Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Bombardier Model DHC-8-102, -103, -106, -201, -202, -301, - 311 and -315 airplanes. This proposed AD would require installation of check valves in Numbers 1 and 2 hydraulic systems, removal of the filters from the brake shuttle valves, and removal of the internal garter spring from the brake shuttle valves. This proposed AD results from two instances of brake failure due to the loss of hydraulic fluid from both Numbers 1 and 2 hydraulic systems and one incident of brake failure due to filter blockage in the shuttle valve. We are proposing this AD to prevent the loss of hydraulic power from both hydraulic systems which could lead to reduced controllability of the airplane; and to prevent brake failure which could result in the loss of directional control on the ground and consequent departure from the runway during landing.