On November 18, 2003, at 0721 mountain standard time, a Swearingen SA226TC, N332BA, owned and operated by Key Lime Air Corp., Wilsonville, Oregon, was substantially damaged when it impacted terrain during landing roll at Walker Field (GJT), Grand Junction, Colorado. The pilot, the sole occupant on board, was not injured. Visual meteorological conditions prevailed. No flight plan had been filed for this non-scheduled cargo flight being conducted under the provisions of Title 14 CFR Part 135. The flight originated at Rifle, Colorado, at approximately 0709. According to the pilot, he was cleared to enter left base for a landing on runway 11. The pilot stated that, as he reduced the airspeed to 160 knots, he lowered the landing gear. He stated that he "heard the gear come down," and he verified "three green in the [landing] gear indicator." He stated that he reduced engine power to flight idle as he entered the "base-leg." During the final approach, he had to add engine power, and then just over the runway threshold, he reduced engine power back to flight idle. He landed the airplane on its "main [landing gear] wheels first" and slowly let the nose of the airplane drop. Although both main landing gear assemblies remained down and locked, the nose landing gear collapsed, allowing the nose of the airplane and both propellers to strike the runway. The airplane slid approximately 3,000 feet, coming to a stop on the right edge of the runway. When the propellers struck the runway, several fractured propeller pieces impacted the left and right sides of the fuselage resulting in substantial damage to two fuselage bulkheads. The fuselage bulkhead, forward of the nose landing gear well, was also substantially damaged due to contact with the runway. The pilot said that, during the approach, from base to final, he did not hear a landing gear warning horn. The pilot stated that the flight was uneventful except for a problem on the previous leg of the flight from Denver International Airport (DEN), Denver, Colorado, to Garfield County Regional Airport (RIL), Rifle, Colorado. During the previous leg, the airplane's "out of trim" warning buzzer came on as he climbed through 16,000 feet msl. He said that it stayed on during the entire flight while at flight level 180 (18,000 feet msl). As he descended through 14,000 feet msl, the warning buzzer turned off. According to an air traffic control specialist, who was working in the Walker Field/Grand Junction Airport Control Tower, he told N332BA to enter a left base for runway 11 and that he was cleared to land. He stated that he observed N332BA roll out on a 2-mile final "with the gear down." As the airplane was rolling down the runway the "nose wheel collapsed." According to another pilot, who had flown N332BA on November 11, 2003, he had problems extending the landing gear while on approach to DEN. On the fourth try, the landing gear extended and locked, and he was able to land. According to the pilot, maintenance personnel examined the airplane that evening. The landing gear was cycled several times. No deficiencies were noted. On December 12, 2003, two FAA maintenance inspectors examined N332BA. Several extension and retraction test were completed while the airplane was in a hanger, on aircraft maintenance jacks, and connected to ground hydraulic power. The landing gear extended and retracted properly. Furthermore, an uneventful free-fall test was completed as well. The FAA inspector stated that, although the landing gear preformed as normal on the first series of tests, he was able to duplicate the nose gear extension failure by manipulating the landing gear's "bypass-valve." Upon examination of the nose landing gear's up-lock mechanism, he noted that it was not properly lubricated in accordance with the Fairchild SA226 Maintenance Manual. Further examination of the nose landing gear assembly revealed that a "critical clearance," between the nose landing gear's bell crank roller and positioning cam, measured in accordance with the Fairchild SA226 Maintenance Manual, was found to be out of tolerance. After properly servicing the up-lock mechanism, the gear problem could no longer be duplicated. The FAA inspector also stated that, during the operation of the landing gear, the engine throttles were advanced to keep the landing gear warning horn from constantly sounding. At one point, when the throttles were retarded, the landing gear warning horn did activate, but it was "barely audible." It was noted that, when moving the throttles fore and aft, the buzz, of the landing gear warning horn, was intermittently below reasonable hearing volume. According to the Fairchild SA226 Maintenance Manual, the landing gear should be lubed every 200 hours. The FAA inspector stated that the approved maintenance inspection sheet for Key Lime Air, did not show the requirement for the main landing gear or nose landing gear to be lubed every 200 hours.