How to update child ticket fields once Parent updated

[Amit Fainer]

Hello,

I am trying to create an Automation that will trigger sub-tasks specific filed change once the Parent same field was change. Example.
Once A User story as an assignee I would like that all the sub-tasks will get the same assignee.
Thanks

[Darryl Lee · Accepted solution]

Hi, the answer below from @Ste Wright describes how to do this in good detail:

• Automation: Ensure All Children inherit the Epics Fix version 

You would simply need to use a Branch rule For sub-tasks instead of For stories and select the field you would want to update.

[Amit Fainer]

Thanks. It's totally make sense but not working for me. I would like to share my example.
I have a custom filed (called FO) set on Stories, Task and SubTask. 
When create a User Story, I assign an FO (user in Jira) for it.
The FO then create the Subtasks.
What usually happen is that subtasks are missing the FO name, so I wanted an Automation that every new SubTask of a story or Task will get the FO name. 
Hope it is clear.
What I was doing :
- Condition: Set FO is not equal the FO from the Parent issue
- Action: Edit issue Field FO (click on set) then choose "copy from parent"

[Ste Wright]

Hi @Amit Fainer 

Is this still not working for you?

Ste