Airworthiness Directives; Bombardier, Inc. Airplanes

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes. This AD was prompted by reports of an in-service incident where the propeller de- icing system became unavailable due to burnt/chafed wires within the alternating current contactor box (ACCB). This AD requires inspection for chafing, damage, and loose wiring within an ACCB and repair if necessary; and requires rework and re-identification of the wiring installation within each ACCB. We are issuing this AD to detect and correct damaged, chafed, or loose wiring within an ACCB, which could affect the operation of the windshield heater, ice detector, angle of attack (AOA) vane heater, pilot probe heater, engine intake heater, or propeller de-icing system, and subsequently adversely affect the airplane's flight characteristics in icing conditions.