Summary
The FAA proposes to supersede Airworthiness Directive (AD) 2011-18-15, which applies to certain Bombardier, Inc., Model DHC-8-400 series airplanes. AD 2011-18-15 requires 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 hardware if necessary. Since the FAA issued AD 2011-18-15, the agency has determined that incorporation of a new design change is necessary to address the root cause of the failure of the barrel nuts. This proposed AD would retain the existing requirements and add new inspections and replacement of certain hardware, which would terminate the repetitive torque checks and inspections. This AD also removes airplanes from the applicability. The FAA is proposing this AD to address the unsafe condition on these products.