AD 99-24-14

This amendment adopts a new airworthiness directive (AD) that is applicable to General Electric Company (GE) CF6-80E1A2 series turbofan engines. This action requires removing from service stage 2 high pressure turbine (HPT) disks and impeller spacers prior to exceeding new, lower cyclic life limits and imposes a drawdown program for those parts that currently exceed, or will exceed, the new lower limits. This amendment is prompted by the results of a refined low cycle fatigue (LCF) analysis. The actions specified in this AD are intended to prevent LCF cracking and failure of stage 2 HPT disks and impeller spacers, which could result in an uncontained engine failure and damage to the aircraft.

Final rule; request for comments.

99-24-14 General Electric Company: Amendment 39-11438. Docket 99-NE-52-AD. Issued October 18, 1999.
Applicability: General Electric Company (GE) CF6-80E1A2 series turbofan engines, with stage 2 high pressure turbine (HPT) disks, part number (P/N) 1639M50P03, and HPT impeller spacers, P/N 1473M85P02, installed. These engines are installed on but not limited to Airbus Industrie A330 series airplanes.
Note 1: This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repairon the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
Compliance: Required as indicated, unless accomplished previously.
To prevent low cycle fatigue (LCF) cracking and failure of stage 2 HPT disks and impeller spacers, which could result in an uncontained engine failure and damage to the aircraft, accomplish the following: Stage 2 HPT Disks Drawdown Plan
(a) Remove from service stage 2 HPT disks, P/N 1639M50P03, and replace with serviceable parts, as follows:
Note 2: GE CF6-80E1A2 Service Bulletin (SB) 72-0169, dated July 22, 1999, describes the stage 2 HPT disk drawdown plan.
(1) For disks that have accumulated greater than or equal to 3,800 cycles-since-new (CSN) on the effective date of this AD, remove within 200 cycles-in-service (CIS) after the effective date of this AD, but not to exceed 6,400 CSN.
(2) For disks that have accumulated greater than or equal to 2,500 CSN on the effective date of this AD and less than 3,800 CSN on the effective date of this AD, remove from service prior to accumulating 4,000 CSN.
(3) For disks that have accumulated greater than or equal to 1,900 CSN on the effective date of this AD and less than 2,500 CSN on the effective date of this AD, remove from service within 1,500 CIS after the effective date of the AD.
(4) For disks that have accumulated less than 1,900 CSN on the effective date of this AD, remove prior to accumulating 3,400 CSN.
New, Stage 2 HPT Disk Lower Life Limit
(b) Except for the provisions of paragraph (d) of this AD, no stage 2 HPT disk, P/N 1639M50P03, may be installed with 3,400 or greater CSN.
New, Lower HPT Impeller Spacer Life Limit
(c) Remove from service HPT impeller spacers, P/N 1473M85P02, prior to accumulating 5,100 CSN. Except for the provisions of paragraph (d) of this AD, no HPT impeller spacer, P/N 1473M85P02, may be installed with 5,100 or greater CSN.
Note 3: GE CF6-80E1A2 SB 72-0169, dated July 22, 1999, describes an HPT impeller spacer drawdown plan that is not utilized in this AD.
Alternative Method of Compliance
(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office (ECO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.
Note 4: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the ECO.
Ferry Flights
(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished.
(f) This amendment becomes effective on December 18, 1999.

The Federal Aviation Administration (FAA) received results of a refined low cycle fatigue (LCF) analysis for stage 2 high pressure turbine (HPT) disks and impeller spacers installed on General Electric Company (GE) CF6-80E1A2 series turbofan engines. GE has advised the FAA that the retirement lives of the CF6-80E1A2 HPT stage 2 disk and impeller spacer identified in Chapter 5 of the Engine Manual need to be reduced. Updated stress analysis showed the operating stresses to be higher than originally predicted, resulting in lower calculated cyclic retirement lives for these components. The lower calculated cyclic lives are below the current retirement lives found in Chapter 5 of the Engine Manual. There have been no reports to date of LCF cracking or distress on these components attributed to parts exceeding the new reduced Chapter 5 retirement lives. The LCF analysis completed as part of a CF6-80E1 derivative model certification program showed significantlydifferent retirement lives for the two engine models with similar components. GE initiated an investigation and assessment of the LCF analysis to understand the disparity and determined the updated and refined analysis resulted in a more complete understanding of the operating stresses for certain critical features for these components. This condition, if not corrected, could result in LCF cracking and failure of stage 2 HPT disks and impeller spacers, which could result in an uncontained engine failure and damage to the aircraft. Service Information
GE CF6-80E1A2 SB 72-0169, dated July 22, 1999, that describes the new, lower life cyclic life limits and a drawdown plan for both the stage 2 HPT disks and impeller spacers. Difference Between AD and SB
The SB, unlike this AD, includes a drawdown plan for impeller spacers. A recent reassessment of the need for a drawdown program for the impeller spacer occurred when a high cycle engine with the affected stage 2 HPT disk and impellerspacer had recently been removed from service due to high vibration. The assessment shows a drawdown program was not required for the impeller spacer.
In addition, the SB includes a drawdown program for the diffuser vane ring which is not included in the AD. Required Actions
Since an unsafe condition has been identified that is likely to exist or develop on other engines of the same type design, this AD is being issued to prevent an uncontained engine failure. This AD requires removing from service stage 2 HPT disks, part number (P/N) 1639M50P03, prior to exceeding new, lower cyclic life limits, and replacing with serviceable parts. The AD also imposes a drawdown program for those parts that currently exceed, or will exceed, the new lower limits. The HPT impeller spacers, P/N 1473M85P02, need only to be removed and replaced prior to exceeding the new, lower cyclic life limit. The FAA has determined, based on a current fleet histogram, that a separate drawdown program for theHPT impeller spacer is not needed since there are no impeller spacers in service which exceed the new reduced cyclic life limit. The new life limits are based on an updated stress and life analysis. Immediate Adoption
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. 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 to the address specified under the caption ADDRESSES. All communications received onor 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 9X-NE-XX-AD." The postcard will be date stamped and returned to the commenter. Regulatory Impact
This rule does not have federalism implications, as defined in Executive Order No. 13132, because it does 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 rule.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant underDOT 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, 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: