[Federal Register Volume 59, Number 244 (Wednesday, December 21, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-31328]
[[Page Unknown]]
[Federal Register: December 21, 1994]
VOL. 59, NO. 244
Wednesday, December 21, 1994
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-187-AD]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped With Pratt & Whitney Model JT9D Series Engines (Excluding
Model JT9D-70 Engines)
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 747 series
airplanes. This proposal would require modification of the nacelle
strut and wing structure, inspections and checks to detect
discrepancies, and correction of discrepancies. This proposal is
prompted by the development of a modification of the strut and wing
structure that improves the fail-safe capability and durability of the
strut-to-wing attachments, and reduces reliance on inspections of those
attachments. The actions specified by the proposed AD are intended to
prevent failure of the strut and subsequent loss of the engine.
DATES: Comments must be received by February 16, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-187-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056. Comments may be inspected at this
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except
Federal holidays.
The service information referenced in the proposed rule may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the FAA,
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington.
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:
Comments Invited
Interested persons are invited to participate in the making of the
proposed 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 above. All
communications received on or before the closing date for comments,
specified above, will be considered before taking action on the
proposed rule. The proposals contained in this notice may be changed in
light of the comments received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with
the substance of this proposal will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 94-NM-187-AD.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules
Docket No. 94-NM-187-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056
Discussion -
The FAA has received numerous reports of fatigue cracking and/or
corrosion in the strut-to-wing attachments on Boeing Model 747 series
airplanes. In two cases, such cracking resulted in the failure of a
strut load path and the subsequent loss of the number 3 engine and
strut. In both cases, catastrophic accidents occurred when the number 3
engine and strut separated from the wing of the airplane and struck the
number 4 engine, causing it to separate from the airplane.
Investigation into the cause of these accidents and other reported
incidents revealed not only that fatigue cracks and corrosion in the
strut-to-wing attachments, if not detected and corrected in a timely
manner, can result in failure of the strut and subsequent separation of
the engine from the airplane, but that the structural fail-safe
capability of the strut-to-wing attachment is inadequate on these
airplanes.
The FAA has previously issued 17 AD's that address various problems
associated with the strut attachment assembly on Boeing Model 747
series airplanes. These AD's have required, among other things,
inspections of the strut, strut-to-wing attachment structure, and wing
backup structure of Model 747 series airplanes that are equipped with
Pratt & Whitney Model JT9D series engines (excluding Model JT9D-70
series engines).
Explanation of Service Information
Boeing recently has developed a modification of the strut-to-wing
attachment structure installed on certain Model 747 series airplanes
equipped with Pratt & Whitney Model JT9D series engines (excluding
Model JT9D-70 engines) that significantly improves the load-carrying
capability and durability of the strut-to-wing attachments. Such
improvement also will substantially reduce the possibility of fatigue
cracking and corrosion from developing in the attachment assembly.
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-54A2159, dated November 3, 1994, which describes procedures for
modification of the nacelle strut and wing structure. This modification
entails the following:
1. Providing a new fail-safe load path by installing a new dual
side load fitting to the strut and the underwing structure and the
associated wing back-up fitting, front spar post, and side links;
2. Strengthening the strut by installing a new midspar web and a
new lower spar web and/or channel stiffener;
3. Strengthening the internal wing structure by installing a new
stiffener at the wing midspar;
4. Improving the strut-to-wing attachments by installing new
stainless steel midspar fittings on the strut, replacing aluminum
fittings with new titanium midspar underwing fittings, and replacing
the upper link and the diagonal brace;
5. Enhancing the diagonal brace underwing fitting by installing
certain new nuts and tension bolts; and
6. Modifying the electrical wiring and hydraulics by rerouting
certain wire bundles around the new dual side load fitting and
installing new hydraulic tubes.
This alert service bulletin specifies that the modification of the
nacelle strut and wing structure is to be accomplished prior to, or
concurrently with, the terminating actions described in the service
bulletins listed in paragraph I.C., Table 2, ``Prior or Concurrent
Service Bulletins,'' on page 13 of this alert service bulletin. These
terminating actions include the following:
1. Replacement of the diagonal brace, midspar, and upper link
fusepins with new third generation 15-5 corrosion-resistant steel
fusepins;
2. Replacement of the diagonal brace strut and wing attachment
fittings;
3. Strengthening of the wing front spar; and
4. Replacement of the forward engine mounting nut.
Paragraph III, NOTES 8, 9, 10, and 11 of the Accomplishment
Instructions on pages 149 and 150 of the alert service bulletin also
describe procedures for inspections and checks to detect discrepancies
of the adjacent structure, and correction of any discrepancies.
