[Federal Register Volume 64, Number 103 (Friday, May 28, 1999)]
[Rules and Regulations]
[Pages 28901-28905]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-13483]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-89-AD; Amendment 39-11183; AD 99-11-12]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-400 Series Airplanes
Powered by Pratt & Whitney PW4000 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 Boeing Model 747-400 series airplanes, that
requires repetitive inspections to ensure proper installation of the
engine thrust link components, and follow-on corrective action, if
necessary; and replacement of the forward engine mount end cap assembly
with an improved end cap assembly. Such replacement, when accomplished,
will terminate the repetitive inspections. This amendment is prompted
by a report of fatigue cracking of end cap bolts, caused by improper
installation. Subsequent
[[Page 28902]]
investigation revealed that properly installed end caps also are
subject to early fatigue cracking. The actions specified by this AD are
intended to prevent failure of the end cap assembly, which could lead
to separation of the engine from the airplane in the event of a primary
thrust linkage failure.
DATES: Effective July 2, 1999.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of July 2, 1999.
ADDRESSES: The service information referenced in this AD may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the Federal
Aviation Administration (FAA), Transport Airplane Directorate, Rules
Docket, 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: Tamara L. Anderson, Aerospace
Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; telephone (425) 227-2771; fax (425)
227-1181.
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 certain Boeing Model 747-400
series airplanes was published in the Federal Register on May 20, 1998
(63 FR 27685). That action proposed to require repetitive inspections
to detect improper installation and fatigue damage of the end cap of
the forward engine mount, and replacement of the forward engine mount
end cap assembly with an improved end cap assembly.
Clarification of the Rule
Since the issuance of the notice of proposed rulemaking (NPRM), the
FAA has clarified certain wording in the final rule to more accurately
describe the inspection requirements, which include the actions
required and the components to be inspected. The Summary of the
proposed AD states that repetitive inspections are required ``to detect
improper installation and fatigue damage of the end cap of the forward
engine mount. * * *'' However, the final rule states that repetitive
inspections are required ``to ensure proper installation of the engine
thrust link components, and follow-on corrective action, if necessary.
* * *''
The FAA considers that such clarification of the inspection
requirements is necessary for several reasons. First, the FAA has
determined that requiring operators ``to ensure proper installation,''
rather than ``to detect improper installation,'' more accurately
describes the action required for the inspection. Second, the FAA
points out that ``fatigue damage of the end cap,'' which involves the
secondary load path, could not be detected until the forward engine
mount was disassembled. In addition, the inspections specified by
Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996, are
inspections of the ``engine thrust link components,'' not the ``end
cap'' itself. This inspection requirement also was clear in the
proposed rule, which correlated the corrective action to the presence
or absence of damage to the engine thrust link components. Therefore,
the FAA has deleted ``fatigue damage'' from the inspection requirements
and has changed ``end cap'' to ``engine thrust link components.'' The
FAA adds that the engine thrust link components, which involve the
primary load path, can be inspected with no disassembly of the forward
engine mount required. The Summary and paragraph (a)(1) of the final
rule have been clarified accordingly.
In addition, although it is implied in the proposed AD that the FAA
requires any discrepancy or damage to be repaired by taking corrective
action, the FAA has clarified this requirement in the final rule. The
first sentence of the Summary of this AD now includes ``and follow-on
corrective action, if necessary.''
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.
One commenter states that it is not affected by the proposal
because it does not operate the affected airplanes. Another commenter
generally supports the proposal.
Request to Withdraw the Proposed AD
One commenter states that ``regulatory action mandating
incorporation of Boeing Alert Service Bulletin 747-71A2283 [dated
October 10, 1996] is unwarranted for PW4000 powered 747 aircraft.''
