CEN10FA042

The in-flight separation of both wings due to aileron flutter. The aileron flutter was the result of inadequate wing stiffness and strength and the lack of aileron counterbalances.

The light-sport airplane experienced an in-flight break-up during a cross-country flight. Flight track data recovered from an onboard global positioning system, and a subsequent performance study, depicted the airplane was maneuvering between the altitudes of 2,500 and 3,500 feet at airspeeds between about 60 and 108 knots calibrated airspeed (KCAS). The airplane performed a number of turns and maneuvers during the hour-plus flight, including a landing approach and pass over an airport. The calculated bank angle for the entire flight never exceeded 30 degrees. At the time when the breakup occurred, the airplane was climbing at about 500 feet per minute through 2,800 feet altitude and had accelerated to 100 KCAS. The estimated angle of attack was about 3 degrees during the last minute of the flight, and the airplane wreckage was spread over 600 feet on the ground. An examination of the airplane wreckage revealed compression buckling and upward and downward bending of both wings. The upward and downward movement, twisting, and flexing of the airplane wing surface was consistent with the occurrence of aerodynamic flutter. In addition, damage was noted on the flap assemblies consistent with over travel. Ultimately both wings failed in down bending. An examination of the engine revealed no anomalies. The accident pilot was experienced in the accident airplane and had built the airplane from a kit.

