See http://forum.mikrokopter.de/topic-post536060.html#post536060 For Redundant systems it also indicates whether the backup FC is operable or is not available (and therefore you have no backup): Redundancy There are new messages in the display: * ERR 36: Redundancy -> the second FC is not ready and can't be used in failsafe-case * ERR 37: Redundancy test -> one of the test switches is in "test" position Thanks, Holger! Andy.