Establishment and Maintenance of Certification Standards for Helicopter and Turboprop Power Transmission Systems

This paper discusses how the Federal Aviation Administration (FAA) develops qualification/certification safety standards for helicopter and engine turboprop drive systems. The rules are always generated in coordination with industry for a minimum of economic impact, and are worded to promote design innovation while maintaining adequate safety. The rules are periodically updated to account for service experience and advancements in the state-of-the-art. A survey of the applicable Federal Aviation Regulations (FAR's) explains how all safety aspects of a new drive system are covered during the initial certification program. The FAR's also provide for continued airworthiness, as service experience is accumulated, such that inspection intervals may be increased to "on condition," or decreased, if service difficulties indicate that an area of redesign is required. As further testing continues, initial limitations on component replacement times are relaxed until operating costs decrease to a minimum as the design reaches maturity. The FAA role is to assist industry in the promotion of aviation without compromising safety. Finally, a reference to the author's 1969 and 1979 papers on the subject of improving reliability and safety of drive systems is discussed with an update of additional concerns to the 1984 time frame. Some recent problems are listed.