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In phase diagrams, operational phase blocks are used to represent any stage of the system's mission that is not dedicated exclusively to the execution of maintenance tasks. Operational phases are always defined by (linked to) a simulation RBD in the current project. Each operational phase has a fixed, predefined duration unless a failure occurs during the phase and then it depends on how the properties of the phase block have been configured.
Operational phase blocks can have unlimited incoming connections and up to two outgoing connections, which may include one success path and one failure path. The success path and the failure path must be different; if both success and failure of the block actually lead to the same outcome, there are two ways to model this:
If the operational phase stops upon failure of the block and the simulation moves to the next phase along the success path, you can use a node block to model this configuration (i.e., the success path links directly to the next phase, and the failure path leads to a node block, which then links to the next phase).
If the operational phase continues for the specified duration despite failure and the simulation then moves to the next phase along the success path, do not create a failure path.
By default, the first connection that you create from an operational phase block is the success path and the second is the failure path. You can right-click either connector and choose Set to Success or Set to Failure to swap the two paths.
You can add an operational phase block to a phase diagram by choosing Phase > Phase > Add Operational Phase.
The Select Diagram for the Block window will appear. The list of available diagrams will show the simulation RBDs in the project. You can use the View area to sort the list hierarchically or alphabetically. The Filter field allows you to enter text to search for in the names of the available diagrams. If the diagram that the operational phase block will be linked to does not yet exist, click the Add RBD icon to add a new diagram to the project.
To open an operational phase block that already appears in the phase diagram, double-click the block or choose Phase > Settings > Block Properties to open the Phase Properties window.
The following properties are available to configure an operational phase block:
Phase name and Description: By default, operational phase blocks are named according to the name of the diagram they represent. You can type new text either instead of or in addition to the default name. You can change the default names by choosing File > Manage Repository > Default Name Formats.
The Phase name field must be populated. Description text is optional. Note that an asterisk is used (*) to represent default block names. The block name that is displayed in the diagram will replace the asterisk with the block's default name; this allows the block name to be updated dynamically.
Phase Properties
Diagram allows you to select a simulation RBD in the current project that you want the phase block to represent. Note that common components across different RBDs are identified by name. In other words, a component with the exact same name in two RBDs is assumed to be the same component working in two different phases.
Phase duration allows you to specify how long the system will operate in the configuration defined for this phase. If a failure has not occurred by the end of the specified phase duration, the simulation will proceed along the success path leading from the phase block. If a failure occurs, the simulation will proceed along the failure path leading from the phase block.
Phase duty cycle allows you to specify a common duty cycle value for the entire RBD that the phase represents, thereby modeling situations where the actual usage of the RBD during system operation is not identical to the usage for which you have data. Continuous operation at the rated load is considered to be a duty cycle of 1. Any other level of usage is expressed as a percentage of the rated load value or operating time. (For more information, see Standard Blocks: Duty Cycle.)
If a duty cycle is specified for the phase and there are also duty cycles specified for blocks within the RBD, their effects are compounded. For example, if the landing gear is only in use 30% of the time during an aircraft’s take-off phase (block duty cycle = .3) and the entire system experiences 1.5 times the normal stress during take-off (phase duty cycle = 1.5) then the effective duty cycle for the landing gear during take-off would be .3 x 1.5 = 0.45.
Phase Throughput properties allow you to specify the maximum output that the entire system can process during the particular phase. (See Throughput Analysis with Phase Diagrams.)
Identifiers: The Comments field allows you to enter additional information about the block.
The Active Phase drop-down list at the bottom of the window allows you to choose another phase that you want to edit without the need to close and reopen the Phase Properties window. This option works in exactly the same way as the Active Block feature in the Block Properties window.
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