Definition
A high-quality, long-staple cotton cloth manufactured to TSO-C15 specifications, historically used as a covering material for fabric-covered aircraft structures. It has a minimum tensile strength of 80 pounds per inch in both warp and fill directions when new, and is applied over the airframe, doped, and finished to form a tight, weather-resistant skin.
Plain English
A strong, aviation-grade cotton cloth used to cover the wings and fuselage of older fabric-covered airplanes. It's stretched over the frame and then treated with chemicals to make it tight and weatherproof.
Context Anchor
Seen in older aircraft maintenance records, restoration work, and discussions of fabric-covered aircraft.
Derivation
"Grade-A" comes from a quality-grading system used in textiles, where Grade-A indicated the highest standard of cotton cloth approved for aircraft use. The grading distinguished it from lower-strength cottons not suitable for flight loads.
Why Pilots Care
Fabric strength is an airworthiness item. As cotton fabric ages, it weakens from sunlight and weather, and once tensile strength drops below the minimum allowed, the aircraft is no longer airworthy until recovered. Pilots flying fabric-covered aircraft need to know what their covering is and how it's tested.
Intuition Check
Do not read “Grade-A” as a casual way of saying “really good.” In this aircraft context, it means the cotton fabric met specific aviation requirements for use as aircraft covering.
Example Sentence 1
The vintage Piper Cub was originally covered with Grade-A cotton fabric, though most surviving examples have since been recovered with modern synthetic materials.
Example Sentence 2
Inspectors require Grade-A Cotton Fabric to meet the specified strength standards before covering proceeds.