AD/DHC-8/141 Amdt 1 Elevator Centering Torsion Springs (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DHC-8/141 and issues the following 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-8/141 Amdt 1 Elevator Centering Torsion Springs 7/2008

Applicability:

Bombardier Inc. DHC-8 Aircraft, Models 400, 401 and 402, Serial Numbers 4001, 4003, 4004 and 4006 through 4081 inclusive.

Requirement:

Replace all elevator centering torsion springs with new springs by incorporating Modsum 4-113482 in accordance with Bombardier Service Bulletin (SB) 84-27-31, dated 27 April 2007 or later revisions approved by Transport Canada.

Note:  Transport Canada AD CF-2008-05R1 dated 27 February 2008 refers.

Compliance:

Within 5,000 flight hours after the effective date of this AD but not to exceed 22,000 flight hours since new.

This Amendment becomes effective on 3 July 2008.

Background:

There was one reported failure of the elevator centering torsion spring.  Investigation revealed that the tangs on the torsion spring had been bent due to difficulty encountered during installation of the elevator centering torsion spring on the horizontal stabilizer torque tube.  The bending of the tangs on the torsion spring would degrade its durability and could lead to premature failure of the elevator centering torsion spring.  A control rod disconnect between the elevator aft quadrant and the elevator Power Control Unit input torque tube, in combination with the loss or reduction in elevator centering capability, could result in a significant reduction in aircraft pitch control.

This amendment adds 1 additional serial number aircraft to the applicability section of this AD with no change to the requirement or compliance sections.

The original issue of this AD became effective on 10 April 2008.

James Coyne
Delegate of the Civil Aviation Safety Authority

22 May 2008