# NTSB CEN13IA024: Flight Design Ctls, N21ZA, Elyria, OH, October 17, 2012 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: October 17, 2012, 13:30 local (17:30 UTC) - Place: Elyria, OH - Coordinates: 41.344165, -82.17778 - Nearby events: https://openairdocs.org/map.md?lat=41.3442&lon=-82.1778&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 15, 2014 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA-Cleveland FSDO - NTSB case key (mKey): 85401 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN13IA024 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/85401/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=85401 - Page: https://openairdocs.org/ntsb/CEN13IA024 ## Probable cause The manufacturing defects in the main landing gear leg, which resulted in its eventual failure. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Flight Design CTLS, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=060005B), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Manufacture/production: equipment manufacture](https://openairdocs.org/ntsb-findings/04013010): Organizational issues › Development · Manufacturer (probable cause); cases with it: [Flight Design CTLS, 2 cases](https://openairdocs.org/ntsb-findings/04013010/cases.md?model=060005B), [All aircraft, 36 cases](https://openairdocs.org/ntsb-findings/04013010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Flight Design CTLS, 8 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=060005B), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis The flight instructor reported that the airplane's fixed right main landing gear collapsed during landing. He reported that the landing was "not extraordinarily hard" and that it should have been well within the airplane's typical performance. Postincident examination of the composite right main landing gear leg revealed several manufacturing defects, including wrinkled layers and layers that terminated at the surface when they should have been continuous, which reduced the landing gear leg's strength and its ability to resist longitudinal cracks. As a result of this investigation, the airplane manufacturer conducted an audit of the subcontractor that manufactured the landing gear legs. The audit revealed that, before the incident, the landing gear manufacturer had become aware of quality issues related to the mold closing process of the landing gear legs during manufacture and had implemented steps to reduce the recurrence of these issues. Based on the available evidence, the manufacturing defects in the composite main landing gear leg likely reduced the leg's load-carrying capacity and resulted in its eventual failure. ## Factual narrative 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 tomold 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. ## Aircraft - Registration: [N21ZA](https://openairdocs.org/aircraft/N21ZA), registered now, S/N F-10-09-04, built 2011 (OpenAirDocs) - Reported make and model: FLIGHT DESIGN CTLS - Registry model: [Flight Design CTLS](https://openairdocs.org/model/flight-design-ctls) (registry code 060005B) (OpenAirDocs) - Registry engine: [Rotax 912ULS series](https://openairdocs.org/engine/rotax-912uls-series) (registry code 55572, 4 cycle) (OpenAirDocs) - Category: Airplane - Serial number: F-10-09-04 - Engines: ROTAX 912 100 horsepower reciprocating - Damage: Minor damage - Flight: Instructional, Part 91 - Operator: Zone Aviation, doing business as Zone Aviation - Registered owner: RAS Aviation LLC - Airworthiness certificate: Special, Special light-sport (Special) - Departed: LPR, Elyria, OH - Destination: LPR, Elyria, OH - Airport: LPR, Lorain County Regional Airport, runway 25, 5,002 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 38; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: right; flight hours: 910 total, 425 in this make and model, 135 in the last 90 days - Student pilot; age 23; injuries: none; student; medical: class 3, without waivers/limitations; seat: left; flight hours: 30 total, 30 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 9 knots - Visibility: 8 statute miles - Lowest ceiling: 9,000 ft overcast - Temperature: 64 °F, dew point 46 °F - Altimeter: 29.77 inHg - Observed at: LPR ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20121017023889I](https://openairdocs.org/incident/20121017023889I), Oct 17, 2012: Flight Design Gmbh CTLS, Elyria, OH, Minor damage. The right main landing gear strut failed shortly after touchdown. This is a fixed gear aircraft. The aircraft, including the landing gear strut is made of… ## Other investigations on N21ZA (2) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB GAA19CA049](https://openairdocs.org/ntsb/GAA19CA049), Nov 4, 2018: Flight Design Ctls (N21ZA), Elyria, OH, substantial damage. Probable cause: The pilot's failure to maintain adequate airspeed during landing in variable gusting crosswind conditions, which resulted in a hard landing and runway excursion. - [NTSB CEN12LA676](https://openairdocs.org/ntsb/CEN12LA676), Jul 20, 2012: Flight Design Ctls (N21ZA), Elyria, OH, substantial damage. Probable cause: The pilot’s misjudged landing flare, which resulted in a hard landing. ## Docket (2 files) The files NTSB released with the investigation on October 27, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=85401. 1.8 MB in all. - Materials Laboratory 15 - Factual Report 13-009 (with images) (item 1, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40386035&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2013-009%20(with%20images)-Master.PDF - Evidence Control Form (item 2, .PDF, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40418220&FileExtension=.PDF&FileName=Evidence%20Control%20Form-Redacted.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.