What happened
During a visual approach following jet traffic, the pilot performed the landing checklist, lowering the flaps and landing gear. The pilot confirmed that all three green lights were illuminated. The flare and touchdown were reported as normal; however, upon applying brake pressure after the nose gear touched the runway, the main landing gear collapsed. This caused the aircraft to lose centerline control and skid on its belly for approximately 270 feet.
The investigation
Post-accident inspection of the aircraft revealed that both the left and right main landing gear had folded backward, leaving the wheels canted sideways against the runway. The nose gear remained in the down position. The landing gear handle was found in the down and locked position. Upon turning on the master switch, the nose gear down lock light was illuminated, but the left and right main gear lock lights were not active.
To facilitate inspection, the aircraft was raised using a forklift and jacks. Once the main landing gear were clear of the runway surface, both gears locked into the down position. When the aircraft was lowered back onto its gear, the two main landing gear lights illuminated as expected. The propellers did not strike the runway during the event, allowing the engines to be started for taxiing back to the operator's hangar.
Findings
An inspection of the main landing gear found no evidence that the main landing gear lock down mechanism had failed on either the left or right side. The crew sustained no injuries during the incident.