Maintainability is the ease with which a product can be maintained in order to isolate defects or their cause, correct defects or their cause, meet new requirements, make future maintenance easier, or cope with a changed environment. The design emphasis on maintainability is to reduce the maintenance burden and Supply Chain by reducing the time, personnel, tools, test equipment, training, facilities and cost to maintain the system. Maintainability and Reliability work together is developing design solutions for a system. One of the exit criteria of the Engineering, Manufacturing and Development (EMD) phase is demonstrating reliability, availability, maintainability, and sustainment features are included in the design of a system. [1,2]
Maintainability engineering includes the activities, methods, and practices used to design minimal system maintenance requirements (designing out unnecessary and inefficient processes) and associated costs for preventive and corrective maintenance as well as servicing or calibration activities. 
In DoD acquisitions, the primary objective of developing maintainability and reliability requirements for a system is to reduce the time it takes for a properly trained maintainer to detect and isolate failures and affect repair. Maintainability requirements are include in the Initial Capabilities Document (ICD) and Capabilities Development Document (CDD) and flowed down to the system specification. Intrinsic factors contributing to maintainability are: 
- Modularity: Packaging of components such that they can be repaired via remove and replace action vs. on-board repair. Care should be taken not to “over modularize” and trade-offs to evaluate replacement, transportation, and repair costs should be accomplished to determine the most cost effective approach.
- Interoperability: The compatibility of components with standard interface protocols to facilitate rapid repair and enhancement/upgrade through black box technology using common interfaces. Physical interfaces should be designed so that mating between components can only happen correctly.
- Physical accessibility: The designed-in structural assurance that components requiring more frequent monitoring, checkout, and maintenance can be easily accessed. This is especially important in Low Observable platforms. Maintenance points should be directly visible and accessible to maintainers, including access for corrosion inspection and mitigation.
- Designs that require minimum preventative maintenance including corrosion prevention and mitigation. Emphasis should be on balancing the maintenance requirement over the life cycle with minimal user workload.
- Embedded training and testing, with a preference for approved DoD Automatic Test Systems (ATS) Families when it is determined to be the optimal solution from a Total Cost and Materiel Availability perspective.
- Human Systems Integration (HSI) to optimize total system performance and minimize life-cycle costs. This includes all HSI domains (Manpower, Personnel, Training, Human Factors Engineering, Environment, Safety, Occupational Health, Survivability, and Habitability) to design systems and incorporate technologies that require minimal manpower, provide effective training, can be operated and maintained by users, are suitable (habitable and safe with minimal environmental and occupational health hazards), and survivable (for both the crew and the equipment).
The DoD Reliability Availability and Maintainability (RAM) Guide provides a structure, references, and resources to aide in implementing a sound strategy.
The Reliability, Availability, Maintainability & Cost (RAM-C) Rationale Report Manual provides guidance in how to develop and document realistic sustainment Key Performance Parameters (KPP) and Key System Attributes (KSA) requirements with their related supporting rationale; measure and test the requirements; and manage the processes to ensure key Stakeholders are involved when developing the sustainment requirements.
- Maintainability should be a designed-in capability and not an add on option because good maintenance procedures cannot overcome poor system and equipment maintainability design. 
AcqLinks and References:
-  Defense Acquisition Guidebook (DAG) – Chapter 5
- Mil-Handbook 502 “DoD Handbook Acquisition Logistics” – 30 May 1997
- DoD Reliability Availability and Maintainability (RAM) Guide
- The Reliability, Availability, Maintainability & Cost (RAM-C) Rationale Report Manual
- Reliability – A look at Four Decades of Reform within the DoD by Larry Crow PhD
-  Website: Wikipedia – Maintainability
- Website: Military Directives, Handbooks and Standards Related to Reliability
- Template: Contract Maintainability Requirement