AD FAA-2014-0129

We are superseding Airworthiness Directive (AD) 2011-15-09 for certain Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes. AD 2011-15-09 required repetitive inspections for proper operation of the main landing gear (MLG) alternate extension system (AES), and corrective actions if necessary. This new AD requires, for certain airplanes, new repetitive inspections for proper operation of the MLG AES, and corrective actions if necessary. This new AD also requires eventually replacing the MLG AES cam mechanism assembly with a new assembly, which terminates the repetitive inspections for those airplanes. This AD was prompted by a determination that, for certain airplanes not affected by AD 2011-15-09, a different MLG AES cam mechanism assembly was installed, resulting in input lever fractures and inability to open the MLG door; those assemblies could be subject to the same unsafe condition in AD 2011-15-09. We are issuing this AD to prevent improper operation of the cam mechanism or rupture of the door release cable, which could result in loss of control of the airplane during landing.