Sikorsky Crack Initiation versus Propagation Certification Methodology

Sikorsky has successfully planned and executed several significant aircraft structural certification programs for military aircraft in the past few decades. These certifications included the CH-53K® with NAVAIR, the HH-60W with the Air Force and the Raider X® Competitive Prototype Aircraft with the Army. The methodologies for these certifications addressed the different requirements of each of these branches of the military as well as satisfying emerging techniques for structural life management ("Sikorsky Airframe Full Spectrum Customer/Supplier Collaboration", Reference 1). Safe Life Crack Initiation, Flaw Tolerant (Enhanced) Safe Life Crack Initiation and Fail Safe Life Limit Crack Propagation analysis had been rigorously pursued and demonstrated in these programs. This paper takes a retrospective look at what turns out to be many similarities in these methodologies that previously have been the subject of significant debate in the industry. The combined knowledge of these techniques can lead to reduced cost and schedule based on reuse of similar data from these prior certifications.