How can you determine the correct spacing for rib stitching when the original spacing is unknown?

The correct method for determining the appropriate rib stitching spacing when the original specification is unknown is to refer to the chart in the AC 43.13-1B. This document is a widely accepted source of information for aircraft maintenance and repair practices within the aviation industry. It includes detailed guidelines, standards, and best practices established by the FAA, ensuring that the maintenance performed adheres to safety and performance standards.

Utilizing this resource allows you to ensure that the stitching is done according to industry standards and enhances the structural integrity of the aircraft. The charts offer specific measurements and guidelines based on type and design, making it a reliable source for maintaining consistency and safety throughout the aircraft structure.

While contacting the manufacturer for specifications could be helpful, not all manufacturers may be accessible or may not have the exact details readily available. Measuring spacing on a similar aircraft may introduce variability that is not in line with the specific design and performance needs of the aircraft in question. Estimating based on visual appearance lacks objectivity and may lead to inappropriate spacing, potentially compromising the structural integrity of the airframe. Thus, relying on the guidelines provided in the AC 43.13-1B is the most accurate and reliable approach.