MTBF Predictions, or MTTF Predictions are conducted to determine the probability of survival and failure rate of your product during early development. MTBF is the abbreviated term for Mean Time Between Failures. It is the average time (in hours) expected between failures of a repairable component.

MTTF on the other hand is the abbreviated term for Mean Time To Failure. It is the average time (in hours) expected to failure of a non-repairable component over a specified time period.

MIL-STD-217 and Telcordia are the most popular MTBF prediction standards. Commercial Bellcore TR-332 or the Commercial Telcordia SR-332 are both available for use. A variety of end-use environments are provided by each standard to allow tailoring of failure rate data to your product’s market.

Reliability is affected by the environment the equipment is operating, in particular temperature plays a degrading role in component life. MTBF Predictions are based around the principle that temperature accelerates reliability degradation.

A report will be generated that can be used by your Marketing and Sales departments or can be issued directly to your customers, if required.

Note: We would much rather help you design an Accelerated Life Test (ALT) to determine the reliability of your product than provide you with a prediction. We understand that typically marketing departments drive the need for MTBF and that the figure is typically ambiguous. If you want to determine failure rate you need to determine the dominant failure mode(s) of your product, no prediction will do this.

Contact us for more information, or for a quote for our MTBF Prediction service.

MTBF Prediction :: Parts Count Analysis

Parts count analysis is a simple and efficient means to calculating system level reliability by using reliability ratings for each component in the system, or sub-system. It is typically conducted early in the design phase to gauge the reliability of the product before prototypes are made.

MTBF Prediction :: Parts Stress Analysis

Parts stress analysis is conducted at a later stage of development and usually provides a lower, and more accurate MTBF figure. Unlike the parts count method, parts stress takes into account a great deal more information about each component, such as:

  • Product Environment
  • Electrical Stress
  • Component Quality Factor
  • Temperature Factor
  • First Year Reliability Estimates

Catering for Redundancy – RBD

Many systems include the provision for redundant operation. MTBF predictions can be coupled with a Reliability Block Diagram (RBD) to model the critical system path, thus increasing MTBF as the redundancy in the system is taken into account.

Information we’ll need in order to quote

All we need from you before producing a quote for MTBF Prediction is:

  • Bill of Materials
  • Preferred Calculation Method
  • Preferred Calculation Environment
  • Temperature range to calculate for

Additionally, if you’d like us to look at system redundancy through a Reliability Block Diagram please include information about critical path components or sub-systems.

If needed please also send through a copy of your company’s Non-Disclosure Agreement (NDA).

MTBF Prediction Report :: Contents

We will run the MTBF prediction based on your requirements and provide you with a comprehensive report including the following information:

  • Prediction parameters
  • Standard used
  • Environment applied
  • Summary of results in 10°C steps providing MTBF in hours and years and FIT
  • Comprehensive reports showing component failure rates and MTBF for three temperatures
  • Chart :: Reliability Vs. Time
  • Chart :: MTBF Vs. Temperature
  • Chart :: FIT Vs. Temperature
  • BoM provided attached or inserted for reference

Which Environment?

MTBF predictions are available for a range of stress-variable environments, depending on your product’s end-use we’ll work together to determine the best environment to apply.

