Replacing worn fabric with a different type previously approved by STC is considered what by the FAA?

When it comes to aircraft fabric covering, the FAA categorizes repairs and modifications based on their impact on the aircraft's safety, performance, and structural integrity. Replacing worn fabric with a different type that has been previously approved by a Supplemental Type Certificate (STC) falls under the definition of a major alteration.

This is because the change involves significant modification to the aircraft's structure or systems that could affect the aircraft's airworthiness. Major alterations require a detailed review and approval process to ensure they meet strict safety and performance criteria. The use of an STC indicates that the new fabric type has been evaluated and approved for use, but the mere act of replacing fabric—especially with a different type—means that it is classified as a major alteration. This classification ensures that the necessary checks and balances are adhered to, maintaining safety standards within aviation operations.