Safety Critical Systems Development

Chris Johnson, Index

The Basics: Hardware Management
Must consider during hardware acquisition:

Operating Temperature Range - parts should be selected which are rated for the operating temperature range to which they will be subjected.
Electrical Characteristics - parts should be selected to meet EMI, frequency, waveform and signal requirements and maximum applied electrical stresses (singularly and in combination).
Stability - parts should be selected to meet parameter stability requirements based on changes in temperature, humidity, frequency, age, etc.
Tolerances - parts should be selected that will meet tolerance requirements, including tolerance drift, over the intended life.
Reliability - parts should be selected with adequate inherent reliability and properly derated to achieve the required equipment reliability. Dominant failure modes should be understood when a part is used in a specific application.
Manufacturability - parts should be selected that are compatible with assembly manufacturing process conditions.
Life - parts should be selected that have "useful life" characteristics (both operating and storage) equal to or greater than that intended for the life of the equipment in which they are used.
Maintainability - parts should be selected that consider mounting provisions, ease of removal and replacement, and the tools and skill levels required for their removal/ replacement/repair.
Environment - parts should be selected that can operate successfully in the environment in which they will be used (i.e., temperature, humidity, sand and dust, salt atmosphere, vibration, shock, acceleration, altitude, fungus, radiation, contamination, corrosive materials, magnetic fields, etc.).
Cost - parts should be selected which are cost effective, yet meet the required performance, reliability, and environmental constraints, and life cycle requirements.
Availability - parts should be selected which are readily available, from more than one source, to meet fabrication schedules, and to ensure their future availability to support repairs in the event of failure.