AD FAA-2012-1157

We are adopting a new airworthiness directive (AD) for all BAE SYSTEMS (OPERATIONS) LIMITED Model BAe 146 and Avro 146-RJ series airplanes. This AD was prompted by a report that certain ceramic terminal blocks, through which the wiring for the engine fire extinguishers, fire detection circuits, and engine and intake anti-ice system are routed, have been found to have moisture ingress, which can degrade the insulation resistance of the ceramic terminal blocks. This AD requires a one-time insulation resistance test of ceramic terminal blocks, and if necessary, replacement of the blocks. We are issuing this AD to prevent latent failure of the number 2 fire bottle, which, in the event of an engine fire, could result in failure of the fire bottle to discharge when activated and possibly preventing the flightcrew from extinguishing an engine fire.