What happened
During a takeoff from runway 07 at Långtora airport, a DG-80AS motor glider experienced a sudden loss of engine power. Shortly after departing, the pilot noted the engine began running roughly. At an altitude of approximately 30 meters, the engine failed completely, forcing the pilot to perform an emergency landing in a nearby crop field. While the pilot escaped the incident without injury, the aircraft sustained substantial damage.
The investigation
Investigators focused on the discrepancy between the fuel level indicated during pre-flight and the actual fuel remaining at the time of the accident. During the pre-flight inspection, the aircraft's electronic fuel gauge showed 11 liters of fuel onboard. However, a post-accident inspection revealed that the fuel tank was entirely empty. Despite the lack of fuel, the gauge continued to display the 11-liter reading.
Technical analysis of the fuel system suggested that inaccurate readings can occur if the condenser plates within the tank are dirty or if the system was calibrated while the tank was not full. While a post-accident re-calibration corrected the gauge's accuracy, the specific reason for the initial error could not be determined. The investigation also reviewed the DG-800B flight manual, which suggests that the electronic gauge is a sufficient method for determining fuel quantity during pre-flight, and noted that the Swedish gliding association's handbook lacked detailed instructions for manual fuel verification.
Findings
- The primary cause of the accident was the lack of adequate procedures for verifying fuel quantity prior to flight.
- The electronic fuel gauge provided a false reading of 11 liters when the tank was actually empty.
- Existing flight manuals and gliding handbooks did not mandate or describe secondary methods to confirm the accuracy of the electronic fuel gauge.
Safety action
Following the investigation, the Swedish gliding association announced plans to revise its gliding handbook. The updated manual will implement a requirement for pilots to use an additional, independent method to verify fuel quantity in addition to relying on the aircraft's electronic gauges.