On June 4, 2022, about 1148 Pacific daylight time, a Cessna P210N, airplane, N4752K, was substantially damaged when it was involved in an accident near Palm Springs, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that during the approach he extended the landing gear and had a down-and-locked green light indication. He also stated that he visually verified that the landing gear was extended. The touchdown was normal, but firm, and shortly thereafter, the main landing gear collapsed. The airplane veered off the runway about midfield and came to rest in the area between the taxiway and runway. A postaccident examination of the airplane’s landing gear system revealed no anomalies. The airplane was placed on jacks for a gear swing and the landing gear was cycled to the retracted and extended position several times. The landing gear cycled appropriately during each cycle. During the extension, when all the landing gear locked into place, the warning horn audio terminated, and the landing gear down-and-locked light illuminated. During the retraction, the landing gear up-and-locked light illuminated appropriately. The landing gear and landing gear pump circuit breakers remained closed during the examination. The hydraulic system fluid indicated full, and the fluid was new. Additionally, during the gear extension the nose gear was observed to lock into place first, and the main landing gear would extend, pivot, and then lock into place. The process to get the main landing gear fully extended and locked took several seconds. During the extension, it was noted that the main landing gear tires would be pivoted outward during the extension and then move into place to lock. Until the main landing gear was extended and locked into place, any contact with the surface would contact the outer edge of the tire. Therefore, the main tires were examined, and contact markings were observed on the outer edge of both main tires. According to witnesses, who were working on the airport ramp, the the nose gear appeared down and locked but the main landing gear was only partially extended for the approach and landing, consistent with the main landing gear in transit for extension and not down and locked. The airplane’s flight manual states that “normal landing gear extension time is approximately 6 seconds.” The manual also describes the landing gear position indicator lights. “Two position indicator lights, mounted adjacent to the landing gear lever, indicate that the gear is either up or down and locked…The gear-down indicator light (green).” The other indicator light is amber and is the gear-up indication light. Further, “The airplane is equipped with a landing gear warning system designed to prevent the pilot from inadvertently making a wheels-up landing.” “When the throttle is retarded below approximately 15 inches of manifold pressure (master switch on), the throttle linkage will actuate a switch which is electrically connected to the gear warning portion of a dual warning unit. If the landing gear is retracted (or not down and locked), an intermittent tone will be heard on the airplane speaker.”