[Federal Register: October 17, 2007 (Volume 72, Number 200)]
[Proposed Rules]
[Page 58777-58781]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr17oc07-17]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2007-0043; Directorate Identifier 2007-NM-058-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-
100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747SR, and
747SP Series Airplanes
AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to supersede an existing airworthiness
directive (AD) that applies to certain Boeing Model 747 series
airplanes. The existing AD currently requires inspecting to detect
cracking in certain lower lobe fuselage skin lap joints, doing
repetitive inspections for cracking at certain fastener locations
having countersunk fasteners, and replacing countersunk fasteners with
protruding head fasteners at certain fastener locations. This proposed
AD would replace a previous high-frequency eddy current (HFEC)
inspection method with a new HFEC inspection method, add a one-time
inspection for cracking of certain airplanes, and terminate the
adjustment factor for the inspection compliance times based on cabin
differential pressure. This proposed AD also would include inspection
at an additional lap joint. This proposed AD results from reports of
fuselage skin cracks found at certain countersunk fastener locations in
the upper row of lap joints near the wing-to-body fairings, and from a
report that the presence of alodine-coated rivets could cause faulty
results during the required inspections using the optional sliding
probe HFEC inspection method specified in the existing AD. We are
proposing this AD to prevent reduced structural integrity of the
fuselage.
DATES: We must receive comments on this proposed AD by December 3,
2007.
ADDRESSES: You may send comments by any of the following methods:
Federal eRulemaking Portal: Go to http://www.regulations.gov.
Follow the instructions for submitting comments.
Fax: 202-493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590.
Hand Delivery: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.
For service information identified in this AD, contact Boeing
Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.
Examining the AD Docket
You may examine the AD docket on the Internet at http://www.regulations.gov
; or in person at the Docket Management Facility
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The AD docket contains this proposed AD, the regulatory
evaluation, any comments received, and other information. The street
address for the Docket Office (telephone 800-647-5527) is in the
ADDRESSES section. Comments will be available in the AD docket shortly
after receipt.
FOR FURTHER INFORMATION CONTACT: Ivan Li, Aerospace Engineer, Airframe
Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind
Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6437;
fax (425) 917-6590.
SUPPLEMENTARY INFORMATION:
Comments Invited
We invite you to send any written relevant data, views, or
arguments about this proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include ``Docket No. FAA-2007-0043;
Directorate Identifier 2007-NM-058-AD'' at the beginning of your
comments. We specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of this proposed AD. We
will consider all comments received by the closing date and may amend
this proposed AD because of those comments.
We will post all comments we receive, without change, to http://www.regulations.gov
, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this proposed AD.
Discussion
On July 13, 1994, we issued AD 94-15-06, amendment 39-8977 (59 FR
37659, July 25, 1994), for certain Boeing Model 747 series airplanes.
That AD requires inspections to detect cracking in certain lower lobe
fuselage skin lap joints; doing repetitive inspections for cracking at
certain fastener locations having countersunk fasteners; and replacing
countersunk fasteners with protruding head fasteners at certain
fastener locations. That AD resulted from reports of cracking of the
fuselage skin in certain areas and findings of additional countersunk
fasteners. We issued that AD to prevent reduced structural integrity of
the fuselage.
Actions Since Existing AD Was Issued
In 1985, Boeing started installing aluminum rivets coated with
alodine in fuselage skins during production and supplied them to
operators in modification kits. Alodine coating on aluminum rivets
increases the rivet/skin electrical conductivity. Certain non-
destructive inspection (NDI) methods rely on disruptions in the
electromagnetic field around cracks in metallic structures to detect
cracking. One such NDI method is the sliding probe high frequency eddy
current (HFEC) inspection, which was an optional inspection method
specified by AD 94-15-06. The effects of these increases in rivet/skin
electricity conductivity could be strong enough to mask a crack
indication during the required inspections using the optional sliding
probe HFEC inspection method specified in AD 94-15-06.
Boeing has informed us that airplanes with line numbers 630 through
814 inclusive could have alodine-coated aluminum rivets installed in
the fastener holes that were required to be inspected in accordance
with AD 94-15-06. The presence of these rivets could cause faulty
results when performing the required inspections using the optional
sliding probe HFEC skin inspection method. Consequently, Boeing has
issued Boeing Alert Service Bulletin 747-53A2312, Revision 3, dated
February 8, 2007. (In AD 94-15-06, we referred to Boeing Service
Bulletin 747-53A2312, Revision 2, dated October 8, 1992, as the
appropriate source of service information for doing the required
actions.) Revision 3 of the alert service bulletin updates the sliding
probe HFEC skin inspection method, and includes a one-time special HFEC
or detailed inspection of the affected fastener holes for airplanes on
which the modification required by AD 94-15-06 has not been
[[Page 58778]]
accomplished and on which the optional sliding probe HFEC inspection
method was used during the last skin inspection. The sliding probe HFEC
inspection specified in the previous revisions of the service bulletin
would no longer be allowed in this proposed AD.
