[Federal Register Volume 68, Number 17 (Monday, January 27, 2003)]
[Rules and Regulations]
[Pages 3805-3808]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-1675]



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  Federal Register / Vol. 68, No. 17 / Monday, January 27, 2003 / Rules 
and Regulations  

[[Page 3805]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NE-19-AD; Amendment 39-13024; AD 2003-02-07]
RIN 2120-AA64


Airworthiness Directives; General Electric Company CF6-50 and 
CF6-80C2 Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This amendment adopts a new airworthiness directive (AD), that 
is applicable to General Electric Company CF6-50 and CF6-80C2 turbofan 
engines. This amendment requires replacement of certain existing CF6-50 
and CF6-80C2 low pressure turbine (LPT) shrouds with new design LPT 
shrouds. This amendment is prompted by 37 LPT uncontained events on the 
CF6-50, 24 uncontained events on the CF6-80C2 engine models since 1993, 
and the development and certification of newly designed shrouds that 
will improve LPT containment capability. The actions specified by this 
AD are intended to prevent uncontained engine failure and possible 
airplane damage.

DATES: Effective March 3, 2003.

ADDRESSES: Information regarding this action may be examined, by 
appointment, at the Federal Aviation Administration (FAA), New England 
Region, Office of the Regional Counsel, 12 New England Executive Park, 
Burlington, MA.

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 AD that is 
applicable to General Electric Company CF6-50 and CF6-80C2 turbofan 
engines was published in the Federal Register on May 17, 2001 (66 FR 
27475). That action proposed to require replacement of certain existing 
CF6-50 and CF6-80C2 LPT shrouds with new design shrouds.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request Withdrawal of Proposed Rule

    Five commenters request that the proposed rule be withdrawn. The 
commenters believe that the new LPT shrouds will not prevent or 
significantly reduce the occurrence or severity of the more severe (SAE 
Category 2 or higher) uncontained events, and therefore, the economic 
impact is not justified by this limited improvement in safety. The 
commenters provided statistics to show that the vast majority (89%) of 
the uncontained LPT events were SAE Category 1 with no aircraft impact, 
and were, therefore, no hazard to continued safe flight. Data was also 
provided that showed that none of the Category 2 events had caused more 
than minor aircraft damage, and that corrective actions (i.e. 
inspection or replacement programs; some required by existing AD's) 
were available from the manufacturer to address the majority of the 
root causes that had led to the Category 2 events.
    The FAA partially agrees. The FAA agrees that because the design 
criteria for the shrouds is based on ballistic containment 
calculations, it is difficult to quantify a benefit for the improved 
LPT shrouds for rub-through or push-through events. However, the FAA 
disagrees that the improved shrouds will not provide some additional 
benefit for those events where the LPT uncontainment was not 
exclusively of a ballistic nature. Although the events occurring to-
date have not resulted in significant hazards to continued safe flight, 
the potential exists for future events to be more significant. 
Therefore, in addition to requiring that the root causes for the 
upstream failures that have led to uncontained LPT events be addressed, 
the FAA believes that the improved LPT shrouds must be incorporated to 
meet the intent of the regulations, which is for the engines to contain 
failures at the engine case level.

Extend or Eliminate Compliance End Date

    Seven commenters request that the compliance end date be extended 
or eliminated. The commenters noted that all of the CF6-50 models would 
likely be in compliance by that date based on their estimated shop 
visit and LPT exposure rates, but that many CF6-80C2 engines would be 
forced off-wing early solely for this compliance, thereby imposing a 
significant financial burden that was not included in the economic 
analysis of the proposal.
    The FAA agrees that the intended improvement in safety can be 
achieved by extending the compliance end date to support the normal 
shop visit and LPT exposure rates and, therefore, the proposed calendar 
end date is changed in the final rule.

