On March 15, 2000, at 2211 central standard time, National Express Flight 510, a Cessna 402C twin engine airplane, N11NX, sustained substantial damage when the left main landing gear collapsed and the airplane exited runway 03 at the San Antonio International Airport, San Antonio, Texas, during the landing roll. The airplane was owned and operated by Texas Air Charters, Inc., dba National Express, of Denton, Texas, under 14 Code of Federal Regulations (CFR) Part 135. The commercial pilot, sole occupant, was not injured. Night visual meteorological conditions prevailed for the non-scheduled cross-country cargo flight that departed the Harlingen Valley International Airport, Harlingen, Texas, at 2042 on an IFR flight plan. The pilot reported that during the final approach, he verified the landing gear was down by the illumination of the three green indicator lights in the cockpit. With the aircraft on short final, another aircraft on the runway was cleared for takeoff. Once that aircraft was airborne, the pilot decided to continue the landing. He reduced the power to 20 inches of manifold pressure and extended the flaps to 25 degrees. At an indicated airspeed of 125 knots and a descent rate of 600 fpm, the pilot reduced the power for the landing flare. He further stated that the "flare was normal and when the nose [landing] gear touched down I see my airspeed is still high and feel that to stop I will have to apply heavy brakes." The pilot performed a go-around. The flaps were retracted to the zero position, full power was applied, and an airspeed of 109 knots attained. The landing gear was not retracted during the go-around. The airplane entered a right traffic pattern for runway 03, and the pilot completed the landing checklist and verified that all the landing gear indicator lights were illuminated. The pilot was cleared to land the airplane, and when the airplane was over the runway numbers, he reduced the power to idle and performed the landing flare/touchdown. After the touchdown, the pilot felt the aircraft pulling to the left side of the runway. The pilot applied right rudder and left aileron to maintain directional control of the aircraft. He further stated that "I feel that I am dragging something on the left side and the aircraft is leaning (banking) to the left." The pilot was unable to make the taxiway for which he was aiming, and the airplane exited the runway onto the grass adjacent to the runway. In a written statement, the pilot reported that a fire ignited as a result of fuel leaking from the left wing coming in contact with a hot wire from the runway edge lights that were damaged when the aircraft exited the runway. The pilot further stated that "the left main landing gear tire with the brake disc and brake pads was found intact (with no damage) 100 (one hundred) feet before the airplane came to rest. The base (top) of the left main landing gear trunnion collapsed and the trunnion was dragged during the deceleration of the aircraft." The airplane was moved from the runway environment to the ramp at Raytheon Aircraft Services. An FAA inspector examined the aircraft and the runway the following morning. The inspector found fire damage to the underside of the left wing, the left wing locker, and the left wing leading edge de-icing boot. The left wing fuel cell was ruptured and structural damage was found in the wheel well and inboard area of the left wing. The leading edge of the left wing had a concave depression consistent with the width of the runway edge lights. Scrape marks consistent with the diameter of the left main landing gear trunnion were found on the runway. The trunnion for the left main landing gear was found separated in half. A review of the company pilot records by the NTSB investigator-in-charge (IIC) revealed that the commercial pilot held a first class medical certificate. The pilot completed the company training requirements in March, 2000, and satisfactorily completed the CFR Part 135 airman competency/proficiency flight check on March 8, 2000, in a Cessna 401 airplane. The flight check was administered by the company check airman. On the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) the company reported that the pilot had accumulated a total flight time of 1,275 hours of which 600 were in the accident make and model of aircraft. The company multiengine training manual Section 3, Description of Maneuvers (missed approach procedures) states in part: The landing gear will be retracted when a positive rate of climb is established. Section 3, Description of Maneuvers (Rejected Landing) states in part: After positive rate of climb is established, the gear will be retracted. Company trip records and load manifest revealed that the pilot was accompanied by the company check airman on March 13th and 14th, 2000, during the line check flights between Harlingen, Texas, and San Antonio, Texas, in N11NX. On the day of the accident, the pilot, sole occupant, flew N11NX from San Antonio, Texas, to Harlingen, Texas. The accident occurred on the return flight to San Antonio, Texas. The maintenance records were reviewed by the NTSB IIC. The aircraft registration for Cessna 402C, serial number 402C-0480, was changed from N341FX to N11NX on June 18, 1999. The last annual inspection was performed on February 19, 2000, at an accumulated airframe time of 15,522.7 hours. Aircraft and engine logbooks did not reveal evidence of any anomalies or uncorrected maintenance defects. On April 4, 2000, a mechanic visually examined the airplane and found the following: fuselage twisted, left wing and empennage bent and twisted, and a puncture in the left fuel cell. The mechanic found the left aileron damaged. The left flap and aileron skins were torn. Fire damage was noted on the left wing, aileron, and flap. On July 21, 2000, under the supervision of FAA personnel, the left main landing gear trunnion, part number 5141102-1, was examined by the Cessna Aircraft Company metallurgists. The trunnion fractured in half, along the central axis of the part in a direction consistent with the line of travel of the aircraft. The force exerted by the upper barrel where it is in contact with the trunnion forced the trunnion apart. Electron microscopy revealed that the fracture surfaces consisted of areas of ductile fracture with some areas of shear fracture, and scraping damage which occurred after the trunnion broke. No microscopic anomalies were found in the trunnion material (2014 T6 aluminum). The metallurgists concluded that "the fracture occurred as a result of an overload situation."