Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain Bombardier, Inc. Model DHC-8-100, -200, and -300 series airplanes. The existing AD currently requires replacing certain parking brake accumulators. Since we issued that AD, we have determined that it is necessary to protect the hydraulic system and airplane structure from possible damage by any faulty screw cap or end cap of any accumulator. This proposed AD would require installing restraint devices around the parking brake accumulator end caps. We are proposing this AD to prevent failure of the parking brake accumulator screw cap or end cap resulting in loss of the number 2 hydraulic system and damage to airplane structures, which could adversely affect the controllability of the airplane.