Summary
We propose to adopt a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This proposed AD was prompted by reports of hydraulic fluid loss from the reservoir of the main landing gear's (MLG's) alternate extension system. This proposed AD would require inspection for correct assembly of the MLG's alternate extension system reservoir lid, and corrective action if necessary. We are proposing this AD to, in the event of a failure of the primary MLG extension system, prevent failure of the alternate MLG extension system to fully extend the MLG into a down-and-locked position, which could result in collapse of both MLG during touchdown.