What happened
On October 3, 2016, a Reims F406 Caravan II, registration OH-OTL, operated by Lapin Tilauslento Oy, was performing a routine cargo flight from Rovaniemi to Oulu. During the flight, the crew noticed that the 'GEAR UNLOCKED' warning light and the hydraulic pressure indicator remained illuminated after the landing gear was retracted. Following available emergency procedures, the crew decided to continue the flight with the gear extended, as the weather conditions were favorable and no immediate landing was required.
Upon landing at Oulu airport in darkness, the pilot began braking at approximately 60 knots. At this moment, the right main landing gear failed, causing the aircraft to tilt sharply to the right. The pilot managed to maintain the aircraft on the runway by applying heavy braking on the left side and utilizing differential engine braking. The aircraft came to a stop approximately 8 and 80 meters from the start of the runway, remaining within the runway boundaries. There were no fatalities and the crew escaped without injury.
The investigation
The investigation focused on the mechanical failure of the landing gear. Investigators examined the aircraft at Oulu and reviewed maintenance records from the operator's facility in Rovaniemi. The inspection revealed that the right main landing gear had failed because the front attachment pivot pin had slipped out of position. The investigation also scrutinized the maintenance procedures and the adequacy of the instructions provided for the landing gear assembly.
Findings
Technical analysis determined that the primary cause of the accident was an installation error made during a recent scheduled maintenance task. While installing the landing gear, the mechanic had failed to ensure the pivot pin was correctly seated. Because the mechanic was supporting the gear by hand to align the components, the pin inadvertently slipped forward. The safety pin and retaining wire were installed, but they were placed behind the pin rather than through the actual hole, failing to secure the component in its proper position.
Contributing factors included inadequate maintenance manuals, which lacked a complete sequence of necessary steps and failed to warn of the possibility of improper pin installation. Additionally, the quality assurance and final inspection processes were insufficient to detect this specific error.