On December 9, 2002, about 1515 Pacific standard time, a Cessna T-210L, N732HJ, experienced a right main landing gear collapse and veered off the runway during the landing roll at Agua Caliente Airport, Agua Caliente Springs, California.The US Customs Service was operating the airplane under the provisions of 14 CFR Part 91. The airline transport pilot (IP) and a pilot undergoing pilot-in-command training (PUT) were not injured; the airplane sustained substantial damage. The local public use training flight departed North Island Naval Air Station (Halsey Field), San Diego, California, about 1445. Visual meteorological conditions prevailed, and a flight plan had not been filed. In a written statement, the IP reported that while en route to the Borrego area for training, he configured the airplane for a simulated an engine failure. In response, the PUT began simulating emergency procedures while maneuvering the airplane toward Agua Caliente, the nearest airport. The PUT made a low pass over the airport and completed the landing checklist, which included lowering the landing gear. The IP visually verified the landing gear were down, by looking outside the cockpit where he could see the right main landing gear out the window and the nose wheel in a mirror attached to the right wing. He also noted that the landing gear light was illuminated green, in indication the gear were in the down position. While on the landing approach, the IP noted that the airplane appeared to be high and instructed the PUT to execute a go-around procedure. They both opted to leave the landing gear down, as to help remedy the airplane's still-too-high altitude. The PUT configured the airplane for a short field landing, and again, completed the landing checklist. The IP again confirmed that the landing gear were in the down position. The airplane was still too high on the approach and the PUT was again instructed to execute a go-around procedure; the landing gear was not retracted. As the PUT completed the downwind leg of the approach, the IP verified that the landing gear were in the down position. Upon the third attempt, the PUT maneuvered the airplane on a normal glide path, but the airspeed was slightly fast. The pilot landed long, with the airplane touching down about 1,000 feet down the runway. The IP stated that the landing attitude was good, and the airplane had a 200-300 feet per minute rate of descent. As the weight of the airplane shifted onto the main landing gear the IP felt the right side of the airplane settle, and sink down toward the runway. The IP looked out the window and observed the right main landing gear in the retracted position. In an effort to maintain a level attitude, the PUT input full left aileron deflection while the left wing moved upward. As the ground speed began to dissipate, the pilots could not maintain control of the airplane and it veered off the runway surface. The airplane slid down a ditch and into a rocky embankment, coming to rest upright. The airplane incurred damage to the horizontal stabilizer, wing tips, and empennage. In a written statement the PUT reported that after the airplane had come to rest in a rocky embankment; he noted that the landing gear indication lights were all still illuminated green. After egressing the airplane, he observed that both the left main landing gear and the nose gear were extended, with the right main landing gear almost fully retracted. A Federal Aviation Administration (FAA) inspector examined the airplane and noted that the right main landing gear actuator housing was cracked. The inspector sent the actuator to Cessna Aircraft Company for examination by their Material and Process division. They conducted the examination under the auspice of an FAA representative. The examination revealed that the actuator, part number 9882000-2 (serial number 21061523), had bulged and cracked along the axis of the hydraulic cylinder, spanning about 3 inches. After conducting numerous tests, the Cessna engineer stated that the fracture surfaces of the crack were indicative of overload facture; he found no evidence of fatigue cracking. He opined that the appearance of the cracking and deformation indicates the likelihood that the actuator had undergone sudden overloading during or as a result of the accident. The complete report is appended to the public docket.