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:
There have been several findings of cracking at the firtrees of LP Turbine discs. Fatigue crack initiation and subsequent crack propagation at the firtree may result in multiple LP Turbine blade release. The latter may potentially be beyond the containment capabilities of the engine casings. Thus, cracking at the firtrees of LP Turbine discs constitutes a potentially unsafe condition.
We are proposing this AD to detect cracks in the low-pressure turbine stage 1, 2, and 3 discs, which could result in an uncontained release of LP turbine blades and damage to the airplane.