What happened
During a navigation exercise conducted by the Swedish Voluntary Air Corps, a flight departed from Ronne and proceeded toward Pukavik, Karlskrona, and Sturkö, with the intention of returning to Ronneby. While flying near Sturkö, the pilot adjusted the fuel tank selector. Shortly after this maneuver, the engine began running roughly before eventually failing completely.
In an attempt to restore power, the crew followed emergency checklists and repeatedly switched the fuel supply between tanks. While there was a brief moment of engine response, the engine failed again. Due to the low altitude, the pilot identified an open field on a nearby island for an emergency landing. During the approach, the aircraft struck a tree and dense vegetation, resulting in the aircraft coming to rest in an inverted position. The aircraft was severely damaged, but the crew sustained no injuries.
The investigation
SHK examined the aircraft's mechanical condition and found no evidence of technical malfunctions, carburetor icing, or contaminated fuel that could have triggered the shutdown. However, investigators determined that the left fuel tank had been depleted. The investigation also highlighted that the method used to calculate onboard fuel was unreliable, even though the total fuel volume was sufficient for the planned mission.
Investigators also scrutinized the post-shutdown actions. They found that the pilot's repeated switching of the tank selector likely introduced air into the fuel lines. Because it can take up to ten seconds for a stable fuel flow to be established after switching from an empty tank, these maneuvers likely prevented a successful engine restart.
Furthermore, the investigation identified delays in the emergency response. While the Swedish Maritime Administration initiated the search promptly, there were significant delays in alerting municipal emergency services and ambulances. Additionally, the white color of the aircraft made it difficult for the SAR helicopter to locate the wreckage against the snow-covered landscape.
Findings
- The primary cause was a lack of adequate fuel planning and monitoring, which led to the left tank being nearly exhausted.
- Repeatedly toggling the fuel selector between tanks after the engine had already failed contributed to the inability to restart the engine by allowing air into the fuel system.
- Deficiencies in communication and coordination between state and municipal rescue services delayed the arrival of medical assistance.
Safety action
- The Swedish Voluntary Air Corps is advised to implement formal routines for the continuous verification of fuel planning and to ensure pilots strictly adhere to these procedures.
- The Swedish Armed Forces, in collaboration with the FFK, are encouraged to finalize the organizational and accountability structures for Home Guard soldiers participating in these flights, specifically regarding command chains and occupational safety.