[Federal Register Volume 62, Number 77 (Tuesday, April 22, 1997)]
[Rules and Regulations]
[Pages 19480-19482]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-9881]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-60-AD; Amendment 39-9996; AD 97-08-08]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777-200 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 777-200 series airplanes. This 
action requires repetitive visual inspections of the forward mounts of 
certain engines to detect damaged, missing, or failed parts, and 
eventual modification of those engines. Accomplishment of this 
modification terminates the requirement for repetitive inspections. 
This amendment is prompted by a report indicating that bolts that 
attach the yoke of the forward mount to the fan case of the engine have 
failed due to fatigue cracking. The actions specified in this AD are 
intended to prevent fatigue cracking in these bolts, which could lead 
to failure of these bolts and consequent separation of the engine from 
the wing.

DATES: Effective May 7, 1997. The incorporation by reference of certain 
publications listed in the regulations is approved by the Director of 
the Federal Register as of May 7, 1997.
    Comments for inclusion in the Rules Docket must be received on or 
before June 23, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-60-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    The service information referenced in this AD may be obtained from 
General Electric Aircraft Engines, GE90 Product Support, One Neuman 
Way, Cincinnati, Ohio 45215-6301. This information may be examined at 
the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the Office of the Federal Register, 800 North Capitol 
Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Stan Wood, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2772; 
fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: During certification testing of the General 
Electric (GE) 90 engine, fatigue cracking was detected in the bolts 
that attach the yoke of the forward mount of the engine to the fan case 
of the engine. Fatigue cracking in the bolts that attach the yoke of 
the forward mount of the engine to the fan case of the engine, if not 
prevented, could lead to failure of these bolts and consequent 
separation of the engine from the wing.
    An analysis revealed that these bolts had a short fatigue life due 
to the large forces that the yoke exerted on them. As a result, the 
original yoke design was not certified as meeting the damage tolerance 
standards of part 25 of the Federal Aviation Regulations (14 CFR part 
25). The engine manufacturer subsequently redesigned the yoke and fan 
case to those standards in order to prevent fatigue cracking in the 
bolts.
    Although the airplane manufacturer did not install GE90 engines 
with the original yoke design on any Model 777-200 series airplanes, 
the engine manufacturer shipped some of these engines to operators as 
replacement engines. The engine manufacturer had apparently concluded, 
in error, that if the yoke complied with the strength requirements of 
part 33 of the Federal Aviation Regulations (14 CFR part 33), it could 
ship engines containing yokes of the original design for use as spare 
engines for these airplanes. The yoke must, in fact, meet both the 
strength standards of part 33 and the damage tolerance standards of 
part 25 in order to be certificated for installation on the Boeing 
Model 777-200 series airplane. The discrepant yokes are installed in 
GE90 engines having serial numbers 900-104, -105, -106, -108, -109, -
110, and -111.

[[Page 19481]]

Explanation of Relevant Service Information

    The FAA has reviewed and approved GE Aircraft Engines Service 
Bulletin 72-183, dated February 28, 1997, which describes procedures 
for conducting a visual inspection of the yoke of the forward mount of 
certain GE90 engines to detect damaged, missing, or failed attachment 
bolts, or failed engine mount links.
    The FAA also has reviewed and approved GE Aircraft Engines Service 
Bulletin 72-275, dated March 4, 1997, which describes procedures for 
modifying GE90 engines by replacing the yoke of the forward engine 
mount with a new yoke. The new yoke has been redesigned so that it 
meets the damage tolerance standards of part 25 of the Federal Aviation 
Regulations (14 CFR part 25), and will preclude fatigue cracking in the 
bolts that attach the yoke to the fan case of the engine. 
Accomplishment of this replacement will eliminate the need for visual 
inspections of the yoke area.

Explanation of Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to prevent fatigue cracking in the bolts that attach the 
yoke of the forward mount of the engine to the fan case of the engine, 
which could lead to failure of these bolts and consequent separation of 
the engine from the wing. This AD requires repetitive visual 
inspections of the yoke of the forward mounts of certain GE90 engines 
to detect damaged, missing, or failed attachment bolts, or failed 
engine mount links; and eventual modification of those engines. 
Accomplishment of the modification terminates the requirement for 
visual inspections of the yoke. The actions are required to be 
accomplished in accordance with the service bulletins described 
previously.

