On December 10, 2001, at 1822 central standard time, a Cessna T210K single-engine airplane, N8299M, was substantially damaged after the right main landing gear collapsed during the landing roll at the San Antonio International Airport (SAT), San Antonio, Texas. The commercial pilot and his passenger were not injured. The airplane was registered to Tejas Aviation Management, Fort Worth, Texas, and operated by the Drug Enforcement Administration, Conroe, Texas. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 flight. The flight departed SAT at 1450, and was terminating at the time of the accident. On the NTSB Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the pilot reported that after completing the assigned mission, he received radar vectors from San Antonio Approach Control to enter a right base for runway 12R. Once established on an extended final approach, the pilot attempted to lower the landing gear, and the landing gear extended. However, the down and locked (green) annunciator light, confirming the landing gear has extended and locked into position, had not illuminated. While performing a low approach over the runway, the pilot requested a visual check from the air traffic control tower. The tower controllers could not confirm the landing gear was extended and locked. The pilot then requested to remain in the traffic pattern to troubleshoot the problem. After cycling the landing gear several times, the pilot still did not receive a down and locked indication. The tower requested the pilot cross over the airport to enter a left downwind for runway 12L, and execute a low pass over the rescue vehicles for another visual check. The pilot cycled the landing gear again at a higher engine RPM setting, and the landing gear "was observed to fully and forcefully extend." Rescue personnel reported that all three gear appeared to be extended. The pilot then executed a landing to runway 12L, which was 5,519 feet in length, 100 feet in width, and had an asphalt surface. During the landing rollout, approximately 200 to 300 feet after touchdown, the airplane began to rapidly veer to the right. The pilot attempted to keep the airplane on the runway, however, after applying the left brake, the aircraft veered to the left, spun 180 degrees, and came to rest 20 feet off the left edge of the runway. According to an FAA inspector, who responded to the accident site, the right horizontal stabilizer spar and elevator were buckled. In a telephone interview, conducted by an FAA inspector, an aircraft mechanic, who was on scene during the airplane recovery, reported that when he first saw the airplane, the right main landing gear was in the up and locked position. The aircraft was lifted by a crane, and the mechanic unlocked the right main gear, via the left wheel well, by releasing the uplock. After unlocking the right landing gear, it dropped and dangled. The mechanic aburptly pushed the landing gear strut forward; however, it never locked into position. The landing gear was held into the full forward position, the aircraft was lowered, and the gear remained in the extended position under the weight of the airplane. The mechanic stated that he manually pulled the right downlock overcenter mechanism to the full lock position with resistance on the downlock. The aircraft was recovered and inspected by the operator. During the inspection, the landing gear system (with the nose gear isolated due to damage) was cycled approximately 5 to 8 cycles, and the system functioned properly through all cycles. The operator sent the engine-driven hydraulic pump to the manufacturer for test and examination. No anomalies were noted with the inspection and testing of the pump in accordance during manufacturer specifications. According to the operator, the aircraft underwent its last annual inspection on November 19, 2001, and had accumulated 8.9 hours since the inspection, at the time of the accident. During the annual inspection, the main landing gear actuators were replaced with new actuators, in accordance with Cessna Service Bulletin SEB 01-2.