History of Flight
On November 6, 2015, about 1135 eastern standard time, an experimental light-sport Zenith CH701 amphibious airplane, registration N56553, impacted the ground in Okeechobee, Florida. The private pilot was fatally injured, and the airplane was destroyed. The airplane was privately owned and operated, and the personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the flight, which departed Homestead General Aviation Airport (X51), Homestead, Florida, destined for River Acres Airport (FD70), Okeechobee, Florida.
According to the owner, the airplane was based at X51 and had not been flown since early 2012; the airplane's last condition inspection was performed during November 2011. The pilot was flying the airplane to FD70 to facilitate a condition inspection and some cosmetic repairs before listing it for sale for the owner.
A private pilot who witnessed the accident from about 1/4 mile south stated that he saw the airplane flying about 100 ft above the ground. It was "flying erratically," and "rocking back and forth." He then heard a loud "snap" sound, which was immediately followed by one or both wings folding up and back about 45°. The airplane entered a steep, "60-degree nosedive" and descended below his field of view. The witness added that he heard the engine during the entire accident sequence and did not note any power interruptions.
A second witness, about 1/4 mile east, stated that the airplane was "tilting its wings," as if acknowledging people on the ground, when the right wing "folded up 90 degrees, like when you park airplanes on an aircraft carrier."
A third witness, on a rooftop about 1/4 mile north-northwest, stated that he saw the airplane descending in an approximate 30° nose-down angle and rolling right "wing over wing." The airplane completed four or five revolutions before he lost sight, and he then heard the sound of an impact.
A fourth witness, about 3/4 mile east, reported that the airplane was flying west and passed overhead at an altitude about 600 to 700 ft. The engine sounded like it was "cutting in and out of power." He saw the airplane circle then slow, and the wings rocked back and forth before descending from view.
The airplane impacted the ground in a residential area and was destroyed by a postcrash fire.
Personnel Information
The pilot, age 62, held a private pilot certificate with a rating for airplane single-engine land. The pilot's logbook was not recovered from the accident site. According to the pilot's family representative, the pilot's logbooks were likely destroyed during the accident. No documentation regarding his flight experience was available. The pilot reported 2,000 hours of total flight experience on his most recent application for a Federal Aviation Administration (FAA) third-class medical certificate, issued on June 2, 2006.
Aircraft Information
The single-engine, two-seat, kit-built, high-wing, amphibious airplane was issued a special airworthiness certificate in the experimental light-sport aircraft category on December 13, 2007. It was powered by a Rotax 912ULS, 100-horsepower engine, equipped with a three-blade Warp Drive composite propeller assembly.
According to FAA airworthiness records and maintenance logbooks, the airplane was purchased by the owner during February 2008. Its most recent condition inspection was completed on November 24, 2011. At that time, the Hobbs meter indicated 62.1 hours, and the engine, installed in November 2010, had been operated for 100.5 total hours since new.
The owner and his family reported that, during May 2010, while on a flight to Key Largo, Florida, the airplane's engine overheated and lost power, and the owner performed an off-shore forced landing in saltwater. The airplane was subsequently disassembled and washed with freshwater. The engine was replaced, and the airplane was transported to the accident pilot's hangar at FD70 where it was reassembled by the accident pilot. It then underwent the November 2011 condition inspection, performed by an airframe and powerplant mechanic at Indiantown Airport (X58), Indiantown, Florida.
In early 2012, the owner flew the airplane from X58 to X51 where it remained and was not flown until the day of the accident. According to the owner, on the day of the accident, the airplane departed with about 15 gallons of fuel in each wing fuel tank. According to an FAA inspector, there was no record of a special flight (ferry) permit requested or issued for the accident flight.
Meteorological Information
At 1135, the weather conditions reported at Okeechobee County Airport (OBE), about 4 nautical miles north of the accident site, included wind from 90° at 9 knots, 10 statute miles visibility, scattered clouds at 4,000 ft, a temperature of 28°C, a dew point of 21°C, and an altimeter setting of 30.16 inches of mercury.
