On November 11, 2006, about 1419 eastern standard time, a Winter J.T/Johnson Kitfox III experimental amateur-built airplane, N727PD, registered to and operated by a private individual, as a Title 14 CFR Part 91 instructional flight, had the flight crew experience aircraft vibrations in-flight, and the crew made a forced landing in Southwest Ranches, Florida. Visual meteorological conditions prevailed, and no flight plan was filed. The commercial-rated flight instructor received no injuries, and the student pilot received minor injuries. The airplane incurred substantial damage. The flight originated in Southwest Ranches, the same day, about 1330. The flight instructor stated that while in cruise flight the engine suddenly began to operate "badly", and the whole airplane vibrated intensely. He said that they flew away from the populated residential areas and made a forced landing in the area of a landfill. During the landing rollout the airplane nosed over, incurring damage. According to the FAA inspector who responded to the scene of the accident, upon inspecting the airplane he found one propeller blade missing, with part of the blade root remaining in the hub.. Furthermore, he found that one blade mounting bolt was loose and the bolt associated with the missing blade had fractured. The inspector noted no other anomalies with the accident airplane. The NTSB sent the propeller, and its associated mounting hardware, minus the missing blade, to the propeller manufacturer, IVOProp Corporation, Long Beach, California, for further examination, under the supervision of an FAA inspector. The examination revealed that the propeller had been improperly assembled, and was missing the required Motion Detector Tape, which resulted in the blade bolt holes elongating, and one blade separating from the hub in flight.