Glossary of Terms

	Title	Definition
	Redundancy	Multiple independent methods incorporated to accomplish a given function, each one of them is sufficient to accomplish the function [AMC to CS25.1309].
	Redundancy.	The presence of more than one independent means for accomplishing a given function or flight operation [AMC to CS25.1309].
	Reliability	The probability ratio that a system or product will perform in a satisfactory manner under stated conditions for a stated period of time, assuming it was in proper condition at the mission beginning.
	Requirements	Statements describing essential, necessary or desired attributes.
	Requirements Specification	Specification that sets forth the requirements for a system or system component.
	Risk	An expression of the possibility and impact of an event in terms of accident severity and accident probability. In other words, it is the combined effect of the probability of occurrence of an undesirable event, and the severity of that event.
	Risk Dimension	A perspective from which risk assessment is being made for the system (eg safety, economic, security). [ISO/IEC 15026, 3.12]
	RMI	Radio Magnetic Indicator.
	RMP	Radio Management Panel.
	RPM (rpm)	Measure of engine speed expressed in revolutions per minute.
	Rudder(s)	Control surface(s) at rear of vertical tail (fin) controlling yawing movement of aircraft.
	Safe-life	The Safe-life design technique is employed in critical systems which are either very difficult to repair or it may cause severe damage to life and property. These systems are designed to work for years without requirement of any repairs.
	Safety	Freedom from those conditions that can cause death, injury, occupational illness or damage to or loss of property, or damage to the environment. It is the state in which risk is lower than the boundary risk. The boundary risk is the upper limit of acceptable risk. It is specific for a technical purpose or state [SAE ARP 4754 p80]. Freedom from those conditions that can cause death, injury, occupational illness, damage to or loss of equipment or property, or damage to the environment [MIL-STD-882D].
	Safety Assessment	The Safety Assessment is a structured body of evidence that provides a convincing and valid argument that a system is adequately safe for a given application in a given environment. It is a collection of documents that, taken together, provides objective evidence that that all reasonable steps were taken to ensure product safety. It may also provide data that the customer finds helpful throughout the life of the product. Note that the Safety Assessment is applicable to one specific point in time only and is a deliverable to the system manager/owner.
	Safety Case	The Health and Safety Commission defines [refer, inter alia, JSP553, 1st edition (para 2.43)] a Safety Case as:

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