AD/CL-600/78 Engine Throttle Control Gearbox (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-600/78 Engine Throttle Control Gearbox 9/2007

Applicability:

Bombardier Inc. Model CL-600-2B19 serial numbers 7003 through 7067, 7069 through 7990, and 8000 and subsequent.

Requirement:

1.    Inspect both left and right engine throttle gearboxes for wear in accordance with Part A of Bombardier SB 601R-76-019 Revision B, dated 16 February 2005, or later NAA approved revisions.

a.     If the inspection results (wear values) are 0.010 inches (0.254 mm) or greater on one or both engine throttle gearboxes, before next flight, replace the applicable gearbox(es) in accordance with Part B of Bombardier SB
601R-76-019 Revision B, or later NAA approved revisions.

b.    If the inspection results (wear values) are between 0.006 inches (0.152 mm) and 0.010 inches (0.254 mm) on both engine throttle gearboxes, before next flight, replace the gearbox with the higher wear value in accordance with Part B of Bombardier SB 601R-76-019 Revision B, or later NAA approved revisions, and replace the other gearbox within the next 1000 flight hours.

c.     If the inspection result (wear value) is between 0.006 inches (0.152 mm) and 0.010 inches (0.254 mm) on one engine throttle gearbox only, within the next 1000 flight hours, replace this gearbox in accordance with Part B of Bombardier SB 601R-76-019, Revision B, or later NAA approved revisions.

d.    If the inspection results (wear values) are below 0.006 inches (0.152 mm) on both engine throttle gearboxes, no further action is required until the next inspection in accordance with Requirement 2 below.

2.    Repeat the inspection (and replacement as required) detailed in Requirement 1.

Note 1:  Prior inspections and replacement of the engine throttle gearboxes (before the effective date of this directive) in accordance with Revision A of Service Bulletin 601R-76-019, or the original issue of SB 601 R-76-019, satisfy the requirements of this AD.

Note 2:  Transport Canada AD CF-2004-01R1 dated 12 April 2005 refers.

Compliance:

1.    Within 1000 flight hours after the effective date of this AD, unless previously accomplished.

2.    At intervals not to exceed 1000 flight hours.

This Airworthiness Directive becomes effective on 30 August 2007.

Background:

There have been numerous reported failures of the Regional Jet engine throttle control gearbox, and some of these failures resulted in in-flight engine shutdowns.  Post-incident investigations revealed that excessive wear within the engine throttle gearbox could alter the rigging position or cause the throttle to jam.  The movement of the throttle towards the idle position then corresponds to a position close to fuel shut-off, which may cause the engine to flame out.

David Punshon
Delegate of the Civil Aviation Safety Authority

25 June 2007