Explanation of the Provisions of the Proposed AD
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would require modification of the nacelle strut and wing
structure, inspections and checks to detect discrepancies in the
adjacent structure, and correction of discrepancies. The actions would
be required to be accomplished in accordance with the alert service
bulletin described previously.
The FAA has determined that long term continued operational safety
will be better assured by design changes to remove the source of the
problem, rather than by repetitive inspections. Long term inspections
may not be providing the degree of safety assurance necessary for the
transport airplane fleet. This, coupled with a better understanding of
the human factors associated with numerous continual inspections, has
led the FAA to consider placing less emphasis on inspections and more
emphasis on design improvements. The proposed modification requirement
is in consonance with these considerations.
Accomplishment of the modification of the nacelle strut and wing
structure would terminate the inspections currently required by the
following AD's:
----------------------------------------------------------------------------------------------------------------
AD No. Amendment No. Federal Register citation Date of publication
----------------------------------------------------------------------------------------------------------------
94-17-17-................. 39-9012- 59 FR 44903-..................... August 31, 1994.
94-10-05-................. 39-8912- 59 FR 25288-..................... May 16, 1994.
93-17-07-................. 39-8678- 58 FR 45827-..................... August 31, 1993.
93-03-14-................. 39-8518- 58 FR 14513-..................... March 18, 1993.
92-24-51-................. 39-8439- 57 FR 60118-..................... December 18, 1992.
92-07-11-................. 39-8207- 57 FR 10415-..................... March 26, 1992.
90-20-20-................. 39-6725- 55 FR 37859-..................... September 14, 1990.
90-17-18-................. 39-6702- 55 FR 33279-..................... August 15, 1990.
89-07-15-................. 39-6167- 54 FR 11693-..................... March 22, 1989.
87-04-13 R1-.............. 39-5546- 52 FR 3421-...................... February 4, 1987.
86-08-03-................. 39-5289- 51 FR 12836-..................... April 16, 1986.
86-07-06-................. 39-5270- 51 FR 10821-..................... March 31, 1986.
86-05-11-................. 39-5255- 51 FR 8479-...................... March 12, 1986.
86-23-01-................. 39-5450- 51 FR 37712-..................... October 24, 1986.
82-22-02-................. 39-4476- 47 FR 46842-..................... October 21, 1982.
80-08-02-................. 39-3738- 45 FR 24450-..................... April 10, 1980.
79-17-07-................. 39-3533- 44 FR 50033-..................... August 27, 1979.
----------------------------------------------------------------------------------------------------------------
The compliance time for accomplishing the proposed modification has
been broken out into separate groupings. Airplanes that are younger
than 15 years must be modified within 56 months after the effective
date of the AD, and airplanes that are 15 years and older must be
modified within 32 months after the effective date of the AD. The FAA's
intent is to require modification of older airplanes at an earlier
date, since they are more likely to be subject to fatigue cracking and
corrosion. -
The FAA recognizes that the modifications described in the service
bulletins listed in paragraph I.D., ``Compliance,'' on page 17 of
Boeing Alert Service Bulletin 747-54A21
59, dated November 3, 1994, upgrades the structural integrity of the
strut. These modifications include replacement of the upper link, lower
spar fitting, diagonal brace, and mounting nut for the forward engine.
Additionally, these modifications entail rework of the midspar fitting
lugs and fitting attachments; and include the installation of third
generation fuse pins at the strut midspar, diagonal brace, and wing-to-
strut attachments of the upper link. The FAA finds that the proposed
compliance time (for installation of the proposed modification of the
nacelle strut and wing structure) for airplanes on which these other
modifications previously have been accomplished may be extended without
compromising the safety of the fleet. Therefore, the FAA has further
divided the proposed compliance times for airplanes that are 15 years
or older to segregate the requirements of those airplanes that have and
have not been modified previously.
For example, for airplanes on which the modifications described in
the service bulletins referenced by paragraph I.D., ``Compliance,'' on
page 17 of the Boeing alert service bulletin, have been accomplished,
modification of the nacelle strut and wing structure would be required
within 56 months; while, for airplanes on which the modifications
referenced by paragraph I.D. have not been accomplished, modification
of the nacelle strut and wing structure would be required within 32
months.
Further, the FAA acknowledges the work that has been accomplished
previously by creating separate groupings for those airplanes on which
certain, but not all, of the modifications have been accomplished.
