AD/DHC-8/149 Spoiler Lift Dump Valve (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-8/149 Spoiler Lift Dump Valve 8/2009

Applicability:

Bombardier Inc. Models DHC-8-400, DHC-8-401 and DHC-8-402, Serial Numbers 4001 through 4237.

Requirement:

Incorporate Bombardier Modsum 4 -113554 to add a Filter/Restrictor Fitting to the Spoiler Lift Dump Valve.

Bombardier Service Bulletin 84-27-43, Initial Revision, dated 29 January 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada provides approved instructions for incorporating Modsum 4 - 113554.

Note:  Transport Canada AD CF-2009-26 dated 21 May 2009 refers.

Compliance:

Within 5,000 flight hours after the effective date of this AD.

This Airworthiness Directive becomes effective on 30 July 2009.

Background:

Several operators have reported cases of inadvertent single spoiler deployment during flight on the DHC-8 Series 400 aircraft.  Investigation has revealed that the probable cause for this deployment is internal contamination of the Lift/Dump (L/D) valve and moisture ingress into the L/D valve armature.  This condition, if not corrected, could cause uncommanded deployment of the spoilers resulting in increased drag and in combination with a loss of aileron, could result in a significant reduction in aircraft roll control.

James Coyne
Delegate of the Civil Aviation Safety Authority

19 June 2009