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 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.
The pilot was participating in an International Formula One (IF1) Pylon Air Race Class pilot qualification flight. The flight was intended to include 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 observed by IF1 personnel on the ramp.
Several witnesses 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. Witnesses stated that at the completion of this first roll, the airplane seemed to "bobble" and "pitch downwards" prior to abruptly leveling off. The roll appeared uncoordinated, and the roll rate was estimated at about 400 degrees per second.
The airplane made a climbing 360-degree turn to the left to set up for a second pass parallel to runway 8. It then leveled off, pitched downwards to gain airspeed, leveled off, and entered a roll to the right at an estimated airspeed in excess of 200 mph (two witnesses estimated 220 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. 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 to perform all three rolls during the same pass. Another witness stated 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 airplane single-engine sea rating. She 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. She 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 reported she had about 4 hours in the accident make/model airplane. Logbook entries in the aircraft maintenance logbook indicated 3.5 hours in the accident airplane as of July 19, 2008, and a flight of about 0.5 hours on September 5, 2008.
Aircraft Information
The single-seat, mid-wing, fixed-gear, amateur-built experimental airplane, serial number DMB-001, was powered by an experimental Continental O-200-A engine. It was originally built and completed in July 2002 using Cassutt plans and Snoshoo SR-1 plans and issued an airworthiness certificate on August 8, 2002. A logbook entry dated May 29, 2005, stated "1st heat 2 of 3 laps, pulled out of race, crash, aircraft destroyed" at a total airframe time of 91.8 hours. The airplane was rebuilt in the spring of 2008, with a new Cassutt fuselage and empennage, and a wing built from Cassutt design plans.
The wing had a twin spar configuration with wood spars, ribs, and skins. The forward spar was laminated spruce, and the rear spars extended from the fuselage attach fitting to each wingtip. The forward spar sat on top of the fuselage truss structure and was fastened with two vertical tension bolts and a cap plate on each side. The horizontal stabilizer was fiberglass-covered foam core with a tubular steel internal frame, and was trimmable in flight via a lever on the left side of the cockpit. The stock Cassutt examined had a tubular steel horizontal stabilizer without foam core, attached with four bolts, and trimmable only on the ground by adding washers.
Wreckage and Impact Information
The airplane came to rest on its left side near runway 32/14. The right wing was located about 2,159 feet west of the main wreckage and the left wing about 1,838 feet west, both north of runway 08. The empennage remained attached. The forward wing spar was fractured in two places about 3-4 inches outboard of the fuselage attach point, with fractures consistent with overload. The right forward tension bolt was fractured and separated. The right side of the center section of the forward wing spar, right cap plate, and right instrument panel were displaced aft and upward. The left wing remained intact with little damage; the right wing tip and half of the aileron were separated, and a large section of lower skin was missing.
Tests and Research
Examination of the forward wing spar by the USDA Forest Products Laboratory determined it was Sitka Spruce with no decay. The fracture surfaces were consistent with a substantial upward force. The right forward tension bolt fracture features were consistent with overload. The horizontal stabilizer trim lever was found in the full forward position, locked by fuselage damage; the control system was intact to the stabilizer.
A representative of National Aeronautics Company, producer of the Cassutt kit, stated there is no published maneuvering speed or never-exceed speed for the Cassutt; estimated maneuvering speed would be around 200 mph. The representative noted that the trim system installed in the accident airplane was not of their design and that movement of the horizontal stabilizer during an abrupt maneuver could produce high G-forces possibly exceeding structural design limits. They believed the horizontal stabilizer should be securely mounted and that a trim tab would be preferable to a moveable stabilizer.