Guidelines for Writing IVHM Requirements for Aerospace Systems
This Aerospace Recommended Practice (ARP) provides guidance on developing requirements for systems that include Integrated Vehicle Health Management (IVHM) capability [REF1], [REF18]. IVHM is increasingly being implemented on military and commercial aircraft. Some examples include the F-35 Joint Strike Fighter (JSF) [REF1] and the AH-64 Apache [REF3] in the military domain, and the B787 [REF4] and A350XWB [REF5] in the commercial domain. This document provides a systematic approach for developing requirements related to the IVHM capabilities of a vehicle system. This document is not intended to repeat general guidelines on good requirements writing [REF13], [REF20]. Instead, the focus is on the unique elements, which need to be considered for IVHM and the resulting specific guidelines that will help define better requirements and hence better systems. The multi-faceted nature of IVHM should include the process of requirements gathering. Therefore, this document presents some guidance on how to go about this task. The document also includes some case studies that illustrate, in a practical manner, what a good set of IVHM requirements might look like. These have been taken from real life examples, but have been generalized for the purpose of this ARP.
Section 3 of this ARP introduces the general requirements and considerations from the perspective of various stakeholders. This is followed by Section 4 describing the entire systems engineering process for IVHM systems showing how IVHM requirements are linked to other systems engineering elements, such as the verification and validation (V&V) process. Section 5 provides a detailed description of the requirements breakdown structure and writing process, including the taxonomy of a requirements document. Section 6 provides some examples of IVHM core (stakeholder) requirements for representative air vehicles, and Section 7 provides an application of the guidelines as an example.
The term Integrated Vehicle Health Management (IVHM) encompasses a set of capabilities that enable efficient sustainable operation and maintenance of components and subsystems within aerospace platforms. It is defined as “the unified capability of a system of systems to assess current or future state of member system health and integrate that picture of system health within a framework of resources and operational demand” [REF1]. Currently, there is little guidance addressing the development of IVHM system requirements. Current practitioners use knowledge developed exclusively through practical experience rather than following an established process. Systems with IVHM capability have unique challenges, which require a designer to look beyond their own field of expertise and consider the constraints and specifications of other interlinked systems. This Aerospace Recommended Practice provides working engineers and program managers overall guidance on all the elements of IVHM they need to consider when developing design requirements for a particular IVHM system.