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On August 25, 2007, about 1820 mountain daylight time, a Flight Design CTSW special light sport airplane (SLSA), N775CT, impacted terrain following a loss of engine power in the traffic pattern for landing on runway 16 at St. George Municipal Airport, St. George, Utah. The airplane sustained substantial damage, and the private pilot and passenger received serious injuries. The airplane was being operated by the pilot under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the personal cross country flight that originated from Salinas, California, about 1430.
The pilot reported that he had just purchased the airplane and was flying it to his home in St. George. He had received several hours of flight training and completed a flight review in the airplane the day before the accident. They departed Salinas with full fuel tanks. The accident flight was uneventful until about 20 miles from St. George, at which point the engine began to run rough. The pilot determined that the choke had "worked its way back about 3/4 of an inch." He "eased" the choke off and the engine roughness stopped. About 5 miles from St. George as the pilot entered the downwind leg for landing on runway 16, the engine "totally stopped."
The pilot declared an emergency on the Unicom frequency, stating he was planning a landing on runway 34. According to the pilot, another pilot reported that he was 9 miles out on straight in final and asked the accident pilot how he "intended to clear the runway so that he could land." The accident pilot then decided "to follow downwind and enter the runway if possible." However, "the sink rate was too great," and he located a small clearing in the boulders on the bluff ahead and prepared "to stall in vertically rather than to tumble over the rocks horizontally." He intentionally stalled the airplane at an altitude of 10 feet above ground and an airspeed of "approximately 24 mph." The airplane impacted the terrain, nosed over and came to rest inverted.
The pilot added that he could have deployed the airplane's BRS parachute (a rocket deployed emergency parachute system), but "chose not to because we could have been blown over the dense population area, very near" to the accident site.
The pilot, age 71, held a private pilot certificate with airplane single engine land and instrument airplane ratings. His most recent medical certificate was a third class medical certificate issued on August 7, 2006, with the limitations, must wear corrective lenses and possess glasses for near and intermediate vision.
The pilot reported that he had accumulated 732 total flight hours of which 10.5 hours were in the Flight Design CTSW. All of the pilot's hours in the Flight Design CTSW were flown on the day before the accident or the day of the accident.
The airplane, a 2005 year model Flight Design CTSW, was issued a special airworthiness certificate in the light sport category on September 9, 2005. According to the airplane's maintenance records, it received its most recent annual condition inspection on August 22, 2007, at a total time in service of 459.1 hours. At the time of this inspection, the engine, a Rotax 912 ULS, had accumulated 459.1 hours since new. The most recent maintenance action recorded for the engine was an oil change also dated August 22, 2007, at a total time since new of 463.9 hours.
The Pilot Operation Handbook (POH) for the airplane describes the CTSW as a three-axis control, high-wing, two seat light sport aircraft of normal scheme with a cruciform tail. The primary structures are made of carbon fiber reinforced plastic. The airplane is equipped with an all-moving stabilator with a trim tab and tricycle landing gear with a steerable nose-wheel. Fuel is supplied from two wing tanks by gravity feed with a total capacity of 34 gallons.
According to the POH, the airplane's stall speed at maximum takeoff weight with flaps at 0 degrees is 42 knots (48 mph), and its maximum service ceiling is about 14,000 feet. The fuel consumption at cruising power ranges from 3.44 to 5.82 gallons per hour.
The reported weather conditions at St. George Municipal Airport at 1815 were wind from 240 degrees at 18 knots gusting to 24 knots, visibility 10 miles, sky clear, temperature 38 degrees C, dew point 12 degrees C, and altimeter setting 29.85 inches. Using the airport elevation of 2,941 feet and the recorded weather conditions, the density altitude at the time of the accident was calculated at 6,426 feet.
WRECKAGE AND IMPACT INFORMATION
Review of photos taken by St. George Police Department personnel revealed that the airplane came to rest on a rocky slope in the inverted position. The engine separated from the fuselage, and the forward (cabin) section of the fuselage was severely fragmented. The wing was intact and had relatively minor impact damage. The tail cone was partially separated from the fuselage, and the empennage remained attached to the tail cone. The vertical stabilizer and rudder were crushed, and the stabilator was intact. All flight control surfaces remained attached to their respective attach points.
A Federal Aviation Administration (FAA) inspector arrived at the scene of the accident the following day. The inspector reported that fuel was leaking from the wreckage.
