[Federal Register Volume 60, Number 124 (Wednesday, June 28, 1995)]
[Rules and Regulations]
[Pages 33338-33342]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-15300]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-224-AD; Amendment 39-9286; AD 95-13-06]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped With General Electric Model CF6-80C2 Series Engines or Pratt &
Whitney Model PW4000 Series 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 series airplanes, that requires
modification of the nacelle strut and wing structure, inspections and
checks to detect discrepancies, and correction of discrepancies. This
amendment is prompted by the development of a modification of the strut
and wing structure that improves the damage tolerance capability and
durability of the strut-to-wing attachments, and reduces reliance on
non-routine inspections of those attachments. The actions specified by
this AD are intended to prevent failure of the strut and subsequent
loss of the engine.
DATES: Effective July 28, 1995.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of July 28, 1995.
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:
Tim Backman, Aerospace Engineer, Airframe Branch, ANM-120S, FAA,
Transport Airplane Directorate, Seattle Aircraft Certification Office,
1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (206)
227-2776; fax (206) 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 series
airplanes was published in the Federal Register on January 6, 1995 (60
FR 2033). That action proposed to require modification of the nacelle
strut and wing structure, inspections and checks to detect
discrepancies in the adjacent structure, and correction of
discrepancies.
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 supports the proposed rule.
Revision of Descriptive Language
One commenter provides additional information to describe the
purpose of the proposed modification of the nacelle strut and wing
structure. This commenter suggests that the rule should specify that
the modification not only significantly improves the load-carrying and
durability of the strut-to-wing [[Page 33339]] attachments, but
``reduces the reliance on non-routine inspections,'' as well. The FAA
concurs with this suggestion and has revised the Summary section of the
preamble to the final rule to include relevant wording.
This same commenter notes that the description of the unsafe
condition that appeared in the Discussion section of the preamble to
the notice refers to ``the structural fail-safe capability of the
strut-to-wing attachment.'' The commenter states that this description
is inaccurate since it implies that the strut-to-wing attachment is
inadequate.
The commenter suggests that a more accurate description would be
``damage tolerance capability of the strut-to-wing attachment.'' The
FAA acknowledges that the commenter's wording is more accurate. The
pertinent wording in the preamble to the final rule has been revised to
reflect this change. Furthermore, the FAA considers that the new
structure of the strut meets the damage tolerance requirements of
amendment 45 of section 25.571, ``Damage--tolerance and fatigue
evaluation of structure,'' of the Federal Aviation Regulations (14 CFR
25.571, amendment 45), which provides an even higher level of safety
than simply fail-safe requirements.
This commenter also provides further clarification of the
description of the requirements of the existing AD's that address
unsafe conditions associated with the strut attachment assemblies on
Model 747 series airplanes equipped with General Electric Model CF6-
80C2 series engines or Pratt & Whitney Model PW4000 series engines. The
description in the Discussion section of the preamble to the proposal
states that the existing AD's require ``inspection of the strut,
midspar fittings, diagonal brace, and midspar fuse pins.'' The
commenter states that a more complete description of the existing AD's
would be ``inspection of the strut midspar fittings, spring beam lugs,
diagonal brace, and midspar fuse pins.'' The FAA acknowledges that the
commenter's description of the requirements of the existing AD's is
more succinct. However, since the Discussion section is not restated in
this final rule, no change to the final rule is necessary.
Further, this commenter states that the description of the
modification that appeared in the Explanation of Service Information
section of the preamble to the proposal is detailed differently from
the wording that appears in the alert service bulletin that is
referenced in the proposal as the appropriate source of service
information. The FAA acknowledges that paragraph I.C., Description, on
page 6 of Boeing Alert Service Bulletin 747-54A2156, dated December 15,
1994, provides another description of the actions involved in
accomplishing the subject modification. However, although the service
bulletin's description is worded somewhat differently, its intent is
comparable to and consistent with the description that appeared in the
preamble to the proposal.
Clarification of Note 1
One commenter requests that Note 1 of the proposal be clarified
since it is too vague to determine exactly when FAA approval of
alternative methods of compliance (AMOC) is necessary. The FAA concurs.
Although every effort is made to keep the language simple and clear, it
is apparent that some additional explanation is necessary to clarify
the intent of Note 1. Performance of the requirements of this final
rule is ``affected'' if an operator is unable to perform those
requirements in the manner described in this AD. For example, if an AD
requires a visual inspection in accordance with a certain service
bulletin, and the operator cannot perform that inspection because of
the placement of a repair doubler over the structure to be inspected,
then ``performance of the AD is affected.''
