NYC08FA158

After stopping for fuel, the pilot departed for the second leg of a cross-country flight. About 45 minutes after departing, witnesses observed the special light sport airplane banking and yawing before one of its wings "folded up" and the airplane descended to the ground. Examination of the wreckage revealed that the left wing had failed in an upward (or positive) direction due to a fracture of the lower left wing spar chord. The subsequent overload failure of the wing resulted in a loss of control of the airplane. Metallurgical examination did not reveal any evidence of preexisting conditions or design or material deficiencies that may have contributed to the in-flight structural failure.

On April 7, 2008 at 1701 eastern daylight time, a Czech Aircraft Works SPOL SRO CH 601 XL RTF, N357DT, was substantially damaged when it impacted trees and terrain following an uncontrolled descent near Polk City, Florida. The certificated private pilot/owner was fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the flight which departed Williston Municipal Airport (X60), Williston, Florida and was destined for Lakeland Linder Regional Airport (LAL), Lakeland, Florida. The personal flight was conducted under 14 Code of Federal Regulations Part 91.

According to a friend of the accident pilot, they both shared a hangar at Lumpkin County Airport (9A0) in Dahlonega, Georgia, and they planned to fly their respective airplanes to an air show in Lakeland, Florida. The accident pilot departed 9A0 about 1240, and the friend departed about 1300. During the flight the friend passed the accident pilot, landed at X60 for a planned fuel stop, and subsequently departed. He last spoke to the accident pilot about 1500, as the accident pilot approached X60. The accident pilot planned to land about 1530, and stated that his airplane was "running fine."

Review of fuel receipts revealed that the pilot purchased fuel in X60 at 1607.

According to Federal Aviation Administration (FAA) radar data, a radar target correlated to be the accident airplane departed Williston at 1614, and proceeded southeast. The radar target transmitted a transponder code of 1200, but did not transmit any altitude data. About 1620, transmissions from the target transponder ceased, and only primary radar returns were observed. The radar target continued southeast before turning south, and the final radar target was observed at 1701 in the vicinity of where the wreckage came to rest.

About 1700, a witness, located about 1/2-mile southeast of the accident site, observed the accident airplane as it approached him from the north. He noted that the airplane was noticeably lower than other airplanes that generally flew in the area, and that it was in a 3- to 5-degree left bank. The airplane then banked right, about the same magnitude, before it returned level for a moment. About 1 to 3 seconds later, the airplane banked to the left and to the right, significantly steeper than during the previous banks.

After returning to level flight, the airplane yawed to the right, and the right wing "folded up." The airplane banked to the right and the left wing "went up" just before the airplane entered a nose dive. The witness described that the wings of the airplane looked perpendicular to their normal position, and that the engine sound changed, as the airplane descended downward. The witness heard the sound of the engine pitch change to the point where it sounded like the engine "over sped" as the airplane descended. He lost sight of the airplane shortly thereafter as it descended behind a building.

Another witness, located about 1/3-mile west of the accident site, stated that he heard a "pop" and that when he looked up he saw the accident airplane. He described that the right wing was folded "back and to the side," and that the accident airplane was spinning as it descended. About 8 to 10 seconds later he heard the sounds of an impact.

Meteorological information

The weather conditions reported at LAL, located about 17 miles southwest of the accident site, at 1658, included winds from 030 degrees at 4 knots, 15 statute miles visibility, scattered clouds at 3,000 feet, broken clouds at 25,000 feet, a temperature of 27 degrees Celsius (C), a dewpoint of 16 degrees C, and an altimeter setting of 29.90 inches of mercury.

Personnel information

The pilot held a private pilot certificate with a rating for airplane single engine land. His most recent FAA second class medical certificate was issued on February 29, 1980. Examination of the pilot's logbook revealed that he had accumulated 514 total hours of flight experience, 71 hours of which were in the accident airplane make and model. According to the pilot's friend, the pilot originally obtained a pilot certificate in the 1970's, and had recently began flying again after purchasing the accident airplane in October 2007.

Aircraft information

The accident airplane was manufactured in 2005 and was classified by the FAA as a Special Light Sport Aircraft. According to maintenance records, the airplane was factory test flown on June 16, 2005. The airplane's most recent annual conditional inspection was completed on September 1, 2007. At the time of the inspection, the airplane had accumulated 142 total hours of operation.

Wreckage and impact information

The airplane came to rest in a heavily wooded area and exhibited various degrees of damage throughout. The trees in and around the accident site had been removed to facilitate access to the wreckage. There was no evidence of either pre or post-impact fire. No evidence or any patterns like those typically associated with a moving in-flight fire were identified. No soot patterns were identified. No melted or splattered aluminum was observed on any of the structure.

The entire fuselage, less the canopy, was located at the main wreckage site. The forward fuselage was buried in a 6-foot deep crater, and the remainder of the fuselage aft of the firewall was protruding from the ground at about a 45 degree angle. The fuselage forward of the firewall was completely destroyed by impact forces. The fuselage aft of the firewall displayed evidence of impact damage and skin wrinkling. The upper left hand side of the fuselage in the area just below the canopy exhibited black transfer marks. The marks were in a 5 inch by 5 inch area. The area extended from about 5 inches below the canopy to about 5 inches forward of a fuselage rivet line beginning at the flap actuation mechanism. The canopy was not recovered, and only several small fragments of the canopy were located at the impact site.

The left and right wings were independent of each other, and joined to a spar carry through structure in the center fuselage, just forward of the main landing gear. Both the left and right wings remained attached to the fuselage. The left wing was bent 90 degrees up at the side of body and was resting on the fuselage. The left lower spar chord, where the left wing attaches to the spar carry through, was fractured and bent upward about 20 inches outboard of butt line zero outboard of the three AN5-15A airframe bolts.

All of the bolts remained attached and were recovered, but the bolt hole at the location of the fracture was deformed out of round. The chord pieces were both fractured vertically through the third hole, outboard of the manufactured edge. The fractures exhibited significant elongation and through the thickness yielding consistent with overstress separations. Deformation at the fractures was indicative of upward bending of the left wing tip. The rivets connecting the two pieces of the left wing lower spar chord were sheared. The left hand upper spar chords were bent upwards at about a 90 degree angle about 7 inches from the inboard end of the outboard spar chord at the 6th fastener hole. The upper spar chord was also bent aft at the 13th fastener hole from the inboard end of the outboard spar chord. The left hand rear spar attachment was fractured and bent aftward and the attachment bolt remained attached to the wing structure.

The right wing was intact, and all of the spar carry through structure remained attached (3 upper and 3 lower bolts) along with the rear spar to fuselage attachment bolt. The right hand side of the wing displayed impact damage and was bent forward, about 60 inches outboard of the fuselage at the flap to aileron intersection. All of the fracture surfaces examined exhibited features consistent with static overload with no evidence of metal fatigue.

The horizontal stabilizer, elevator and rudder remained attached to the fus