A Reims F406 Caravan II aircraft (OH-OTL), departed for a routine cargo flight from Rovaniemi Airport to Oulu. The aircraft had a two-pilot crew and carried 347 kg of mail. There were no other persons on board besides the crew. Flight preparation, aircraft loading and taxiing from the stand to take-off position were uneventful. Taxiing distance was about 800 m. The aircraft took off on runway 03 at 19:30 LT. The weather was good and it was starting to become dark at that time in the evening. When the landing gear was retracted, the GEAR UNLOCKED warning light and the HYD PRESS ON indicator for the hydraulic system remained on. At the pilot-in-command’s request, the co-pilot selected gear back down, and the three green lights indicating that the gear was down and locked illuminated normally. The HYD PRESS ON indicator and GEAR UNLOCKED warning were also extinguished as usual. The pilot-in-command continued flying towards Oulu, and the co-pilot searched the emergency checklists for suitable procedures for the situation. Any procedures directly applicable to this malfunction were not found, but the pilots decided to follow the procedure for cases where the HYD PRESS ON light remained on continuously. The procedure assisted in isolating the fault to the landing gear system, but the exact nature of the malfunction was not clear. The pilots took the actions as instructed, except that the point “landing gear switch – rapidly recycle” was omitted, since the gear was already extended and the indicator lights showed that it was down and locked. The pilot-in-command decided to continue to Oulu with the gear down, as the procedure did not call for landing as soon as possible and the weather was good. Approach and landing at Oulu were performed in darkness at 20:05. The aircraft touched down at the beginning of the runway, and the landing run was normal at first. When the plane had decelerated to a speed of about 60 kt, the pilot-in-command started braking, at which time the right main landing gear collapsed and the aircraft tilted to the right. The pilot-in-command stated that he had managed to keep the plane on the runway using nose wheel steering, braking hard on the left side and applying reverse thrust in the left engine. The aircraft stopped quickly after the landing gear had collapsed, within a distance of about 80 m. The aircraft came to a stop on the right edge of runway 30, remaining well on the paved surface. The engines were running until the plane stopped and were then shut down. The pilot in-command asked the co-pilot to report the incident to the ATC and request a tow vehicle. After sending the report, electrical power was switched off. ATC alerted the rescue services, and the pilots exited the plane uninjured. Probable causes The accident was caused by an installation error in the right main landing gear. Checks made during installation were inadequate, and even the final inspection of the work did not cover the correct fitting or securing of the pivot pin. The pivot pin installation procedure is not complex, and the principle is easy to understand. Working conditions were good and the mechanic who fitted the pin was fairly experienced, so a clear and explicit cause for the error could not be determined. Even though this phase of installation was important structurally and for flight safety, one significant possibility may be that the mechanic’s concentration was not focused on the seemingly simple task. A contributing factor to the error was that the maintenance instructions did not adequately support the correct performance and quality assurance of the work.