On June 10, 2019, about 1846 eastern daylight time, a Rockwell 690A airplane, N197GB, was substantially damaged when it was involved in an accident near Jacksonville, Florida. The pilot and two crew members were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 firefighting flight. One of the pilots reported that, while returning to the airport after a reconnaissance flight, he extended the landing gear, but the nose landing gear (NLG) position light did not illuminate. The crew cycled the gear, then completed the checklist for a gear malfunction; but were unable to resolve the discrepancy. The pilot advised the tower controller of their situation and requested a low approach to verify the position of the NLG. The tower controller told the crew that the landing gear appeared to be down. They requested a second flyby to allow a company representative to look; he also reported that the landing gear appeared down, but suggested diverting to another airport where crash rescue was available. The flight crew agreed and diverted. During the subsequent landing, the NLG collapsed. Examination of the NLG assembly found that the roll pin installed in the spacer assembly was fractured. The fractured roll pin remained installed in the right and left sides of the spacer, which connects the nose wheel steering cylinder and the NLG strut. Metallurgical examination of the fractured roll pin revealed evidence of bending and shear stresses, which had resulted in an overstress fracture. With the assistance of maintenance personnel, the NLG was cycled using the gear extension handle in the cockpit. As the NLG was lowered, the nose wheel cylinder and actuator arm interfered with the nose wheel well main frame and jammed; the nose wheel would not extend past its gear doors. The forward nose landing gear doors were reinstalled and the NLG was cycled again. The nose wheel actuator rod jammed on the left forward gear door actuating rods, matching impact marks observed on the actuating rods.