COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes AD/DHC-8/65 Thunderstorm Lights 10/99 Applicability: DHC-8 Series 100 aeroplanes Serial Numbers 003 through 020 inclusive without Modification 8/0198 incorporated. Requirement: Install Bombardier Modification 8/0198 (Electrical Power - Thunderstorm Lights - Change Power Supply from Left Secondary Bus to Left Essential Bus) in accordance with Bombardier Regional Aircraft Ltd Service Bulletin 8-24-69 dated 8 December 1998. Note: Transport Canada AD CF-99-21 refers. Compliance: Within six months from the effective date of this Directive. This Airworthiness Directive becomes effective on 7 October 1999. Background: In aeroplanes without Modification 8/0198, the thunderstorm lights are supplied with electrical power from the left secondary bus rather than the essential bus. Should an aeroplane without the modification lose all generated electrical power, compliance with the flight manual emergency procedures will result in cockpit lighting not being available. This Directive ensures that this anomaly is corrected.