MIL-HDBK-217 Environments

  • Ground, Benign (GB)
  • Ground, Fixed (GF)
  • Ground, Mobile (GM)
  • Naval, Sheltered (NS)
  • Naval, Unsheltered (NU)
  • Airborne, Inhabited, Cargo (AIC)
  • Airborne, Inhabited, Fighter (AIF)
  • Airborne, Uninhabited, Cargo (AUC)
  • Airborne, Uninhabited, Fighter (AUF)
  • Airborne, Rotary Winged (ARW)
  • Space, Flight (SF)
  • Missile, Flight (MF)
  • Missile, Launch (ML)
  • Cannon, Launch (CL)
Environment Symbol Description
Ground, Benign GB Nonmobile, temperature and humidity controlled environments readily accessible to maintenance; includes laboratory instruments and test equipment, medical electronic equipment, business and scientific computer complexes, and missiles and support equipment in ground silos.
Ground, Fixed GF Moderately controlled environments such as installation in permanent racks with adequate cooling air and possible installation in unheated building; includes permanent installation of air traffic control radar and communications facilities.
Ground, Mobile GM Equipment installed on wheeled or tracked vehicles and equipment manually transported; includes tactical missile ground support equipment, mobile communication equipment, tactical fire direction systems, handheld communications equipment, laser designations and range finders.
Naval, Sheltered NS Includes sheltered or below deck conditions on surface ships and equipment installed in submarines.
Naval, Unsheltered NU Unprotected surface shipborne equipment exposed to weather conditions and equipment immersed in salt water. Includes sonar equipment and equipment installed on hydrofoil vessels.
Airborne, Inhabited, Cargo AIC Typical conditions in cargo compartments, which can be occupied by an aircrew. Environment extremes of pressure, temperature, shock and vibration are minimal. Examples include long mission aircraft such as the C130, C5, B52 and C141. This category also applies to inhabited areas in lower performance smaller aircraft as the T38.
Airborne, Inhabited, Fighter AIF Same as AIC but installed on high performance aircraft such as fighters and interceptors. Examples include the F15, F16, F111, F/A18 and A10 aircraft.
Airborne, Uninhabited, Cargo AUC Environmentally uncontrolled areas, which cannot be inhabited by an aircraft, crew during flight. Environmental extremes of pressure, temperature and shock may be severe. Examples include uninhabited areas pf long mission aircraft such as the C130, C5, B52 and C141. This category also applies to uninhabited areas pf lower performance smaller aircraft such as the T38.
Airborne, Uninhabited, Fighter AUF Same as AUC but installed on high performance aircraft such as fighters and interceptors. Examples include the F15, F16, F111, and A10 aircraft.
Airborne, Rotary Winged ARW Equipment installed on helicopters. Applies to both internally and externally mounted equipment such as laser designators, fire control systems, and communications equipment.
Space, Flight SF Earth orbital. Approaches benign ground conditions. Vehicles neither under powered flight nor in atmospheric reentry; include satellites and shuttles.
Missile, Flight MF Conditions related to powered flight or air breathing missiles, cruise missiles, and missiles in unpowered free flight.
Missile, Launch ML Severe conditions related to missile launch (air, ground, and sea), space vehicle boost into orbit, and vehicle re-entry and landing by parachute. Also applies to solid rocket motor propulsion powered flight, and torpedo and missile launch from submarines.
Cannon, Launch CL Extremely severe conditions related to canon launching of 155mm and 5 inch guided projectiles. Conditions apply to the projectile from launch to target impact.

Telcordia / Belcore SR-332 Environments:

  • Ground, Fixed, Controlled (GB)
  • Ground, Fixed, Uncontrolled (GF)
  • Ground, Mobile (both vehicular mounted and portable) (GM)
  • Airborne, Commercial (AC)
  • Spacebased, Commercial (SC)
Environment Symbol Description
Ground, Fixed, Controlled GB Nearly zero environmental stress with optimum engineering operation and maintenance. Typical applications are central office, environmentally controlled vaults, environmentally controlled remote shelters, and environmentally controlled customer premise areas.
Ground, Fixed, Uncontrolled GF Some environmental stress with limited maintenance. Typical applications are manholes, poles, remote terminals, customer premise areas subject to shock, vibration, temperature, or atmospheric variations.
Ground, Mobile (both vehicular mounted and portable) GM Conditions more severe than Gf , mostly for shock and vibration. More maintenance limited and susceptible to operator abuse. Typical applications are mobile telephone, portable operating equipment, and test equipment.
Airborne, Commercial AC Conditions more severe than for Gf, mostly for pressure, temperature, shock, and vibration. In addition, the application is more maintenance limited than for Gf . Typical applications are in the passenger compartment of commercial aircraft.
Spacebased, Commercial SC Low earth orbit. Conditions as for AC, but with no maintenance. Typical applications are commercial communication satellites.

For more information, or for any questions you have please contact us.