That commenter also states that this alert service bulletin was issued
on the basis of one report of a broken end cap bolt by one operator of
a Model 747-400 series airplane. In addition, the commenter states that
the discrepancy was revealed during engine overhaul and that the cause
of the bolt failure was attributed to a personnel error when the end
cap was installed backwards. The commenter adds that the redesigned end
cap specified in the alert service bulletin does not prevent improper
installation and does not address the original issue of
misinstallation. Further, the commenter states that, during routine
magnetic particle inspections of the end caps and bolts, no cracked end
caps or bolts have been found. The commenter also states that such an
incident should not lead to the conclusion that an unsafe condition
exists or is likely to exist.
The FAA does not concur that the alert service bulletin is
unwarranted or that the proposed AD should be withdrawn. The FAA points
out that the current configuration of the end cap has been shown to
fail if it is installed backwards because the end cap would contact the
adjacent bearing, which is loaded during each flight. In addition, the
end cap has insufficient fatigue life for such loading, and may not
prevent separation of an engine in the event of failure of the primary
thrust load path. However, the FAA has determined that the redesigned
end cap specified in the alert service bulletin will prevent the end
cap from contacting the adjacent bearing even if the redesigned end cap
is installed backwards.
The FAA acknowledges that, if the redesigned end cap was installed
backwards, several problems could occur. First, only a portion of the
threads of the fasteners would engage and the few engaged threads could
strip, resulting in inadequate torque of the fasteners. Second, if the
installation procedure was continued, a mechanical interference could
occur between the fan case and the fastener heads. However, the FAA
points out that, because inadequate torque of the fasteners could be
easily detected, installation of the engine would not be continued
until corrective action was taken. The new design also would prevent
inadvertent loading of the secondary thrust load path, which is
reserved for use in the event of a failure in the primary thrust load
path.
In light of this information, the FAA has determined that the
redesigned end cap would significantly reduce the probability of
inadvertent error in engine installation. In addition, the FAA was
informed by the manufacturer that the original end cap assembly, if
installed correctly, has insufficient fatigue life to prevent
separation of an engine in case of a primary thrust link failure.
[[Page 28903]]
Request To Correct the Name of the Component To Be Inspected
One commenter, the manufacturer, requests that the inspection
described in the ``Explanation of Relevant Service Information'' and in
paragraph (a)(1) of the proposed AD be changed from ``end cap of the
forward engine mount'' to ``engine thrust link components'' in the
final rule.
The FAA concurs with this request. As described earlier in the
``Clarification of the Rule'' paragraph, the FAA agrees that the
``engine thrust link components'' are the correct components to be
inspected. The FAA points out that, although the alert service bulletin
specifies an inspection of the ``forward engine mount,'' the FAA agrees
with the manufacturer that the ``engine thrust link components'' are
the appropriate components to be inspected. The FAA has made this
change throughout the final rule, including the Summary and paragraph
(a)(1). No change was made in the ``Explanation of Relevant Service
Information'' because this paragraph does not appear in the final rule.
Request To Change a Reference to the Airplane Maintenance Manual
One commenter suggests changing a reference in the ``Differences
Between Proposed Rule and Service Bulletin'' of the proposed AD from
``Chapter 71-00-00 of the Boeing 747 Airplane Maintenance Manual
(AMM)'' to ``paragraph (a)(2) of this AD.''
The FAA concurs. The FAA acknowledges that the reference to Chapter
71-00-00 of the AMM in the ``Differences Between Proposed Rule and
Service Bulletin'' of the proposed AD is incorrect because that chapter
of the AMM does not include procedures for replacing the end cap and
bolts. The FAA agrees that paragraph (a)(2) correctly references the
appropriate work package of the alert service bulletin for such
replacement procedures. However, the FAA has determined that further
clarification is necessary, and has placed such clarification in the
paragraph titled ``Additional Differences Between This AD and the
Service Information,'' below. In that paragraph, the FAA has deleted
the reference to the AMM and added that the end cap and bolts be
replaced ``in accordance with the alert service bulletin referenced in
paragraph (a)(2) of this AD.''
