# 63 FR 27001: Airworthiness Directives; General Electric Company CF6-6 Series Turbofan Engines > Federal · Regulations · In force URL: https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-12915 ## Section - **Citation:** 63 FR 27001 - **Heading:** Airworthiness Directives; General Electric Company CF6-6 Series Turbofan Engines - **Jurisdiction:** Federal - **Kind:** Regulations - **Status:** In force - **Text as of:** August 14, 2026 - **Source:** Compiled text - **Location:** Federal Register / Vol. 63 / 63 FR 27001 ## Text DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. 98-ANE-18-AD] RIN 2120-AA64 Airworthiness Directives; General Electric Company CF6-6 Series Turbofan Engines AGENCY: Federal Aviation Administration, DOT. ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to General Electric Company (GE) CF6- 6 series turbofan engines. This proposal would require removal from service of affected low pressure turbine (LPT) stage 4 disks prior to reaching new, reduced cyclic life limits, and replacement with serviceable parts. This proposal is prompted by reports of LPT stage 4 disk cracking in the blade dovetail slot bottom area. The actions specified by the proposed AD are intended to prevent LPT stage 4 disk cracking, which could result in an uncontained engine failure and damage to the aircraft. DATES: Comments must be received by June 15, 1998. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 98-ANE-18-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: ``9-ad- [email protected]''. Comments sent via the Internet must contain the docket number in the subject line. Comments may be inspected at this location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. FOR FURTHER INFORMATION CONTACT: Karen Curtis, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7192, fax (781) 238-7199. SUPPLEMENTARY INFORMATION: Comments Invited e inspected at this location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. FOR FURTHER INFORMATION CONTACT: Karen Curtis, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7192, fax (781) 238-7199. SUPPLEMENTARY INFORMATION: Comments Invited Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received. Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal 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 98-ANE-18-AD.'' The postcard will be date stamped and returned to the commenter. Availability of NPRMs Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 98-ANE-18-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Discussion The Federal Aviation Administration (FAA) has received reports of low card will be date stamped and returned to the commenter. Availability of NPRMs Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 98-ANE-18-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Discussion The Federal Aviation Administration (FAA) has received reports of low pressure turbine (LPT) stage 4 disk cracking on General Electric Company (GE) CF6-6 series turbofan engines. The investigation revealed that the dovetail slot bottoms of the LPT stage 4 disks, part numbers (P/Ns) 9010M40P01, 9010M40P02, 9010M40P07, 9010M40P09, and 9010M40P12, have higher than predicted levels of stress during engine operation. In addition, the low cycle fatigue (LCF) material properties have been found to be lower than the original design intent. The disk cracks were found by inspection during engine shop visits. Extensive material testing, and stress and life analyses revealed a minimum calculated LCF cyclic life lower than the published LCF cyclic retirement life for the stage 4 LPT disks. This condition, if not corrected, could result in LPT stage 4 disk cracking, which could result in an uncontained engine failure and damage to the aircraft. Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require removal from service of affected LPT stage 4 disks prior to reaching new, reduced cyclic life limits, and replacement with serviceable parts . There are approximately 257 engines of the affected design in the worldwide fleet. The FAA estimates that 242 engines installed on aircraft of U.S. registry would be affected by this proposed AD, and that required parts, on a prorated basis, would cost approximately $22,432 per engine. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $5,428,544 e are approximately 257 engines of the affected design in the worldwide fleet. The FAA estimates that 242 engines installed on aircraft of U.S. registry would be affected by this proposed AD, and that required parts, on a prorated basis, would cost approximately $22,432 per engine. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $5,428,544. The regulations proposed herein would not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. For the reasons discussed above, I certify that this proposed regulation (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 copy of the draft regulatory evaluation prepared for this action 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, Safety. The Proposed Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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] Proposed Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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 adding the following new airworthiness directive: General Electric Company: Docket No. 98-ANE-18-AD. Applicability: General Electric Company (GE) CF6-6 series turbofan engines, installed on but not limited to McDonnell Douglas DC-10-10 series aircraft. 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 repair on 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 pressure turbine (LPT) stage 4 disk cracking, which could result in an uncontained engine failure and damage to the aircraft, accomplish the following: safe 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 pressure turbine (LPT) stage 4 disk cracking, which could result in an uncontained engine failure and damage to the aircraft, accomplish the following: (a) Remove from service LPT stage 4 disks, part numbers (P/Ns) 9010M40P01, 9010M40P02, 9010M40P07, 9010M40P09, and 9010M40P12, and replace with serviceable parts, in accordance with the following schedule: (1) For disks with 12,300 or more cycles since new (CSN) but less than 24,000 CSN on the effective date of this AD, remove from service affected disks at the earliest of the following: (i) The next piece-part exposure after the effective date of this AD; or (ii) The next engine shop visit after accumulating 16,500 CSN; or (iii) Within 4,200 cycles in service (CIS) after the effective date of this AD; or (iv) Prior to exceeding 24,000 CSN. (2) For disks with 5,000 or more CSN, but less than 12,300 CSN, on the effective date of this AD, remove from service affected disks at the earlier of the following: (i) Prior to exceeding 16,500 CSN; or (ii) Within 7,300 CIS after the effective date of this AD. (3) For disks with less than 5,000 CSN on the effective date of this, remove from service affected disks prior to exceeding 12,300 CSN. (b) This AD establishes a new cyclic retirement life limit for LPT stage 4 disks of 12,300 CSN. Thereafter, except as provided in paragraph (d) of this AD, no alternative cyclic retirement life limits may be approved for LPT stage 4 disks. ## Nearby sections - [63 FR 176 Aluminum in Large and Small Volume Parenterals Used in Total Parenteral Nutrition](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-76.md) - [63 FR 446 Federal Employees Health Benefits Program: Removal of Minimum Salary Requirement](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-102.md) - [63 FR 456 Approval and Promulgation of Implementation Plan; Indiana](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-241.md) - [63 FR 714 Approval and Promulgation of Implementation Plans Alabama: Revisions to Several Chapters of the Alabama Department of Environmental Management (ADEM) Administrative Code for the Air Pollution Control Program](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-358.md) - [63 FR 1074 Airworthiness Directives; British Aerospace (Jetstream) Model 4101 Airplanes](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-475.md) - [63 FR 1396 Notice of Meeting](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-588.md) - [63 FR 1807 Endangered and Threatened Species; Withdrawal of Proposed Rule to List Snake River Spring/Summer Chinook Salmon and Fall Chinook Salmon as Endangered](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-622.md) - [63 FR 2353 General Regulations and Standards for Certain Agricultural Commodities](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-920.md) - [63 FR 2916 Kansas Regulatory Program and Abandoned Mine Land Reclamation Plan](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-1216.md) - [63 FR 3052 Peter G. Crane; Receipt of an Amended Petition for Rulemaking, Extension of Comment Period](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-1379.md) - [63 FR 3057 Withholding on Interest in the Case of Sales of Obligations Between Interest Payment Dates; Hearing Cancellation](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-1403.md) - [63 FR 3070 Closed Captioning of Video Programming](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-1394.md) - [63 FR 3272 Airworthiness Directives; Saab Model SAAB 2000 Series Airplanes](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-1425.md) - [63 FR 3275 Airworthiness Directives; CFM International CFM56-2, -2A, -2B, - 3, -3B, and -3C Series Turbofan Engines](https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-1484.md) --- Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/FR_PRORULE_98-12915. Check the current official text before relying on it. Not legal advice.