Eustis, FL, USA
N98YW
AIRBORNE WINDSPORTS PTY LTD EDGE XT 912 L
The pilot had recently purchased the weight-shift-control trike and was performing his first flight in it. The pilot completed three takeoffs and three landings within the length of the runway, each time taking off, climbing to about 30 ft above ground level, landing, and taking off again. The pilot then taxied back to the beginning of the runway and performed two more short takeoffs and landings. While performing a third takeoff, the pilot continued climbing the trike and joined the airport traffic pattern for landing. Witnesses stated that the pilot overshot the turn from the downwind to base leg of the traffic pattern, and again overshot the turn to the final approach leg. The pilot then made a sharp left turn to intercept the final approach leg of the traffic pattern, and the wings of the trike began rocking up and down. The right wing then "went down," the engine was heard accelerating, and the trike impacted the ground. Review of weather information revealed the presence of a 6 knot headwind for the landing runway about the time of the accident and no evidence of gusts or convective activity. Examination of the fuselage and wing found no evidence of fatigue on any flight control cable or wing support structure tubing, and the damage observed was consistent with impact. Examination of the engine, along with a postaccident engine run, also revealed no evidence of any preimpact failure or malfunction that would have precluded normal operation. The pilot had flown another weight-shift-control aircraft for 5 1/2 years before purchasing the accident aircraft; however, the accident aircraft was equipped with a more powerful engine, was considerably faster, had a higher stall speed and this was the first time he had flown this particular make and model. The pilot overshooting both the base and final legs of the traffic pattern suggest that he may have been experiencing difficulty managing the aircraft's speed in the pattern, which would have been consistent with his lack of experience in the higher performance aircraft. He likely then let the aircraft's speed decay as he attempted a steep turn to intercept the final approach leg to the runway. The angle of bank during that turn would have resulted in an increased load factor and significantly increased the aircraft's stall speed, which was already higher than the pilot was accustomed to. As a result, the aircraft likely rapidly exceeded its critical angle of attack and subsequently experienced an aerodynamic stall at an altitude that precluded recovery.
HISTORY OF FLIGHTOn February 25, 2018, about 0810 eastern standard time, an Airborne Windsports Edge XT-912-L trike, N98YW, was substantially damaged when it was involved in an accident near Eustis, Florida. The sport pilot was fatally injured. The weight-shift-control aircraft was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot had recently purchased the aircraft and spent the day before the accident assembling it. The accident flight was the pilot's first flight in the aircraft. He taxied the trike to runway 18, where he performed three takeoffs and landings within the length of the runway, each time taking off, climbing to about 30 ft above ground level, landing, and taking off again. The pilot then taxied back to the beginning of runway 18 and performed two more short takeoffs and landings. While performing a third takeoff, he continued to climb and joined the airport traffic pattern. Witnesses saw the aircraft on the downwind leg and then turn onto and overshoot the base leg of the traffic pattern. It then continued toward final approach, overshooting the extended centerline of the runway. The aircraft then made a hard left turn toward the final approach leg of the traffic pattern and its wings began rocking up and down. The right wing then "went down," the engine was heard accelerating, and the aircraft impacted the ground. PERSONNEL INFORMATIONAccording to Federal Aviation Administration (FAA) airmen records, the pilot held a sport pilot certificate with an endorsement for weight-shift-control land aircraft. He also held a light sport aircraft repairman certificate. The pilot was issued a sport pilot certificate on December 15, 2012. On the application for the certificate, the pilot reported that he had accrued 35 total hours of flight experience. The pilot's logbook was never recovered, and no other documentation of his flight experience was found. AIRCRAFT INFORMATIONThe term "trike" describes an aircraft configured with a wing (also known as a sail) usually composed of synthetic fabric-covered surfaces, with battens (ribs) that form an airfoil supported by a structure and associated hardware. An engine and a flight deck, or fuselage, with a three-wheeled undercarriage (much like a tricycle arrangement with one wheel in front and two in back), is attached underneath the structure that supports the sail. The accident trike was a two place, tandem-configured weight-shift-control aircraft with a framed pivoting wing and a fuselage controllable only in pitch and roll as the pilot changed the aircraft's center of gravity with respect to the wing. Flight control of the aircraft depended on the wing's ability to deform flexibly, rather than on the use of control surfaces. AIRPORT INFORMATIONThe term "trike" describes an aircraft configured with a wing (also known as a sail) usually composed of synthetic fabric-covered surfaces, with battens (ribs) that form an airfoil supported by a structure and associated hardware. An engine and a flight deck, or fuselage, with a three-wheeled undercarriage (much like a tricycle arrangement with one wheel in front and two in back), is attached underneath the structure that supports the sail. The accident trike was a two place, tandem-configured weight-shift-control aircraft with a framed pivoting wing and a fuselage controllable only in pitch and roll as the pilot changed the aircraft's center of gravity with respect to the wing. Flight control of the aircraft depended on the wing's ability to deform flexibly, rather than on the use of control surfaces. WRECKAGE AND IMPACT INFORMATIONAccident Site Examination Examination of the accident site by an FAA inspector revealed that the trike impacted the ground on airport property north of the runway 18 threshold, right of the extended centerline, in a nose-low, right wing down attitude. Trike Base and Wing Examination The trike base and wing displayed significant impact damage. The flight control bar on the control frame had separated from the left hand down tube but had remained attached to the right hand down tube. Above the pilot seat, the main mast tube fractured 4 inches from its root attach point but remained attached to the airframe via a leather and Velcro sleeve wrapped around the mast. The backup loop, which had one soft friction pad wrapped around it, was found in the wreckage separated from its attach point. The hand throttle was found in the idle position, and both ignition switches were in the "ON" position. The pilot's seat and fuel tank remained attached to the trike base. The left and right main landing gear wheels and hubs remained attached to their respective swing arms and compression struts. The nosewheel assembly was separated from the trike base. The base tube fitting was also separated from the trike base and displayed impact damage. The brake lever and throttle foot pedals remained attached to their attach points. About 2 ft of the throttle cable remained attached to the foot throttle lever. Examination of the break in the cable revealed features consistent with tensile overload. The Mylar and Dacron sail did not exhibit any large tears and remained in one piece. Both the left and right side leading edge tubes displayed extensive impact damage. Multiple aluminum battens were discovered in the sail and the main wreckage. Many of the battens from both wings displayed impact damage. The right wing D-tube airfoil strut had separated from its attach point and was found with the wreckage. The keel tube had fractured 10 inches from its forward starting beam. The right wing leading edge tube was found in one piece and remained attached to the nose plates. The right wing cross bar remained attached to its bracket. The right wing lift strut was found separated from its attach points. The pivot sprog remained attached to its bracket and right wing leading edge tube. The wing trimmer handle for the speed trim remained attached to the strut, and the trim cable remained attached to its control arm and wheel. The swage on the trimmer wire, which was used as a pointer on the trimmer placard, indicated that the trimmer setting was in the "INCREASE TRIM SPEED" range. A rear flying wire, which had separated, displayed evidence of tensile overload. The left wing leading edge tube displayed impact damage and was fractured 9 inches outboard of the center attach point. The outboard end of the left wing cross bar remained attached to the left wing leading edge tube and displayed impact damage. The left wing lift strut was separated into two pieces and displayed impact damage. The fracture occurred 3 ft from its upper attachment point. The left wing pivot sprog remained attached to its attach point. The left wing down tube airfoil strut was found fractured 3 ft 9 inches from its center point attachment. The piece displayed impact damage. The left wing front flying wire remained attached to the left wing down tube. Examination of a sample from the broken flying wires at the NTSB Materials Laboratory revealed that none of the wire ends