Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes

The FAA is superseding Airworthiness Directive (AD) 2011-18- 15, which applied to certain De Havilland Aircraft of Canada Limited Model DHC-8-400 series airplanes. AD 2011-18-15 required initial and repetitive torque checks of the bolt preload; detailed inspection of the barrel nuts and cradle for cracking, pitting, and corrosion if the bolt preload is correct; and replacement of certain hardware if necessary. This AD continues to require those actions. This AD also requires new inspections and replacement of certain hardware, which would terminate the repetitive torque checks and inspections; and removes airplanes from the applicability. This AD was prompted by in- service reports of cracked barrel nuts found at the front spar locations of the wing-to-fuselage attachment joints, and a loose washer in the barrel nut assembly. The FAA is issuing this AD to address the unsafe condition on these products.