Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes. That NPRM proposed to require an inspection to determine if certain rudder feel trim units (RFTUs) are installed, an operational check for signs of seizure of affected parts, repetitive lubrication for certain RFTUs, and replacement of the RFTU if necessary. Installing replaced RFTUs with conformal bushings would terminate the repetitive lubrication requirements. That NPRM was prompted by reports of movement of the rudder pedals being impeded due to corrosion of the trunnion shaft of the RFTU. This action revises that NPRM by reducing compliance times, increasing compliance costs, expanding affected parts to include additional serial numbers and include those parts with a suffix `A,' and adding the condition of rough movement to the operational check. We are proposing this AD to detect and correct any sign of rough movement or seizure of thetrunnion shaft and its bushing, which could cause a rudder control jam or a large and rapid alternating rudder input leading to a structural failure of the vertical fin. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.