In addition, performance of the requirements of an AD is
``affected'' if it is physically possible to perform the requirements,
but the results achieved are different from those specified in the AD.
For example, if the AD requires an NDT inspection in accordance with a
certain service bulletin, and the operator is able to move the NDT
probe over the specified area in the specified manner, but the results
are either meaningless or inaccurate because of the repair doubler over
that area, then ``performance of the AD is affected.''
While Note 1 itself is not capable of addressing every possible
situation, ``affected'' is normally an easy standard to apply: either
it is possible to perform the requirements as specified in the AD and
achieve the specified results, or it is not possible. Therefore, if the
requirements of this AD cannot be performed, then operators must submit
a request for an approval of an AMOC from the FAA, in accordance with
the provision of paragraph (d) of this final rule.
Accomplishment of any modification requirement of an AD, such as
the modification of the nacelle strut and wing structure required by
this final rule, does not ``affect performance of the AD;'' it is
performance of the AD. Every AD includes a provision, with which
operators are familiar, that states, ``Compliance required as
indicated, unless accomplished previously.'' If an operator performs
such a requirement before the AD is issued, the FAA is confident that
the operator will recognize that it has already complied with the AD
and no further action (including obtaining approval of an AMOC) is
required. This is consistent with current law and practice, which Note
1 is not intended to change.
Compliance Time for Modification
One commenter requests that the compliance time of proposed
paragraph (a), which requires modification of the nacelle strut and
wing structure, be extended by 4 months. The commenter notes that a 4-
month extension of the compliance time would coincide with the time
recommended in the referenced Boeing Alert Service Bulletin 747-54A2156
for that modification. Further, this commenter alleges that a
difference of 4 months will ``significantly impact'' its operations.
The FAA does not concur with the commenter's request. In developing
an appropriate compliance time for this action, the FAA considered not
only the degree of urgency associated with addressing the subject
unsafe condition, but the manufacturer's recommendation as to an
appropriate compliance time, the availability of required parts, and
the practical aspect of installing the required modification within a
maximum interval of time allowable for all affected airplanes to
continue to operate without compromising safety. Further, the FAA took
into account the 7-year compliance time recommended by the
manufacturer, as well as the number of days required for the rulemaking
process; in consideration of these factors, the FAA finds that 80
months after the effective date of this final rule will fall
approximately at the same time for compliance as recommended by the
manufacturer.
However, under the provisions of paragraph (b) of the final rule,
any operator may submit requests for adjustments to the compliance time
along with data demonstrating that such requests will not compromise
safety. In evaluating such requests for adjustments to the compliance
time, the FAA will closely examine the operator's explanation of why an
extension is needed. The FAA will also consider the operator's good
faith attempt at complying within the compliance time contained in this
final rule, which can be demonstrated by accomplishing the modification
on a significant percentage of the airplanes in the operator's fleet
prior to submitting a request for adjustment to the compliance time.
The FAA will take into consideration the [[Page 33340]] number of
airplanes in the operator's fleet on which the modification has been
accomplished and the number of unmodified airplanes remaining in the
operator's fleet. Additionally the operator would be asked to submit a
schedule for accomplishing the modification on the airplanes remaining
in its fleet.
Requirements Redundant to Part 121
One commenter requests that proposed paragraph (b) be deleted since
the proposed inspection and repair of components (referenced in Notes
8, 9, and 10 of the Accomplishment Instructions on page 91 of Boeing
Alert Service Bulletin 747-54A2156, dated December 15, 1994) are
redundant to the requirements of part 121 of the Federal Aviation
Regulations (14 CFR 121).
The FAA does not concur with the commenter that the requirements of
paragraph (b) should be deleted from the final rule. According to
section 39.1 of the Federal Aviation Regulations (14 CFR 39.1), the
issuance of an AD is based on the finding that an unsafe condition
exists or is likely to develop in aircraft of a particular type design.
Further, it is within the FAA's authority to issue an AD to require
actions to address unsafe conditions that are not otherwise being
addressed (or addressed inadequately) by normal maintenance procedures.
The FAA points out that fatigue cracking and corrosion in the strut-to-
wing attachments have resulted in several incidents and catastrophic
accidents. Although 14 CFR 121 addresses damage found on components
during other maintenance activities, the FAA has determined that the
catastrophic consequences of the unsafe condition are such that
reiterating the necessity of performing inspections and repairs when
any damage or corrosion is found while performing the modification of
the nacelle strut and wing structure is warranted and necessary. The AD
is the appropriate vehicle for mandating such actions.
