The objective of aviation safety management systems (SMS) is to
When aviation service provider evaluates their risk to operational safety, they have to ask themselves a very pointed, and sometimes uncomfortable question: "What is our risk appetite?"
The term Acceptable Level of Safety (ALoS) defines an aviation service provider’s minimum level of acceptable risk for a given safety issue. “Acceptable” describes the need for no further mitigatory actions on the part of the service provider for the safety concern in question. This determination will be made based on the probability and severity of the evaluated safety concern.
Absolute safety is an impossible goal, yet service providers need to be able to set standards for how much risk is admissible. ALoS is the response to this dilemma. Because of this, ALoS is “exclusively concerned with safety performance measurement” (ICAO SSP: 6).
What this means is that, in terms of safety performance, ALoS marks the point at which, for any given hazard or potential mishap:
It’s important to note that while defining a level of acceptable safety is a requirement for providers, it’s up to each provider to establish just what is and what isn’t acceptable. In this way, service providers define their ALoS, and then show (e.g., with safety data), that they operating within an acceptable range of risk.
Acceptable Level of Safety is subjective and can change as the environment changes. As an operator becomes more successful and attracts more clients, this operator may become emboldened and increase its risk appetite. When one considers an inverse economic scenario, an operator may determine that their ALoS is too aggressive and that they need to either:
The Risk Matrix is the backbone of ALoS in terms of:
During the early stages of an aviation SMS risk management process, service providers use initial risk assessments from reported safety issues and audit findings to decide whether or not the evaluated concern meets the criteria for acceptable risk. For example, an organization might define acceptability as any risk assessment that is:
The reason there is a variance between aviation service providers is either:
ALoS absolutely requires very clear criteria for probability and severity in order to have consistent risk assessments across the life span of the implemented SMS.
Aviation service providers have the opportunity to define criteria for severity and probability of their risk matrix that aligns with the operator's:
This kind of flexibility allows each service provider to define risk assessment criteria that best fit the needs and environment of each operation.
Complex operators may have more than one risk matrix in their aviation SMS. Each risk matrix will be used to risk assess safety concerns for their specific division, whether the "division" is:
Other complex operators may be operating charter flight services and also maintain one or more FBOs or part 145 repair stations. I've also seen these types of companies use different risk matrices based on their "divisions."
While some aviation service providers have distinct risk matrices for each division, the general rule of thumb is to use the same risk matrix across the entire company. While this is not required, it is certainly a best practice as it increases consistency and reduces ambiguity and confusion among the managers who have to review reports based on risk assessments.
Risk matrix criteria are simply the tangible “markers” of a particular level of severity/probability. For example, you might define specific criteria for a level of severity based on:
The more criteria listed for each level of severity the better. Next, you might define specific criteria for a level of probability based on:
Operators should create their risk matrix criteria, and decide which combination of severity likelihood is the minimum requirement for acceptance. The practices for creating a risk matrix that is swiftly being adopted is to color code cells and maybe label them as:
Of course, each aviation service provider will need to establish what is “acceptable” as they document their aviation SMS risk management processes. However, as safety management systems are organic, “living” entities, the criteria for acceptability may change over time as:
Basically, at certain points in the development of an SMS' risk management processes, it makes sense to intensify the requirement for acceptability to strive towards continuous improvement and to also reduce risk to as low as reasonably practical (ALARP). These “intensifications” should be small/subtle adjustments, such as making a change that risk assessments of 2C are no longer within an acceptable range (a 2b is now required).
Whenever modifications to a risk matrix are considered, management must decide on how to treat legacy data that had been risk assessed using the historical criteria. Small changes to the risk matrix will have significantly less impact on historical reports than a large change. What can be construed as a large change? Examples include:
As discussed, you need to justify your established criteria for the level of acceptable risk. Justifying risk matrix criteria involves using:
Safety targets and key performance indicators are composed using:
A good way to begin this process is to review:
For a list of leading indicators that can help you get started with defining your acceptable level of safety, please see the following free resource:
Last updated October 2024.