AD/PT6B/1 Gas Generator Case (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.

Pratt & Whitney Canada Turbine Engines - PT6B Series

AD/PT6B/1 Gas Generator Case 13/2010

Applicability:

All PT6B-36 and -36A engine models not incorporating:

(a)   gas generator case P/N 3112048-01 identified by P&WC SB 11041, or

(b)   superseding parts incorporating the intent of SB 11041, or

(c)   stiffening plates P/N 3102444-01.

Requirement:

1.    Unless previously accomplished, inspect the gas generator case for seam weld cracking in accordance with Part 2A of the Accomplishment Instructions of P&WC SB 11031R1 or later revision.

2.    Repair all seam weld cracking in accordance with Part 2B of the Accomplishment Instructions of P&WC SB 11031R1 or later revision.  This repair constitutes terminating action of this AD.

Note:  Transport Canada AD CF-88-01R1 refers.

Compliance:

1.    Prior to gas generator cases accumulating 1200 hours time in service since new or within the next 100 hours time in service from the effective date of this AD, whichever occurs last.  Thereafter at intervals not exceeding 600 hours time in service.

2.    Prior to further flight.

This Airworthiness Directive becomes effective on 9 July 2010.

Background:

A number of gas generator case longitudinal seam welds have been found cracked. An undetected weld seam crack could lead to the rupture of the pressure vessel and a subsequent unsafe condition.  This AD requires dye penetrant inspection of the gas generator case longitudinal seam and repair if found cracked.  This AD is issued as a result of an audit of Transport Canada ADs.

Mike Higgins
Delegate of the Civil Aviation Safety Authority

22 June 2010