On August 2, 1996, about 1100 Alaska daylight time, a deHavilland DHC-4 airplane, N800NC, registered to and operated by Greatland Air Cargo, sustained substantial damage while landing at the New Stuyahok airstrip, New Stuyahok, Alaska. The commercial certificated captain and first officer were not injured. The 14 CFR Part 135 cargo flight operated in visual meteorological conditions. During a telephone interview with the NTSB investigator-in-charge on August 5, the captain related that during the landing roll at New Stuyahok, the nose gear suddenly collapsed. The captain said the landing was normal and uneventful until the nosegear collapsed. He also said that the green, gear down and locked light, was appropriately illuminated, and that he was uncertain why the nosegear collapsed. The airplane was returned to its maintenance base and repaired. According to the pilot, the nose gear hydraulic drag strut actuator malfunctioned, and failed to remain in the down locked position. He said the part was changed, and the nosegear operated properly. He also indicated that the drag strut actuator service life is "on condition." The failed part, part number 5460-3, had approximately 1400 service hours at the time of failure. The pilot, who is also a certificated aviation mechanic, believes that additional inspections of the drag strut and associated hoses are warranted.