Request To Add a Statement Regarding Repair
One commenter requests adding ``repair all discrepancies or damage
found in accordance with an approved FAA procedure* * *'' to the
requirements of paragraph (a)(1)(ii) of the proposed AD.
The FAA acknowledges that adding a statement regarding the repair
requirement is necessary for clarification of the final rule. As
discussed earlier in the ``Clarification of the Rule'' paragraph, the
FAA considers that the repair requirement was inherent in the proposed
rule. The FAA agrees with the commenter that the repair requirement
should be more explicit and has added this requirement to the final
rule.
However, the FAA has determined that it is unnecessary to add that
the repair must be ``in accordance with an approved FAA procedure.''
The FAA points out that because the repairs required by this AD are
considered common industry practice, it is unnecessary to require that
such repairs must be accomplished in accordance with an approved FAA
procedure. Since the suggested change would increase the burden to the
operator and require issuance of further rulemaking to allow
opportunity for public comment, the FAA has determined that such a
change would be inappropriate in light of the identified unsafe
condition.
In light of this information, the FAA has added the repair
requirement to paragraph (a)(1)(ii)(A) of the final rule, but has not
added the requirement that the repair be accomplished ``in accordance
with an approved FAA procedure.''
Request To Allow an Operator's Equivalent Procedure for Certain
Tasks
One commenter states that it objects to paragraph (c) of the
proposed AD because it eliminates the option to perform certain tasks
in accordance with an operator's equivalent procedure. The commenter
also states that operators often incorporate changes to maintenance
manual procedures and work cards by resequencing or improving the work
steps to improve efficiency. The commenter maintains that its
operator's procedures are equivalent to those specified in the AMM and
will ensure accomplishment of the work specified in the AMM. For these
reasons, the commenter requests that paragraph (c) of the proposed AD
be deleted.
The FAA concurs with the commenter's request to delete paragraph
(c) of the proposed AD and to allow the use of an operator's equivalent
procedure for accomplishment of certain actions required by the final
rule. The FAA points out that it did not intend to require the
accomplishment of access procedures prior to inspection and closure
procedures after inspection in accordance with only the AMM. The FAA
also intended to allow the accomplishment of access and closure
procedures in accordance with an operator's equivalent procedure. The
FAA has determined that accomplishment of the access and closure
procedures, in accordance with an operator's equivalent procedure, and
accomplishment of the inspection requirements, in accordance with
Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996, will
adequately address the identified unsafe condition and provide an
acceptable level of safety.
In light of this, the FAA has deleted paragraph (c) that was
included in the proposed AD, which did not allow the actions required
by the proposed AD to be accomplished in accordance with an operator's
equivalent procedure. In addition, the reference to paragraph (c) has
been deleted from paragraphs (a) and (b) of the final rule.
Additional Differences Between This AD and the Service Information
Boeing Alert Service Bulletin 747-71A2283 divides the affected
airplanes into two groups depending upon the particular engine
configuration of the affected airplane, and provides different
procedures depending upon group classification and engine on-wing
flight cycles. Operators should note that, whereas the alert service
bulletin specifies that operators of Group 1 airplanes should contact
the manufacturer for disposition of the terminating action, this AD
requires that the end cap and bolts be replaced in accordance with the
alert service bulletin referenced in paragraph (a)(2) of this AD as
terminating action.
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 previously
described. The FAA has determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
the AD.
Cost Impact
There are approximately 133 Model 747-400 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 36
airplanes of U.S. registry will be affected by this AD: 35 Group 1
airplanes, and 1 Group 2 airplane.
[[Page 28904]]
It will take approximately 36 work hours per Group 1 airplanes (9
work hours per engine) to accomplish the required inspection at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of this inspection on U.S. operators is estimated to be
$75,600, or $2,160 per airplane, per inspection cycle.