Clarification of Note 11 in the Alert Service Bulletin
This same commenter also notes that a torque check would be more
appropriate to detect loose fasteners of the diagonal brace fittings
(referenced in Note 11 of the alert service bulletin). Further, the
commenter asserts that these torque checks should be accomplished in
accordance with the actual Accomplishment Instructions of the Boeing
Alert Service Bulletin 747-54A2156, rather than in accordance with a
Note that precedes the actual Accomplishment Instructions as stated in
proposed paragraph (b).
The FAA concurs that a torque check would be more appropriate to
detect loose fasteners. The FAA's intent was to require a torque check
and the follow-on corrective action indicated in Note 11 of the alert
service bulletin. Obviously, the torque check was inadvertently omitted
from that version of the alert service bulletin; however, the follow-on
action to ``torque any loose fasteners'' was included in that version
of the alert service bulletin. The manufacturer has notified the FAA
that Revision 1 of the alert service bulletin, planned for release
later this year, will correct this omission. However, the FAA does not
consider that delaying this action until after the release of the
revision of the service bulletin is warranted. Therefore, paragraph (b)
of the final rule has been revised to clarify that a torque check must
be performed to detect loose fasteners.
Clarification of Cost Estimate Information
One commenter requests that the cost estimate be revised to include
the cost of out-of-service time for each aircraft during the time that
the modification is accomplished, and the additional fuel costs that
would be incurred due to the additional weight added to each aircraft
by the modification hardware. Another commenter, Boeing, requests that
the cost estimate be revised to indicate that it will absorb the cost
of labor to accomplish the proposed modification of the nacelle strut
and wing structure. However, the commenter states that any costs in
excess of those quoted in Boeing Alert Service Bulletin 747-54A2156,
dated December 15, 1994, will be borne by the operator.
The FAA concurs that a revision to the cost estimate is necessary
to remove the labor costs that the manufacturer will incur; therefore,
the economic impact information, below, has been revised accordingly.
However, the FAA does not concur that a revision is necessary to
include the costs for out-of-service time or the costs for additional
fuel. The appropriate number of hours required to accomplish the
required actions, specified as 6,253 work hours in the economic impact
information, below, was developed with data provided by the
manufacturer.
Note: The manufacturer has informed the FAA that it will incur
labor costs up to a maximum of 6,253 work hours.
This number represents the time required to gain access, remove
parts, inspect, modify, install, and close up. The cost analysis in AD
rulemaking actions typically does not include out-of-service time for
each aircraft or additional fuel costs, as was suggested by the
commenter. These costs would be impossible to calculate accurately due
to the differences in out-of-service time for each operator.
Furthermore, the increase in fuel costs due to the weight added by the
modification, would vary greatly from operator to operator, depending
upon airplane utilization.
The Air Transport Association of America (ATA) requests that the
FAA include costs ``beyond just parts and labor costs'' when
calculating the estimated costs to accomplish the proposed actions. The
ATA points out that the FAA should consider such costs to avoid
requiring actions that the ATA considers inconsequential.
The FAA does not concur. Contrary to the ATA's assertion, in
establishing the requirements of all AD's, the FAA does consider cost
impact to operators beyond the estimates of parts and labor costs
contained in AD preambles. For example, where safety considerations
allow, the FAA attempts to impose compliance times that generally
coincide with operator's maintenance schedules. However, because
operators' schedules vary substantially, the FAA is unable to
accommodate every operator's optimal scheduling in each AD. Each AD
does allow individual operators to obtain approval for extensions of
compliance times, based on a showing that the extension will not affect
safety adversely. Therefore, the FAA does not consider it appropriate
to attribute to the AD, the costs associated with the type of special
scheduling that might otherwise be required.
Furthermore, because the FAA generally attempts to impose
compliance times that coincide with operator's scheduled maintenance,
the FAA considers it inappropriate to attribute the costs associated
with aircraft ``downtime'' to the cost of the AD, because, normally,
compliance with the AD will not necessitate any additional downtime
beyond that of a regularly scheduled maintenance hold. Even if, in some
cases, additional downtime is necessary for some airplanes, the FAA
does not possess sufficient information to evaluate the number of
airplanes that may be so affected or the amount of additional downtime
that may be required. Therefore, attempting to estimate such costs
would be futile.
The FAA points out that this AD is an excellent example of the fact
that costs to operators are fully considered beginning at the earliest
possible stages of AD development. In this case, the alert service
bulletin that is referenced [[Page 33341]] in this final rule was
developed by Boeing only after extensive and detailed consultations
with large numbers of operators of Model 747 series airplanes. The
compliance times and various optional means of compliance presented in
his AD are based on those consultations, and were developed in order to
minimize the economic impacts on operators to the extent possible
consistent with the service bulletin's and this AD's safety objectives.
