AD/DHC-8/132 Utility and Observer Lights (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes

AD/DHC-8/132 Utility and Observer Lights 11/2007

Applicability:	DHC-8 Aircraft Models 102, 103, 106, 201, 202, 301, 311, 314 and 315, Serial Numbers 003 through 639 and Models 400, 401 and 402, Serial Numbers 4003, 4004, 4006 and 4008 through 4149.
Requirement:	1.    DHC-8 Aircraft Models 102, 103, 106, 201, 202, 301, 311, 314 and 315 - Install Modsum 8Q101603 to replace the affected carbon moulded resistive element potentiometers with wire-wound type potentiometers, for both the pilot and co-pilot utility lights.  Bombardier Service Bulletin (SB) 8-33-53, original issue dated 1 December 2006, Revision A dated 14 March 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provide instructions for incorporating Modsum 8Q101603.
2.    DHC-8 Aircraft Models 400, 401 and 402 - Install Modsum 4-126381 to replace the affected carbon moulded resistive element potentiometers with wire-wound type potentiometers, for the pilot, co pilot and observer utility lights.  Bombardier SB 84-33-10, original issue dated 1 December 2006, Revision A dated 14 March 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provide instructions for incorporating Modsum 4-126381.
Note:  Transport Canada AD CF-2007-11 refers.
Compliance:	Within 18 months after the effective date of this Directive.
This Airworthiness Directive becomes effective on 25 October 2007.

Background: Transport Canada has advised that several cases have been reported where the pilot, co-pilot or observer utility light system has failed, resulting in a burning smell within the cockpit.  An investigation has revealed that, due to the orientation and location of the carbon moulded potentiometers used to control the intensity of the light, the potentiometers can fail and overheat in such a way that burning of the ceiling panel and the associated insulation blanket could occur.  This could lead to the presence of smoke in the cockpit, requiring that the pilots carry out the appropriate emergency procedure.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

10 September 2007