Since the Airbus A310/300 vertical tail entered serial production in 1985, the composite ratio in the aircraft structures has continuously increased to reach around 50% today with the A350XWB and the B787. As far as rulemaking dedicated to composite structures is concerned, an intense activity took place in the early 80's which ended up with just a composite dedicated Advisory Circular, the AC 20 107A in 1984, never updated since then. Meanwhile, the 25.571 Fatigue and Damage Tolerance regulatory paragraph continued to evolve, on the basis of the lessons learned with metallic structures only, without any input coming from the composite community and without the need for a composite dedicated additional regulatory paragraph would be deemed necessary. Unlike transport category aircraft (Part 25), the need for such a dedicated Fatigue and Damage Tolerance rule was identified for small aircraft category (Part 23) and a new paragraph 23-573 incorporated in 1993 while, for rotorcraft, new 27.573 and 29.573 regulatory paragraphs are expected soon. Nevertheless, the way "Part 25" composite structures have been substantiated so far to meet such 'metal minded' 25.571 regulatory paragraph has been continuously evolving. This paper will present, from the beginning, the various philosophies and means of compliance that have been successively applied with their rationale and will end with possible trends for the future. The presentation is based on the experience of the Author who has been contributing to the certification of a majority of these composite structure applications in Europe, as Assistant Specialist for composite structures to the French DGAC, the JAA, and the EASA Certification Agency.
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