In addition, paragraph (e)(2) of AD 94-15-06 did not include the
lap joint at stringer location S-46L in the list of lap joints
requiring inspection for Model 747SP series airplanes. This proposed AD
would include that stringer location.
Relevant Service Information
We have reviewed Boeing Alert Service Bulletin 747-53A2312,
Revision 3, dated February 8, 2007. The procedures in Revision 3 of the
alert service bulletin are similar to those in Revision 2, dated
October 8, 1992. However, Revision 3 changes the instructions for the
optional sliding probe HFEC inspection method and also gives
instructions for a special (one-time) inspection for cracking of
airplanes that were not previously modified according to the service
bulletin and on which the sliding probe HFEC inspection method was used
during the last skin inspection, and repair if necessary. Accomplishing
the actions specified in the service information is intended to
adequately address the unsafe condition.
FAA's Determination and Requirements of the Proposed AD
We have evaluated all pertinent information and identified an
unsafe condition that is likely to develop on other airplanes of the
same type design. For this reason, we are proposing this AD, which
would supersede AD 94-15-06 and would retain certain requirements of
the existing AD. This proposed AD would also require accomplishing the
additional actions specified in the alert service bulletin described
previously, except as discussed under ``Differences Between the
Proposed AD and the Alert Service Bulletin.''
Differences Between the Proposed AD and the Alert Service Bulletin
Although the alert service bulletin specifies to submit certain
information to the manufacturer, this proposed AD does not include that
requirement.
The service bulletin specifies to contact the manufacturer for
appropriate action, but this proposed AD would require inspection or
repairing those conditions, as applicable, in one of the following
ways:
Using a method that we approve; or
Using data that meet the certification basis of the
airplane, and that have been approved by an Authorized Representative
for the Boeing Commercial Airplanes Delegation Option Authorization
Organization whom we have authorized to make those findings.
Changes to Existing AD
This proposed AD would retain certain requirements of AD 94-15-06.
Paragraphs (c) and (d) of that AD specify that it is not necessary to
count flight cycles at 2.0 psi or less cabin differential pressure; and
that for Boeing Model 747SR airplanes, the modification compliance
times specified in paragraphs (a) and (b) of that AD may be multiplied
by a 1.2 adjustment factor. We find that insufficient data exist to
support these adjustments. Consequently, this proposed AD would no
longer allow for these adjustment factors. This change has been
coordinated with Boeing.
In addition, since AD 94-15-06 was issued, the AD format has been
revised, and certain paragraphs have been rearranged. As a result, the
corresponding paragraph identifiers have changed in this proposed AD,
as listed in the following table:
Revised Paragraph Identifiers
------------------------------------------------------------------------
Corresponding requirement in
Requirement in AD 94-15-06 this proposed AD
------------------------------------------------------------------------
Paragraph (a)........................... Paragraph (f).
Paragraph (b)........................... Paragraph (g).
Paragraph (c)........................... Paragraph (h).
Paragraph (d)........................... Paragraph (i).
Paragraph (e)........................... Paragraph (j).
Paragraph (f)........................... Paragraph (k).
Paragraph (g)........................... Paragraph (l).
Paragraph (h)........................... Paragraph (m).
Paragraph (i)........................... Paragraph (n).
Paragraph (j)........................... Paragraph (o).
Paragraph (k)........................... Paragraph (p).
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Costs of Compliance
This proposed AD would affect about 348 airplanes in the worldwide
fleet; 90 of those airplanes are of U.S. registry. The issue associated
with alodine-coated aluminum rivets affects 162 airplanes in the
worldwide fleet and 24 airplanes of U.S. registry. The following table
provides the estimated costs for U.S. operators to comply with this
proposed AD. The average labor rate is $80 per work hour.
Estimated Costs
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Number of
Action Work hours Parts affected Cost per airplane Fleet cost
airplanes
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Inspections (required by AD 90-10- 14 $0 90 $1,120, per $100,800, per
07 and retained in AD 94-15-06 inspection cycle. inspection cycle.
and this AD).
Inspections (required by AD 94-15- 82 $0 90 $6,560, per $590,400, per
06 and retained in this proposed inspection cycle. inspection cycle.
AD).
Modification (required by AD 94- 124 Minimal 90 $9,920.............. $892,800.
15-06 and retained in this
proposed AD).
One-time inspection (new proposed 4 $0 24 $320................ $7,680.
action).
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Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, Section 106, describes the
authority of the FAA Administrator. Subtitle VII, Aviation Programs,
describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701, ``General
requirements.'' Under that section, Congress charges the FAA with
promoting safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce. This regulation is within
the scope of that authority because it addresses an unsafe condition
that is likely to exist or develop on products identified in this
rulemaking action.
Regulatory Findings
We have determined that this proposed AD would not have federalism
implications under Executive Order
[[Page 58779]]
13132. This proposed AD would not have a substantial direct effect 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.
For the reasons discussed above, I certify that the 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. 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.
