Accident Overview
On October 17, 2012, at approximately 1330 eastern daylight time, a Flight Design GMBH CTLS, registration N21ZA, experienced a collapse of the right main landing gear while landing on runway 25 at Lorain County Airport (LPR) in Elyria, Ohio. The aircraft was being operated under 14 Code of Federal Regulations Part 91 as an instructional flight, with a flight instructor and a student pilot on board. Neither occupant was injured. The airplane sustained substantial damage, though the landing gear itself was described as having minor damage. Visual meteorological conditions prevailed, and no flight plan was filed.
Landing and Previous Incident
The flight instructor reported that the landing was "not extraordinarily hard" and, based on his experience in the same aircraft model, should have been within typical performance parameters. This was the second landing gear failure for this particular aircraft; it had previously been involved in a landing accident on July 19, 2012 (CEN12LA676) that also resulted in a fracture of the right main landing gear leg.
Examination of the Landing Gear Leg
The damaged right main landing gear leg was retained for detailed examination. The leg was constructed from composite materials including unidirectional glass fibers, glass fiber fabric, and basalt fiber fabric. Flexible plastic tubes ran the length of the leg, enclosed within ribbed plastic tubes near the leading and trailing edges, with foam filling the space between the tubes and a center internal cavity. The legs were manufactured in a mold with a split line at the leading and trailing edges. Sectioning of the leg revealed wrinkling of fibers, causing their orientation to be angled relative to the surface rather than parallel. Additionally, several layers terminated at the leading and trailing edges, and these termination points corresponded with longitudinal cracks found along those edges.
Manufacturing Quality Issues
As part of the investigation, the aircraft manufacturer contacted the sub-contractor responsible for producing the landing gear legs. An audit by the aircraft manufacturer identified previous quality issues related to the mold closing process during manufacture. The landing gear manufacturer had acknowledged these issues and had implemented corrective steps to reduce the risk of recurrence. A search of part requests and difficulty reports concerning the main landing gear, across a fleet of 370 aircraft, found three occurrences that resulted in complete collapse of the landing gear leg. All other reported fractures were discovered during inspections after hard landings or during taxi when reduced stiffness was detected.