Request for Exemption of Certain LPT Cases and LPT Shroud 
Configurations

    Four commenters request that engines configured with a certain LPT 
case configuration and certain LPT shroud configurations be exempt from 
the proposed AD. The commenters note that the improved LPT case, part 
number (P/N) 1647M68G15, introduced by GE Aircraft Engines Service 
Bulletin (GEAE SB) 72-0946 in conjunction with certain LPT shrouds 
provides equivalent containment to the older design LPT case with the 
newest shrouds referenced by the proposed rule.
    The FAA agrees. The manufacturer has provided data to show that 
CF6-80C2 engines configured with the later LPT cases and certain LPT 
shrouds provide equivalent containment capability. Therefore, CF6-80C2 
engines configured with the combination of LPT case, P/N 1647M68G15, 
and LPT stage 2 shroud, P/N 1862M62G01 or 1862M62G03; and LPT stage 3 
shroud, P/N 1862M63G01 or 1862M63G03; and LPT stage 4 shroud P/N 
1862M64G01 or 1862M64G03 are exempted from this rule. The final rule is 
revised to reflect this change, and the economic analysis of the final 
rule is reduced to reflect this change.

[[Page 3806]]

Request for Relaxed Compliance Requirements

    Three commenters request that relaxed compliance requirements be 
provided for engines with certain configurations that reduce the 
probability of an upstream failure that has been known to result in the 
higher severity uncontained LPT events. The commenters believe that 
addressing the root causes of the uncontained LPT failures will be more 
effective than the new shrouds for improving containment and reducing 
the frequency and severity of the events.
    The FAA partially agrees. The FAA agrees that upstream failures 
that lead to uncontained LPT events must be addressed and has already 
mandated corrective actions for many of those known failure mechanisms. 
However, as stated in the proposed rule, not all such possible upstream 
failure modes can be predicted or anticipated. Therefore, the FAA 
disagrees that relaxed compliance schedules for engines configured with 
certain root cause fixes will achieve the necessary safety improvement 
that will be realized by incorporation of the improved LPT shrouds. No 
changes will be made to this AD.

Request for Equivalent Replacement Parts

    Five commenters request that any FAA-approved Parts Manufacturing 
Approval (PMA) or repaired configurations of the manufacturer's design 
be allowed as equivalent replacement parts for the GE service bulletin 
parts.
    The FAA agrees. The final rule is revised to include all of the 
known FAA-approved equivalent parts for each of the engine models as 
acceptable configurations.

Service Bulletin Accepted as Compliance to Proposed Rule

    One commenter requests that GE CF6-50 SB 72-1170, Revision 1, dated 
November 30, 1999, be accepted as compliance for the proposed rule. The 
commenter notes that this revision clarifies the engines that are 
affected by explicitly listing all of the earlier shroud part numbers 
that should be replaced with the new shroud part numbers.
    The FAA partially agrees. The FAA agrees that the revised SB 
provides additional clarification on the affected engines. However, as 
noted in the FAA response to the previous comment on equivalent 
replacement parts, there are other parts in addition to those 
referenced in that SB that can be used to comply with this AD. The 
final rule is changed to eliminate the incorporation by reference of 
any version of the SB.

Analysis Request To Quantify Containment Improvement

    One commenter requests that an analysis be provided to quantify the 
containment improvement provided by the new shrouds. The commenter 
believes that the new design shrouds do not improve the containment 
capability as intended because the minimum thickness of the shear 
section is not changed.
    The FAA disagrees. The FAA feels that the containment capability of 
the shrouds can not be determined based on shear section thickness 
alone. No changes will be made to this AD.

Request for Engine Containment Test

    One commenter requests that the OEM be required to perform an 
engine containment test to demonstrate the effectiveness of the new 
design shrouds. The commenter believes that other OEM's have been 
required to perform such tests in order to substantiate improved 
containment. The commenter believes that the high cost of compliance 
with the proposed rule warrants such a test demonstration.
    The FAA does not agree. The regulations for the most part address 
primary blade containment. Test demonstrations for secondary failure 
modes, due to multiple upstream failures, as in this case, are not 
normally required. In addition, the regulations allow the use of 
analysis in lieu of a test demonstration, and a test is not always 
required for substantiation. No changes will be made to this AD.

