[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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