1.5.3 Implementation
The State of the Operator, should ensure that the ICA is being followed by the operator and its maintenance organization.
1.6 Certification maintenance requirements and airworthiness limitations
1.6.1 Introduction
1.6.1.1 Annex 8 places an obligation on States of Design to ensure that information is provided for use in developing procedures for maintaining the aircraft in an airworthy condition. It requires that mandatory maintenance requirements that have been specified by the State of Design as part of the approval of the type design shall be identified as such.
1.6.1.2 Where the maintenance tasks result from a system safety analysis, they are usually known as certification maintenance requirements (CMRs). A CMR is a required periodic task, established during the design certification of the aircraft as an operating limitation of the Type Certificate. Notwithstanding the importance of the other airworthiness limitations, this chapter is primarily intended to provide an introduction to the concept of CMRs, their relevance to an aircraft maintenance programme and their importance as an integral part of the in-service validation of the type design. It is not intended for this chapter to provide comprehensive guidance on the responsibilities associated with the organizations responsible for the type design.
1.6.1.3 It should be noted that some CMRs require the performance of certain flight crew procedures. When included in a CMR, these procedures are mandatory and should be shown as such in the flight manual or equivalent document. It is likely that future design developments will limit the use of CMR to maintenance tasks.
1.6.2 Background information for helicopters
1.6.2.1 Helicopter type designs are unique in comparison to aeroplane designs in that transmissions, rotors, and some elements of the flight control systems have critical components that may be adversely affected by operating conditions and time in service, cycle, and retirement index number (RIN) exposure.
1.6.2.2 The instructions for continued airworthiness (ICA) mandate airworthiness limitations and maintenance instructions for helicopters. ICAs contain airworthiness limitations (structural life limits associated with fatigue requirements for helicopter structures), maintenance provisions, and allow for CMRs. In addition, helicopters systems are increasingly complex and are capable of performing more safety-critical functions. CMRs for helicopters, while not traditionally included in ICAs, may be needed in order to detect and rectify possible hidden (latent) failures.
1.6.2.3 For a number of years, helicopter systems were evaluated to specific requirements, to the single fault criterion, or to the fail-safe design concept.
1.6.2.4 As more demanding helicopter operating environments evolved, more safety-critical functions were required to be performed which generally resulted in an increase in the complexity of the system designed to perform these functions. The potential hazards to the helicopter and its occupants that could arise in the event of loss of one or more functions provided by a system, or the effect of that system’s malfunction, had to be considered, as did the interaction between systems performing different functions.
Note.— The guidance provided in the following paragraphs for aeroplanes should be adapted, as appropriate, for helicopters. The airline/manufacturer maintenance programme plan document described below was targeted for aeroplanes. However, elements from the programme plan document can also be used for helicopters, adjusting the procedures as appropriate to account for the differences between the two products.
1.6.3 Background
1.6.3.1 For a number of years, aeroplane systems were evaluated to specific requirements, to the single fault criterion, or to the fail-safe design concept.
1.6.3.2 As later generation aeroplanes evolved, more safety-critical functions were required to be performed which generally resulted in an increase in the complexity of the system designed to perform these functions. The potential hazards to the aeroplane and its occupants that could arise in the event of loss of one or more functions provided by a system, or the effect of that system’s malfunction, had to be considered, as did the interaction between systems performing different functions.
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