Cost Impact

    No Model 777-200 series airplane powered by the General Electric 90 
engines affected by this action is on the U.S. Register. All airplanes 
included in the applicability of this rule currently are operated by 
non-U.S. operators under foreign registry; therefore, they are not 
directly affected by this AD action. However, the FAA considers that 
this rule is necessary to ensure that the unsafe condition is addressed 
in the event that any of these subject airplanes are imported and 
placed on the U.S. Register in the future.
    Should an affected airplane be imported and placed on the U.S. 
Register in the future, it would require approximately 1 work hour to 
accomplish the required inspection, at an average labor charge of $60 
per work hour. Based on these figures, the cost impact of the required 
inspection of this AD would be $60 per airplane.
    Additionally, it would require approximately 72 work hours to 
accomplish the required modification, at an average labor charge of $60 
per work hour. Required parts would be supplied by the manufacturer at 
no cost to operators. Based on these figures, the cost impact of the 
required modification of this AD would be $4,320 per airplane.

Determination of Rule's Effective Date

    Since this AD action does not affect any airplane that is currently 
on the U.S. register, it has no adverse economic impact and imposes no 
additional burden on any person. Therefore, prior notice and public 
procedures hereon are unnecessary and the amendment may be made 
effective in less than 30 days after publication in the Federal 
Register.

Comments Invited

    Although this action is in the form of a final rule and was not 
preceded by notice and opportunity for public comment, comments are 
invited on this rule. Interested persons are invited to comment on this 
rule by submitting such written data, views, or arguments as they may 
desire. Communications shall identify the Rules Docket number and be 
submitted in triplicate to the address specified under the caption 
ADDRESSES. All communications received on or before the closing date 
for comments will be considered, and this rule may be amended in light 
of the comments received. Factual information that supports the 
commenter's ideas and suggestions is extremely helpful in evaluating 
the effectiveness of the AD action and determining whether additional 
rulemaking action would be needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
Rules Docket for examination by interested persons. A report that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 97-NM-60-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    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, Incorporation by 
reference, 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 the following new 
airworthiness directive:

97-08-08  Boeing: Amendment 39-9996. Docket 97-NM-60-AD.

    Applicability: Model 777-200 series airplanes powered by General 
Electric (GE) 90 engines having serial number 900-104, -105, -106, -
108, -109, -110, or -111; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been

[[Page 19482]]

otherwise modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes 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 fatigue cracking in the bolts that attach the yoke of 
the forward mount of the engine to the fan case of the engine, which 
could lead to failure of these bolts and consequent separation of 
the engine from the wing, accomplish the following:
    (a) For airplanes powered by GE90 engines having serial numbers 
900-105 and -110:
    (1) Within 125 landings after the effective date of this AD, 
conduct a visual inspection of the yoke of the forward mount of the 
engine to detect damaged, missing, or failed attachment bolts, or 
failed engine mount links, in accordance with GE Aircraft Engines 
Service Bulletin 72-183, dated February 28, 1997.
    (i) If no discrepancy is found, repeat this inspection 
thereafter at intervals not to exceed 125 landings.
    (ii) If any discrepancy is found, prior to further flight, 
modify the engine in accordance with GE Aircraft Engines Service 
Bulletin 72-275, dated March 4, 1997. No further action is required 
by this AD for that engine.
    (2) Within 1,000 landings after the effective date of this AD, 
modify the engine in accordance with GE Aircraft Engines Service 
Bulletin 72-275, dated March 4, 1997. Accomplishment of this 
modification constitutes terminating action for the repetitive 
inspections of that engine required by paragraph (a)(1)(i) of this 
AD.
    (b) As of the effective date of this AD, no operator shall 
install on any airplane any GE90 engine having serial number 900-
104, 900-106, 900-108, 900-109, or 900-111 unless that engine has 
been modified in accordance with GE Aircraft Engines Service 
Bulletin 72-275, dated March 4, 1997.
    (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, Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate. 
Operators shall submit their requests through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, Seattle ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) 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 airplane to a location where 
the requirements of this AD can be accomplished.
    (e) The inspections and modification shall be done in accordance 
with GE Aircraft Engines Service Bulletin 72-183, dated February 28, 
1997, and GE Aircraft Engines Service Bulletin 72-275, dated March 
4, 1997. This incorporation by reference was approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51. Copies may be obtained from General Electric 
Aircraft Engines, GE90 Product Support, One Neuman Way, Cincinnati, 
Ohio 45215-6301. Copies may be inspected at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or 
at the Office of the Federal Register, 800 North Capitol Street, 
NW., suite 700, Washington, DC.
    (f) This amendment becomes effective on May 7, 1997.

    Issued in Renton, Washington, on April 10, 1997.
Darrell M. Pederson,
Acting Manager,
Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 97-9881 Filed 4-21-97; 8:45 am]
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