SEA08FA196

The movement of the airplane’s modified horizontal stabilizer trim system during an intentional high speed aerobatic maneuver that resulted in exceedence of the design stress limits of the airplane and an in-flight structural failure. Contrubuting to the accident was that the builder’s deviation from the airplane designer's original trim system.

During an air race class qualification flight, the pilot was performing a series of maneuvers required to obtain a class license. During a required roll maneuver, as the airplane passed through about 90 to 120 degrees of roll at an estimated speed of 220 to 230 miles per hour, the right wing separated from the airframe, followed almost immediately by the left wing. The amateur built experimental airplane was fitted with an in-flight adjustable pitch trim system, which was a deviation from the original ground-only trim adjustment design. The trim system, designed by the airplane's builder, allowed the pilot to adjust the pitch trim by moving the horizontal stabilizer in flight. The in-flight system was composed of a lever attached to the fuselage structure, and its movement was restricted with friction washers between the fuselage and the lever. Full travel of the lever resulted in one inch of vertical movement of the horizontal stabilizer's leading edge. The manufacturer of the airframe kit stated that the trim system installed on the accident airplane was not of their design. They further stated that any movement of the horizontal stabilizer during an abrupt maneuver could produce an extremely high amount of G-forces and possibly exceed the structural design limits of the airplane. Post accident examination of the wreckage revealed no evidence of pre-existing anomalies with the airframe or flight control system. The wooden wing spar was tested and found to be of proper grade wood. No anomalies were noted with the spar material. The fracture surfaces of both the left and right wing forward wing spars were consistent with a "substantial upward force" and overload. It is unknown if the horizontal trim system was moved in-flight by commanded or uncommanded action. Amateur built airplanes with experimental certificates are not subject to the airworthiness standards in 14 CFR Parts 23 and 47 of the Federal Aviation Regulations, and builders and owners are free to make any modifications to the airplane at will.