Therefore, if the modification described in Boeing Service Bulletin
747-54-2118, dated July 25, 1986 (which is one of the service bulletins
referenced by paragraph I.D., ``Compliance,'' on page 17 of the Boeing
alert service bulletin), has not been accomplished, but all other
modifications referenced by paragraph I.D. have been accomplished, the
FAA's intent is to allow operators of these airplanes to continue to
perform the inspections of the fastener holes that currently are
required by AD 87-04-13 R1, amendment 39-5546 (52 FR 3421, February 4,
1987). However, those inspections must be performed at a reduced
interval of 1,000 landings, until such time that the proposed
modification of the nacelle strut and wing structure is accomplished.
For these airplanes, modification of the nacelle strut and wing
structure would be required within 56 months after the effective date
of this AD.
Similarly, if rework of the midspar fitting lugs or spring beam aft
lugs described in Boeing Alert Service Bulletin 747-54A2152, dated
December 23, 1992, or Revision 1, dated July 15, 1993, has not been
accomplished, but all other modifications referenced by paragraph I.D.
have been accomplished, then the rework should be done in accordance
with Revision 2 of that alert service bulletin. Operators of these
airplanes that have already reworked the midspar fitting lugs or spring
beam aft lugs in accordance with the original issue or Revision 1 of
that alert service bulletin can receive an extension of the compliance
time to 56 months, provided that ultrasonic inspections are performed
(to detect cracking of the inboard and outboard midspar fitting lugs or
spring beam aft lugs of each strut) within 2,500 landings or 3 years
since accomplishment of the rework, whichever occurs earlier, in
accordance with Revision 2 of Boeing Alert Service Bulletin 747-
54A2152, dated September 16, 1993. For these airplanes, repetitive
inspections would be required at intervals not to exceed 500 landings
for inboard struts and 1,000 landings for outboard struts. The FAA has
approved Revision 2 of this alert service bulletin as an alternative
method of compliance to accomplish the requirements of AD 93-17-07,
amendment 39-8678 (58 FR 45827, August 31, 1993), which references
Revision 1 and the original issue of that alert service bulletin as the
appropriate sources of service information to perform this ultrasonic
inspection. The FAA acknowledges that this compliance time is earlier
than that required by AD 93-17-07; however, performance of this
inspection would defer modification of the nacelle strut and wing
structure until 56 months after the effective date of this AD for these
airplanes.
As a result of recent communications with the Air Transport
Association (ATA) of America, the FAA has learned that, in general,
some operators may misunderstand the legal effect of AD's on airplanes
that are identified in the applicability provision of the AD, but that
have been altered or repaired in the area addressed by the AD. The FAA
points out that all airplanes identified in the applicability provision
of an AD are legally subject to the AD. If an airplane has been altered
or repaired in the affected area in such a way as to affect compliance
with the AD, the owner or operator is required to obtain FAA approval
for an alternative method of compliance with the AD, in accordance with
the paragraph of each AD that provides for such approvals. A note has
been included in this notice to clarify this requirement.
Cost Estimate
There are approximately 600 Model 747 series airplanes equipped
with Pratt & Whitney Model JT9D series engines (excluding Model JT9D-70
engines) of the affected design in the worldwide fleet. The FAA
estimates that 146 airplanes of U.S. registry would be affected by this
proposed AD.
The proposed modification may take as many as 7,700 to 8,892 work
hours to accomplish, depending upon the configuration of the airplane.
The manufacturer would incur the cost of labor, on a pro-rated basis,
with 20 years being the expected life of these airplanes. The total
cost impact of the proposed AD on U.S. operators is based on the median
age for the fleet of Model 747 series airplanes equipped with Pratt &
Whitney Model JT9D series engines, which is estimated to be 15 years.
The average labor rate is estimated to be $60 per work hour. Required
parts would be supplied by the manufacturer at no cost to the operator.
Based on these figures, the cost impact of this proposal on U.S.
operators is estimated to be between $50,589,000 ($346,500 per
airplane) and $58,420,440 ($400,140 per airplane).
This cost impact figure 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 13 of Boeing Alert Service Bulletin 747-54A2159, dated November 3,
1994, that are proposed 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. As
indicated earlier in this preamble, the FAA invites comments
specifically on the overall economic aspects of this proposed rule. Any
data received via public comments to this notice will aid the FAA in
developing an accurate accounting of the cost impact of the rule.
