What happened
On April 8, 2010, an experimental amateur-built Snow Rocket F1, registration N28VS, crashed in the desert near Borrego Springs, California. The aircraft was being operated by the pilot for a practice session in preparation for the annual Borrego Hammerhead Roundup aerobatic competition.
At approximately 12:58 PDT, the pilot entered the designated aerobatic box at an altitude between 2,700 and 3,000 feet above ground level. To gain the energy required for maneuvers, the pilot entered a 30-to-35-degree descent. During this descent, the pilot transmitted via radio that he had "no back stick."
As the aircraft descended through 1,800 to 2,000 feet, ground observers attempted to communicate with the pilot to see if the aircraft was under control; the pilot responded that it was not. When advised to use the aircraft's trim, the pilot stated, "there is no trim." The aircraft was observed descending through 600 feet before the descent angle steepened further, and the airplane impacted terrain behind a sand dune. The pilot, the sole occupant, sustained 1 fatal injury.
The investigation
An examination of the wreckage by the FAA revealed the aircraft was resting inverted. The engine had separated from the fuselage, and the fuselage was crushed aft.
NTSB investigators examined the elevator flight control system and found multiple separations between the rear control stick and the elevator control surface, all showing signs of overload. The front and rear control sticks had separated from their control columns.
Metallurgical analysis of the control components showed that fractures in the interconnected control column, portions of the sticks, the elevator control servo, and the control rod were all caused by overstress. Specifically, the fracture in the front control stick initiated at the edge of a 0.22-inch diameter hole drilled into the tube wall. While the aluminum alloy composition of the sticks was within specification, the hardness and conductivity measurements were consistent with a T4 or lower strength T6 condition.