Summary
We propose to adopt a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This AD was prompted by reports of interior emergency lights remaining ``ON'' following routine operational checks of the emergency light system. We are proposing this AD to require changing the wiring gauge for the affected emergency lights power supplies wiring to prevent overheating in the wires. Overheating can damage the wire insulation, causing a fire.