Request To Limit the Number of Times a Shroud Can Be Repaired

    One commenter requests that the proposed rule be revised to limit 
the number of times a shroud can be repaired. The commenter notes, as 
stated in the proposal, that multiple repairs can lead to reduced 
backsheet thickness and result in reduced containment system 
capability.
    The FAA partially agrees. The FAA agrees that multiple repairs can 
possibly result in reduced backsheet thickness. However, the FAA 
disagrees that the specific number of repairs that will result in this 
condition can be defined. Instead, the engine manufacturer has made 
modifications to the engine manual to require a check of the backsheet 
thickness in order to determine the serviceability of the shroud. 
Compliance with the revised manual limit will ensure that the minimum 
backsheet thickness required to achieve the system containment 
capability is maintained. No changes will be made to this AD.

Request for Revision to Notice of Proposed Rulemaking (NPRM)

    One commenter requests that the proposed rule be revised to include 
improved stage 1 and stage 5 shrouds for the CF6-80C2. The commenter 
believes that a recent in-service event indicates that improved 
containment is necessary in stages 1 and 5 as well as stages 2, 3, and 
4 that have already been proposed. The commenter recommends that an 
engineering analysis be performed to verify that these additional 
shrouds are adequate to prevent the failure mode recently demonstrated 
in plane 5 of the LPT.
    The FAA does not agree. The most recent event referred to by this 
commenter exhibited an unusual variation of LPT uncontainment in which 
an extensive rub-through occurred in plane 5. The shrouds mandated for 
incorporation by this rule were redesigned primarily to address 
ballistic type containment events at stages where field experience and 
the manufacturer's analysis had shown deficiencies. In addition, the 
manufacturer has advised the FAA that although new part numbers for 
stage 1 and stage 5 LPT shrouds were introduced to the field at the 
same time as the stage 2 through 4 shrouds, the redesigns of those 
shrouds were made primarily to improve manufacturing and would have no 
appreciable affect on ballistic containment capability and no affect on 
the rub-through type of failure. Potential redesigns to address the 
case rub-through scenario are under consideration. Further rule making 
activity to address the rub-through failure scenario will be considered 
once redesigns are certified. No changes will be made to this AD.

Request for Additional Replacement Criteria

    One commenter requests that replacement be allowed on the basis of 
attrition only and that minimum dimensional requirements be defined or 
other repairs be developed for the existing shrouds to allow these 
shrouds to be returned to service in lieu of the new shrouds. The 
commenter believes that an equivalent level of safety can be achieved 
with properly repaired or restored versions of the current shroud 
design while reducing the cost burden of the proposed rule on the 
operators.
    The FAA partially agrees. The FAA agrees that the existing shrouds 
may be repaired in such a way as to restore the original or achieve the 
latest design capability. Such repairs that have been

[[Page 3807]]

approved by the FAA and are known to the FAA have been included as 
equivalent parts for compliance with this rule. Also the engine 
manufacturer has updated their manuals to include minimum dimensional 
requirements for repairability and serviceability of their parts. The 
FAA disagrees that replacement by attrition will ensure the intended 
improvement in safety. No changes will be made to this AD.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes described 
previously. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Economic Analysis

    There are approximately 5,055 GE CF6-50 and CF6-80C2 turbofan 
engines of the affected design in the worldwide fleet. The FAA 
estimates that 1,006 engines installed on airplanes of U.S. registry 
would be affected by this AD. Because this AD calls for the replacement 
of shrouds at piece part exposure, the FAA does not expect that 
additional labor costs will be accrued beyond that normally required to 
remove the existing shroud. New shrouds will cost approximately $63,250 
for the CF6-50 engines, and $87,020 for the CF6-80C2 engines. Based on 
these figures, the total cost to retrofit all installed U.S. registered 
engines is estimated to be $76,393,990 over an eight year period, or 
$9,549,248 annually.

Regulatory Analysis

    This final rule does not have federalism implications, as defined 
in Executive Order 13132, because it would 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 final rule.
    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 the 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 
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.

