Summary
We propose to adopt a new airworthiness directive (AD) for certain Pratt & Whitney Canada Corp. (P&WC) PT6C-67C turboshaft engines. This proposed AD was prompted by five reported incidents of second stage power turbine (PT) disk damage. This proposed AD would require initial and repetitive borescope inspections to verify the presence of a retaining ring securing the PT baffle located near the second stage PT disk. If the engine fails the inspection, this proposed AD would also require removing the engine from service before further flight. We are proposing 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.