NTSB Factual Report

HISTORY OF FLIGHT

On November 6, 2015, about 1135 eastern standard time, an experimental light-sport Zenith CH701 amphibious airplane, 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 to the airplane before listing it for sale for the owner.

A private pilot, who witnessed the accident from about 1/4 mile south of the accident site, 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, who saw the accident from about 1/4 mile east of the accident site, stated that the airplane was "tilting its wings," as if the pilot was acknowledging people on the ground below, when the right wing "folded up 90 degrees, like when you park airplanes on an aircraft carrier."

A third witness, who was working on a rooftop about 1/4 mile north-northwest of the accident site, 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 of it, and he then heard the sound of an impact.

A fourth witness, who was located about 3/4 mile east of the accident site, 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 the airplane descended 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 and 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, which was 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 information obtained from 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 airplane's Hobbs meter indicated 62.1 hours, and the engine, which was 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, which was performed by an airframe and powerplant mechanic at the 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 left and right 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), which was located 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 INFORMATION

All major portions of the airplane were accounted for at the accident site. Two windscreen fragments, including one that was about 18 inches 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. There were impact and scraping marks across the driveway.

The left wing was separated; however, it was located next to the fuselage and extended 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 of the left wing was consumed by fire. The two bolts that attached the left wing to the fuselage contained melted material from the spar; however, both were still bolted to the fuselage. The upper surface of the right wing was generally intact and minimally distorted from impact; however, the wing tip leading edge was deformed consistent with ground contact. The deformation was angled about 30° from the leading edge aft and outboard. The two bolts that attached the right wing to the fuselage contained melted material from the spar; however, both were still bolted to the fuselage.

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 the 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. The aluminum portions were not present. The rudder hinge bolts were present. The rudder cables were attached to the rudder pedals. The left rudder cable was attached to the left rudder control horn. The attaching hardware at the right rudder control horn had melted and the cable was separated.

All portions of the airplane's wing struts were located. One or more portions of the struts contained bends, impact damage, fire damage, corrosion, and/or separations; however, all their respective attachment bolts and nuts were in place and secure. The wing struts were removed and forwarded to the NTSB Materials Laboratory, Washington, DC, for further examination.

The engine was severely impact- and fire-damaged. Most accessories, including the carburetors, were impact-separated and fire-damaged. The No. 3 cylinder was fractured in several locations and fragmented during removal from the crankcase. The engine was partially disassembled at the accident site. The crankshaft could not be rotated and the engine was subsequently further disassembled and inspected at a maintenance facility under the supervision of an FAA inspector. The main bearings, crankshaft, and connecting rods were intact and displayed no evidence of oil starvation. The camshaft lobes were in good condition and did not exhibit any gouges, grooves, or wear. Examination of the respective cylinder heads, valves, and pistons did not reveal any preimpact mechanical anomalies.

The propeller hub remained attached to the engine. One of the composite propeller blades was broken at the root. The blade was located in the debris path and exhibited impact damage at the tip and chordwise scratches along most of its leading edge. The remaining two propeller 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 performed on specimens from the pilot by a local laboratory were negative for alcohol and drugs.

Toxicological testing performed on specimens from the pilot 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 and the exterior paint was charred and missing in several locations. When handled, copious quantities of corrosion deposits would exit the open areas of all the 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 manufacturer's 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 which extended 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 to be 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.

ADDITIONAL INFORMATION

Handheld GPS

A Garmin GPSMAP 276C was recovered at the accident site; it was examined and downloaded at the NTSB Vehicle Recorder Laboratory. The data extracted included 81 track logs; however, there was no data recorded on the date of the accident.

Zenith Service Letter / Notification

After the accident, ZenAir, the kit manufacturer for Zenith Aircraft, issued a Service Letter (SL)/Notification, which included an inspection of wing strut assemblies for internal corrosion. The SL specifically recommended that the wing struts be removed from the airplane and inspected for rust within the next 50 hours, and then annually on a continuing basis.

NTSB Probable Cause

An in-flight structural failure due to a severely corroded wing strut, which resulted in a loss of airplane control.