AD/PA-25/40 Amdt 9 Wing Lift Struts (Cth)

AIRWORTHINESS DIRECTIVE

On the commencement date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below repeals Airworthiness Directive (AD) AD/PA-25/40 Amdt 8 and issues the following AD under subregulation 39.001 (1) of CASR 1998 and subsection 33 (3) of the Acts Interpretation Act 1901. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct an 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.

Laviasa (Piper) PA-25 (Pawnee) Series Aeroplanes

AD/PA-25/40 Amdt 9 Wing Lift Struts 26/2016

Applicability:

Model PA-25, PA-25-235, and PA-25-260 aircraft, serial numbers 25-1 to 25‑8156024.

Requirement:

Comply with the requirements of FAA AD 2015-08-04, as in force at the date of this AD.

Inspections carried out in accordance with previous issues of this AD are considered acceptable for past repetitive inspection requirements of the FAA AD.

Note:  The FAA AD refers to Piper Mandatory Service Bulletin (MSB) No. 528D dated 19 October 1990 and Piper MSB 910A, dated 10 October 1989.

Compliance:

In accordance with FAA AD 2015-08-04.

This AD commences on 6 January 2017.

Background:

The manufacturer considers inspection of the lower bottom area of the struts critical.

The detection of internal corrosion in struts is in most cases difficult, and may not become apparent until advanced completely through the tube wall. Amendment 3 clarified assessment by a CAR 35 Authorised Person of struts that have corrosion indicated radiographic inspection.

Amendment 4 updated the reference document, and allowed new sealed struts as terminating action. The new strut also incorporates a redesigned strut fork.

Amendment 5 introduced a reduced corrosion inspection interval following two reports of excessive corrosion appearing within the 5 year interval. The requirement that the wing struts must be removed was also clarified, since service history revealed that water may enter the struts and resulting corrosion may go undetected if the struts are not removed. This has led directly to at least one fatal accident.

Amendment 6 corrected the compliance paragraph to allow 24 months since last X-ray inspection.

Amendment 7 introduced inspection of the strut upper end if the upper cuff fairing is attached by a screw. Reports were received of severe internal corrosion of wing struts at the upper cuff fairing screw attachment hole area.

Amendment 8 aligned this AD with the requirements of a new state of design FAA AD which supersedes AD 93-10-06; which was referenced in Amendment 7 of this AD.

This Amendment 9 accepts and aligns to the requirements of FAA AD 2015-08-04 now that the USA is not the State of design. CASR Part 39 foreign state-of design requirements may not provide for automatic acceptance of the FAA AD. References to alternative X-Ray inspection have been removed and any AMOC application will be assessed by the CASA.

Ben Wilson
Delegate of the Civil Aviation Safety Authority

12 December 2016