Ad/CL-600/69 - Horizontal Stabiliser Trim - Uncommanded Movement (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 (Canadair) CL-600 (Challenger) Series Aeroplanes

AD/CL-600/69 Horizontal Stabiliser Trim - Uncommanded Movement 11/2006 TX

Applicability:

Model CL-600-2B16 (CL-604), serial number 5301 and subsequent.

Requirement:

If not previously accomplished, amend the Aircraft Flight Manual (AFM) by inserting Temporary Revision (TR) 604/21 dated 01 August 2006 or later Transport Canada approved change to this TR.

Note:  Transport Canada AD CF-2006-21 refers.

Compliance:

Within seven days after the effective date of this Directive.

This Airworthiness Directive becomes effective on 6 September 2006.

Background:

Transport Canada has received reports of uncommanded horizontal stabilizer trim motion on two CL-600-2B16 (CL-604) aircraft.  In each case, the aircraft landed safely.

An investigation has revealed that a motherboard in the horizontal stabiliser trim control unit (HSTCU) had not had appropriate environmental protection applied during manufacture.  The absence of corrosion protection and the accumulation of moisture during flight, caused short circuits that resulted in autopilot disconnect and trim system malfunctions.  The trim problems included uncommanded trim, trim in a direction opposite to that selected, loss of trim position indication and, in one case, potential loss of trim disconnect capability.

James Coyne
Delegate of the Civil Aviation Safety Authority

31 August 2006