The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom (UK), recently notified the Federal Aviation Administration (FAA) that an unsafe condition may exist on Rolls-Royce plc (RR) RB211-524G2-T-19; RB211-524G3-T-19; RB211-524H2-T-19; and RB211 Trent 768-60 and 772-60 turbofan engines. The CAA advises that it has received six reports of failures of high-pressure compressor (HPC)-to-high-pressure turbine (HPT) joint bolt assemblies, part number (P/N) BLT5543. In one case, a bolt head separated from the rest of the bolt and was propelled toward the HPC stage 6 disk where it caused impact damage to the stage 6 disk. A crack could initiate from the damage and propagate to disk failure. The investigation by the CAA has revealed that material selection, INCO 909, contributed to the failure of the HPC-to-HPT joint bolt assemblies, P/N BLT5543. This condition, if not corrected, could result in failure of the HPC-to-HPT joint bolt assemblies, which could result in a cracked stage 6 HPC disk, possible uncontained engine failure, and damage to the airplane. Manufacturer's Service Information
RR has issued mandatory service bulletin (SB) RB.211-72-C491, Revision 1, dated October 8, 1999, that specifies procedures for replacement of the INCO 909 HPC-to-HPT joint bolt assemblies, P/N BLT5543, with INCO 718 HPC-to-HPT joint bolt assemblies, P/N BLT5541, during the next normal overhaul when the module is sufficiently disassembled to allow access to the bolts, but no later than June 30, 2000. The CAA classified this service bulletin as mandatory and issued AD 004-10-99, dated October 8, 1999, in order to assure the airworthiness of these RR engines in the UK.
Bilateral Airworthiness Agreement
These engine models are manufactured in the UK and are type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. The FAA has examined the findings of the CAA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States. Required Actions
Since an unsafe condition has been identified that is likely to exist or develop on other engines of the same type design registered in the United States, this AD requires replacement of the INCO 909 HPC-to-HPT joint bolt assemblies, P/N BLT5543, with INCO 718 HPC-to-HPT joint bolt assemblies, P/N BLT5541, before further flight. The actions would be required to be accomplished in accordance with the SB described previously. Difference of Compliance Times Between the Manufacturer's Service Bulletin and This AD
RR SB No. RB.211-72-C491, Revision 1, dated October 8, 1999, requires that the joint bolts bereplaced before June 30, 2000. The FAA has determined that since none of these engines are currently in use in the United States, the AD may require that the joint bolts be replaced before further flight. Immediate Adoption
Since there are currently no domestic operators of this engine model, notice and opportunity for prior public comment are impracticable. Therefore, a situation exists that allows the immediate adoption of this regulation. Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption ADDRESSES. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 99-ANE-59-AD." Thepostcard will be date stamped and returned to the commenter. Regulatory Impact
The regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order (EO) No. 13132.
The FAA has determined that this regulation is a nonsignificant regulation that may be issued immediately to correct an unsafe condition in engines, and is not a "significant regulatory action" under EO No. 12866. It has been determined further that this action involves a nonsignificant regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: