What happened
A private pilot reported performing a hard landing on a paved runway in a Piper Cub equipped with tundra tires. During the landing, the aircraft struck the runway on its tail wheel, which subsequently caused the left main landing gear assembly to collapse. The impact resulted in structural damage to the left wing of the aircraft. There were no injuries reported.
The investigation
An inspection of the main landing gear assembly was conducted by the NTSB investigator-in-charge and FAA certification engineers. The investigation revealed that the landing gear assembly used was not an approved component, despite being stamped with "PMA" (Parts Manufacturer Approval) to indicate it was an authorized part.
Further analysis of the gear assembly determined that the component had fractured at the shock strut attachment lugs. The investigation found that these lugs possessed only approximately one-half the strength of the original factory equipment. This specific landing gear assembly has been available for several years and is capable of being retrofitted to all aircraft in the Piper Cub series.
Findings
The investigation concluded that the failure was due to the use of a substandard landing gear component that lacked the necessary structural strength at the shock strut attachment lugs. Following the discovery, the FAA aircraft certification branch and the manufacturer initiated a design review. The manufacturer indicated plans to publish a Service Bulletin for a strengthened version of the gear, while the FAA planned to issue either a Special Airworthiness Information Bulletin or an Airworthiness Directive.