AD 2012-20-08 77 FR 63711

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This AD was prompted by reports of alternating current (AC) generator failures in-service due to incomplete fusion in the weld joint of the rotor band assembly. This AD requires inspecting the AC generator to determine the part number, and replacing the AC generator if necessary. We are issuing this AD to prevent rotor windings from coming in contact with the generator housing, which could result in debris contaminating and potentially blocking the engine oil scavenge system, leading to loss of oil pressure and an in-flight shutdown of the engine.