A Beechcraft 300 Super King Air 350 sustained severe damage in a landing gear collapse accident at Singapore-Seletar Airport. The aircraft, RP-C1587 took off from Seletar runway 21 at 16:11 hours for an acceptance test flight after undergoing a 5-year inspection/maintenance programme performed by a maintenance company at Seletar Airport. After takeoff, the tower controller noticed that the aircraft’s left main landing gear was not retracted. The controller informed the pilot immediately. The pilot checked and confirmed that the left main landing gear was not retracted and locked. The pilot also noticed that the landing gear circuit breaker had tripped and the red light on the landing gear control handle was illuminated. The pilot reset the circuit breaker and cycled the landing gears down. However, the left main landing gear remained unlocked and the circuit breaker tripped again. The pilot attempted to retract the landing gears again. The left main landing gear remained un-retracted and unlocked, and the circuit breaker tripped again. The pilot decided to carry out an emergency gear extension and return to Seletar Airport. Upon landing on runway 21 at 16:25 hours, the left main landing gear of the aircraft collapsed and the aircraft skidded onto the grass verge on the left of the runway. There was no fire. Contributory Factors: “The left main landing gear collapsed because the landing gear was not locked. The landing gear was not able to be locked because the actuator clevis had fractured under bending load. The bending load was induced because of insufficient spacing washers at the clevis head. There is also evidence that the clevis was embrittled during manufacture.”