The cost impact figure discussed above is based on assumptions that
no operator has yet accomplished any of the proposed requirements of
this AD action, and that no operator would accomplish those actions in
the future if this AD were not adopted.
The FAA recognizes that the obligation to maintain aircraft in an
airworthy condition is vital, but sometimes expensive. Because AD's
require specific actions to address specific unsafe conditions, they
appear to impose costs that would not otherwise be borne by operators.
However, because of the general obligation of operators to maintain
aircraft in an airworthy condition, this appearance is deceptive.
Attributing those costs solely to the issuance of this AD is
unrealistic because, in the interest of maintaining safe aircraft,
prudent operators would accomplish the required actions even if they
were not required to do so by the AD.
A full cost-benefit analysis has not been accomplished for this
proposed AD. As a matter of law, in order to be airworthy, an aircraft
must conform to its type design and be in a condition for safe
operation. The type design is approved only after the FAA makes a
determination that it complies with all applicable airworthiness
requirements. In adopting and maintaining those requirements, the FAA
has already made the determination that they establish a level of
safety that is cost-beneficial. When the FAA, as in this proposed AD,
makes a finding of an unsafe condition, this means that the original
cost-beneficial level of safety is no longer being achieved and that
the proposed actions are necessary to restore that level of safety.
Because this level of safety has already been determined to be cost-
beneficial, a full cost-benefit analysis for this proposed AD would be
redundant and unnecessary.
Regulatory Impact
The regulations proposed herein would 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
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);
and (3) if promulgated, 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 copy of the draft
regulatory evaluation prepared for this action is contained in the
Rules Docket. A copy of it may be obtained by contacting 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.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend
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:
Boeing: Docket 94-NM-187-AD.
Applicability: Model 747 series airplanes having line positions
001 through 814 inclusive, equipped with Pratt & Whitney Model JT9D
series engines (excluding Model JT9D-70 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) 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) Accomplish the modification of the nacelle strut and wing
structure in accordance with Boeing Alert Service Bulletin 747-
54A2159, dated November 3, 1994, at the time specified in either
paragraph (a)(1) or (a)(2) of this AD, as applicable. All of the
terminating actions described in the service bulletins listed in
paragraph I.C., Table 2, ``Prior or Concurrent Service Bulletins,''
on page 13 of Boeing Alert Service Bulletin 747-54A2159, dated
November 3, 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.
(1) For airplanes that are younger than 15 years on the
effective date of this AD, within 56 months after the effective date
of this AD, accomplish the modification.
(2) For airplanes that are 15 years or older on the effective
date of this AD, accomplish the modification, and other required
actions, at the time specified in paragraph (a)(2)(i), (a)(2)(ii),
(a)(2)(iii), (a)(2)(iv), or (a)(2)(v) of this AD, as applicable.
(i) For airplanes on which all of the modifications described in
the service bulletins referenced by paragraph I.D., ``Compliance,''
on page 17 of Boeing Alert Service Bulletin 747-54A2159, dated
November 3, 1994, have been accomplished: Within 56 months after the
effective date of this AD, accomplish the modification of the
nacelle strut and wing structure and perform the inspections of the
adjacent structure that has not been replaced by the modification.
Note 2: Paragraph I.D., ``Compliance,'' on page 17 of Boeing
Alert Service Bulletin 747-54A2159, dated November 3, 1994,
references the following Boeing service bulletins. Subsequent
revisions of the following service bulletins are acceptable and
preferred for accomplishment of the modifications described therein:
------------------------------------------------------------------------
Service bulletin No. Revision level Date
------------------------------------------------------------------------
747-54-2027-........... 1...................... February 23, 1973.
747-54-2030-........... Initial release........ February 23, 1973.
747-54-2062-........... 5...................... June 1, 1984.
747-54A2069-........... 6...................... October 22, 1982.
747-54-2118-........... Initial release........ July 25, 1986.
747-54-2123-........... 1...................... March 1, 1990.
747-54A2151-........... Initial release........ October 6, 1992.
747-54A2152-........... 2...................... September 16, 1993.
747-54A2155-........... Initial release........ September 23, 1993.
747-57A2235-........... Initial release........ June 27, 1986.
747-71A2269-........... 1...................... July 7, 1994.
------------------------------------------------------------------------
(ii) For airplanes on which all of the modifications described
in the service bulletins referenced by paragraph I.D.,
``Compliance,'' on page 17 of Boeing Alert Service Bulletin 747-
54A2159, dated November 3, 1994, have been accomplished, excluding
the modification described in Boeing Service Bulletin 747-54-2118,
dated July 25, 1986:
(A) Within 56 months after the effective date of this AD,
accomplish the modification of the nacelle strut and wing structure
and perform the inspections of the adjacent structure that has not
been replaced by the modification.
