At what percentage of its original strength is fabric considered unairworthy?

Fabric is considered unairworthy when it has lost a significant amount of strength due to factors such as wear, exposure to environmental elements, and aging. The threshold for declaring fabric unairworthy is set at less than 70% of its original strength. This standard ensures that the fabric can withstand the stresses of flight and maintain structural integrity.

When fabric loses more than 30% of its original strength, it may no longer adequately perform its role in the overall structure of the aircraft, which could lead to safety concerns during operations. Therefore, maintaining fabric above this threshold is critical for ensuring the safety and airworthiness of the aircraft.