non-functional for approximately two years. While the front tank had a mechanical float indicator, the rear tank had no alternative method for monitoring fuel levels. The investigation also noted discrepancies in how technical maintenance information was shared during the flight school's transition to an electronic logbook system.
Findings
- The engine failure was caused by a lack of fuel supply.
- A faulty installation of the fuel selector valve caused the pilots to inadvertently drain the rear tank.
- The electrical fuel gauge was defective, preventing the crew from monitoring the rear tank's level.
- The aircraft's weight and center of gravity were within limits at the time of the accident.
- The transition to electronic logbooks created a risk factor by causing inconsistent access to technical maintenance information among pilots, maintenance providers, and authorities.
Safety action
SUST issued Safety Recommendation No. 568, directing the Federal Office of Civil Aviation (FOCA) to ensure that when transitioning to electronic logbook systems, all authorized personnel maintain full access to information regarding the technical condition of aircraft to prevent information gaps.