MIL-HDBK-217 Environmental Conditions | SQC Online

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MIL-HDBK-217 Environmental Conditions

All part reliability models include the effects of environmental stresses through the environmental factor πE (except for the effect of ionizing radiation). The descriptions of these environments are shown in the following table. The πE factor is quantified within each part failure rate model. These environments encompass the major areas of equipment use. Environmental test chambers are often used to emulate various environmental conditions.

Some equipment will experience more than one environment during its normal use, e.g., equipment in spacecrafts. In such a case, the reliability analysis should be segmented. In the spacecraft example, the segmentation would be into missile launch (ML) conditions during boost into and return from orbit, and space flight (SF) while in orbit.

Environment Symbol Description
Ground, BenignGBNonmobile, 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, FixedGFModerately 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, MobileGMEquipment 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, ShelteredNSIncludes sheltered or below deck conditions on surface ships and equipment installed in submarines.
Naval, UnshelteredNUUnprotected surface shipborne equipment exposed to weather conditions and equipment immersed in salt water. Includes sonar equipment and equipment installed on hydrofoil vessels.
Airborne, Inhabited, CargoAICTypical 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, FighterAIFSame 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, CargoAUCEnvironmentally 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, FighterAUFSame as AUC but installed on high performance aircraft such as fighters and interceptors. Examples include the F15, F16, F111, and A10 aircraft.
Airborne, Rotary WingedARWEquipment installed on helicopters. Applies to both internally and externally mounted equipment such as laser designators, fire control systems, and communications equipment.
Space, FlightSFEarth orbital. Approaches benign ground conditions. Vehicles neither under powered flight nor in atmospheric reentry; include satellites and shuttles.
Missile, FlightMFConditions related to powered flight or air breathing missiles, cruise missiles, and missiles in unpowered free flight.
Missile, LaunchMLSevere 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, LaunchCLExtremely severe conditions related to canon launching of 155mm and 5 inch guided projectiles. Conditions apply to the projectile from launch to target impact.

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