AD/LA-4/23 Amdt 1 Wing Fitting Carry Through Structure (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/LA-4/23 and issues the following 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.

Consolidated Aeronautics, Colonial and LA-4 Series Aeroplanes

AD/LA-4/23 Amdt 1 Wing Fitting Carry Through Structure 10/2005

Applicability:

All models.

Requirement:

Perform the modification, inspection and corrosion treatment of the wing carry through structure in accordance with the instructions contained in Aerofab Service Advisory No. A-001 Dated 4 May 1991 or later revision approved by the Type Certificate holder.

Note:  The previous amendment of this AD required the wings to be removed to perform a corrosion inspection.  This amendment does not require wing removal as the required inspection is now performed using a borescope inserted through a small hole in the wing carry through structure.

Compliance:

Initial modification and first inspection:

For aircraft inspected in the last 3 years to the original issue of this AD or previously inspected in accordance with an exclusion allowing the inspection to be carried out in accordance with Aerofab Service Advisory No A-001, accomplish the inspection and treatment no later than 3 years since the last inspection.

For aircraft recently imported and not inspected previously to the original issue of this AD or inspected in accordance with an exclusion allowing the use of Aerofab Service Advisory No A-001, perform the initial modification and inspection within 3 months from the effective date of this AD.

Subsequent repeat inspections:

Repeat inspections every 3 years for aircraft subject to predominantly salt water activity*.

*Predominantly salt water activity is defined as landings and takeoffs being made in salt water as the primary surface, involving more than weekly landings/takeoffs in salt water (i.e. 4 or more per month) or mooring the aircraft for extended periods of time in salt water for greater than 60 days per year.

Or, repeat inspections every 6 years for aircraft subject to predominantly fresh water operations*.

*Predominantly fresh water operations are operations where salt water is encountered infrequently i.e. less than weekly landings/takeoffs in salt water (i.e. less than 4 times a month) or mooring the aircraft in salt water for less than 60 days per year.

This Amendment becomes effective on 29 September 2005.

Background:

Reports have been received by the Authority of severe corrosion damage affecting the wing fuselage carry through structures, which if undetected could lead to structural failure.

This amendment allows the use of a procedure approved by the manufacturer, which uses a borescope to inspect the centre section for corrosion.  The new procedure does not require removal of the wings and hence minimises disturbance of the structure and thus greatly minimises the time taken to do the inspection.

There is no change to the compliance time of a minimum inspection period of 3 years. However, in some cases, operators will now have up to 6 years between inspections depending on the type of environment the aircraft is predominantly operated in.  The requirements of the AD are changed to reflect the current manufacturer approved method of inspecting the wing centre section for corrosion using a borescope, instead of wing removal and a normal unaided visual inspection.

The original issue of this AD became effective on 13 July 1989.

David Villiers
Delegate of the Civil Aviation Safety Authority

8 August 2005