AD/PT6A/32 - Exhaust Duct Cracking

Administered by Department of Infrastructure, Transport, Regional Development, Communications, Sport and the Arts

Legislation au F2006B06368 In force Legislative Instrument

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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 39.1 (1) of CAR 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.

 

Pratt and Whitney Canada Turbine Engines - PT6A Series

 

AD/PT6A/32 Exhaust Duct Cracking 3/2003

 

Applicability: All PT6A-6, -6A, -6B, -11, -11AG, -15AG, -20, -20A, -20B, -21, -25, -25A, -25C, -

27, -28, -34, -34AG, -34B, -36, -110, -112, -135, and –135A series turboprop engines fitted with turbine exhaust ducts that are not in compliance with Pratt and Whitney Canada (P&WC) Service Bulletins (SB) 1610, 1610R1, 1610R2 or 12173R1.

 

Requirement: 1. Inspect the turbine exhaust duct for low-quality welds, created during repair, on the turbine exhaust duct near flange “A”, in accordance with Paragraphs 3B through 3E of:

 

  1. P&WC SB PT6A-72-1610 Revision 2 for models PT6A-6, -6A, -6B, -20, - 20A, -20B, -21, -25, -25A, -25C, -27, -28, -34, -34AG, -34B, -36, -135, and - 135A engines; or

 

b.        P&WC SB PT6A-72-12173 Revision 1 for models PT6A-11, -11AG, - 15AG, -110, and -112 engines.

 

2.        If it is determined that the welds meet acceptable criteria as detailed in Requirement 1a or 1b of this Directive:

 

  1. Return the duct to service.

 

b.        Carry out an internal inspection of the exhaust duct for cracking in accordance with the applicable P&WC Engine Overhaul Manual.

 

3.        If it is determined that the welds do not meet acceptable criteria as detailed in Requirement 1a or 1b of this Directive:

 

  1. Replace the duct with a serviceable part; or

 

b.        Carry out an inspection as detailed in Requirement 4 of this Directive.

 

4.        Use a 5x magnification to visually inspect the circumference of the forward area of the exhaust duct from the propeller reduction gearbox mounting flange to 2 inches aft of the flange for any crack indication:

 

  1. If no cracks are found, return the duct to service and repeat the initial inspection as detailed in Requirement 4 at the detailed interval.

 

Pratt and Whitney Canada Turbine Engines - PT6A Series

 

AD/PT6A/32 (Continued)

 

b.        If cracks are found exceeding the limits below, replace the duct with a serviceable part;

 

  1. If 3 or less cracks are found, and the total cumulative length of the cracks exceeds 2 inches; or

 

ii.        If any one crack exceeds 1 inch in length; or

 

iii.      If any 2 cracks are separated by less than 6 times the longest crack (6L) or 3 inches or less, whichever is the closest separation; or

 

iv.      If more than 3 cracks are found.

 

c.         If cracks are found that are within the limits set by requirement 4b(i) through

(iv) of this Directive, mark all allowable cracks on the duct with a suitable metal marking material; and record the length of the crack, location, number of duct operating hours, and time since overhaul; and

 

  1. Repeat the inspection and replace ducts exceeding the limits of Requirement 4b(i) through (iv) of this Directive;

 

ii.        Monitor the growth of existing cracks. For cracks exceeding a growth rate of 0.015 inches per hour time in service since the last inspection, replace the duct with a serviceable part.

 

Note 1: Canadian AD CF 2002-47 refers.

 

Note 2: Suitable marking materials can be found in the PWC Engine Manual.

 

Note 3: A replacement duct is one that meets the acceptability limits of this Directive.

 

Compliance: 1. At the next shop visit or within 150 flight hours from the effective date of this Directive, whichever occurs first.

 

2.        a. At the completion of Requirement 1 of this Directive.

 

b. At the next overhaul.

 

3.        Prior to further flight.

 

4.        a. At intervals not to exceed 150 flight hours.

 

b.        Prior to further flight.

 

c.         At intervals not to exceed 25 flight hours.

 

This Airworthiness Directive becomes effective on 20 March 2003.

 

Pratt and Whitney Canada Turbine Engines - PT6A Series

 

AD/PT6A/32 (Continued)

 

Background: This Directive requires the inspection of certain turbine exhaust ducts for cracks. The cracks have developed following repairs using a different welding process. Excessive cracking of the turbine exhaust duct could lead to reduction gearbox separation and/or decoupling of the power turbine shaft, which could in turn lead to the release of turbine blades.


