AD NUMBER: 2008-11-19
MANUFACTURER: Rolls Royce
SUBJECT: Airworthiness Directive 2008-11-19
SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This 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: Three Trent 700 IP Turbine discs that exhibited signs of wear at the bore following failure of the bearing chamber sealing sleeve were returned to service.

This was based on the fact that Non-Destructive Testing (NDT) did not reveal micro cracking on the affected disc areas. Further engineering investigation considered that, although no micro cracking had been found, the worn disc bore surfaces would have an associated fatigue penalty compared to an unaffected bore.

A crack developing from these rubbed surfaces could potentially lead to a disc burst. As the described wear, present at the bores of those three discs, presents a potential unsafe condition, this Airworthiness Directive requires identification of the three affected serial numbers of IP Turbine Discs (P/N FK20795) and removal from service prior to attaining a certain number of cycles, as indicated.

We are issuing this AD to prevent a failure of the intermediate pressure (IP) turbine disc that could result in an uncontained failure of the engine and possible damage to the airplane.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/