SNOW ROCKET F1 — Borrego Springs, CA

What happened

The pilot was practicing aerobatics in preparation for a local aerobatic competition. A witness on the ground observed the pilot's practice sessions as well as monitored his radio communications. The pilot flew into the designated aerobatic box and performed an aerobatic sequence twice. The pilot then performed a spin maneuver and departed the aerobatic box. The witness recalled that the pilot was requested to repeat a maneuver and reentered the aerobatic box at an altitude between 2,700 and 3,000 feet above ground level (agl). The airplane entered a 30- to 35-degree nose-down descent angle to begin his sequence. Shortly thereafter, the pilot made a radio transmission in the blind saying "I have no back stick." The witness estimated that the airplane was descending through about 1,800 to 2,000 feet agl when the witness heard someone ask the pilot if the airplane was under control. The pilot responded that it was not. A few seconds later, the witness heard another transmission telling the pilot to use the airplane’s trim; the pilot responded that "there is no trim" as the airplane was observed descending through about 600 feet agl. No further radio transmissions were heard from the pilot and the airplane continued to steepen its descent angle just before ground impact.

A postaccident examination revealed that the elevator flight control system exhibited numerous areas of separations consistent with overload from the rear control stick to the elevator control surface. The front and rear control sticks were found separated from their control columns. The interconnected control column, portions of the separated front and rear control sticks, elevator control servo, and portions of control rod were found to be fractured due to overstress. Examination of the front control stick revealed that it was fractured in overstress due to cantilever bending just above the control column fitting; the fracture initiated at a 0.22-inch diameter hole drilled into the front wall of the stick tube. The upper portion of the front control stick was not located. The chemical composition and hardness of the front and rear control sticks were within specifications.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.