On April 8, 2010, a SNOW ROCKET F1 (registration N28VS) operated by SNOW VAN E was involved in an aviation accident near Borrego Springs, CA. One person was killed. Investigators recorded the probable cause as: The pilot's inability to maintain control due to the in-flight failure and separation of the pilot's flight control stick. The reason for the flight control stick failure could not be determined. This summary draws on records from NTSB.
An experimental amateur-built Snow Rocket F1, N28VS, crashed near Borrego Springs, California, on April 8, 2010, killing the pilot. The aircraft was maneuvering during an aerobatic practice session when the pilot reported control issues.
Accident Overview and Flight History On April 8, 2010, at approximately 1258 Pacific daylight time, an experimental amateur-built Snow Rocket F1, registration N28VS, was substantially damaged when it impacted terrain near Borrego Springs, California. The aircraft was registered to and operated by the pilot under Title 14 Code of Federal Regulations Part 91. The private pilot, who was the sole occupant, was killed in the accident. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight. The local flight originated from Borrego Valley Airport (L08) in Borrego Springs at approximately 1250. The pilot was scheduled to participate in the annual Borrego Hammerhead Roundup aerobatic competition, for which a 10-minute practice session was allotted in the designated aerobatic area. A witness on the ramp at L08 reported establishing radio contact with the pilot in the primary holding area southeast of the airport. The pilot then entered the aerobatic box and performed a sportsman sequence twice while receiving coaching from a person on the ground. He subsequently performed a spin maneuver and departed the aerobatic box to the north. The pilot was requested to repeat the “goldfish figure,” and the witness informed him he had two minutes left on his allotted practice time. The pilot transmitted that he was going to reenter the aerobatic box from the west while traveling east. The witness advised him to take his time, and the pilot acknowledged. The witness estimated the aircraft was at an altitude of between 2,700 and 3,000 feet above ground level when the pilot made a right turn to enter the aerobatic box. The aircraft entered a 30- to 35-degree descent to obtain speed and energy for his maneuvers. Shortly after, the pilot transmitted in the blind, “I have no back stick.” The witness estimated the aircraft was descending through about 1,800 to 2,000 feet above ground level when someone asked the pilot if the aircraft was under control. The pilot responded, “no, not at all.” A few seconds later, another transmission told the pilot to “try your trim.” The pilot responded, “there is no trim,” as the aircraft was observed descending through about 600 feet above ground level. No further radio transmissions were heard from the pilot. The witness reported that the aircraft continued to steepen its descent angle and gain airspeed before disappearing behind a sand dune. The wreckage came to rest inverted in the open desert about one mile northeast of L08. All major structural components were located at the accident site. The fuselage was crushed aft, and the engine was separated from the fuselage. The left and right wings remained attached to the fuselage and were crushed aft to the main spar throughout their respective spans. The wreckage was recovered to a secure location for further examination. ## Personnel and Aircraft Information The pilot, age 58, held a private pilot certificate with an airplane single-engine land and instrument airplane ratings. An FAA third-class airman medical certificate was issued on March 10, 2010, with no limitations stated. The pilot reported on his most recent medical certificate application that he had accumulated 2,100 total flight hours. Review of the pilot’s personal logbook revealed that as of the most recent logbook entry dated April 4, 2010, the pilot had accumulated a total of 1,268.7 flight hours, of which 10.2 were within the preceding 30 days and 19.3 hours within the preceding 90 days of the accident. The two-seat, low-wing, fixed-gear airplane, serial number 001, was built in 2008. It was powered by a Lycoming IO-540-EXP engine, serial number L-51474-04, rated at 340 horsepower. The aircraft was equipped with a Whirlwind three-bladed adjustable-pitch propeller. It had two sets of controls, consisting of front and rear control sticks and two sets of rudder pedals. The two control sticks were interconnected via a torque tube assembly. Review of the aircraft maintenance logbooks revealed that the most recent 100-hour inspection was completed on December 18, 2009, at a tachometer time and airframe total time of 191.4 hours. ## Medical and Pathological Information The County of San Diego Medical Examiner conducted an autopsy on the pilot on April 9, 2010. The medical examiner determined that the cause of death was “multiple blunt force injuries.” The FAA’s Civil Aeromedical Institute in Oklahoma City, Oklahoma, performed toxicology tests on the pilot. According to the report, volatiles and drugs were tested with negative results. ## Tests and Research The wreckage was examined at the facilities of Aircraft Recovery Services in Pear Blossom, California, on April 28, 2010, by the National Transportation Safety Board investigator-in-charge. The examination of the airframe revealed that the elevator flight control system exhibited numerous areas of separation from the rear control stick to the elevator control surface. All areas of separation exhibited signatures consistent with overload. 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, the elevator control servo, and a portion of the control rod were removed from the wreckage and sent to the NTSB Materials Laboratory in Washington, D.C., for further examination. The upper portion of the front control stick was not located. An NTSB senior metallurgist reported that all fractures associated with these components were inspected using a 5X to 50X stereo zoom microscope. All fracture surfaces on the control column and both flight control sticks were found to be due to overstress. The front control stick had a 0.22-inch diameter hole drilled in the forward side of the tube wall about 0.42 inches above the top of the stick socket. The overstress fracture initiated at the edges of this hole. The rear control stick had a 0.15-inch diameter hole drilled in the forward and aft sides of the tube wall (clearance holes to accommodate a mounting bolt) about 0.40 inches below the top of the stick socket. The overstress fracture in the rear stick initiated at the edges of the forward hole. The linkage fractures associated with the elevator control servo assembly were inspected using a 5X to 50X stereo zoom microscope. In all instances, the fractures were found to be consistent with bending overstress. A control linkage that measured approximately 18 inches long and 0.5 inch in diameter had threaded ends. Both threaded end fracture surfaces were consistent with bending overstress as indicated by inspection. Examination of the front control stick revealed that it was fractured in overstress due to cantilever bending just above the control column fitting. Near the top of the front control stick, six 4-40 NC threaded holes were located within the tube. The threads appeared to be stripped within holes labeled one, four, and six. Hole number four exhibited a second untapped hole overlapping it. The top of the front control stick appeared to be saw-cut and hand-filed. According to a representative from Team Rocket LP, the control sticks were fabricated from aluminum alloy 6061 and tempered to the T6 condition. Examination of the front and rear control sticks revealed that the aluminum alloy composition and tube wall thickness were within specification limits. The hardness and conductivity measurements for both control sticks were found consistent with aluminum alloy 6061 in a T4 or a lower-strength T6 condition.