A replica Wright B Flyer built in Dayton, Ohio, crashed for unknown reasons on July 30, 2011, killing both volunteer pilots, and the NTSB's October 30 Factual Report doesn't determine a cause but does note deficiencies with a weld. According to the NTSB, the aircraft's left propeller shaft tube exhibited a separation at its aft weld. Contact points in that area exhibited evidence of rotational rubbing. The aircraft was equipped with a modern engine and avionics, and video recovered from onboard recorders showed circumstantial evidence that could lead some to an early conclusion not yet officially supported by the NTSB.
According to the NTSB (PDF), the video ends before the flight's final moments. It does show that near the end of the flight "the airplane yawed." The footage showed both pilots manipulating the controls after the yaw and the NTSB concluded the airplane "was controllable" after the yaw event. Witness statements said the airplane's engine sounded "like its rpm varied," according to the NTSB. Other witnesses identified the aircraft flying slow and banking to the left and right. "One witness reported that the airplane spiraled downward," the NTSB reported. The NTSB has determined that multiple welds from the left propeller shaft tube exhibited visible defects like pores and voids as well as incomplete penetration. Weather during the flight was mild with few clouds at 1,000 feet and five miles visibility with mist.