Abstract
The Modular Open Systems Approach (MOSA) represents a strategic standardization initiative by the U.S. Department of Defense (DoD). It was adopted to lower risk and accelerate innovation by enabling interoperability between software components. A key focus of MOSA is designing modular interface commonality with the intent to reduce costs and enhance sustainability efforts that are central to the ongoing readiness of defense equipment over its effective lifecycle.
Simulation software used for flight simulation, often face challenges in maintaining adaptability, scalability, and compliance with modern standards, particularly in domains requiring MOSA compliance. In fact, modern flight simulators often rely on legacy simulation software, especially in cases where the underlying systems have demonstrated reliability, accuracy, and proven integration with hardware. It is estimates that 30-50% of modern flight simulators still incorporate legacy software components, particularly in foundational simulation software modules like aerodynamics, avionics, and aircraft system.
This paper presents an approach of redesigning a legacy simulation software package, the Aircraft Survival Equipment (ASE), originally developed in the 1980s, to align with MOSA approach. The redesign work aimed to enhance modularity, maintainability, and interoperability in alignment with MOSA principles, ensuring the system’s continued relevance and extendibility. The process included a thorough analysis of the legacy system to identify its core functionalities and dependencies, followed by the encapsulation of related functions into objects and the application of design patterns to improve system cohesion and reduce coupling. The paper presents the lessons learned from this effort, highlighting the importance of balancing legacy system constraints with modern design objectives. Additionally, the effort underscored the necessity of preserving domain-specific expertise embedded in legacy systems while leveraging modern development paradigms to achieve compliance with evolving standards like MOSA. This work provides a blueprint for similar modernization efforts in simulation systems requiring adaptability and modularity to meet future demands.