What happened
During the landing roll of an Aero Commander, both main landing gear units collapsed approximately 100 feet down the runway. The resulting impact caused the aircraft to skid, which ground off the belly skin and caused damage to several structural components of the airframe.
An observer on board, who was also a pilot, noted that three green landing gear lights were illuminated prior to the collapse. This observer and the pilot had both performed a visual check confirming that the landing gear was in the down position. During the landing and subsequent roll, the observer noted that the pilot maintained control with one hand on the throttle and the other on the control yoke.
The investigation
Post-accident inspections included a physical examination of the landing gear, which revealed no anomalies. When the aircraft was placed on jacks, the gear functioned normally. Additionally, the actuators were tested on a bench and found to be functioning properly. The investigation noted that the Aero Commander utilizes hydraulic pressure to maintain the locked position of the gear, with the landing gear handle operating in two positions: gear up and gear down.