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 emergency lights circuitry. This proposal is prompted by reports of the emergency lights turning on inadvertently due to voltage spikes from other equipment, and reports that the existing emergency light switch arrangement allows the flight compartment and flight attendant's panel switches to override each other. The actions specified by the proposed AD are intended to prevent such failures of the emergency light systems, which could prevent the use of the emergency lights in the event of an emergency.