What happened
On July 8, 2018, a Bücker Bü 133C Jungmeister, registration SE-AJA, departed from Birzai, Lithuania, as part of a three-aircraft formation flying to Spilve, Latvia. While entering Latvian airspace, the pilot reported low oil pressure and initiated an emergency landing procedure.
During the attempt to land, the aircraft performed a U-turn and subsequently collided with the ground in the Bauska district. The impact caused substantial damage to the engine and fuselage. The pilot, who was the sole occupant, sustained fatal injuries.
The investigation
The TAIIB examined the wreckage and the engine, a Siemens/Bramo SH 1 and A4. The investigation included an inspection of the engine components at a workshop in Germany. Investigators found that the engine showed clear evidence of overheating and inadequate lubrication on the piston rod bearings.
Technical analysis revealed that the engine's oil system had been modified with a separate oil tap, but no supporting documentation for this modification was available. Furthermore, a "ROTAX" oil filter had been installed on the aircraft's fire bulkhead, which did not comply with the engine's type certification. This non-compliant filter potentially restricted oil flow. Additionally, the investigation noted that the pilot's blood contained an alcohol concentration of 0.51‰, which exceeded the legal limit of 0.2‰.
Findings
- The engine failed due to reduced lubricant supply, which led to a loss of engine power.
- The installation of a non-compliant oil filter may have restricted the flow of oil to the engine.
- The pilot was unable to maintain control of the aircraft during the emergency landing maneuver, which occurred at low altitude and low airspeed during a U-turn.
- The pilot's physiological and psychological state was affected by alcohol consumption, as blood alcohol levels were found to be above the legal limit.
- The engine showed traces of overheating and bearing wear consistent with insufficient oil supply.