This Master’s Thesis has been developed within the Leonardo S.p.a. - Helicopters Division - Military Airworthiness Office - Technical Department - located in Cascina Costa di Samarate, Varese, Italy, with the support of the Head of Military Airworthiness. The work presented through this Thesis has been part of an Intern with the aim to develop a Certification Manual for the Company. While the whole Certification Process for Civil Helicopters is ruled by Certification Criteria, made up by the main Authorities such as European Union Aviation Safety Agency (EASA) in Europe and Federal Aviation Administration (FAA) in the United States of America, in the current Military Airworthiness each EU State is responsible through their own regulations of their Military Rotorcraft, owning their unique National Regulations.