This document covers the recommended procedure for inspecting the condition of an Airmaster sensorbrush assembly and checking for correct installation.
The brushes that run on the slipring will progressively wear down during service. Once they have become so worn that the springs behind them are at full extension, the brushes will no longer provide sufficient contact with the slipring. This may be observed during an inspection of the propeller or may become apparent as an open circuit alarm (as indicated by all lamps flashing red on the controller).
Sensor Brush Assy Inspection 
