NTSB: Spectrum 33 Was Misrigged
In its preliminary report, the NTSB says the controls of the Spectrum 33 (very) light-jet prototype that crashed on July 25 in Spanish Fork, Utah, just short of its 50th flight, were misrigged. "Specifically, the linkage was connected such that left roll input from the side sticks would have deflected the ailerons to produce right roll of the airplane," the report says. The jet entered a right roll almost immediately after takeoff. The roll continued to about 90 degrees right wing-down when the right wingtip impacted the ground. The two crewmen on board were killed. Roll control on the airplane was from the pilots' side sticks to the ailerons through a mechanical system of torque tubes and push-pull tubes, the NTSB said. The left side stick was primary, and the right side stick was slaved to the left side stick. The roll control motion of the left side stick was linked through a quadrant below the cockpit floor to the lower torque tube. The lower torque tube ran from the quadrant to the aft pressure bulkhead. The translation linkage -- the linkages and bell cranks that translated the rotational motion of the lower torque tube to a linear motion of the aileron push-pull tubes -- was located on the aft side of the pressure bulkhead in the main landing gear (MLG) gearbox area.
According to information provided by the operator to the NTSB, the airplane had accumulated about 44 hours total flight time since its first flight on Jan. 7. Prior to the accident flight, the airplane's most recent flight, flight number 46, had taken place on June 30. During the time between flight 46 and the accident flight, the airplane had been undergoing maintenance. The maintenance included removal of the MLG in order to stiffen the MLG struts. Upon reinstallation of the MLG, it was found that inadequate clearance now existed between the left MLG strut and the aileron upper torque tube V-bracket. The V-bracket was removed and redesigned to allow proper clearance of the MLG. Removal of the V-bracket required disconnection and removal of a portion of the translation linkage. The NTSB investigation is continuing and a final report will be released sometime in the future.