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Reliability Key System Attribute (KSA)

ALCL 132


One of the mandatory KSAs that supports the Sustainment Key Performance Parameter (KPP). It is a measure of the probability that the system will perform without failure over a specified interval, under specified conditions. Reliability must be sufficient to support the warfighting capability requirements within expected operating environments. Considerations of reliability must support both availability metrics, that is, Materiel Availability and Operational Availability. More than one reliability metric may be specified as Key System Attributes (KSAs) or Additional Performance Attributes (APAs), as appropriate. For continuous use systems, such as aircraft, reliability should be measured in terms of its primary usage metric (e.g., operating hours, miles or flight hours). For discrete systems, such as a single use munition, reliability should be measured as a probability. (JCIDS Manual) See “Reliability” for a more general definition.

General Information


The Manual for the Operation of the Joint Capabilties Integration and Development System (JCIDS Manual) states that the Sustainment KPP  is comprised of several mandatory components:  Am and Ao, and three mandatory attributes: R, Maintainability (M), and Operating and Support (O&S) cost. It goes on to clarify that Availability (including both Am and Ao) is intended to ensure an adequate quantity of the capability solution will be ready for tasking to support operational missions, the supporting R, M, and O&S Cost KSAs ensure that the Sustainment KPP is achievable and affordable in its operational environment. Together, the KPP and supporting KSAs ensure early sustainment planning, enabling the requirements and acquisition communities to provide a capability solution with optimal availability, maintainability, and reliability to the warfighter at an affordable life cycle cost.

Design Trade Space

The fact that the Sustainment KPP and the three supporting KSAs are mandatory is not coincidental. Achieving high R has a cost, as does achieving superior M and a high Availability. These Sustainment metrics taken together bound the trade space for “designing in” supportability and planning affordable life-cycle product support.

The JCIDS manual identifies R as a measure of the probability that the system will perform without failure over a specific interval, under specified conditions. Highlighted is the point that R shall be sufficient to support the warfighting capability requirements, within expected operating environments.

More than one R metric may be specified, as KSAs for a system as appropriate.

  • For continuous use systems (such as an aircraft), R should be measured in terms of its primary usage metric (such as operating hours, miles or flight hours).
  • For discrete systems (such as a single use munition), R should be measured as a probability.

In all cases, the sponsor should define specific criteria which constitute failure.

Guide for Developing Appropriate Sustainment Metrics

Table 1 from the JCIDS Manual included below provides a guide for developing the appropriate sustainment metrics for different categories of systems as an aid for the Sustainment KPP:

  Distinguishing Characteristics Materiel Availability Operational Availability
Ship Platforms Naval vessels with multiple missions and multiple large or complex systems. Planned down time. The availability of the entire population of systems for tasking when a ship is not in a planned maintenance availability or unavailable due to Casualty Report, category 4 failure. Percentage of time an operationally deployed ship is not in a Casualty Report, category 4 failure state over a given operating period.
Aircraft Platforms Aviation programs with integrated systems, multiple missions. Number of available aircraft/Total aircraft inventory. Uptime/Total Time.
Ground Vehicles or Mobile Ground Systems Wheeled or tracked platforms, either towed or self-propelled. Number of available vehicles/Total vehicle inventory. Uptime/Total Time.
Weapons Single use (e.g., air-launched weapons, missiles). Number of available weapons/total weapon inventory. Repairable devices must include the pipeline or depot inventory. Number of times system is available/number of times system is required.
Satellite Systems (including hosted payloads) Sub-types include an individual, single purpose satellite, a constellation of two or more satellites, and hosted payloads that share certain satellite infrastructure functions. Unless unique circumstances exist (e.g., periodic software uploads), once the system is on-orbit Materiel Availability is not applicable. Functional Availability: the probability of satisfying the minimum level of performance for a specific mission as a function of time. Typically expressed as a probability of success.
(Notes 1 & 2)
Modification Programs Replacement or upgrade of existing systems or subsystems.
(Note 3)
Determine applicability dependent on existing system type. Up Time/Total Time.
Subsystems Clearly defined interfaces, installed in host platform. Number of available subsystems /Total subsystem inventory. Up Time/Total Time.
System of Systems or Unmanned Systems Collection of distinct system elements that create a combined mission capability. (Define Am, Ao, Reliability parameters for each system element) Number of available systems/ total system inventory. Uptime/Total time.
1. Hosted payloads: Functional Availability may also be a function of the reliability of shared infrastructure depending on the CONOPS.
2. Constellation: Functional Availability is a function of the reliability of the necessary minimum of satellites and the mission success criteria.
3. Modification Systems should consider the existing system requirements structure.