EASA poised to overhaul 'unrepresentative' engine endurance testing

Certification requirements for turbofan endurance testing are set to be overhauled by European regulators, to take better account of modern engine design characteristics. The update is contained in a proposal put forward by the European Union Aviation Safety Agency. It also intends to improve the level of confidence in the robustness of engine design prior to entry-into-service by requiring a test to demonstrate the powerplant’s initial maintenance programme. “Some turbofan engines have faced unexpected failures shortly after entry-into-service,” says EASA in its proposal. “Such issues required urgent corrective actions to control the associated safety risk posed by multiple engine shutdown occurrences. “The root cause of such failures may have been identified during the engine endurance test if the test conditions and the engine configuration had been more representative.” While EASA does not identify any specific powerplants, engines including the Rolls-Royce Trent 1000 for the Boeing 787 and, more recently, the Pratt & Whitney PW1000G have each suffered premature in-service durability issues. EASA’s current certification standard for engine endurance requires an “accelerated severity” test to demonstrate a minimum level of operability and durability within approved engine limitations. But it states that the origins of the test date back 60 years, when it was intended for the operational characteristics of reciprocating engines. “The fundamental approach – the demonstration of concurrent redline speed and temperatures – has been retained because these conditions are undeniably conservative and desirable from a safety-demonstration perspective,” says EASA. But it acknowledges that the test running conditions are becoming “harder to achieve” as engine designs have evolved and adapted to the needs of modern air transport.<br/>