On July 6, 1998, the Federal Aviation Administration (FAA) issued airworthiness directive (AD) 98-15-03, Amendment 39-10654 (63 FR 37761, July 14, 1998), to require:
Initial and repetitive eddy current inspection (ECI) for cracks in the high pressure compressor (HPC) stage 2-6 spool spacer arms, forward and aft of the stage 3-4 and stage 4-5 interstage seal teeth, and, if necessary, replacement with serviceable parts.
A shop level ECI for cracks in the HPC stage 2-6 spool interstage seal teeth, and, if necessary, replacement with serviceable parts.
That action was prompted by reports of cracked HPC stage 2-6 spools installed on General Electric Company (GE) GE90-76B, -77B, -85B, -90B, and -92B model turbofan engines. That condition, if not corrected, could result in failure of the HPC stage 2-6 spool due to cracks, which could result in an uncontained engine failure and damage to the airplane.
Since that AD was issued, the FAA has determined that either of the inspection methods required by the current AD may be used to satisfy either inspection requirement if done in accordance with the applicable Service Bulletins. Furthermore, certain spools have been approved as terminating the need for continuing inspections. Lastly, the FAA has determined that the affected spools are required to be removed from service no later than a specified number of engine cycles or by June 30, 2005, whichever occurs first.
The manufacturer has confirmed the design integrity of two of the spools affected by the current AD, P/N 350-005-770-0 (except for SN LAO37677) and P/N 350-005-771-0. Based on additional test and analysis, these spools need no further inspection. In addition, the manufacturer has introduced a new design HPC stage 2-6 spool, P/N 350-005-780-0 and a repair procedure which creates two other spools part numbers, P/N 350-005-775-0 and P/N 350-005-776-0. With spools having any of these five part numbers installed, this AD will no longer apply to the engine, terminating the requirement for additional inspections. Also, reference to the GE90-92B model is removed from the AD applicability because the manufacturer has informed the FAA that no engines of that model were produced and has requested the FAA remove this model designation from the GE90 Type Certificate. In addition, HPC spool P/N 350-005-769-0 is deleted since the manufacturer has informed the FAA that this P/N spool has never been produced and will not be produced.
Manufacturer's Service Information
The FAA has reviewed and approved the technical contents of GE Service Bulletin No. GE90 S/B 72-0352, Revision 4, dated July 31, 2000, that describes ECI procedures for cracks in the HPC stage 2-6 spool interstage seal teeth, and GE Alert Service Bulletin (ASB) No. GE90 72-A0357, Revision 4, dated July 31, 2000, that describes procedures for ECI for cracks in the HPC stage 2-6 spool spacer arm, forward and aft of the stage 3-4 and stage 4-5 interstage seal teeth. This ASB also removes the inspection requirement for HPC spools P/N 350-005-770-0 (except for S/N LAO37677) and P/N 350-005-771-0.
FAA's Determination of an Unsafe Condition and Required Actions
Although none of these affected engine models are used on any airplanes that are registered in the United States, the possibility exists that the engine models could be used on airplanes that are registered in the United States in the future. Since an unsafe condition has been identified that is likely to exist or develop on other GE90 series turbofan engines of this same type design, this AD is being issued to prevent failure of the HPC stage 2-6 spool due to cracks, which could result in an uncontained engine failure and damage to the airplane. This AD requires:
Initial and repetitive ECI for cracks in the HPC stage 2-6 spool spacer arms, forward and aft of the stage 3-4 and stage 4-5 interstage seal teeth, and, if necessary, replacement with a serviceable part.
A shop level ECI for cracks in the HPC stage 2-6 spool interstage seal teeth, and, if necessary, replacement with serviceable parts.
Removal of affected part number HPC stage 2-6 spools from service based on either engine cycles or calendar date, whichever occurs first.
The actions must be done in accordance with the service bulletins described previously.
Immediate Adoption of This AD
Since there are currently no domestic operators of these engine models, notice and opportunity for prior public comment are unnecessary. 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, thus, 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 action must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 98-ANE-17-AD." The postcard will be date stamped and returned to the commenter.
Regulatory Analysis
This final rule does not have federalism implications, as defined in Executive Order 13132, because it would 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this final rule.
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained by contacting 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.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing Amendment 39-10654 (63 FR 37761, July 14, 1998), and by adding a new airworthiness directive, Amendment 39-12622, to read as follows: