What happened
On May 5, 2020, at approximately 19:45 UTC, a Beechcraft B200, registration PT-WOF, was performing a passenger transport flight from Sobral to Fortaleza, Brazil. The aircraft was carrying one pilot and five passengers. During the landing roll on runway 13 at Pinto Martins Airport (SBFZ), the right main landing gear retracted unexpectedly. The pilot applied reverse thrust, which triggered the collapse, causing the aircraft to veer toward the right edge of the runway. The aircraft sustained minor damage to the right propeller assembly, the underside of the right wing, fairings, doors, and the right main gear wheels and tires. All six occupants were unharmed.
The investigation
CENIPA investigators examined the aircraft's landing gear system, which utilizes a mechanical retraction and extension mechanism powered by a 28-volt electric motor. During the final approach, the pilot noted that the right main gear indication failed to confirm it was locked down. Despite attempting manual extension procedures and receiving visual confirmation from the control tower that the gear appeared to be down, the gear failed to remain locked upon touchdown.
Laboratory analysis of the damaged components, specifically the downlock hook and actuator nut, revealed fracture surfaces consistent with overload. Metallographic examinations ruled out fatigue or corrosion as causes. Investigators also reviewed maintenance records, noting that a 1,000-cycle/30-month inspection had been performed on March 1, 2020. However, the documentation for this inspection lacked clear details regarding the specific maintenance methods used or the final results, and the associated service order was unavailable, hindering full traceability of the work performed on the landing gear actuators.