(B) Repeat the ultrasonic inspections to detect cracking of the
aft-most two fastener holes in both strut midspar fittings on the
inboard and outboard nacelle struts, as required by AD 87-04-13 R1
at intervals not to exceed 1,000 landings, in accordance with Boeing
Service Bulletin 747-54-2118, dated July 25, 1986, until the
modification of the nacelle strut and wing structure is accomplished
in accordance with Boeing Alert Service Bulletin 747-54A2159, dated
November 3, 1994.
Note 3: These inspections of the fastener holes are required by
AD 87-04-13 R1, amendment 39-5546, at 4,000-landing intervals.
Accomplishment of the inspections of the fastener holes, as required
by this paragraph at 1,000-landing intervals, constitutes compliance
with paragraph A. of AD 87-04-13 R1.
(iii) For airplanes on which all of the modifications described
in the service bulletins referenced by paragraph I.D.,
``Compliance,'' on page 17 of Boeing Alert Service Bulletin 747-
54A2159, dated November 3, 1994, have been accomplished; except that
rework of the midspar fitting lugs or spring beam aft lugs was
accomplished in accordance with Boeing Alert Service Bulletin 747-
54A2152, dated December 23, 1992, or Revision 1, dated July 15,
1993, instead of Revision 2, dated September 16, 1993:
(A) Within 56 months after the effective date of this AD,
accomplish the modification of the nacelle strut and wing structure
and perform the inspections of the adjacent structure that has not
been replaced by the modification.
(B) Prior to the accumulation of 2,500 landings or 3 years since
rework of the lugs, whichever occurs earlier, perform an ultrasonic
inspection to detect cracking of the inboard and outboard midspar
fitting lugs or spring beam aft lugs of each strut, in accordance
with Boeing Alert Service Bulletin 747-54A2152, Revision 2, dated
September 16, 1993. Repeat this inspection thereafter as required by
AD 93-17-07.
Note 4: This ultrasonic inspection is required by AD 93-17-07,
amendment 39-8678, to be performed prior to the accumulation of
5,000 landings or 5 years since accomplishment of the rework of the
lugs, whichever occurs earlier, in accordance with Boeing Alert
Service Bulletin 747-54A2152, dated December 23, 1992, or Revision
1, dated July 15, 1993. Repetitive inspections are required by that
AD at intervals not to exceed 500 landings for inboard struts and
1,000 landings for outboard struts. Since the issuance of that AD,
the FAA has approved Revision 2 of Boeing Alert Service Bulletin
747-54A2152, dated September 16, 1993, as an alternative method of
compliance for accomplishment of these ultrasonic inspections and
rework of the lugs. Revision 2 of the alert service bulletin
recommends that lugs that have been reworked in accordance with the
original issue or Revision 1 of the alert service bulletin be
inspected prior to the accumulation of 2,500 landings or 3 years
since accomplishment of the rework of the lugs, whichever occurs
earlier. Therefore, accomplishment of ultrasonic inspections prior
to the accumulation of 2,500 landings or 3 years since
accomplishment of rework of the lugs, whichever occurs earlier, and
thereafter as required by AD 93-17-07, constitutes compliance with
paragraph (e)(2)(i)(A) of AD 93-17-07.
(iv) For airplanes on which all of the modifications described
in the service bulletins referenced by paragraph I.D.,
``Compliance,'' on page 17 of Boeing Alert Service Bulletin 747-
54A2152, dated November 3, 1994, have been accomplished; except that
rework of the midspar fitting lugs or spring beam aft lugs was
accomplished in accordance with the Boeing Alert Service Bulletin
747-54A2152, dated December 23, 1992, or Revision 1, dated July 15,
1993, instead of Revision 2, dated September 16, 1993; and excluding
the modification described in Boeing Service Bulletin 747-54-2118,
dated July 25, 1986:
(A) Within 56 months after the effective date of this AD,
accomplish the modification of the nacelle strut and wing structure
and perform the inspections of the adjacent structure that has not
been replaced by the modification.
