What happened
On November 8, 1969, a pilot was conducting a series of solo training flights at the Sitterdorf airfield for the purpose of transitioning to the Brigadyr L-60. During the third solo flight of the session, the aircraft experienced a sudden engine failure at an altitude of approximately 50 meters while the pilot was retracting the landing flaps.
In an attempt to avoid nearby buildings in the village of Sitterdorf, the pilot initiated a right-hand turn and attempted an emergency landing in a nearby meadow. However, the aircraft was unable to clear a slight rise in the terrain. The plane struck the crown of an orchard tree before the right wheel and right wingtip impacted a steep embankment. The force of the impact caused the aircraft to leap over the crest, rotate 180 degrees, and come to rest upside down.
The investigation
The investigation examined the fuel levels and the functionality of the aircraft's monitoring systems. It was determined that the aircraft had been fueled on November 2, 1969, with 67 liters added to the left tank, bringing that side to a total of 100 liters. The right tank had not been replenished and contained only approximately 25 liters.
Investigators checked the fuel sight glasses and found that while the system was functional, the readings could be inaccurate depending on the aircraft's attitude. Upon inspection after the crash, the left tank was found to be nearly empty (0.3 liters remaining), while the right tank contained 23 liters. The fuel selector valve had been set to the left tank.
Findings
- The primary cause of the accident was fuel exhaustion occurring immediately after takeoff during a critical phase of flight.
- The pilot had mistakenly believed the left tank was sufficiently full based on visual inspections of the sight glasses during previous flight segments.
- The emergency landing was unsuccessful due to the low altitude and the unfavorable terrain configuration.
- The pilot's actions following the engine failure, including attempting to restart the engine and maneuvering to avoid structures, were considered appropriate.