 

James Coyne

Delegate of the Civil Aviation Safety Authority 3 February 2003

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


The above AD is notified in the Commonwealth of Australia Gazette on 26 February 2003.

Overview

The Airworthiness Directive (AD) 2003/32, issued under the Civil Aviation Act 1988, addresses the issue of exhaust duct cracking in Pratt and Whitney Canada PT6A Series turboprop engines, specifically those fitted with turbine exhaust ducts that have been repaired using substandard welding techniques. This AD was issued by the Civil Aviation Safety Authority (CASA) to ensure the safety of aircraft using these engines by mandating specific inspection and repair actions to prevent potential catastrophic failures. The directive outlines the necessity for inspections to detect low-quality welds and cracks in the turbine exhaust ducts, with clear instructions on when and how these inspections should be conducted, along with criteria for the replacement of defective parts. The directive aims to mitigate the risk of turbine blade release, which could result from excessive cracking and subsequent mechanical failures.

Scope and Application

This Airworthiness Directive (AD) applies to all PT6A-6, -6A, -6B, -11, -11AG, -15AG, -20, -20A, -20B, -21, -25, -25A, -25C, -27, -28, -34, -34AG, -34B, -36, -110, -112, -135, and –135A series turboprop engines fitted with turbine exhaust ducts that are not in compliance with Pratt and Whitney Canada (P&WC) Service Bulletins (SB) 1610, 1610R1, 1610R2 or 12173R1. This AD is applicable to all aircraft operators and maintenance entities that possess and operate these specified engine models. The AD's jurisdiction is the Commonwealth of Australia, issued under subregulation 39.1 (1) of the Civil Aviation Regulations 1998 (CAR 1998) by a delegate of the Civil Aviation Safety Authority (CASA). The AD is intended to ensure the safety of air travel by addressing a known unsafe condition related to the turbine exhaust ducts of the specified engine series. Compliance with the AD is mandatory and must be met within the specified timeframes; failure to comply could result in grounding of the affected aircraft. This AD does not specify any exclusions or exemptions, thereby applying universally to all entities and aircraft meeting the specified criteria.

Key Provisions

The Pratt and Whitney Canada Turbine Engines - PT6A Series AD/PT6A/32 Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA) under subregulation 39.1 (1) of the Civil Aviation Regulations 1998 (CAR 1998) applies to all PT6A series turboprop engines with turbine exhaust ducts that do not comply with Pratt and Whitney Canada (P&WC) Service Bulletins 1610, 1610R1, 1610R2 or 12173R1. The directive requires a series of inspections and actions to be taken to address potential safety issues related to exhaust duct cracking. Specifically, the AD mandates inspections of the turbine exhaust duct for low-quality welds near flange "A" (Section 1), and if acceptable welds are found, the duct can be returned to service. If the welds do not meet acceptable criteria, the duct must be replaced with a serviceable part or an internal inspection for cracking must be performed (Section 2). Additionally, the AD requires visual inspection of the exhaust duct for cracks using 5x magnification, and depending on the findings, either the duct is returned to service, cracks are marked and monitored, or the duct is replaced (Section 4). The AD imposes several obligations on the parties or entities it governs. Owners and operators of affected aircraft must ensure that inspections and actions as outlined in the AD are carried out in a timely manner. This includes conducting inspections at the next shop visit or within 150 flight hours from the effective date of the AD, whichever comes first (Compliance Section 1). If cracks are found during the inspection, the duct must be replaced or marked, and further inspections must be carried out at specified intervals (Compliance Sections 2 and 4). Failure to comply with the AD may result in the aircraft being deemed unairworthy, leading to potential grounding and operational disruptions. Failure to comply with the requirements of this AD can result in serious consequences. Under the Civil Aviation Act 1988, non-compliance may constitute an offence, leading to potential criminal charges. Additionally, the AD specifies that any aircraft found to be non-compliant may be deemed unairworthy, which can result in the aircraft being grounded until the necessary actions have been taken to bring it into compliance. The AD does not specify a particular penalty for non-compliance, but potential penalties for aviation-related offences can include substantial fines and imprisonment.

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Sourced from the Federal Register of Legislation at 26 August 2026. For the latest information on Australian Government law please go to https://www.legislation.gov.au.