AD/CL-600/86 Nose Landing Gear(NLG) and NLG Door Selector Valves (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-600/86 Nose Landing Gear(NLG) and
NLG Door Selector Valves 9/2007

Applicability:

Bombardier Inc. Models:

CL-600-1A11 - Serial numbers 1004 through 1085

CL-600-2A12 - Serial numbers 3001 through 3066

CL-600-2B16 - Serial numbers 5001 through 5194

CL-600-2B16 - Serial numbers 5301 through 5699.

Requirement:

1.    Check the installed NLG and nose gear door selector valves and subsequently rework, replace and test as necessary, in accordance with the instructions of the applicable Service Bulletin (SB) listed below, or later NAA approved revision.

Model	Service Bulletin	Date
CL-600-1A11 (CL-600)	SB 600-0721, Revision 01	20 February 2006
CL-600-2A12 (CL-601)	SB 601-0558, Revision 01	20 February 2006
CL-600-2B16 (CL-601-3A/3R)	SB 601-0558, Revision 01	20 February 2006
CL-600-2B16 (CL-604)	SB 604-32-021, Revision 02	20 February 2007

Checking and subsequent action carried out in accordance with the basic issue, dated 15 December 2003, of any one of the above service bulletins does NOT satisfy the requirements of this directive.

For CL-600-2B16 (CL-604) aircraft Serial numbers 5301 through 5630, checking and subsequent action carried out in accordance with Service Bulletin 604-32-021, Revision 01, dated 20 February 2006, satisfies the requirements of this directive.

2.    No replacement/spare NLG and nose gear door selector valve, part number 601R75146-1 (Tactair part number 750006000), with a serial number in the range 0001 through 0767 is permitted to be installed on any aircraft unless it is identified with the marking “SB750006000-1”(ref: Tactair Service Bulletin SB750006000-1) close to the nameplate.

Note:  Transport Canada AD CF-2006-16R1 dated 4 June 2007 refers.

Compliance:

1.    Within 500 flight hours or within 12 months of the effective date of this AD whichever occurs first after the effective date of this AD.

2.    From the effective date of this AD.

This Airworthiness Directive becomes effective on 30 August 2007.

Background:

Some NLG and nose gear door selector valves, part number 601R75146-1 (Tactair part number 750006000), may have been incorrectly lock-wired and/or incorrectly torqued during assembly.  This condition can lead to the end cap backing off, with consequent damage to a seal and internal leakage within the valve.  Subsequently, if electrical power is transferred or removed from the aircraft before the NLG safety pin is installed, any pressure, including residual pressure, in the No. 3 hydraulic system can result in an uncommanded NLG retraction.

Although there have been no such cases reported on the Challenger models covered by this directive, there have been five cases reported on CRJ (CL600-2B19) aircraft, the most recent of which resulted in the collapse of the NLG at the departure gate.

David Punshon
Delegate of the Civil Aviation Safety Authority

20 July 2007