HISTORY OF FLIGHT On November 6, 2009, at 1005 central standard time, a Zenith Aircraft Company Zodiac 601 XL, experimental light sport airplane, N538CJ, was destroyed when it impacted terrain, following an in-flight breakup near Agnos, Arkansas. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. The sport pilot was fatally injured. The cross country flight departed Sharp County Regional Airport (KCVK), Ash Flat, Arkansas, at 0848. The property owner discovered the wreckage of the accident airplane in his field. There were no known or identified witnesses to the events that led up to the accident flight or impact sequence. Federal Aviation Administration (FAA) radar data was not available for the accident flight. The pilot was not in communications with other pilots or airport ground personnel in the area or air traffic control at the time of the accident. The debris field was scattered over 600 feet on a magnetic bearing of 35 degrees initiating with the right wing assembly which came to rest in a pond. The left wing assembly came to rest forward of the right wing. The left wing spar, left wing fuel tank, various cockpit items, and personal effects were located in the debris field. The fuselage, empennage, engine, and propeller assembly came to rest, inverted, approximately 600 feet from the right wing. There were no ground scars identified between the right wing and the main wreckage that could be associated with the left or right wing, empennage, or fuselage. The wreckage was recovered and relocated to a facility in Clinton, Arkansas, for further examination. PERSONNEL INFORMATION The pilot, age 71, held a sport pilot certificate issued on January 12, 2008. In addition, he held a repairman certificate for light sport aircraft – Zodiac 601 XL, N538CJ. He was issued a third class airman medical certificate/student pilot certificate on July 24, 2007. The medical certificate contained the limitations “holder must wear corrective lenses” and “not valid for any class after May 31, 2008.” The pilot held a valid driver’s license for the state of Illinois. The pilot’s personal flight logbook was located in the vicinity of the main wreckage. The cover and first four pages of the logbook had torn and were not found within the main wreckage or debris field. A review of the logbook indicated that the pilot had logged 116 hours of flight time, of which 77 hours were in the accident airplane make and model. The pilot had logged two hours in the previous 90 days. According to the logbook, the pilot successfully demonstrated the skills required to be proficient for a sport pilot certificate on January 12, 2008. AIRCRAFT INFORMATION According to FAA records, the pilot/owner manufactured the 2007 experimental light sport airplane, a Zenith Zodiac 601 XL (serial number 6-6528). It was registered with an FAA special airworthiness certificate in the category of experimental for light sport operations. Block 8A “Existing Aircraft without an airworthiness certificate & do not meet 103.1” was checked. A Jabiru 3300 engine rated at 120 horsepower at 3,300 rpm powered the airplane. The engine was equipped with a two-blade Sensenich propeller. The airplane registered to and operated by the pilot was maintained under an annual condition inspection program. The maintenance records were not with the airplane wreckage. Several requests were sent to the owner’s estate, requesting that the maintenance records and airplane information, or copies of those records and information be provided to the National Transportation Safety Board (NTSB) for their review. These records were not located by the bank handling the estate. Requests sent to family members were not responded to. FAA records showed that Zenith Aircraft Company manufactured the accident airplane. However, the bill of sale for the airplane showed that it was a kit that had been sold from Zenith Aircraft Company, Mexico, Missouri, and the aircraft manufacturer was listed as “Charles Cummings,” with the Zodiac 601 XL designated as a kit. Following the accident, a representative from Zenair in Canada (also a party to the accident investigation) informed the NTSB investigator-in-charge (IIC) that the accident pilot had previously experienced and reported an encounter with flutter in the accident airplane. The NTSB made contact with the owner of Flight Crafters who was identified as the source of this report. This individual clarified that the pilot had not reported this encounter to him, but rather he had heard of this encounter through other pilots in the area. Multiple attempts were made to locate the individual with whom the pilot had spoken with regarding the flutter event. This report could not be substantiated through first hand information, fact gathering, or interviews. A review of the Experimental Aircraft Association (EAA) safety program records revealed that the owner/builder had not participated in either the EAA Flight Adviser or the EAA Technical Counselor Programs. METEOROLOGICAL INFORMATION The accident site was located between several official weather observation stations. The closest official weather observation station was Batesville Regional Airport (KBVX), Batesville, Arkansas, located 35 nautical miles (nm) south of the accident site. The elevation of the weather observation station was 465 feet mean sea level (msl). The routine aviation weather report (METAR) for KBVX, issued at 1015, reported winds 170 degrees at 10 knots, gusting to 15 knots, visibility 10 statute miles, sky condition few clouds at 3,400 feet, temperature 17 degrees Celsius (C), dew point 04 degrees C, altimeter 30.25 inches of Mercury. The METAR report for Walnut Ridge Regional Airport (KARG), Walnut Ridge, Arkansas, issued at 0955, (located 38 nm east-southeast of the accident site) reported winds 180 degrees at 8 knots, visibility 10 statute miles, sky condition clear, altimeter 30.27 inches of Mercury. Temperature and dew point were not reported. The METAR report for Ozark Regional Airport (KBPK), Mountain Home, Arkansas, issued at 0953 (located 38 nm west of the accident site) reported winds 180 degrees at 8 knots, visibility 9 statute miles, sky condition clear, temperature 18 degrees C, dew point 10 degrees C, altimeter 30.19 inches of Mercury. Two regional pilot reports (PIREPS) issued at 1153 and 1444 reported no turbulence. An Airmen’s Meteorological Information (AIRMET) for moderate turbulence below 8,000 feet was in effect for the accident airplane’s route of flight. There were no Significant Meteorological Information (SIGMETS) active for the area at the time of the accident. In addition to the official weather observation stations, a Department of Interior weather station, designation ESDA4, was located 12 nm south-southwest of the accident site at an elevation of 538 feet. The station reported winds at 179 degrees at 4.33 knots with wind gusts to 10.44 knots. FLIGHT RECORDERS A Garmin GPSMap 296 handheld global positioning system (GPS) unit was located within the wreckage of the accident airplane. The unit was recovered and sent to the NTSB Vehicle Recorders Laboratory in Washington, D.C., for download. Upon arrival at the lab, power was applied to the unit and the recorded waypoint, route, and track log data were successfully downloaded from the unit via the USB port. Eighty-six user defined waypoints, one user defined route, and 118 track logs were downloaded from the unit. This data included date, time, altitude, distance from previous update, time since previous update, average groundspeed since previous update, average course since previous update, and the latitude and longitude at the time of the update. The track log data from the date of the accident started at 08