NYC00MA048 · Israel Aircraft Industries 1124A

After a 5-hour flight, the Westwind jet began its descent to the airport. Air traffic control instructed the flight crew to cross a VOR at 18,000 feet. The flight crew was then instructed to cross an intersection at 6,000 feet. The flight crew needed to descend the airplane 12,000 feet, in 36 nautical miles, to make the crossing restriction. The flight crew acknowledged the clearance, and no further transmissions were received from the airplane. The airplane struck treetops and impacted the ground in a wooded area. The accident flight was the airplane's first flight after maintenance. Work that was accomplished during the maintenance included disassembly and reassembly of the horizontal stabilizer trim actuator. Examination of the actuator at the accident site revealed that components of the actuator were separated and that they displayed no damage where they would have been attached. Examination of the actuator by the Safety Board revealed that the actuator had not been properly assembled in the airplane. A similar actuator was improperly assembled and installed in a static airplane for a ground test. When the actuator was run, the jackscrews of the actuator were observed backing out of the rod end caps within the first few actuations of the pitch trim toward the nose-down position. As the pitch trim continued to be actuated toward the nose-down position, the jackscrews became disconnected from the rod end caps, and the horizontal stabilizer became disconnected from the actuator.

Verbatim NTSB analysis and probable cause from the NTSB dataset