N21ZAFlight Design Gmbh CTLS · 2011

The pilot reported that during landing, the airplane encountered a gusting crosswind from the right. The airplane was configured with 0° flaps, and his airspeed was about 55 knots when the airplane was 5ft AGL. He reported that the airplane's airspeed was too slow for the gusting right crosswind conditions, and the airplane landed hard on the runway. The right main landing gear wheel separated from the airplane during the landing, and the airplane exited the runway to the right.

The airplane sustained substantial damage to the right main landing gear attachment points and the cabin's monocoque structure.

The pilot reported that there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation.

The METAR at the airport reported that about the time of the accident, the wind was from 140° at 11 knots, and gusting to 19 knots.

On October 17, 2012, about 1330 eastern daylight time, a Flight Design GMBH model CTLS, N21ZA, sustained substantial damage while landing on runway 25 at the Lorain Couty Airport (LPR), Elyria, Ohio. The flight instructor and student pilot were not injured. The airplane sustained minor damage to the landing gear during the mishap. The aircraft was registered to RAS Aviation LLC, Elyria, Ohio, and operated by Zone Aviation, Elyria, Ohio, under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated at an unconfirmed time.

The flight instructor reported that the flight was a training flight and on the first landing the right main landing gear collapsed. He stated that the landing was "not extraordinarily hard". He went on to add that based on his experience in the same model airplane that the landing should have been well within typical performance of the airplane.

During the investigation it was discovered that this same airplane was involved in a landing accident on July 19, 2012 (CEN12LA676). The July accident also resulted in a fracture of the right main landing gear leg.

The damaged right main landing gear leg from this incident was retained for further examination. The main landing gear leg was made of composite material. The fiber reinforcements used in the composite construction included unidirectional glass fibers, glass fiber fabric, and basalt fiber fabric. Flexible plastic tubes extended the length of the legs enclosed within ribbed plastic tubes located near the leading and trailing edges of the leg. Foam filled space between the plastic tubes and a center internal cavity. The legs were manufactured in a mold with the split line at the leading and trailing edges. During the layup process, layers were placed in a mold half representing the upper half of the leg, and layers were wrapped around the internal tubes, foam, center cavity, and preformed layers. The mold was then closed with a mold piece representing the lower half of the landing gear, and the center internal cavity was pressurized during curing. Examination and sectioning of the landing gear leg showed wrinkling of the fibers resulting in their orientation being angled with relation to the surface rather than parallel to the surface. Additionally several layers terminated at the leading and trailing edges. The location of theses terminating layers corresponded with the location of longitudinal cracks found along the leading and trailing edges of the landing gear.

As a result of the investigation, the manufacturer of the airplane was contacted regarding the landing gear manufacturing process. The landing gear legs were manufactured by a sub-contractor to the airplane manufacturer. The airplane manufacture conducted an audit of the sub-contractor and determined that there were some previous quality issues with regard to mold closing during the manufacture of the landing gear legs. It was reported that the landing gear manufacturer had recognized these issues and had implemented steps to reduce the risk of recurrence of these issues. The airplane manufacturer also conducted a search of part requests and difficulty reports related to the main landing gear. This records search showed 3 occurrences which resulted in complete collapse of the landing gear leg out of a fleet of 370 airplanes. All other reported landing gear leg fractures were discovered either during inspection after a hard landing, or during taxi operation when significantly reduced stiffness was encountered.

On July 19, 2012, about 2200 eastern daylight time, a Flight Design GMBH model CTLS, N21ZA, sustained substantial damage while landing on runway 7 at the Lorain County Airport (LPR), Elyria, Ohio. The private pilot who was the sole occupant was not injured. The airplane sustained damage to the landing gear, engine mount and firewall during the mishap. The aircraft was registered to RAS Aviation LLC, Elyria, Ohio, and operated by Zone Aviation, Elyria, Ohio, under the provisions of 14 Code of Federal Regulations Part 91. The airplane was rented by the pilot for a personal flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated at an unconfirmed time.

The accident was not initially reported to authorities and was discovered while investigating another incident that happened with this airplane. On October 17, 2012, about 1330 the airplane sustained minor damage while landing on runway 25 at LPR (CEN13IA024). In both instances, the right composite landing gear leg fractured.

Regarding the July accident, the pilot reported that he was performing takeoff and landing practice. He performed 3 landings during the daylight and he reported that he was pleased with these landings. After a 45 minute break he took off again to perform night landings to regain night currency requirements. He reported that on the first night landing he misjudged the landing and bounced. He performed a go-around and came back in for another landing. He again misjudged the landing and "bounced hard". The airplane came back down striking the nose wheel. As the airplane came to a stop the pilot realized there was something wrong and upon de-planing, discovered a flat nose tire. He pushed the airplane from the runway and acquired a tow from ramp personnel.

The damaged right main landing gear leg was retained for further examination. The main landing gear leg was made of composite material. The fiber reinforcements used in the composite construction included unidirectional glass fibers, glass fiber fabric, and basalt fiber fabric. Flexible plastic tubes extended the length of the legs enclosed within ribbed plastic tubes located near the leading and trailing edges of the leg. Foam filled space between the plastic tubes and a center internal cavity. The legs were manufactured in a mold with the split line at the leading and trailing edges. During the layup process, layers were placed in a mold half representing the upper half of the leg, and layers were wrapped around the internal tubes, foam, center cavity, and preformed layers. The mold was then closed with a mold piece representing the lower half of the landing gear, and the center internal cavity was pressurized during curing. Examination and sectioning of the landing gear leg showed wrinkling of the fibers resulting in their orientation being angled with relation to the surface rather than parallel to the surface. Additionally several layers terminated at the leading and trailing edges. The location of theses terminating layers corresponded with the location of longitudinal cracks found along the leading and trailing edges of the landing gear.

As a result of the investigation, the manufacturer of the airplane was contacted regarding the landing gear manufacturing process. The landing gear legs were manufactured by a sub-contractor to the airplane manufacturer. The airplane manufacture conducted an audit of the sub-contractor and determined that there were some previous quality issues with regard to mold closing during the manufacture of the landing gear legs. It was reported that the landing gear manufacturer had recognized these issues and had implemented steps to reduce the risk of recurrence of these issues. The airplane manufacturer also conducted a search of part requests and difficulty reports related to the main landing gear. This records search showed 3 occurrences which resulted in complete collapse of the landing gear leg out of a fleet of 370 airplanes. All other reported landing gear leg fractures were discovered either during inspection after a hard landing, or during taxi operation when significantly reduced stiffness was encountered.