What happened
On 3 June 2009, a de Havill and DHC-6-300, registration SE-GEE, was preparing for a non-commercial flight at Gryttjom airfield in Sweden. The aircraft was loaded with 21 passengers for a scheduled skydiving operation. During the low-speed taxi phase toward runway 36, the right main landing gear suddenly failed. The collapse caused the aircraft to tip to the right, leading the right wing to strike the ground. The pilot successfully managed the situation, initiating an emergency evacuation of all 21 passengers and the crew. No injuries were reported, though the aircraft sustained substantial damage.
The investigation
Investigators from the Swedish Accident Investigation Board (SHK) conducted a technical examination of the wreckage and the landing gear assembly. The investigation focused on the structural integrity of the right main landing gear leg, which consists of two welded steel pipes. The inquiry examined previous maintenance records, including the most recent "Check D" inspection, and reviewed the manufacturer's service bulletins regarding known fatigue risks in the landing gear components. The investigation also looked into the history of weld repairs performed on the gear leg.
Findings
Technical analysis revealed that the right main landing gear leg had been weakened by multiple fatigue cracks that had grown and merged into a single large fracture. These cracks originated at an external welded joint. While the aircraft's maintenance program required periodic non-destructive testing (NDT), investigators found that the aluminium coating had not been fully removed during the previous major inspection, which may have obscured the developing cracks. Furthermore, the investigation noted that the cracks likely initiated at a site of previous weld repairs, where metallurgical defects such as internal stress or localized hardening may have promoted crack formation.
Safety action
SHK identified that the existing maintenance system was inadequate for detecting such cracks, noting that the current inspection intervals based on calendar time and flying hours do not sufficiently account for the number of landing cycles. It is recommended that EASA, the Swedish Transport Agency, and the manufacturer review the maintenance requirements to better address the risk of fatigue crack formation in the landing gear.