What happened
On September 6, 2015, a Grob G 103C SL motorglider, registration LN-GAN, was conducting a training flight near Haugesund lufthavn, Karmøy. The flight, operated by Haugaland seilflyklubb, involved an instructor in the rear seat and a student in the front seat. After completing a period of soaring near Vikefjellet, the crew attempted to return to the airport.
During the return leg, the crew encountered difficulties deploying the engine. Despite multiple attempts by the student and the instructor, including switching to a reserve battery, the engine failed to deploy properly and subsequently failed to start. Due to the engine issues, the instructor decided to perform an off-field landing at a pre-designated field near Norheim, located approximately 6 km east-northeast of the airport. The instructor took control of the aircraft to execute the landing.
During the landing roll, the left wing dipped and made contact with the ground at an estimated speed of 40 km/h. This contact caused the aircraft to undergo a ground loop, pivoting approximately 45 degrees before coming to a halt. While both occupants were unharmed, the aircraft sustained a broken tail boom.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the circumstances surrounding the engine deployment failure and the subsequent landing. Investigators looked into the mechanical state of the engine, the deployment mechanism, and the electrical system. No mechanical faults were discovered in the engine or its deployment hardware. Additionally, no technical defects were found in the battery, though the flight club opted to replace it as a precaution.
Findings
- The difficulty in deploying and starting the engine was likely caused by insufficient battery capacity during the flight.
- The decision to land at the off-field site was made with enough altitude to perform a standard landing pattern.
- The ground loop was triggered by the left wing catching the ground or vegetation, a common risk during landings on uneven terrain.