Consultation expired with comments. The proposed Certification Memorandum (CM) has been updated based on the comments received, and the corresponding Comment-Response Document (CRD) has been completed by EASA.
Details
Identification of issue
Turbine Drive Arms fulfil the same torque transmission function as conventional shafts, and their failure consequences are similar, including the potential for Hazardous complete loss of load on a turbine rotor. Several Turbine Drive Arms failures in service have highlighted inconsistencies in application CS-E to these features. To ensure a consistently high level of safety, this Certification Memorandum establishes the applicability of CS-E regulations to Turbine Drive Arms and outlines acceptable approaches to showing compliance.
For the purpose of this Certification Memorandum, “Turbine Drive Arm” refers to a feature delivering torque between a turbine disc and a turbine shaft, as well as to a feature delivering torque between turbine rotor stages, also referred to here as an “Interstage Turbine Drive Arm”. Turbine Drive Arms are typically integral to the turbine disc itself, although they can also be separate components. Turbine Drive Arms are considered to meet the definition of “Shafts” in AMC E 850(1)(a).
Where drive is delivered to or from a turbine disc via features directly mounted on the disc (e.g. via a curvic coupling, or bolted flange), these should be considered as part of the disc and not as a Turbine Drive Arm.
