• Affected human elements (e.g., pilots, controllers, maintenance personnel, supervisors, etc.), and 

• Operational procedures related to or affected by the concept. 

## 5.1.3 Determine and List Functions 

Using the concept description and preliminary input from the FA, identify and list the required functions (including those that are performed by the users). For example, the primary function of a precision navigation system is to provide ATC and flight crews with vertical and horizontal directional guidance to the desired landing area. If desired, these functions could be split into vertical and horizontal guidance. Supporting functions would be those that provide the solution with the ability to perform the primary function. A supporting function of the precision navigation system would be transmission of the radio frequency energy for horizontal guidance. The PO must determine how to group these functions and to what level of rigor to take the analysis. 

## 5.1.4 Develop and Document the OSED 

Develop and document the OSED from the information obtained in the first three steps (i.e., the steps outlined in Section 5.1.1 through Section 5.1.3). 

## 5.2 OHA Development Process 

Once the solution has been bounded and described and the functions have been identified in the OSED, an SRM panel must identify the associated hazards via an OHA. 6 In developing an OHA, the panel must develop a PHL 7  using a systematic analysis of solution functions and functional failures to identify hazards. Each hazard must be subsequently classified according to its potential severity after considering causes and effects. The OHA uses the severity identified for each hazard to identify safety objectives and safety requirements for the solution that will result in an acceptable level of safety risk. 

In general, as severity increases, the safety objectives and safety requirements must be designed to achieve the lowest possible likelihood of occurrence. A safety objective or “goal” in the context of the OHA is the desire to reduce the likelihood of an identified safety hazard. The associated safety requirement (i.e., minimum level of acceptable performance) is the means of attaining that objective. The OHA must establish safety objectives that ensure an inverse relationship between the probability of a hazard leading to an incident or accident and the severity of the hazard’s outcome. The safety objective should result in the lowest practicable acceptable level of safety risk. 

The OHA may be performed using either qualitative or quantitative methods. However, it is preferable to use quantitative data to support the assessment. 8 Figure C.3 provides an overview of the steps required to conduct an OHA. 

