Airworthiness Directives; Bombardier, Inc. Airplanes

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 corrosion in the low-rate discharge tubes of the fire protection system leading to the forward baggage compartment, and perforation of one or more tubes. This AD requires repetitive checks for leakage of the discharge tubes of the fire protection system. This AD also mandates eventual replacement of all existing aluminum tube assemblies with new, improved corrosion-resistant stainless steel tube assemblies. We are issuing this AD to prevent perforation of the low- rate discharge tubes, which could result in insufficient fire extinguishing agent reaching the forward baggage compartment in the event of a fire, which could result in damage to the airplane and injury to the occupants.