E6-4923. Airworthiness Directives: Rolls-Royce Deutschland (RRD) (Formerly Rolls-Royce plc) Tay 650-15 Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Proposed rule; withdrawal.

SUMMARY:

This action withdraws a notice of proposed rulemaking (NPRM). That NPRM proposed a new airworthiness directive (AD) that applies to certain RRD Tay 650-15 series turbofan engines. That proposed action would have required initial and repetitive inspections of the high pressure compressor (HPC) shaft and high pressure turbine (HPT) shaft for spline flank wear. Since we issued that NPRM, the Luftfahrt-Bundesamt (LBA), which is the airworthiness authority for Germany, notified us that the spline flank wear inspections are now downgraded by RRD from “mandatory” to “recommended”. Accordingly, we withdraw the proposed rule.

FOR FURTHER INFORMATION CONTACT:

Ian Dargin, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

The FAA proposed to amend 14 CFR part 39 with a proposed airworthiness directive (AD). The proposed AD applies to RRD Tay 650-15 series turbofan engines. We published the proposed AD in the Federal Register on October 4, 2004 (69 FR 59148). That proposed action would have required initial and repetitive inspections of the HPC shaft and HPT shaft for spline flank wear. That proposed action resulted from a number of occurrences of excessive HPC shaft and HPT shaft spline flank wear discovered during on-wing and in-shop inspections.

Since we issued that NPRM, the LBA notified us that RRD downgraded the spline flank wear inspections from “mandatory” to “recommended”. RRD based the downgrade on performance calculation, rig test, and statistical analysis derived using the variation of HP spline wear rate, measured during engine teardowns and from data submitted by operators when accomplishing RRD Service Bulletin No. TAY-72-1485. We reviewed the RRD risk assessment and agree that we no longer need to require the inspections.

On further consideration, we withdraw the proposed rule based on RRD's analysis and our conclusion stated above.

Withdrawing this NPRM constitutes only that action, and does not prevent us from issuing another NPRM in the future, nor does it commit us to any course of action in the future.

Since this action only withdraws an NPRM, it is neither a proposed nor a final rule. Executive Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979) do not cover this withdrawal.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Withdrawal

Accordingly, we withdraw the notice of proposed rulemaking, FAA-2004-19157; Directorate Identifier 2004-NE-30-AD, published in the Federal Register on October 4, 2004 (69 FR 59148).

Issued in Burlington, Massachusetts, on March 30, 2006.

Peter A. White,

Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service.