GM1 ATM/ANS.AR.C.035(b) Decision to review
a notified change to the functional system
ED Decision 2017/001/R
SELECTION CRITERIA FOR REVIEWING A NOTIFIED CHANGE TO THE FUNCTIONAL SYSTEM
The need for review should be based on a combination of the likelihood that the safety (support) argument may be complex or unfamiliar to the service provider undertaking the change and the severity of the consequences associated with the change. This is a risk function and is referred to as the ‘risk posed by the change’.
The following two aspects of the change:
— the novelty of the change; and
— the capabilities of the service provider (e.g. the effectiveness of the service provider’s (safety) management system),
as well as the service provider performing the change contribute to the service provider’s unfamiliarity of the necessary argument. The assessment of the severity of the consequence is made at a very early stage in the development of the change and, therefore, will be based on coarse data. It should, therefore, be conservative.
The risk posed by a change could be a scalar measure associated with the change and be some combination of the two inputs: the probability of a complex or unfamiliar argument and the severity of the consequences of the proposed change. The result is that the risk posed by a particular change is the sum of the inputs.
One possibility may be based on the use of a risk matrix in which risk parameters are represented according to a coarse-grained measurement scheme, and the selection criteria establish the boundary beyond which changes will be selected for review, as shown below:
The selection criterion, a function of risk with the value ‘significant’, is then a straight line, if the scales are logarithmic.