Airworthiness Directives; General Electric Company GE90 Series Turbofan Engines

[Federal Register Volume 65, Number 25 (Monday, February 7, 2000)]
[Rules and Regulations]
[Pages 5761-5762]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-2686]



[[Page 5761]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-51-AD; Amendment 39-11559; AD 2000-03-02]
RIN 2120-AA64


Airworthiness Directives; General Electric Company GE90 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 certain General Electric Company (GE) GE90 series 
turbofan engines, that requires reducing the cyclic life limits for 
certain fan mid shafts with undesirable microstructure, and removing 
from service those mid fan shafts prior to exceeding the new limits and 
replacing with serviceable parts. This amendment is prompted by reports 
of magnetic particle inspections conducted by the manufacturer 
identifying segregation in the raw material, resulting in lower fatigue 
life properties. The actions specified by this AD are intended to 
prevent fan mid shaft failure, which could result in a total loss of 
thrust and inflight engine shutdown.

DATES:  Effective April 7, 2000.

FOR FURTHER INFORMATION CONTACT:  William S. Ricci, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone 781-
238-7742, 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) 
GE90-90B, -85B, and -76B series turbofan engines was published in the 
Federal Register on November 26, 1999 (64 FR 66415). That action 
proposed to reduce the cyclic life limits for certain fan mid shafts 
with undesirable microstructure, and remove from service those fan mid 
shafts prior to exceeding the new limits and replace with serviceable 
parts. That action was prompted by reports of magnetic particle 
inspections conducted by the manufacturer identifying segregation in 
the raw material, resulting in lower fatigue life properties. That 
condition, if not corrected, could result in fan mid shaft failure, 
which could result in a total loss of thrust and inflight engine 
shutdown.

Comments Received

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

Change Unsafe Condition Language

    One commenter states that the statement of unsafe condition in the 
proposed rule is not accurate. The commenter believes that the language 
used does not correctly reflect the failure consequences of the fan mid 
shaft. The commenter also is concerned that the engine is not in 
compliance with Federal Aviation Regulations (FAR) 33 (14 CFR 33) 
requirements regarding shaft failure. The FAA concurs in part. Though 
the language used in the statement of unsafe condition in the proposal 
is typical of life limited parts ADs, a more accurate description of 
the failure consequences of the fan mid shaft would be a total loss of 
thrust and inflight engine shutdown. The statement of unsafe condition 
in this final rule has been changed accordingly.

GE90 Engine Model Applicability

    The same commenter believes the proposal should apply to all GE90 
engine models and not just those listed in the applicability. The FAA 
does not concur. The proposal addresses those fan mid shaft part 
numbers (P/Ns) and engine models that have had their published life 
limits reduced. This proposal does not address the fan mid shafts P/Ns 
and engine models that have had their published life limits increased. 
These fan mid shafts P/Ns and engine model combinations are discussed 
in GE90 Alert Service Bulletin 72-A0389, Revision 1, dated August 25, 
1999.

Delete Ferry Flight Authorization

    The same commenter believes that the special flight permit 
authorization paragraph included in the proposal should be deleted. The 
commenter believes that ferry flight permits should not be authorized 
in the case of a life reduction AD. The FAA concurs and that paragraph 
has been removed from this final rule.

Concurrence

    One commenter concurs with the rule as proposed.

Conclusion

    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 118 engines of the affected design in the 
worldwide fleet. The FAA estimates that 4 engines installed on aircraft 
of US registry will be affected by this AD and that the prorated life 
reduction will cost approximately $71,000 per engine. Based on these 
figures, the total cost impact of the AD on US operators is estimated 
to be $284,000.

Regulatory Impact

    The regulations adopted herein will 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order (EO) 13132.
    For the reasons discussed above, I certify that this action (1) Is 
not a ``significant regulatory action'' under EO 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 5762]]

Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:
2000-03-02  General Electric Company: Amendment 39-11559. Docket 98-
ANE-51-AD.
    Applicability: General Electric Company (GE) GE90-90B, -85B, and 
-76B series turbofan engines, with fan mid shafts, part numbers (P/
Ns) 1767M71G01, 1767M71G02, and 1767M75G02, installed. These engines 
are installed on but not limited to Boeing 777 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 (c) 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 fan mid shaft failure, which could result in a total 
loss of thrust and inflight engine shutdown, accomplish the 
following:

Reduced Life Limits

    (a) Remove from service fan mid shafts and replace with 
serviceable parts prior to the following new, lower cyclic life 
limits:
    (1) For fan mid shafts, P/N 1767M71G01, installed on GE90-85B 
and -90B series engines, the new life limit is 4,200 cycles-since-
new (CSN).
    (2) For fan mid shafts, P/N 1767M71G02, installed on GE90-85B 
and -90B series engines, the new life limit is 4,200 CSN.
    (3) For fan mid shafts, P/N 1767M75G02, installed on GE90-76B, -
85B, and -90B series engines, the new life limit is 8,200 CSN.
    (b) This AD establishes new life limits for fan mid shafts, P/N 
1767M71G01, 1767M71G02, and 1767M75G02. Except as provided in 
paragraph (c) of this AD, no alternate life limits for these 
affected parts may be approved.

Alternative Methods of Compliance

    (c) 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.


    (d) This amendment becomes effective on April 7, 2000.

    Issued in Burlington, Massachusetts, on February 1, 2000.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 00-2686 Filed 2-4-00; 8:45 am]
BILLING CODE 4910-13-U

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