SAE ARP7122

The process detailed within this document is generic and applies to the entire end-to-end health management capability, covering both on-board and on-ground elements in both commercial and military applications throughout their life cycle. While some guidance related to usage of ground-based health management equipment for airworthiness credit exists in certain areas, this document provides a general mechanism to ensure a level of integrity commensurate with the potential aircraft-level consequences of the relevant failure conditions. The practical application of this standardized process is detailed in the form of a checklist. In order to provide some detailed guidance utilizing the process and checklist, some high-level examples of successful cases of approved “Maintenance Credit” applications for airworthiness credit (and one case where the approval is in process in 2024) are included. This document does not teach how to design an IVHM function, how to do a safety or risk analysis, prescribe hardware or software assurance levels, or answer the question, “How much mitigation and evidence are enough?” The criticality level and mitigation methods will be determined between the applicant and the regulator, using existing guidance from SAE International and other sources. Note that the focus of this document is to ensure appropriate process integrity for the creation of a candidate IVHM function, but it may not address all the elements required to operationalize that function. This document uses the term IVHM to refer to any health management function applied to an air vehicle. The SAE standards committees have been using this term for decades; however, other communities within this industry have used terms such as Aircraft Health Management or Monitoring (AHM), Integrated Aircraft Health Management (IAHM), Vehicle Health Management (VHM), and Rotorcraft Health and Usage Monitoring System (HUMS) to refer to the same concept. At the subsystem level, terms such as Structural Health Monitoring (SHM), Equipment Health Management (EHM), Engine Condition Monitoring (ECM), and Engine Health Management (EHM) are also commonly used. It should be understood that all these terms refer to the same function. There are cases where this process is applicable but is not required because of historic precedents. For example, there is a historical precedent for using an off-board health management solution to achieve compliance with extended-range twin-engine operations performance standards (ETOPS) (refer to AC 120-42A). Regulatory approval has been provided to some engine and aircraft Original Equipment Manufacturers (OEMs) to allow the use of health management functionality to comply with Airworthiness Directives (AD), extend inspection intervals, comply with MSG guidance, or more effectively utilize component lives to optimize “their service life.” This document has been written to provide a consistent approach for obtaining approval to use aerospace Integrated Vehicle Health Management (IVHM) systems for airworthiness credit. The objective of this SAE Aerospace Recommended Practice (ARP) is to help applicants prepare the materials needed for regulators to carry out assessments of the merits of an airworthiness credit application with a view to provide approval. Given that many specifics related to this topic are still evolving, the initial version of this document provides high-level steps for ensuring adequate integrity of a health management function. The intent is to identify gaps in guidance in a companion “statement of concerns” document, which will then be used to inform future improvements to this document as industry consensus evolves. This document was originally derived from ARP5987, which was published by the SAE E-32 (Propulsion Systems Health Management) standards committee. In response to a request from the Airlines for America (A4A) Maintenance Programs Industry Group (MPIG), SAE agreed that the HM-1 (Integrated Vehicle Health Management) standards committee would publish an equivalent document at the aircraft level rather than focus on the engine level. One of the objectives of this aircraft-level document is to provide the International Maintenance Review Board Policy Board (IMRBPB) with information on industry experience as the policy board works to harmonize guidance related to health management for airworthiness credit. HM-1 and E-32 then agreed to retire ARP5987 and establish joint ownership of the vehicle-level document: ARP7122. These two committees will maintain a joint working group to define the strategy and content for future revisions.

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