Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to adopt a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes. This proposed AD was prompted by reports of movement of the rudder pedals being impeded due to corrosion of the trunnion shaft of the rudder feel trim unit (RFTU). This proposed AD would require inspecting to determine if certain RFTUs are installed, an operational check for signs of seizure of affected parts, repetitive lubrication for certain RFTUs, and replacing the RFTU with a new RFTU if necessary. Installation of replaced RFTUs with conformal bushings terminates the repetitive lubrication requirements. We are proposing this AD to detect and correct any sign of seizure of the trunnion 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.