If you go into the Aircraft/System Failures menu you will see that there are 7 options in the drop down box.
These are the values that you can use with the failure datarefs to select the X-Plane options.
- 0 - always working
- 1 - mean time until failure
- 2 - exact time until failure
- 3 - fail at exact speed KIAS
- 4 - fail at exact altitude AGL
- 5 - fail if CTRL f or JOY
- 6 - inoperative
Generally you only need to use 0 or 6 if you are implementing your own failure system.
1 - 4 use values that have to be entered into that settings screen.
If you do not need to change those from the default then you can use them.
If you need to change from the default this cannot be done from the plugin SDK as those values are not available.
However, it would be very simple to implement them within a plugin.