(B) Repeat the ultrasonic inspections to detect cracking of the
aft-most two fastener holes in both strut midspar fittings on the
inboard and outboard nacelle struts, as required by AD 87-04-13 R1,
at intervals not to exceed 1,000 landings, in accordance with Boeing
Service Bulletin 747-54-2118, dated July 25, 1986, until the
modification of the nacelle strut and wing structure is accomplished
in accordance with Boeing Alert Service Bulletin 747-54A2159, dated
November 3, 1994.
(C) Prior to the accumulation of 2,500 landings or 3 years since
rework of the lugs, whichever occurs earlier, perform an ultrasonic
inspection to detect cracking of the inboard and outboard midspar
fitting lugs or spring beam aft lugs of each strut, and repeat the
inspection thereafter as required by AD 93-17-07, until the
modification of the nacelle strut and wing structure is accomplished
in accordance with Boeing Alert Service Bulletin 747-54A2159, dated
November 3, 1994.
Note 5: Notes 3 and 4 are also applicable to this paragraph.
(v) For all other airplanes not subject to the requirements of
paragraph (a)(2)(i), (a)(2)(ii), (a)(2)(iii), or (a)(2)(iv) of this
AD: Within 32 months after the effective date of this AD, accomplish
the modification of the nacelle strut and wing structure and perform
the inspections of the adjacent structure that has not been replaced
by the modification.
Note 6: The following table graphically illustrates the
applicability and compliance times for accomplishing the
modification of the nacelle strut and wing structure for as required
by paragraph (a)(2) of this AD.
------------------------------------------------------------------------
Accomplishment of Revision
Paragraph service bulletins level Compliance time
------------------------------------------------------------------------
(i)-............. All in paragraph I.D.- ........... 56 months.
(ii)............. All except 747-54-2118 ........... 56 months.
(iii)............ All except 747-54A2159 2 56 months.
(iv)............. All except 747-54-2118 2 56 months.
and 747-54A2159.
(v)-............. (\1\)................. ........... 32 months.
------------------------------------------------------------------------
\1\Paragraph (a)(2)(v) of this AD is applicable to all airplanes, other
than those addressed in paragraphs (a)(2)(i), (a)(2)(ii), (a)(2)(iii),
and (a)(2)(iv) of this AD. As such, these airplanes may have
accomplished some or none of the service bulletins listed in paragraph
I.D. of Boeing Alert Service Bulletin 747-54A2159, dated November 3,
1994.
(b) Perform the inspections and checks specified in paragraph
III, NOTES 8, 9, 10, and 11 of the Accomplishment Instructions on
pages 149 and 150 of Boeing Alert Service Bulletin 747-54A2159,
dated November 3, 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 found, 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-
54A2159, dated November 3, 1994, constitutes terminating action for
the inspections required by the following AD's:
----------------------------------------------------------------------------------------------------------------
AD No. Amendment No. Federal Register citation Date of publication
----------------------------------------------------------------------------------------------------------------
94-17-17.................. 39-9012 59 FR 44903...................... August 31, 1994.
94-10-05.................. 39-8912 59 FR 25288...................... May 16, 1994.
93-17-07.................. 39-8678 58 FR 45827...................... August 31, 1993.
93-03-14.................. 39-8518 58 FR 14513...................... March 18, 1993.
92-24-51.................. 39-8439 57 FR 60118...................... December 18, 1992.
92-07-11.................. 39-8207 57 FR 10415...................... March 26, 1992.
90-20-20.................. 39-6725 55 FR 37859...................... September 14, 1990.
90-17-18.................. 39-6702 55 FR 33279...................... August 15, 1990.
89-07-15.................. 39-6167 54 FR 11693...................... March 22, 1989.
87-04-13 R1............... 39-5546 52 FR 3421....................... February 4, 1987.
86-08-03.................. 39-5289 51 FR 12836...................... April 16, 1986.
86-07-06.................. 39-5270 51 FR 10821...................... March 31, 1986.
86-05-11.................. 39-5255 51 FR 8479....................... March 12, 1986.
86-23-01.................. 39-5450 51 FR 37712...................... October 24, 1986.
82-22-02.................. 39-4476 47 FR 46842...................... October 21, 1982.
80-08-02.................. 39-3738 45 FR 24450...................... April 10, 1980.
79-17-07.................. 39-3533 44 FR 50033...................... August 27, 1979.
----------------------------------------------------------------------------------------------------------------
(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 Aircraft Certification Office (ACO), FAA, Transport Airplane
Directorate.
Note 7: 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
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.
Issued in Renton, Washington, on December 15, 1994.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-31328 Filed 12-20-94; 8:45 am]
BILLING CODE 4910-13-P
