Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Bombardier Model DHC-8-400 series airplanes. This proposed AD would require inspecting to determine the manufacturer's date of certain V-band clamps on the engine exhaust shroud assembly, and doing related investigative/corrective actions if necessary. This proposed AD results from a report of a discrepancy found during a maintenance inspection on a V-band clamp located on the engine exhaust duct shroud. The clamp ends were touching (although the correct fastener torque had been applied), resulting in reduced clamp force on the flanges. We are proposing this AD to prevent vibration in the duct shroud and fretting of the V-band clamp and flanges, which could result in cracking of the flanges and consequent release of hot exhaust gases from the engine tailpipe and damage to adjacent structure. This situation could trigger the fire warning system and result in an in-flight emergency, such as the flightcrew shutting down the engine and activating the fire suppression system.