Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Bombardier Model DHC-8-400 series airplanes. The existing AD currently requires revising the airplane flight manual (AFM) to advise the flightcrew of appropriate procedures to follow in the event that a main landing gear (MLG) fails to extend following a gear-down selection. The existing AD also currently requires repetitive replacement of the left and right MLG uplock assemblies with new assemblies; and an inspection of the left and right MLG uplock rollers for the presence of an inner low friction liner, and corrective actions if necessary. This proposed AD would revise the requirement for replacing the left and right MLG uplock assemblies by allowing replacement with alternative parts. For a certain MLG uplock assembly, this proposed AD would require repetitive inspections of the uplock hatch lower jaw for the presence of a wear groove and replacement with an improved part if necessary. For a certain MLG uplock assembly, this proposed AD also would require repetitive inspections of the uplock roller to ensure that it rotates freely and replacement with a new part if necessary. This proposed AD would allow optional replacement of the left and right MLG uplock assemblies with improved parts, which ends the requirements of the AFM revision and repetitive replacement and inspections. This proposed AD would remove airplanes from the applicability. This proposed AD results from development of a terminating action. We are proposing this AD to ensure that the flightcrew has the procedures necessary to address failure of an MLG to extend following a gear-down selection; and to detect and correct such failure, which could result in a gear-up landing and possible injury to passengers and crew.