Airworthiness directives: General Electric Co.,
[Federal Register: August 31, 1998 (Volume 63, Number 168)]
[Rules and Regulations]
[Page 46164-46165]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr31au98-4]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-ANE-18-AD; Amendment 39-10726; AD 98-18-10]
RIN 2120-AA64
Airworthiness Directives; General Electric Company CF6-6 Series Turbofan Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
SUMMARY: This amendment adopts a new airworthiness directive (AD), applicable to General Electric Company (GE) CF6-6 series turbofan engines, that requires 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 amendment is prompted by reports of LPT stage 4 disk cracking in the blade dovetail slot bottom area. The actions specified by this AD are intended to prevent LPT stage 4 disk cracking, which could result in an uncontained engine failure and damage to the aircraft.
DATES: Effective September 30, 1998.
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: A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to General Electric Company (GE) CF6- 6 series turbofan engines was published in the Federal Register on May 15, 1998 (63 FR 27001). That action proposed to 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.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
One commenter states that they have already incorporated the GE service bulletin and gives a cost estimate compatible with the FAA's estimate.
One commenter states that it does not operate any affected engines.
One commenter states that the AD should establish a ``cycles since'' date that is at least 7 days after the effective date of the AD in order to give operators time to prepare their time tracking systems. The commenter requests this change on the basis that without prior knowledge of the effective date of the AD, it would be necessary to manually backtrack records to determine disks times for a date already passed. The FAA disagrees. For non-emergency ADs such as this, the effective date of the AD must be at least 30 days after the publication date to allow affected operators time to prepare. That 30-day period should provide ample time for operators to make whatever adjustments are necessary in tracking systems that should already keep track of the life limited parts that operator uses in service.
After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.
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 will be affected by this AD, and that required parts, on a prorated basis, will cost approximately $22,432 per engine. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $5,428,544.
The regulations adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
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 DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 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
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The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
[[Page 46165]]
Sec. 39.13 [Amended]
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Section 39.13 is amended by adding the following new airworthiness directive:
98-18-10 General Electric Company: Amendment 39-10726. Docket 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:
(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 AD, 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.
(c) For the purpose of this AD, the following definitions apply:
(1) An engine shop visit is defined as separation of a major, static flange.
(2) Piece-part exposure is when the affected part is completely disassembled in accordance with the disassembly instructions in the engine manual or section of the Instructions for Continued Airworthiness.
(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. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.
Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(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 September 30, 1998.
Issued in Burlington, Massachusetts, on August 25, 1998. Jay J. Pardee, Manager, Engine and Propeller Directorate, Aircraft Certification Service.
[FR Doc. 98-23362Filed8-28-98; 8:45 am]
BILLING CODE 4910-13-U