The engine was examined by the NTSB investigator in charge and an engine manufacturer's representative on November 13, 2007, at the facilities of Air Transport in Phoenix, Arizona. The engine remained bolted to the engine mount, and the propeller hub remained bolted to the engine's propeller shaft. All three propeller blades were separated near their blade roots. Initially, the engine could not be rotated by hand. The propeller and the engine's propeller gearbox were removed. A broken snap ring was found jamming the gears in the gearbox. According to the engine manufacturer's representative, it is common to find this snap ring broken in engines that have sustained impact damage. After the propeller gearbox was removed, the engine could be turned by hand, and thumb compression was obtained on all cylinders. No further disassembly of the engine was performed. The engine was shipped to a facility where it could be test run.
The pilot reported that following the crash, he and his passenger were "hanging upside down in what was left of the fuselage" and fuel was dripping onto them. "Some kind of rubber-like cables" were wrapped around their lower legs.
According to a report prepared by the St. George Police Department, when officers reached the accident site, they could see the pilot's legs sticking up in the air and noted "a yellow strap pinching the circulation out of them." Police and fire department personnel extricated both occupants from the airplane, and they were transported to a hospital.
The pilot reported that his injuries were "two splintered ankles with bones extruded and a fractured right arm with bones extruded." The passenger's injuries were "a multiple fracture at her left ankle with bones extruded and with lacerations on both lower legs just above the ankle."
TESTS AND RESEARCH
The engine was run at the facilities of Lockwood Aviation in Sebring, Florida, under the supervision of an FAA inspector on February 20, 2008. The electric starter motor, which had sustained impact damage, and the broken snap ring in the propeller gearbox were replaced. No alteration to the carburetion jetting or settings was made. The run was performed with a calibrated test propeller and exhaust system installed. The engine was started, warmed up, run at fast idle, and then the throttle was opened. The engine developed near 100 percent performance. Oil pressure was normal. The ignition system was checked and functioned normally. No discrepancies were noted that would have prevented normal engine operation and production of power.
During the engine examination on November 13, 2007, it was noted that the engine firewall was constructed of carbon fiber reinforced plastic. Numerous holes had been cut in the firewall to accommodate passage of wires and hoses; these holes were not sealed. It was also noted that sections of fire sleeve had been placed on fuel hoses in the engine compartment; however, the ends of the fire sleeve were either unsecured or secured with automotive style C-clamps.
American Society for Testing and Materials (ASTM) consensus standards designation F 2245-07 Section 7 - Powerplant, 7.3.9 states "fuel lines located in an area subject to high heat (engine compartment) must be fire resistant or protected with a fire-resistant covering." ASTM consensus standards designation F 2245-07 Section 7 - Powerplant, 7.6 states "the engine, if enclosed, must be isolated from the rest of the airplane by a firewall or shroud. It must be constructed as far as practical to prevent liquid, gas, or flames, or a combination thereof, from entering the airplane. The use of any one of the following materials shall be acceptable without further testing: 7.6.1 Stainless steel, not less than 0.46 mm (0.018 in.) thick, 7.6.2 Mild steel (corrosion-protected), not less than 0.46 mm (0.018 in.) thick, or 7.6.3 Alternative materials that provide protection equivalent to 7.6.1 or 7.6.2."
A representative of the United States (U.S.) importer of Flight Design airplanes stated that the fuel lines are covered with fire protection hoses as required by the standards. He further stated that the holes in the firewall were made "very tight" on purpose to function like a seal. Regarding the firewall, he reported that the carbon composite material is coated with flame retardant resin in this area.
The representative reported that Flight Design airplanes delivered from early 2007 on come from the factory with secured fire sleeves and a fire wall blanket installed. The representative indicated that there was a program in process to upgrade all airplanes delivered in the U.S. without these items to this standard. He further stated that Flight Design had not mandated a specific time limit for the upgrade, but was offering it free to the owners and suggesting it be done at major service such as an annual or 100 hour inspection. He provided copies of two sections from Flight Design's Improved Fire Protection Retro-Fit Manual for US LSA Airplanes. Both sections were dated July 7, 2006. One section was titled, "Fuel and Oil Tubes Securing," and provided instructions for installing fire sleeve on all fuel and oil tubes in the engine compartment. The instructions included directions to secure the fire sleeve ends with "FSC" clamps. The other section was titled, "Fire Wall Protecting," and provided instructions for gluing a "fire protecting part" to the firewall.
The representative reported that a total of 140 airplanes were eligible for the upgrade, and 29 had been modified as of May 12, 2008. As of that date, Flight Design was considering making the upgrade mandatory by issuing a service bulletin with a compliance time limit.