exhibited fracture features consistent with pre-existing crack propagation. In addition, while there was corrosion present on the wire fracture surfaces and between the wires, there was no indication of any features consistent with fracture from corrosion. On February 26, 2018, the airport manager advised the FAA that when they moved the trike from the accident site, they found the airspeed indicator; the instrument "was stuck on 34 knots." Propeller and Engine Examination The propeller was fragmented from the propeller hub; the pieces were located in the main wreckage. The engine air filters were crushed from the impact, and the carburetor for the Nos. 1 and 3 cylinders was displaced from the intake socket. No fuel return line was installed. The intake manifolds were equipped with coolant-filled aftermarket aluminum blocks as a means of carburetor ice prevention. There were no fire sleeves installed on the fuel lines. The top of the oil tank lid was in line with the bottom of the oil pump. The fuel shut-off was found in the on (open) position. The carburetor vent lines were routed correctly. The fuel pump vent was unobstructed, and no vent line was attached. Examination of the carburetor float bowl for the Nos. 1 and 3 cylinders revealed no fuel and small amounts of contamination. A portion of material was missing from one of the floats. The main fuel jet was unobstructed. Examination of the carburetor float bowl for the Nos. 2 and 4 cylinders revealed small amounts of fuel with the odor of automotive gasoline within the float bowl. The fuel tested negative for water. The floats were in good physical condition and the main fuel jet was unobstructed. The ignition system was examined, and no anomalies were observed. The spark plugs were in good physical condition. All plugs had a similar burn pattern with black/oily deposits on the threaded portion of the plugs. The electrodes and insulators appeared in good condition (not worn), and the isolators were white in color. The No. 1 spark plug connection probe was bent and displayed impact damage. The engine drive train was rotated by hand and continuity and thumb compression were established for all cylinders. The drive train rotated smoothly, and no unusual noises were heard during rotation. Following examination, the engine was prepared for a test run, and was subsequently started and run at different power settings with no anomalies noted. The engine was shut down by cutting off the air supply to the carburetors. ADDITIONAL INFORMATIONFor about 5 1/2 years before purchasing the accident aircraft, the pilot had flown a Krucker Manufacturing Tundra 582, which was a cable-braced weight-shift-control trike Its cruise speed was 47 knots (55 mph) and its stall speed was less than 26 knots (30 mph). Unlike the Tundra's wing, the accident trike's arrow wing was a high aspect ratio, performance flex wing design, which had a quicker roll rate and used struts instead of bracing cables to reduce drag and carry the flight and landing loads imposed on the wing structure. The design of the arrow wing and the higher horsepower of the accident trike's engine resulted in both a higher cruise speed and a higher stall speed than that of the pilot's previous trike; 75 knots (86 mph) and 35 knots (40 mph), respectively. Review of the Weight-Shift Control Aircraft Flying Handbook (FAA-H-8083-5) revealed that, regardless of the airspeed or the type of aircraft involved, a given angle of bank in a turn during which altitude is maintained always produces the same load factor. It also stated and that an additional load factor increases the stalling speed at a significant rate, as stalling speed increases with the square root of the load factor. For example, a light aircraft that stalls at 40 knots in level flight stalls at nearly 57 knots in a 60° bank. According to the Edge XT-912 Aircraft Operating Instructions, no person who is untrained or unqualified in weight-shift-controlled flight, or who is unfamiliar with the wing and base combination, should ever attempt to pilot the aircraft unless under professional instruction. MEDICAL AND PATHOLOGICAL INFORMATIONThe State of Florida District 5 Medical Examiner, Leesburg, Florida, performed an autopsy of the pilot. The cause of death was multiple blunt force injuries. The FAA Forensic Sciences Laboratory conducted toxicological testing on specimens from the pilot. The results were negative for ethanol and drugs of abuse.
The pilot's exceedance of the weight-shift-control aircraft's critical angle of attack while maneuvering for landing, which resulted in an aerodynamic stall and collision with terrain. Contributing to the accident was the pilot's lack of experience in the accident aircraft.
Source: NTSB Aviation Accident Database
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