AD/PA-25/43 Exhaust System and Related Areas Inspection (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.

Piper PA-25 (Pawnee) Series Aeroplanes

AD/PA-25/43 Exhaust System and Related Areas - Inspection 12/2008

Applicability:

Piper PA-25-235 with serial numbers from 25-2000 to 25-4171 inclusive, except aircraft fitted with muffler and exhaust stack clamps included in muffler installation kit, Piper Part Number 753-753.

Requirement:

Inspect the entire exhaust system for signs of cracks, burn-throughs, weld separations, failed internal baffles etc.  The muffler need not be removed from the aircraft provided visual inspection with a probe light and mirror are made through the muffler tail pipe outlet and one end of the muffler stack connection.

This inspection must be performed in accordance with either USA AD 67-14-07 or Piper Service Bulletin No. 241A.

Compliance:

At each scheduled inspection for issue of a maintenance release following the date of effectivity of this Airworthiness Directive.

This Airworthiness Directive becomes effective on 20 November 2008.

Background:

The original issue of AD/PA-25/12 in 1962 applied to all models of PA-25 and specified inspection of the exhaust system in accordance with Piper Service Letter No. 324B.

The original issue of AD/PA-25/26 in 1968 also specified inspection of the exhaust system in accordance with Piper Service Bulletin No. 241 and USA AD 67-14-07, and was applicable to PA-25-235 serial numbers 25-2000 to 25-4171.  It was accompanied by amendment of AD/PA-25/12 to exclude PA-25-235 with serial numbers given above.

AD/PA-25/26 was cancelled in 1974 and PA-25-235 with serial numbers given above were restored to AD/PA-25/12.  This action was taken because SB No. 241 and AD 67-14-07 do not require periodic inspection of the exhaust system after installation of Piper muffler and exhaust stack clamps included in muffler installation kit, Piper Part Number 753-753.  The service history of the PA-25 in Australia at the time suggested that periodic inspection of the exhaust system was unavoidable, and SL No. 324B and C provided a suitable inspection regime.

AD/PA-25/12 Amdt 2 has been reviewed.  Mandatory application of SL No. 324C to PA-25 is unique to Australia.  The service history of the exhaust system in PA-25 in Australia has improved and indicates that use of an AD to mandate SL No. 324C is no longer warranted.  AD/PA-25/12 is to be cancelled.

This AD is the same as AD/PA-25/26 prior to cancellation, and mandates the periodic inspection specified in USA AD 67-14-07 and Piper SB No. 241A.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

9 October 2008