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.


Sec.  39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
to read as follows:

2003-02-07 General Electric Company: Amendment 39-13024. Docket No. 
2001-NE-19-AD.

    Applicability: This airworthiness directive (AD) is applicable 
to General Electric Company (GE) CF6-50 and CF6-80C2 turbofan 
engines, except CF6-80C2 engines configured with the combination of 
low pressure turbine (LPT) case, part number (P/N) 1647M68G15; and 
LPT stage 2 shroud, P/N 1862M62G01 or 1862M62G03; and LPT stage 3 
shroud, P/N 1862M63G01 or 1862M63G03; and LPT stage 4 shroud, P/N 
1862M64G01 or 1862M64G03. These engines are installed on, but not 
limited to, DC-10-15, DC-10-30, MD11, 747, 767, A300 and A310 
airplanes.

    Note 1: This 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: Compliance with this AD is required as indicated, 
unless already done.
    To prevent uncontained engine failure and possible airplane 
damage, do the following:

CF6-80C2 Engines

    (a) For CF6-80C2 engines configured with the combination of low 
pressure turbine (LPT) case, part number (P/N) 1647M68G15; and LPT 
stage 2 shroud, P/N 1862M62G01 or 1862M62G03; and LPT stage 3 
shroud, P/N 1862M63G01 or 1862M63G03; and LPT stage 4 shroud, P/N 
1862M64G01 or 1862M64G03, no further action is required.
    (b) At the next shroud piece-part exposure, but no later than 
July 31, 2010, remove existing stage 2, 3, and 4 LPT CF6-80C2 
shrouds and replace with new design P/N's listed in the following 
Table 1:

          Table 1.--CF6-80C2 Acceptable New Shroud Part Numbers
------------------------------------------------------------------------
               Stage                              Part No.
------------------------------------------------------------------------
2.................................  2083M12G01, PCT2083M12G01,
                                     KT2083M12G01, or H042 \1\
3.................................  2083M13G01, PCT2083M13G01,
                                     KT2083M13G01, or H042 \1\
4.................................  2083M14G01, PCT2083M14G01,
                                     KT2083M14G01, or H042 \1\
------------------------------------------------------------------------
\1\ Parts marked with H042, H036, or H037 are parts that have been
  repaired by an FAA-approved process specification. In addition to this
  process specification marking, each part must show its original (i.e.
  before repair) part number and a work order number (i.e. WOxxxxx).

CF6-50 Engines

    (c) At the next shroud piece-part exposure, but no later than 
July 31, 2010, remove existing stage 1, 2, 3 and 4 LPT CF6-50 
shrouds and replace with new design P/N's as listed in the following 
Table 2:

           Table 2.--CF6-50 Acceptable New Shroud Part Numbers
------------------------------------------------------------------------
               Stage                              Part No.
------------------------------------------------------------------------
1.................................  1822M35G01, PCT1822M35G01,
                                     KT1822M35G01, or H036 \1\
2.................................  1822M36G01, PCT1822M36G01,
                                     KT1822M36G01, or H037 \1\
3.................................  1822M36G02, PCT1822M36G02,
                                     KT1822M36G02, or H037 \1\
4.................................  1822M37G01, PCT1822M37G01,
                                     KT1822M37G01, or H037 \1\
------------------------------------------------------------------------
\1\ Parts marked with H042, H036, or H037 are parts that have been
  repaired by an FAA-approved process specification. In addition to this
  process specification marking, each part must show its original (i.e.
  before repair) part number and a work order number (i.e. WOxxxxx).

Alternative Methods 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 must submit their request through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, ECO.


[[Page 3808]]


    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from ECO.

Special Flight Permits

    (e) Special flight permits may be issued in accordance with 
Sec. Sec.  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 done.

Effective Date

    (f) This amendment becomes effective on March 3, 2003.

    Issued in Burlington, Massachusetts, on January 17, 2003.
Francis A. Favara,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 03-1675 Filed 1-24-03; 8:45 am]
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