Wreckage and Impact Information
All major portions of the airplane were accounted for at the accident site. Two windscreen fragments, including one about 18 by 11.5 inches, were found on the ground about 150 ft northeast of the initial ground scar, opposite the airplane's direction of travel.
The airplane came to rest inverted. The cockpit and cabin were consumed by a postcrash fire. Both wings and the landing gear were severely fire damaged. Ground scars and debris were located on a heading about 260°. The fuselage and right wing came to rest about 39 ft from an initial ground scar, just east of a concrete driveway. Impact and scraping marks crossed the driveway.
The left wing was separated but located next to the fuselage, extending to about 61 ft from the initial ground scar. The upper surface of the left wing was generally intact and minimally distorted from impact. The inboard section was consumed by fire. The two bolts attaching the left wing to the fuselage contained melted material from the spar but were still bolted. The upper surface of the right wing was generally intact and minimally distorted; however, the wing tip leading edge was deformed consistent with ground contact, angled about 30° from the leading edge aft and outboard. The two bolts attaching the right wing to the fuselage also contained melted spar material but were still bolted.
Due to the condition of the wreckage, flight control system continuity was not established. The steel tubes, including the "Y" portions of the yoke for flaperons and elevator control, were located but severely fire damaged. All aluminum components were absent. The two flaperon pushrods from the main control to the aileron bellcranks were attached. All bolts and nuts attached to the steel portions of the control system were present. The steel portions of the elevator control were present with all bolts and nuts attached; aluminum portions were absent. The rudder hinge bolts were present. The rudder cables were attached to the rudder pedals; the left cable was attached to the left rudder control horn; the attaching hardware at the right horn had melted and the cable separated.
All portions of the wing struts were located. Some struts contained bends, impact damage, fire damage, corrosion, and/or separations; however, all their attachment bolts and nuts were in place and secure. The wing struts were removed and forwarded to the NTSB Materials Laboratory for further examination.
The engine was severely impact- and fire-damaged. Most accessories, including carburetors, were impact-separated and fire-damaged. The No. 3 cylinder was fractured and fragmented during removal. The crankshaft could not be rotated; the engine was further disassembled and inspected under FAA supervision. Main bearings, crankshaft, and connecting rods were intact with no evidence of oil starvation. Camshaft lobes were in good condition. Examination of cylinder heads, valves, and pistons revealed no preimpact mechanical anomalies.
The propeller hub remained attached to the engine. One composite propeller blade was broken at the root, located in the debris path with impact damage at the tip and chordwise scratches along most of its leading edge. The remaining two blades were fire-damaged.
Medical and Pathological Information
The Office of the Chief Medical Examiner, District 19, Fort Pierce, Florida, performed an autopsy on the pilot. According to the autopsy report, the cause of death was "multiple blunt trauma injuries." Toxicological testing by a local laboratory was negative for alcohol and drugs.
Toxicological testing by the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, was negative for alcohol. Amlodipine, a non-impairing prescription medication normally used to treat high blood pressure, was found in urine and blood specimens.
Tests and Research
Wing Struts Examination
Examination of the wings' front and rear struts was performed by an NTSB senior metallurgist. The strut pieces had been exposed to fire; the exterior paint was charred and missing in several locations. When handled, copious quantities of corrosion deposits would exit the open areas of all struts. Each strut was manufactured from two pieces of tubing welded together within a surrounding sleeve. The tube end construction differed from sample engineering drawings available from the kit manufacturer; the tube ends on the accident airplane were shaped and welded to form closed tube ends instead of the round, open tube ends depicted on the drawings.
The left wing struts were separated at multiple locations. Visual and magnified optical examination found that the wall thickness of the forward tube of the left wing had been reduced to knife edges by internal corrosion, extending for significant lengths beyond the location of both separations.
The right wing struts were separated at the inboard ends and bent and deformed in several locations. Magnified optical examination found the separations consistent with overstress fractures after significant bending/buckling deformation. Longitudinal sectioning of the aft strut tube at the separation revealed significant internal corrosion and localized wall loss at portions of the separation.