ANSI Standard ANSI/VITA 51.1


Reliability Prediction MIL-HDBK-217F2 Subsidiary Specification



This new specification provides standard defaults and methods to adjust the models in Mil-hdbk-217-F2 (M217F2). This is not a revision of M217F2 but a standardization of the inputs to the M217F2 calculations to give more consistent results.
When planning military or high reliability applications, knowledge is needed regarding the potential life of electronic components involved in that system. More and more of the electronic components used in such systems are Commercial Off-The-Shelf (COTS) items. As such, the military program has very little control of the design, development, and availability of these modules. A reliable method to predict the failure rate of these systems is essential for planning sparing. Reliability is considered to be an important aspect of any electronic system, especially when utilizing COTS products. Reliability assurance is a very critical element in the acquisition and life-cycle management of military systems and especially challenging with the broad use of COTS items. In 1961, the first edition of M217F2 was published, providing a basic failure rate prediction methodology that is still in widespread use today, despite problems, limitations and inaccuracies that have been identified with the M217F2 methodology. Manufacturers and electronic reliability engineers use different methods to adjust the models in M217F2 for newer technologies, use different defaults for unknown stress conditions, and make differing assumptions of quality and complexity factors for COTS items. These differing methods yield results that are not comparable. The new standard is intended to provide a standard method for reliability engineers to perform failure rate predictions for COTS items used in military or high reliability applications.



Reliability engineers in the government and industry sectors continue to use M217F2 to perform failure rate predictions. Because M217F2 has not been updated recently, there are many new developments in electronics that are not accounted for, thus, reliability engineers must make changes to the M217F2 methodology to make their failure rate predictions more realistic. This specification provides a standard method of performing reliability predictions on COTS modules using M217F2. This is not a revision or a modification of M217F2 but a standardization of the inputs to the M217F2 calculations to give more consistent MTBF numbers. This specification will assist the user in determining the credibility of published failure rate information and outline the techniques necessary for developing and applying this information to military or high reliability applications.

How VITA compares with other MTBF calculation methods?


The following figure presents MTBF calculations for a circuit (34 active and 50 passive components ) according to:

  • Telcordia T332.3 – Blue Curve, Red Squares
  • MIL HDBK 217G – Green Curve, Red Pentagons
  • MIL HDBK 217F2 with Vita – Yellow Curve, Red Circles
  • MIL HDBK 217F2 – Red Curve, Red Stars
Screenshot of MTBF software

BQR’s MTBF prediction software supports ANSI/VITA 51.1