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

Fabric on an aircraft is typically considered unairworthy when it has lost a certain percentage of its original strength. When the strength of the fabric decreases to 70% of its original condition, it is deemed unsafe for continued use in aviation. This standard is crucial because the structural integrity of the fabric affects the overall safety and performance of the aircraft.

Fabric strength is a critical factor in ensuring that the aircraft can withstand the stresses of flight. Therefore, if the fabric has worn and degraded to below this threshold, it cannot function effectively, leading to potential failures during operation. The 70% mark serves as a reliability indicator, ensuring that the fabric maintains sufficient strength to meet safety requirements.

This threshold aligns with industry standards and practices in maintaining aircraft, emphasizing the importance of regular inspections and fabric testing.