N930SAFlight Design Gmbh CTLS · 2008

On July 25, 2012, at 0930 central daylight time, a Flight Design GmbH model CTLS light-sport airplane, N930SA, was substantially damaged while landing at Dennis F Cantrell Field Airport (CWS), Conway, Arkansas. The commercial pilot and passenger were not injured. The airplane was registered to and operated by Sparrow Aviation Group, LLC, under the provisions of 14 Code of Federal Regulations Part 91, without a flight plan. Day visual meteorological conditions prevailed for the personal flight that originated from Searcy Municipal Airport (SRC), Searcy, Arkansas, about 0900.The pilot reported that after completing an uneventful straight-in approach to runway 26 (4,875 feet by 100 feet, asphalt) the right main landing gear collapsed upon touchdown. The airplane subsequently swerved to the right, departing off the right side of the runway. The airplane came to a stop aligned about 180-degrees from the original runway heading. The fuselage, firewall, empennage, and right wing were substantially damaged during the accident sequence.

The closest aviation weather reporting facility was located at Little Rock Air Force Base (LRF), about 17 miles southeast of the accident site. At 0955, the LRF automated surface observing system reported the following weather conditions: wind 220 degrees at 10 knots, gusting 16 knots; surface visibility 10 miles; sky clear; temperature 33 degrees Celsius; dew point 21 degrees Celsius; and an altimeter setting of 29.97 inches of mercury.

The accident airplane, serial number 08-02-05, was manufactured by Flight Design GmbH of Leinfelden-Echterdingen, Germany, and then was imported into the United States by Airtime Aviation Inc. of Tulsa, Oklahoma. The light-sport airplane obtained a special airworthiness certificate from the Federal Aviation Administration on May 24, 2008. The airplane was subsequently sold to the owner-of-record on June 4, 2008. When the accident occurred, the airplane had accumulated 1,149.9 hours since new. A review of the available maintenance information established that the main landing gear legs had never been repaired or replaced. On December 2, 2011, at 1,025 hours total service time, the fuselage structure was reinforced in the landing gear attachment area per Flight Design GmbH Service Instruction SI-ASTM-CTLS-07.

The main landing gear legs were sent to the National Transportation Safety Board's (NTSB) Materials Laboratory Division for examination. The right main landing gear leg had a longitudinal crack along the leading edge and a transverse fracture near the point where the leg intersected the fuselage. The left main landing gear leg remained intact. The NTSB laboratory examination confirmed that the fiber reinforcements used in the composite construction included unidirectional glass fibers, glass fiber fabric, basalt fiber fabric, and basalt/aramid fiber fabric. According the airplane manufacturer, the landing gear was designed in accordance with ASTM Standard F2245-06 (Standard Specification for Design and Performance of a Light Sport Airplane) and compliance with the standard was shown through a series of drop tests.

The upper surface of the right leg was bent upward in the area between the fracture and the fuselage intersection. Fiber pullout was observed and was greatest at the lower side of the transverse fracture. Additionally, parallel transverse cracks were observed in the paint adjacent to the fracture and were consistent with a bending load with the lower surface in tension and the upper surface in compression.

A longitudinal crack was observed at the leading edge of the right main landing gear. A step in the transverse fracture occurred where the transverse fracture intersected the longitudinal crack. The longitudinal crack had a jagged appearance. Parallel cracks in the paint were observed emanating from the longitudinal crack and were consistent with shear stress where the outboard end was loaded upward relative to the inboard end. Additional examination of the landing gear construction revealed a cross-section that was consistent with the specified manufacturing layup with the exception of an additional layer each of 0/90-degree glass fabric, 45-degree basalt fabric, and 0-degree glass fiber bundles. No preexisting damage or manufacturing anomalies were noted with the right main landing gear that would have reduced its design strength.