Action
Notice of proposed rulemaking (NPRM).
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 engine fire/overheat detector assemblies advance pneumatic detectors (APDs) failing to reset after activation due to permanent deformation of the detector switch diaphragm after being exposed to high temperatures. This proposed AD would require replacing all three APDs with new detector assemblies. We are proposing this AD to prevent a continued engine fire indication in the cockpit after the actual fire has been extinguished, which is misleading and may influence the pilot to conduct a potentially hazardous "off-airport" landing.