How can one determine correct stitching spacing if the original is unknown?

Consulting the chart in AC 43.13-1B is the most reliable method to determine the correct stitching spacing when the original is unknown. AC 43.13-1B provides guidelines and specifications deemed acceptable by the FAA for different fabric and aircraft configurations, ensuring that the stitching meets safety and performance standards. This official document serves as a trusted resource for aircraft maintenance and repair, thereby giving specific recommendations on stitching types and spacing that comply with regulatory requirements.

Using measurements from a similar model could be misleading, as variations in design, size, and type of the aircraft can lead to differences in performance and safety needs. While contacting a certified fabric specialist for recommendations could also provide valuable guidance, relying solely on their expertise without reference to standardized guidelines may not ensure compliance with industry norms. Guessing based on visual estimation lacks precision and is not advisable, as improper stitching can contribute to structural failures or safety issues in the fabric covering of an aircraft.