Here's the issue: Suppose you want to refurbish the interior of your FAA-certificated light plane with new carpet and upholstery. Further suppose that you have found a reputable auto upholstery shop that does great work and will reupholster your seats and cut you new carpets if you bring the stuff to them. What does the FAA have to say about the materials you or the shop uses?
This is a companion discussion topic for the original entry at https://www.avweb.com/features_old/interiors-legalities-and-part-91-aircraft