What happened
On October 2, 2015, an instructor and a student were conducting an aerobatic training flight departing from Reinsvoll Airport in a American Champion Aircraft Corp. 8KCAB, registration LN-LCU. During the return to the airfield, the crew encountered significantly changed wind conditions, with gusts reaching 10–15 knots.
While attempting to land on runway 16, the student pilot experienced a hard landing following a heavy gust that displaced the aircraft's longitudinal axis. The impact caused the right landing gear leg to fracture. After realizing the gear had failed, the crew initiated a go-around and climbed to a safe altitude. Due to the lack of emergency services at Reinsvoll and concerns regarding fuel endurance, the crew decided to divert to Oslo Airport, Gardermoen.
Upon arrival at Gardermoen, the instructor performed a controlled emergency landing on runway 19R. To mitigate the risk of the aircraft veering due to the broken gear, the pilot landed off-center and manually kept the right wing elevated for as long as possible. The aircraft eventually came to a stop after rotating approximately 120 degrees from its original heading. No injuries were reported.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the fractured steel landing gear leg, sending it to the Norwegian Defence Research Establishment for microscopic analysis. The investigation also reviewed the aircraft's maintenance history, noting that a 100-hour/annual inspection had been performed the previous November, which included a visual check for nicks, scratches, and corrosion.
Findings
- The primary cause of the landing gear failure was fatigue cracks originating from the surface of the steel component.
- These fatigue cracks created a latent structural weakness that was not detectable through standard visual inspections, as the component was painted.
- While strong winds and turbulence were present at the time of the accident, the investigation concluded that the crew and the aircraft were capable of handling the weather conditions had the gear remained intact.
- The crew's professional management of the emergency prevented the incident from escalating into a more serious accident.