On July 1, 2014, the FAA published a new Airworthiness Directive (AD) 2014-11-05 applicable to certain Pratt & Whitney Canada Corp. (P&WC) turboprop engines. This proposal would require installation of a reinforcement liner to the power turbine (PT) containment ring. Various models in the PT6A line are affected either as a whole model or certain serial numbers within a model. Pay close attention to the applicability list in the AD. For example, model PT6A-34AG, with serial numbers PCE-57312 and earlier as well as all engines converted to PT6A-34AG are applicable.

The AD was prompted by in-service events involving the perforation of engine cases as a result of the liberation of PT blades and the fracture/displacement of the PT containment ring. The AD is issued to prevent uncontained engine failure and damage to the airplane.

On Jan. 7, 2014, a notice of proposed rulemaking (NPRM) was issued giving the proposed action of this AD. The public was given the opportunity to comment and those comments were addressed by the FAA. As a result, the proposed compliance time was changed from 24 months to 48 months and estimated labor cost of compliance was changed to about $1,655 per engine.

The proposed AD would require, within 48 months of the effective date of this AD, modification of the existing PT containment ring. Use paragraph 2, Accomplishment Instructions, of P&WC Service Bulletin (SB) No. 12076, Revision 3, dated Jan. 17, 1992, or paragraph 3, Accomplishment Instructions, of P&WC SB No. PT6A-72-A1427, Revision 3, dated Jan. 27, 2012, as applicable, to make the modification.