The flight departed Newton City at 11:55 on a test flight which was to establish a performance baseline prior to a modification to the aircraft. The purpose of the modification was the development of a new supplemental type certificate (STC). The test flight profile was to execute a high-speed dive to verify and establish the vibration and buffeting characteristics of the unmodified aircraft prior to a delta-fin modification to the aft-fuselage. The test flight was determined to be a high risk. The flight crew reported that during the high-speed descent, at approximately 24,000 feet, the control yoke began to vibrate rapidly for approximately 3-5 seconds after which elevator control was lost. After declaring an emergency the crew diverted to Salina. Pitch control was established by using horizontal stabilizer pitch trim. The flight crew reported that during final approach to the runway the aircraft nose began to drop and that the flying pilot was unable to raise the nose using a combination of horizontal stabilizer trim and engine power. The aircraft landed short of the runway, striking an airport perimeter fence and a berm. PROBABLE CAUSE: “The PIC’s delayed remedial action during the elevator system oscillation, resulting in the failure of the aft elevator sector clevis due to reverse bending fatigue caused by vibration, and subsequent loss of elevator control. Factors contributing to the accident were high and gusting winds, the crosswind, the airport perimeter fence, and the berm.”