Transport Canada has ordered operators to ground aircraft powered by some Pratt & Whitney Canada (P&WC) PT6 turboprops pending turbine blade replacements, a move coming in response to failures of three second-stage power turbine blades.
The order affects 160-180 PT6A and PT6E turboprops, according to P&WC parent RTX. The manufacturer adds that the issue is unrelated to a powder-metal manufacturing problem affecting Pratt & Whitney PW1000G geared turbofans.
Transport Canada says affected engines contain blades manufactured from the same batch of materials used to produce the three failed blades.
Those failed blades were all relatively new, having accumulated less than 25h of flight time, the regulator says in a 15 February airworthiness directive.
That order takes effect on 16 February and requires operators to replace affected blades “prior to next flight”.
It applies to about two dozen PT6A and PT6E variants, including those that power aircraft including Beechcraft 1900Ds, Daher TBMs, Embraer Super Tucanos, Piaggio Avantis and Pilatus PC-12s and PC-21s.
“Pratt & Whitney Canada has recently identified a limited sub-population of high-power PT6A and PT6E engines that require part replacement before returning to service,” RTX says. “The population is limited to engine parts with less than 50 flight hours… manufactured from a single batch of sourced product.”
Those 50 flight hours include total hours, hours since a last shop visit and hours since an engine underwent a second-stage power turbine repair.
Transport Canada’s order responds to reports of three second-stage power turbine blade failures on PT6s. Two of those failures occurred “during testing at the manufacturer’s facility”, and one involved an in-service PT6, the regulator says.
Transport Canada does not elaborate about the in-service failure, but RTX says it resulted in an aborted take-off.
“P&WC is still investigating the root cause of the blade failures, but preliminary investigation determined that the power turbine modules in all event engines contained newly manufactured blades… from the same raw material,” Transport Canada says. “In all cases, the blades had accumulated less than 25h air time since new.”
