The Italian aviation safety agency, ANSV, issued four recommendations on August 2 to the EASA and Transport Canada about the Pratt & Whitney Canada PW127 turboprop engine that powers the ATR 72 regional airliner. The recommendations came after a series of engine failures that all occurred during the initial climb.
The ANSV attributes all the incidents to failure of the power turbine first stage rotor blade, causing subsequent damage and heavy imbalance in the power turbine (PT) assembly. This situation led to an imbalance in the low-pressure (LP) rotor and eventually oil leakage due to failure of the number six and seven bearing-compartment retaining bolts. In two of three incidents, the fire warning systems in the aircraft also sounded, with smoke entering the cabin.
The ANSV recommends operators “review the emergency procedures on ATR aircraft to ensure efficient removal of persisting smoke and appropriate cockpit/passenger cabin ventilation.”
Other recommendations suggest “Early withdrawal from service of PT1 rotor blades manufactured before the introduction of nondestructive testing (NDT) improvements or, alternatively, urgent introduction of a one-time X-ray inspection of all blades that have accumulated a number of cycles beyond a limit to be established.” Tomography checks are recommended to ensure the turbine blades are crack free. The Italian agency concludes by seeking agreement on the effective date for these recommendations and the EASA’s updates to them.