by Jan Meyer
Safety and risk are not the same things. Risk is measured. Safety is judged. Safety is the personal or societal acceptance of a given risk.
Risk is a measured quantity. Risk is the product of the probability of something happening and the severity of harm when it does happen. Risk equals "how often" times "how bad". Probabilities can be divided into 5 categories: Frequent, Probable, Occasional, Remote and Improbable. Severity can be divided into 4 categories: Catastrophic, Critical, Marginal and Negligible. Risk is then given as "Frequent-Negligible" for rubber bands breaking or "Remote-Catastrophic" for a double malfunction. Most malfunctions will have a risk of "Occasional-Catastrophic" or "Occasional-Critical" depending on how survivable landing the malfunction would be.
All events in skydiving could be assigned some risk value, based on the definition just given. The risk value should be based on data collected over many years or test drops. In essence, the risk value for an event should be based on a large set of measurements and observations. Unfortunately, this is not always the case.
Risk assessment is often based on subjective perceptions of risk. Events that are voluntary and within your control are given higher risk values than events that are mandatory and beyond your control. (Breathing air is less riskier than skydiving.)
Risks are higher for events that have a dreaded result or catastrophic consequence. Risks in sports and occupations that have fatalities are higher than sports and occupations that don't generally have fatalities. (Cowboys have riskier jobs than secretaries.)
Maturity of a technology affects risk perceptions, too. Nuclear power plants have higher risks than coal-powered plants because so much more is known about burning coal than nuclear energy.
System complexity will increase risks. Complex systems are harder to understand. They fail in complex ways. Sometimes a failed or degraded system is difficult to detect. The more complex a system is the more important it becomes to understand the system, how it works, how it fails and learn preventative and corrective actions.
Risk values depend on "how often" (probability) and "how bad" (severity). The frequency and danger of an event comes from a full and comprehensive understanding of a system. Effective and accurate risk assessments should be obtained by learning about the system's operational modes. The "how"s and "why"s of a system must be learned. System performance must be observable and recognizable. Performance must also be continually monitored, so that a degrading system is detected quickly. How a system fails should also be understood as well as how to recognize a failure or degraded system performance. Failures can arise from mechanical, human or environmental factors. Risks can be reduced further with preventative or corrective action plans.
Risk and Skydiving
Events in skydiving can be assigned a risk value. The risk is based on a through knowledge of a parachute system. An understanding of "which handle does what", "how parachutes deploy and inflate", "flight characteristics", "weather conditions", etc. will reduce risks. Methods to detect malfunctions will reduce risks: "Look at the parachute", "check your decent rate", "Spit -if it goes down you're probably okay, if it goes up it's a malfunction." These techniques monitor system performance. A proper course of action needs to be taken to reduce risks in the event of a degraded or malfunctioned system. Alternative plans or emergency procedures reduce risk by providing another way to escape injury.
Effective risk assessment and risk reduction comes from understanding parachute systems, knowing the proper roles of the controls, recognizing degrading system performance and having preventive and corrective plans.
Some concepts in this article were extracted from "Perception of Risk in Automotive Systems", D. G. Mac Gregor and P. Slovic, Human Factors, V 31, #4, August 1989.
Originally published in Sport Parachutist's Safety Journal V2, #2 Nov/Dec. 1989.
Dedicated to enhancing sport parachuting safety by disseminating information about equipment, environments and human factors.