HISTORY OF FLIGHT On September 6, 2008, about 0906 Pacific daylight time, an amateur-built Debus J/Mountain S/Bowes E Debus-Casst-Snoshoo experimental airplane, N102MB, was substantially damaged when it impacted terrain following an in-flight breakup while maneuvering at the Reno/Stead Airport (4SD), Reno, Nevada. The commercial pilot, the sole occupant of the airplane, was killed. The airplane was registered to Miss Lynn Racing LLC of Lincoln, Nebraska and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the local personal flight that originated from 4SD about 10 minutes prior to the accident. Information obtained from a Federal Aviation Administration (FAA) inspector revealed that the pilot was participating in an International Formula One (IF1) Pylon Air Race Class pilot qualification flight. The flight was intended to be composed of a series of maneuvers which included a 360-degree roll to the left, 360-degree roll to right, and a 180-degree roll to the left followed by a 180-degree roll to the right. These maneuvers were being observed by Formula One Class personnel located on the ramp of 4SD for the purposes of the pilot obtaining an IF1 Racing Pilot License. Several IF1 personnel located on the ramp of 4SD reported observing the airplane depart from runway 8 and enter a normal climb into the demonstration area. The airplane was observed on an east to west heading parallel to runway 8 about 1,500 to 1,800 feet above ground level (agl), and the pilot performed a 360-degree roll to the left at an estimated airspeed in excess of 200 miles per hour. The witnesses stated that at the completion of this first roll, the airplane seemed to "bobble" and "pitch downwards" prior to abruptly leveling off. The witnesses added that it appeared the aileron roll was similar to an International Aerobatic Club (IAC) style slow roll and seemed uncoordinated. The witnesses estimated the roll rate was about 400-degrees per second. The airplane made a climbing 360-degree turn to the left in order to setup for a second pass parallel to runway 8. The witnesses further reported that the airplane exited the 360-degree turn, leveled off, pitched downwards in order to gain airspeed, leveled off, and proceeded to enter a roll to the right at an estimated airspeed in excess of 200 miles per hour (MPH) with no pitch changes noted. Two witnesses estimated the airspeed from 220 mph to 240 mph. As the airplane rolled through about 90 to 120 degrees, witnesses stated the right wing separated from the airframe followed by the left wing separating shortly after. Subsequently, the airplane impacted terrain and came to rest on its left side west of runway 32/14 and north of runway 26/08. One witness stated that prior to the accident flight; the pilot had briefed him that she intended on performing all three rolls during the same pass. Another witness stated that he was "surprised" when the pilot did not complete all three rolls on the initial pass. PERSONNEL INFORMATION The 32 year old pilot held an airline transport pilot certificate with airplane multi-engine land rating, a commercial pilot certificate with airplane single-engine land and glider ratings, and a private pilot certificate with an airplane single-engine sea rating. In addition, the pilot possessed type ratings in the BE-1900, CE-525, and CE-560XL aircraft. A first-class airman medical certificate was issued on April 4, 2008 with the limitation “must wear corrective lenses.” The pilot's flight logbooks were not located during the investigation. The pilot reported on her 2008 National Championship Air Races entry form that she had accumulated in excess of 7,000 hours of flight time, of which 100 hours were in the previous 90 days. A family member of the pilot reported that she had accumulated about 4 hours in the accident make/model airplane. Logbook entries within the aircraft maintenance logbook indicated that the pilot had logged 3.5 hours of flight time in the accident airplane as of July 19, 2008. According to an FAA inspector, the pilot had conducted a flight on September 5, 2008 that was about 0.5 hours in length. AIRCRAFT INFORMATION The single seat, mid-wing, fixed-gear, amateur-built experimental airplane, serial number (S/N) DMB-001, was powered by an experimental Continental O-200-A engine. Review of the aircraft logbooks indicated that the airplane was originally built and completed in July 2002 in accordance to Cassutt plans and Snoshoo SR-1 plans and subsequently issued an airworthiness certificate on August 8, 2002. A logbook entry dated May 29, 2005, stated in part "1st heat 2 of 3 laps, pulled out of race, crash, aircraft destroyed" at a total airframe time of 91.8 hours. A logbook entry dated July 2, 2008, stated in part "rebuild N201MB, serial # DMB-001, as follows: replace fuselage truss with stock Cassutt truss. Empennage replaced with stock Cassutt empennage, replaced Snoshoo SR-1 wing with Cassutt 111M wing, replace ST-1 engine cowl with stock Cassutt Cowl. Rebuilt turtle deck and canopy deck. Replace Experimental Continental O-200 engine, replaced Twisted Composites propeller, rebuilt motor mount." An additional logbook entry dated July 5, 2008, stated in part "flight operations will be conducted VFR day only, inflight test area for a minimum of 5 hours to re-establish compliance with FAR 91.319 (b)." The entry was followed by an additional logbook entry on July 9, 2008 stating in part "…this aircraft has been inspected in accordance with the scope and detail of Appendix 'D' of Part 41 and found to be in condition for safe operation." According to the builder of the accident airplane, a complete rebuild of the airplane was completed in the spring of 2008. He stated that the original registered airplane was comprised of a Cassutt fuselage with Snoshoo wings and was substantially damaged during an accident in 2005. The accident airplane was rebuilt using a new Cassutt fuselage and empennage. The wing was built using Cassutt design plans. The Cassutt is an IF1 race airplane. The accident airplane had a tube and fabric fuselage. The fuselage was a tubular steel truss structure that tapered in the cross-section toward the aft end of the airplane. The one-piece wing was of a twin spar configuration and manufactured with wood spars, ribs and skins. The ailerons extended the full length along the trailing edge of each wing. The forward wing spar was made of laminated spruce and extended from wingtip to wingtip. The spruce rear spars extended from the fuselage attach fitting to the wingtip on each side. When installed, the forward spar sits on top of the fuselage truss structure at the forward end of the cockpit and is fastened to the fuselage with two vertical tension bolts and a cap plate on each side. The inboard end of each rear spar had a metal clevis fitting that attached to the fuselage lug with a longitudinal bolt. The vertical stabilizer, rudder, horizontal stabilizer, and elevator were fiberglass covered foam core structures with tubular steel internal frames. The horizontal stabilizer had a twin tube forward spar and a single tube rear spar. The horizontal stabilizer and elevator were one-piece units. The horizontal stabilizer on the accident airplane was designed to be trimmable in flight and attached to the fuselage truss at the rear spar through a lateral pivot pin. The forward spar was attached to the fuselage frame through two vertical bolts and allowed to move up and down a total of about 1 inch. The horizontal stabilizer trim was controlled with a lever installed on the left side of the cockpit (All of the directions in the following are referenced while viewing the control system from the left side of the airplane). The lever was attached to the outboard side of one of the fuselage tubes with a bolt. A f