What happened
On June 24, 2007, at 11:20 local time, a privately owned BMW Lazer Ipsos microlight, registration F-JZUH, performed a forced landing in a marsh near Petsmo village. The flight had departed Pori airport (EFPO) at 09:24, bound for Kokkola (EFKK), following a route along the coastline at altitudes between 200 and 400 meters.
During the flight, the engine stopped approximately 20 km north of Vaasa airport. The pilot attempted an emergency landing in the only available open area, a marshland known as Siklaxmossen. While the initial touchdown was normal, the soft surface of the marsh caused the aircraft to roll twice along its longitudinal axis. The impact resulted in heavy damage to the airframe, including a bent structural tube and a broken mast. The pilot sustained serious injuries, while the passenger remained uninjured.
The investigation
The investigation established that the engine failure was triggered by the snapping of the generator drive belt. Because the engine's ignition, fuel injection, and fuel pump systems all rely on electrical power, the loss of the generator forced the aircraft to rely solely on battery power. The investigation found that the battery was able to sustain the engine for approximately one hour after the belt failure, at which point the voltage dropped to roughly nine volts, causing the engine to shut down.
Investigators also examined the pilot's familiarity with the aircraft's instrumentation. It was noted that the instrument panel lacked instructional placards for the warning lights. Furthermore, bright sunlight may have obscured the visibility of the charging warning light.
Findings
Several contributing factors were identified in the sequence of events:
- The snapping of the generator drive belt was the primary cause of the engine failure.
- The pilot's lack of sufficient knowledge regarding the specific electrical systems of this four-stroke engine model meant the generator failure went undetected.
- The pilot did not recognize the significance of the battery voltage indicator or the charging warning light.
- The selection of a marsh as a landing site, while the only available option, contributed to the aircraft's rollover due to the soft terrain.
- The absence of instructional labels for warning lights on the instrument panel hindered the pilot's ability to identify the electrical malfunction.