AD/DHC-8/128 Wing Root Electrical Wire Chafing (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-8/128 Wing Root Electrical Wire Chafing 9/2006

Applicability:	DHC-8 aircraft, Models 102, 103, 106, 201, 202, 301, 311, 314 and 315, Serial Numbers 003 through 606.
Requirement:	1.    Visually inspect for damage and repair as required the following electrical wiring harness in accordance with the instructions contained in Bombardier Service Bulletin (SB) 8-24-83, Revision A, dated 2 August 2005, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada:
a.     Left electrical cable harness assembly 82440073-001 (DHC-8 Models 100/200) or 82440073-301 (DHC-8 Models 300) located on the left wing root to fuselage aft seal assembly 85350712-001 at station Yw43.00.
b.    Right electrical cable harness assembly 82440074-001 (DHC-8 Models 100/200) or 82440074-301 (DHC-8 Models 300) located on the right wing root to fuselage aft seal assembly 85350711-001 at station Yw43.00.
Prior inspections of the wiring harnesses and modification of the seal assemblies, before the effective date of this Directive, in accordance with the original issue of Bombardier SB 8-24-83, satisfy the requirements of this Directive.
2.    Install Bombardier ModSum 8Y122031 to rework the seal assemblies to create a clearance between the electrical cable assemblies and the edge of the fairing panel. Bombardier SB 8-24-83, Revision A, dated 2 August 2005, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, contains approved instructions for incorporating Modsum 8Y122031.
Incorporation of Bombardier ModSum IS8Q2400005, before the effective date of this Directive, is equivalent to Bombardier ModSum 8Y122031, and satisfies the requirements of this Airworthiness Directive.
Note:  Transport Canada AD CF-2006-15 refers.
Compliance:	For Requirements 1 and 2 - Within 6 000 hours time in service after the effective date of this Directive.
This Airworthiness Directive becomes effective on 31 August 2006.

Background:

Transport Canada has received a report of an incident in which a DHC-8 aircraft encountered an un-commanded propeller feathering during climb, resulting in an emergency landing.  Investigation revealed that the wing to fuselage aft seal assembly had chafed through the wires associated with the auto-feather control system.  Both the left and right wing to fuselage aft seal assemblies could potentially exhibit this condition.

Chafing and/or grounding of the wiring against the aft seal assemblies may interrupt the operation of various aircraft systems, including propeller feather control, AC electrical power, and/or standby hydraulic power, resulting in potential flight safety hazards.  This Airworthiness Directive requires that the left and right electrical harness be inspected for chafing and, if necessary, the accomplishment of any repairs.

James Coyne
Delegate of the Civil Aviation Safety Authority

21 July 2006