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AD/CL-600/123 - Wing Anti-Ice System - Outboard Low-Heat Detection Switches

Bombardier (Canadair) CL-600 (ChallengerBombardier (Canadair) CL-600 (Challenger) Series Aeroplanes

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Bombardier (Canadair) CL-600 (Challenger) Series Aeroplanes

AD/CL-600/123	Wing Anti-Ice System - OutboardLow-Heat Detection Switches	21/2009

Applicability:	Model CL-600-2B19 aeroplanes, Serial Numbers (S/N) 7003 through 8101.
Requirement:	1. Amend the Aircraft Flight Manual (AFM), CSP A-012, by inserting Temporary Revision (TR) No RJ/164-2, dated 12 May 2009, or later approved changes to this TR. Advise all flight crews of the changes introduced by the AFM TR.
	2. Revise the approved maintenance schedule by incorporating the inspection requirements contained in TR 2A-46, dated 24 July 2009, of the Maintenance Requirements Manual, CSP A-053, Part 2, Appendix A, Certification Maintenance Requirements.
	3. Replace the existing Data Concentrator Units (DCU) (Part Numbers (P/N) 622-9820-007 and/or -008 and/or -009) with modified DCUs (P/N 622-9820-010) and also, if applicable, modify the Configuration Strapping Units (CSUs), in accordance with the Accomplishment Instructions in Bombardier Service Bulletin (SB) 601R-31-034, Revision A, dated 10 April 2008, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.
	Note 1: The modified DCUs have been installed in production on CL-600-2B19 aircraft, serial numbers 8096 and subsequent.
	Note 2: Accomplishment in accordance with the original issue of Bombardier SB 601R-31-034, dated 19 November 2007, also meets the intent of Requirement 3 of this Directive.
	4. Install the outboard low-heat detection switches, wing A/ICE box assembly and associated wires in accordance with the Accomplishment Instructions in Parts A, C, D and E of Bombardier SB 601R-30-031, Revision A, dated 8 September 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.
	Note 3: Accomplishment of Parts A, C, D and E of Bombardier SB 601R-30-031, Revision A, dated 8 September 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, may be performed separately from each other.

	Note 4: Accomplishment in accordance with Part A of the original issue of Bombardier SB 601R-30-031, dated 15 May 2009, also meets the intent of Requirement 4 of this Directive.

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	Note 5: There have been a small number of cases reported in which piccolo ducts were found to have been installed in the opposite wing, resulting in the incorrect orientation of the bleed holes. During reinstallation of the piccolo ducts and leading edge assemblies after installation of the low-heat detection switches, particular attention should be paid to the correct alignment of the piccolo ducts (Refer Aircraft Maintenance Manual Task 30-11-41-820-801).
	5. Activate the outboard low-heat detection switches in accordance with the Accomplishment Instructions in Part F of Bombardier SB 601R-30-031, Revision A, dated 8 September 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.
	Note 6: Accomplishment in accordance with Part B of the original issue of Bombardier SB 601R-30-031, dated 15 May 2009, also meets the intent of Requirement 5 of this Directive.
	Note 7: Within the constraints of the compliance times specified below, each Requirement of this Directive may be accomplished separately from the other Requirements.
	Note 8: Transport Canada AD CF-2009-0037 refers.
Compliance:	For Requirements 1 and 2 - Within 30 days after the effective date of this Directive.
	For Requirements 3 and 4 - Prior to accomplishment Requirement 5 of this Directive, but no later than 1 November 2010.
	For Requirement 5 - Following accomplishment of Requirements 3 and 4 of this Directive, but no later than 1 November 2010.
	This Airworthiness Directive becomes effective on 16 October 2009.
Background:	At present, the Wing Anti-Ice System (WAIS) sufficient heat switches/sensors on CL-600-2B19 aircraft are located at the inboard end of each wing and require a simultaneous low-pressure signal to generate a L or R WING A/ICE amber caution. However, there have recently been several in-service occurrences that have highlighted the inability of the existing system to detect a low-heat condition in the wing leading edge at all times, with the potential consequence of unannunciated asymmetric ice build-up on the wing. These have included partial failure of several piccolo ducts [AD/CL-600/83 (Transport Canada AD CF-2008-30) refers] and partial (not fully closed or open) failure of a modulating and shut-off valve, the latter resulting in unannunciated asymmetric ice build-up on the wing leading edge. Such a condition, in combination with manoeuvres close to stick shaker activation, could possibly result in reduced controllability of the aircraft.
	This Directive mandates:a) Revision of the AFM to notify the flight crew that, following installation and activation of the low-heat detection switches, certain WAIS mode selection changes may result in a two-minute inhibition of the wing anti-ice message, if posted;b) Revision of the approved maintenance schedule to include one revised and three new functional checks that are required following activation of the low-heat detection switches;c) Replacement of the DCUs with DCUs incorporating a software update that caters for the new outboard low-heat detection switches and generates the appropriate anti-ice message for the flight crew when a low-heat condition is detected;
	Note 9: Although not related to this Directive, the software update also corrects the sampling rate of two previously non-compliant Flight Data Recorder (FDR) parameters, normal acceleration and pitch attitude.
	d) Installation of the low-heat detection switches in the wing outboard leading edges, the wing A/ICE box assembly and associated wires; ande) Activation of the low-heat detection switches.