[Federal Register Volume 63, Number 168 (Monday, August 31, 1998)]
[Rules and Regulations]
[Pages 46164-46165]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-23362]


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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.

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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

    1. 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]

    2. 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. 98-23362 Filed 8-28-98; 8:45 am]
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