Airworthiness Directives; de Havilland Model DHC-7 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain de Havilland Model DHC-7 series airplanes, that requires modification of the emergency lights circuitry. This amendment 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 this 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.