AD/SD3-60/70 Engine and Landing Gear Control Cables (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.

Short SD3-60 Series Aeroplanes

AD/SD3-60/70 Engine and Landing Gear Control Cables 4/2007 TX

Applicability:

Short Brothers PLC SD3-60 aeroplanes.

Requirement:

1.    Inspect the affected cable assembly end fittings in accordance with Short Brothers PLC Service Bulletin (SB) SD360-76-A12 Revision 1 or later EASA approved revision.

2.    If no pitting/corrosion or cracking is found repeat the inspection detailed in Requirement 1 of this AD.

3.    If pitting/corrosion or cracking is found during inspection detailed in Requirement 1 or 2 of this AD, replace the affected cable assembly with a new cable assembly.

4.    Repeat the inspection of any new cable assembly end fittings in accordance with Short Brothers PLC SB SD360-76-A12 Revision 1or later EASA approved revision.

Note:  EASA Emergency AD 2007-0039-E dated 16 February 2007 refers.

Compliance:

1.    No later than 9 March 2007.

2.    Within 12 months of the original inspection and thereafter at intervals not to exceed 12 months.

3.    Before further flight after the effective date of this AD.

4.    After replacement at intervals not to exceed 15 years.

This Airworthiness Directive becomes effective on 23 February 2007.

Background:

Following the identification of a failed propeller RPM cable end fitting and an LP fuel lever cable end fitting on an SD3 aircraft, several subsequent occurrences of control cable end fittings (type MS21260) with signs of pitting corrosion or cracking have been reported to Bombardier Shorts.  All reported instances being identified during ground maintenance inspections on the SD3 fleet.  Bombardier Shorts have performed examinations on the failed cable end fittings and established the root cause of failure as stress corrosion cracking of the SAE-AISI 303 stainless steel material they are manufactured from, initiated by pitting corrosion on the surface.  The root cause of the stress corrosion is sustained tensile stress in a corrosive (warm, humid and salty) atmosphere.

An analysis of the cable operated control systems installed on the SD3 aircraft types that use MS 21260 type end fittings has identified a number of potentially unsafe conditions due to a combination of failures that may result from this common mode cause.

David Punshon
Delegate of the Civil Aviation Safety Authority

20 February 2007