Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
During quality inspections in repair centre some 2nd stage Nozzle Guide Vanes (NGVs) to be installed on Pre TU 148 standard Arriel 1B were found not conforming to the definition. The affected parts had been repaired and were found drilled on the rear flange instead of the front flange. This configuration corresponds to 2nd stage Turbine NGVs to be installed on post-TU 148 standard Arriel 1B engines. This non compliance may only be found on post-TU 76 standard 2nd stage Turbine NGVs (i.e., with flexible hub).
This non compliance would increase hot gas ingestion and generate an increase of temperature in the Gas Generator (GG) turbine rotor,potentially resulting in turbine damage and an uncommanded in-flight shutdown.
We are proposing this AD to prevent over-temperature damage of the gas generator turbine, which could result in an uncommanded in-flight engine shutdown, and a subsequent forced autorotation landing or accident.