Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain de Havilland Model DHC-7 series airplanes. This proposal would require modification of the power control relay installation of the emergency lights. The proposed AD also would require revising the FAA-approved Airplane Flight Manual to include procedures for turning off and on the emergency lights switch in certain conditions. This proposal is prompted by a report that the emergency lights do not automatically illuminate when all generated electrical power on the airplane is lost and the power to the left essential bus is maintained from the aircraft batteries. The actions specified by the proposed AD are intended to ensure that the emergency lights illuminate when needed in an emergency situation.