Therefore, the costs that the ATA asserts were not considered by the
FAA have, in fact, been a major consideration throughout this AD
process; the fact that the FAA has not attempted to quantify
speculative costs does not diminish the extent of this consideration.
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 257 Model 747 series airplanes equipped
with General Electric Model CF6-80C2 series engines or Pratt & Whitney
Model PW4000 series engines of the affected design in the worldwide
fleet. The FAA estimates that 36 airplanes of U.S. registry will be
affected by this AD.
The full strut modification required by this AD will take
approximately 6,253 work hours per airplane to accomplish, at an
average labor cost of $60 per work hour. The manufacturer will incur
the cost of labor up to a maximum of 6,253 work hours per airplane.
However, if the operator exceeds 6,253 work hours to accomplish the
modification, the additional labor costs must be borne by the operator.
The FAA does not have the ability to predict those additional work
hours for operators to accomplish the modification. Therefore,
attempting to estimate such costs would be futile. Required parts will
be supplied by the manufacturer at no cost to the operators. Based on
the above data, the requirements of this AD may have no cost impact to
U.S. operators.
However, the cost impact, above, does not reflect the cost of the
terminating actions described in the service bulletins listed in
paragraph I.C., Table 2, ``Prior or Concurrent Service Bulletins,'' on
page 7 of Boeing Alert Service Bulletin 747-54A2156, dated December 15,
1994, that are required to be accomplished prior to, or concurrently
with, the modification of the nacelle strut and wing structure. Since
some operators may have accomplished certain modifications on some or
all of the airplanes in its fleet, while other operators may not have
accomplished any of the modifications on any of the airplanes in its
fleet, the FAA is unable to provide a reasonable estimate of the cost
of accomplishing the terminating actions described in the service
bulletins listed in Table 2 of the Boeing alert service bulletin.
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 Federal 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 Rule 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. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
95-13-06 Boeing: Amendment 39-9286. Docket 94-NM-224-AD.
Applicability: Model 747 series airplanes having line positions
679 through 1046 inclusive, equipped with General Electric Model
CF6-80C2 series engines or Pratt & Whitney Model PW4000 series
engines; 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 use the authority
provided in paragraph (d) of this AD to request approval from the
FAA. This approval may address either no action, if the current
configuration eliminates the unsafe condition; or different actions
necessary to address the unsafe condition described in this AD. Such
a request should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent failure of the strut and subsequent loss of the
engine, accomplish the following:
(a) Within 80 months after the effective date of this AD,
accomplish the modification of the nacelle strut and wing structure
in accordance with Boeing Alert Service Bulletin 747-54A2156, dated
December 15, 1994. All of the terminating actions described in the
service bulletins listed in paragraph I.C., Table 2, ``Prior or
Concurrent Service Bulletins,'' on page 7 of Boeing Alert Service
Bulletin 747-54A2156, dated December 15, 1994, must be accomplished
in accordance with those service bulletins prior to, or concurrently
with, the accomplishment of the modification of the nacelle strut
and wing structure required by this paragraph.
(b) Perform the inspections and checks (including a torque check
to detect loose fasteners) specified in paragraph III, Notes 8, 9,
10, and 11 of the Accomplishment Instructions on page 91 of Boeing
Alert Service Bulletin 747-54A2156, dated December 15, 1994,
concurrently with the modification of the nacelle strut and wing
structure required by paragraph (a) of this AD. Prior to further
flight, correct any discrepancies in accordance with the alert
service bulletin.
(c) Accomplishment of the modification of the nacelle strut and
wing structure in accordance with Boeing Alert Service Bulletin 747-
54A2156, dated December 15, 1994, constitutes terminating action for
the inspections required by the following AD's:
[[Page 33342]]
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Amendment Federal Register
AD No. No. citation Date of publication
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93-17-07. 39-8678 58 FR 45827............. Aug. 31, 1993.
93-03-14. 39-8518 58 FR 14513............. Mar. 18, 1993.
93-24-51. 39-8439 57 FR 60118............. Dec. 18, 1992.
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(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 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.
(e) Special flight permits may be issued in accordance with
Secs. 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.
(f) The modification, inspections, checks, and correction of
discrepancies shall be done in accordance with Boeing Alert Service
Bulletin 747-54A2156, dated December 15, 1994. 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.
(g) This amendment becomes effective on July 28, 1995.
Issued in Renton, Washington, on June 16, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-15300 Filed 6-27-95; 8:45 am]
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