As the airplane approached its destination, the cabin-entry door inadvertently opened, departed the airframe, and struck the pusher-type propeller. The airplane experienced a significant loss of engine power and the pilot performed a forced landing into a nearby wheat field. The left wing was substantially damaged when the left main landing gear collapsed during landing. The amateur-built airplane was equipped with a single, gull-wing type, cabin door. The door, located on the left side of the cabin, articulated around a hinge on the top of the fuselage. The door latch-pins were designed to engage the fuselage using three capturing latch assemblies installed in the fuselage sidewall. These capturing latches functioned collectively using a single door latch handle. A post-accident inspection and testing of the fuselage-mounted latch assemblies and their common latch handle failed to reveal any anomalies or damage. All three corresponding latch-pins remained attached to the recovered door frame and appeared undamaged.