These are working fine on my native helicopter: SimVar.GetSimVarValue("MASTER WARNING ACTIVE", "Bool"); SimVar.SetSimVarValue("K:MASTER_WARNING_SET", "Bool", 1); // or 0 Using
avionics from fixed wing is likely to run into this problem though:
https://devsupport.flightsimulator.com/t/5148 There appears to be a big
chunk of the sim that diverges for helicopters, and for now this excludes
helicopter from other avionics packages working directly. So you may need to
look deeper to find the actual API which is failing.