It will take approximately 272 work hours per airplane (68 work
hours per engine) for both Group 1 and Group 2 airplanes to accomplish
the required replacement of the forward engine mount end cap and/or end
cap bolts at an average labor rate of $60 per work hour. Required parts
will cost approximately $1,000 per airplane. Based on these figures,
the cost impact of this replacement on U.S. operators is estimated to
be $623,520, or $17,320 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the requirements of this
AD action, and that no operator would accomplish those actions in the
future if this AD were not adopted.
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:
99-11-12 Boeing: Amendment 39-11183. Docket 97-NM-89-AD.
Applicability: Model 747-400 series airplanes powered by Pratt &
Whitney PW4000 engines, as listed in Boeing Alert Service Bulletin
747-71A2283, dated October 10, 1996; certificated in any category.
Note 1: This AD applies to each airplane 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 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 (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 possible separation of the engine from the airplane
in the event of a primary thrust linkage failure, accomplish the
following:
Initial Inspection and Corrective Actions
(a) For Group 1 airplanes, as identified in Boeing Alert Service
Bulletin 747-71A2283, dated October 10, 1996: Accomplish paragraphs
(a)(1) and (a)(2), of this AD, as applicable.
(1) Within 500 hours time-in-service after the effective date of
this AD, perform a detailed visual inspection (Work Package 1) to
ensure proper installation of the engine thrust link components, in
accordance with the alert service bulletin.
(i) If no attachment hardware is found loose or missing, and if
no part shows signs of damage, repeat the inspection thereafter at
intervals not to exceed 5,000 hours time-in-service or 15 months,
whichever occurs first, until the requirements of paragraph (a)(2)
of this AD have been accomplished.
(ii) If any attachment hardware is found loose or missing, or if
any part shows signs of damage, prior to further flight, accomplish
the actions required by paragraphs (a)(1)(ii)(A) and (a)(1)(ii)(B).
(A) Repair any discrepancy or damage.
(B) Replace the existing end cap and end cap bolts of the
forward engine mount end cap assembly with an improved end cap and
end cap bolts (Work Package 2) in accordance with the alert service
bulletin.
Terminating Action
(2) Replace the existing end cap and end cap bolts of the
forward engine mount end cap assembly with an improved end cap and
end cap bolts (Work Package 2), in accordance with Boeing Alert
Service Bulletin 747-71A2283, dated October 10, 1996, at the earlier
of the times specified in paragraphs (a)(2)(i) and (a)(2)(ii) of
this AD. Accomplishment of the replacement constitutes terminating
action for the requirements of this AD for Group 1 airplanes.
(i) Prior to the accumulation of 16,000 total flight cycles on
any engine, or within 500 hours time-in-service after the effective
date of this AD, whichever occurs later; or
(ii) Within 3 years after the effective date of this AD.
(b) For Group 2 airplanes, as identified in Boeing Alert Service
Bulletin 747-71A2283, dated October 10, 1996: Within 3 years after
the effective date of this AD, replace the existing end cap bolts of
the forward engine mount with improved end cap bolts (Work Package
3), in accordance with the alert service bulletin.
Spares
(c) As of the effective date of this AD, no person shall install
on any airplane a forward engine mount end cap having part number
310T3026-1.
Alternative Method 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, Seattle ACO. 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.
Special Flight Permits
(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 airplane to a location where
the requirements of this AD can be accomplished.
Incorporation by Reference
(f) The inspections and replacement shall be done in accordance
with Boeing Alert Service Bulletin 747-71A2283, dated October 10,
1996. 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 Boeing Commercial Airplane
Group, P.O. Box 3707, Seattle, Washington 98124-2207. 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.
[[Page 28905]]
(g) This amendment becomes effective on July 2, 1999.
Issued in Renton, Washington, on May 20, 1999.
D.L. Riggin, Acting Manager,
Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 99-13483 Filed 5-27-99; 8:45 am]
BILLING CODE 4910-13-P
