[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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