Airworthiness Directive · Amendment 39-17349 · Pratt & Whitney Canada Corp Turboshaft Engines
Pratt & Whitney Canada Corp Turboshaft Engines
This AD applies to Pratt & Whitney Canada Corp. (P&WC) PT6C-67C turboshaft engines that have not had P&WC Service Bulletin (SB) No. PT6C-72-41056 incorporated.
We are adopting a new airworthiness directive (AD) for certain Pratt & Whitney Canada Corp. (P&WC) PT6C-67C turboshaft engines. This AD requires initial and repetitive borescope inspections to verify the presence of a retaining ring securing the power turbine (PT) baffle located near the second stage PT disk. If the engine fails the inspection, this AD also requires removing the engine from service before further flight. This AD was prompted by five reported incidents of second stage PT disk damage. We are issuing this AD to prevent damage to the PT disk which, if undetected, could cause uncontained PT disk failure and loss of control of the helicopter.
Unless already done, do the following actions.
(1) Borescope-inspect to verify the presence of a retaining ring securing the PT baffle located near the second stage PT disk, as follows:
(i) For engines with 2,200 PT cycles or more on the effective date of this AD, inspect within 100 operating hours or 150 PT cycles, whichever occurs first.
(ii) For engines with more than 1,400 PT cycles but fewer than 2,200 PT cycles on the effective date of this AD, inspect within 250 operating hours, 350 PT cycles, or before exceeding 2,350 PT cycles, whichever occurs first.
(iii) For engines with 1,400 PT cycles or fewer on the effective date of this AD, inspect within 500 operating hours, 750 PT cycles, or before exceeding 1,750 PT cycles, whichever occurs first.
(2) Thereafter, repetitively borescope-inspect to verify the presence of the retaining ring securing the PT baffle located near the second stage PT disk, on or before an additional 600 flight hours or 900 PT cycles, whichever occurs first.
(3) Use P&WC Alert SB No. PT6C-72-A41060, Revision 3, dated October 11, 2012, paragraphs 3.A.(1) through 3.A.(6) to do the borescope inspections required by this AD.
(4) If the retaining ring is missing or the PT baffle is out of position, then remove the engine from service before further flight.
Performing the engine improvement modifications in P&WC SB No. PT6C-72-41056, Revision 5, dated January 17, 2013, paragraphs 3.A. through 3.C.(12) and 3.E.(1) through 3.E.(15), is an optional terminating action to the repetitive inspections required by this AD.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
