On July 22, 2019, about 1147 mountain daylight time, a Cessna 402B airplane, N7947Q, sustained substantial damage when it was involved in an accident near Boise, Idaho. The two pilots and the FAA observer were uninjured. The airplane was operated under Title 14 Code of Federal Regulations (CFR) Part 91, in accordance with a Part 135.297 instrument proficiency check and a Part 135.399 check airman observation flight. The first pilot, who was the operator's director of operations, reported that he was receiving an instrument proficiency check from the second pilot, the operator's chief pilot; with an FAA aviation safety inspector in the passenger cabin observing the check ride for the purposes of a check airman observation flight. The first pilot stated that, after completing a series of required flight maneuvers, they returned to the departure airport, and the airplane was subsequently cleared to land. During the landing approach, he selected the landing gear selector switch to the down position, which was followed by "three greens," indicating that the landing gear was down, locked, and safe for landing. He noted that all three occupants verified and verbally confirmed that the landing gear was "down and locked." The first pilot stated that, after an uneventful landing, the airplane continued down the runway as the airplane decelerated. When the pilot started a left turn to exit the runway, the right main landing gear collapsed, and the right wing impacted the ground, sustaining substantial damage. A postaccident examination of the landing gear system revealed that the right main landing gear assembly bell crank pivot bolt (p/n NAS464P4-26) had sheared and displayed features consistent with a ductile overstress fracture failure. Figure 1, from the applicable parts catalogue, depicts the main landing gear retraction linkage. The affected bolt from the accident airplane is labeled as #29. Figure 1. Cessna 402 Main Landing Gear Retraction Linkage Installation