Which of the following fibers is NOT a synthetic fiber used in aircraft covering?

Cotton is the correct answer because it is a natural fiber rather than a synthetic one. Synthetic fibers are man-made and typically derived from chemical processes, resulting in materials that have specific performance characteristics suited for aviation applications.

Nylon, Orlon, and Dacron are all examples of synthetic fibers. Nylon is known for its strength and elasticity, making it suitable for various applications in aircraft covering. Orlon, which is a brand name for acrylic fibers, is used for its durability and resistance to sunlight. Dacron, a type of polyester fiber, is favored for its moisture resistance and is commonly used in aircraft coverings due to its stability and low shrinkage characteristics.

Cotton, on the other hand, while it has been used historically in aircraft covering, does not fall under the category of synthetic fibers. Instead, it is a natural fiber that can absorb moisture and is less resilient than synthetic options, which makes it less desirable in modern aircraft applications.