Transport Canada issued emergency airworthiness directive (AD) CF-2024-05 today covering a large number of Pratt & Whitney Canada (P&WC) PT6 turbine engines. The AD requires compliance by removal of affected PT2 (power turbine) blades before further flight.
According to the AD, “There has been one recent in-service report of PT2 blade failure on a PT6A-67 engine. In addition, there have been two other events of PT2 blade failures during testing at the manufacturer’s facility. The blade failures in all cases were contained.”
While P&WC is investigating the root cause of these failures, it has determined that newly manufactured blades with part number 3056693-01 were all made from the same raw material and that they had all accumulated fewer than 25 hours air time since they were new. “Failure of PT2 blades could lead to engine power loss or in-flight shut down, potentially resulting in reduced control of the aeroplane,” the AD noted. The in-service report “resulted in an aborted takeoff,” P&WC told AIN.
Affected blade serial numbers are listed in a table in the AD and also “have accumulated less than 50 hours air time since new, or since shop visit, or since second-stage power turbine repair.” These blades must be removed and not used.
According to the company, “[P&WC] has recently identified a limited subpopulation of high power PT6A and PT6E engines that require part replacement before returning to service. The population is limited to engine parts with less than 50 flight hours (total, or since last shop visit, or total time since second stage power turbine repair) manufactured from a single batch of sourced product. [P&WC] is working with airframers, operators, and Transport Canada to issue fleet instructions and to schedule maintenance.” The company pointed out that the issue with the PT2 blades “is not powder-metal-related.”
Replacement of the affected blades should take, P&WC said, “from one to four weeks. Single aircraft operators with limited access to an overhaul facility will take closer to four weeks, while those with access to shops can turn an engine in less than a week.”
About 5,000 blades made from the suspect raw material are affected. “Each PT6 engine has 43 blades on the second turbine disk, but each engine may have a blade population sourced from various raw material (co-mingled inventory).”
The AD applies to the following models: PT6A-64, PT6A-66, PT6A-66A, PT6A-66B, PT6A-66D, PT6A-66T, PT6A-67, PT6A-67A, PT6A-67AF, PT6A-67AG, PT6A-67B, PT6A-67D, PT6A-67F, PT6A-67P, PT6A-67R, PT6A-67RM, PT6A-67T, PT6A-68, PT6A-68B, PT6A-68C, PT6A-68D, PT6A-68T, PT6E-67XP, and PT6E-66XT.