AD 99-21-27 64 FR 56161

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Bombardier Model DHC-8-311 and -315 series airplanes, that currently requires replacement of the nitrogen cylinder assemblies that inflate the airplane's ditching dams with improved nitrogen cylinder assemblies. This amendment expands the applicability of the existing AD. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent failure of the ditching dams to inflate fully during an emergency water landing, which could result in water entering the airplane.