What is the maximum permissible deterioration of aircraft fabric before it is considered unworthy?

The maximum permissible deterioration of aircraft fabric is considered to be 30%. This standard is set to ensure the safety and integrity of the aircraft's structure. When the fabric of an aircraft deteriorates beyond this threshold, it may no longer provide the necessary support and protection, thereby compromising the safety of the aircraft. This is particularly critical because fabric coverings are designed to maintain aerodynamic properties and structural strength.

Fabric deterioration can occur due to various factors, such as exposure to UV light, moisture, and environmental conditions, which can weaken the material over time. Maintenance protocols require regularly checking the fabric for signs of wear, and if the deterioration exceeds 30%, it necessitates replacement or repair to uphold safety standards.

This percentage is standardized to ensure consistency among maintenance practices and helps maintenance personnel to make informed decisions regarding the airworthiness of an aircraft's fabric covering.