We prepared a regulatory evaluation of the estimated costs to
comply with this proposed AD and placed it in the AD docket. See the
ADDRESSES section for a location to examine the regulatory evaluation.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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. The Federal Aviation Administration (FAA) amends Sec. 39.13 by
removing amendment 39-8977 (59 FR 37659, July 25, 1994) and adding the
following new airworthiness directive (AD):
Boeing: Docket No. FAA-2007-0043; Directorate Identifier 2007-NM-
058-AD.
Comments Due Date
(a) The FAA must receive comments on this AD action by December
3, 2007.
Affected ADs
(b) This AD supersedes AD 94-15-06.
Applicability
(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B
SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747SR, and
747SP series airplanes, certificated in any category, as identified
in Boeing Alert Service Bulletin 747-53A2312, Revision 3, dated
February 8, 2007.
Unsafe Condition
(d) This AD results from reports of fuselage skin cracks found
at certain countersunk fastener locations in the upper row of lap
joints near the wing-to-body fairings, and from a report that the
presence of alodine-coated rivets could cause faulty results during
the required inspections using the optional sliding probe HFEC
inspection method specified in AD 94-15-06. We are issuing this AD
to prevent reduced structural integrity of the fuselage.
Compliance
(e) You are responsible for having the actions required by this
AD performed within the compliance times specified, unless the
actions have already been done.
Requirements of AD 94-15-06
Inspections for Airplanes Having Line Numbers 201 Through 765
Inclusive
(f) For airplanes having line numbers 201 through 765 inclusive:
Conduct a high frequency eddy current (HFEC) inspection to detect
cracking of the lower lobe lap joints in the vicinity of the wing-
to-body fairings, in accordance with Boeing Alert Service Bulletin
747-53A2312, dated June 12, 1989; Revision 1, dated March 29, 1990;
Revision 2, dated October 8, 1992; or Revision 3, dated February 8,
2007; except as provided by paragraph (u) of this AD; at the time
specified in paragraph (f)(1), (f)(2), (f)(3), or (f)(4) of this AD,
as applicable. As of the effective date of this AD, only Revision 3
shall be used. Repeat this inspection thereafter at intervals not to
exceed 4,000 landings until the inspection required by paragraph (j)
of this AD is accomplished.
(1) For airplanes that have accumulated less than 11,200 total
landings as of February 5, 1990 (the effective date of AD 90-01-07,
amendment 39-6440, which was superseded by AD 94-15-06): Prior to
the accumulation of 11,000 total landings, or within the next 1,000
landings after February 5, 1990, whichever occurs later.
(2) For airplanes that have accumulated 11,200 or more total
landings but less than 15,201 total landings as of February 5, 1990:
Within the next 1,000 landings after February 5, 1990, or prior to
the accumulation of 15,500 total landings, whichever occurs earlier.
(3) For airplanes that have accumulated 15,201 or more total
landings but less than 18,200 total landings as of February 5, 1990:
Within the next 300 landings after February 5, 1990, or prior to the
accumulation of 18,250 total landings, whichever occurs earlier.
(4) For airplanes that have accumulated 18,200 or more landings
as of February 5, 1990: Within the next 50 landings after February
5, 1990.
Repair and Modification for Airplanes Having Line Numbers 201
Through 765 Inclusive
(g) For airplanes having line numbers 201 through 765 inclusive:
Accomplish the requirements of paragraphs (g)(1) and (g)(2) of this
AD.
(1) If any cracking is detected during the inspections required
by paragraph (f) of this AD, prior to further flight, repair in
accordance with Boeing Alert Service Bulletin 747-53A2312, dated
June 12, 1989; Revision 1, dated March 29, 1990; Revision 2, dated
October 8, 1992; or Revision 3, dated February 8, 2007; except as
provided by paragraph (u) of this AD. As of the effective date of
this AD, only Revision 3 shall be used.
(2) Prior to the accumulation of 20,000 total landings or within
the next 3,000 landings after February 5, 1990 (the effective date
of AD 90-01-07), whichever occurs later, modify the airplane by
replacing countersunk fasteners in the upper row of the lower lobe
lap joints in the vicinity of the wing-to-body fairings with
protruding head fasteners, in accordance with the procedures
described in Boeing Alert Service Bulletin 747-53A2312, dated June
12, 1989; Revision 1, dated March 29, 1990; Revision 2, dated
October 8, 1992; or Revision 3, dated February 8, 2007; except as
provided by paragraph (u) of this AD. As of the effective date of
this AD, only Revision 3 shall be used.
Adjustments for Cabin Differential Pressure for Airplanes Having
Line Numbers 201 Through 765 Inclusive
(h) For airplanes having line numbers 201 through 765 inclusive:
Before the effective date of this AD, for purposes of complying with
paragraphs (f) and (g) of this AD, the number of landings may be
determined to equal the number of pressurization cycles where the
cabin pressure differential was greater than 2.0 psi.
(i) For airplanes having line numbers 201 through 765 inclusive:
Before the effective date of this AD, for Model 747SR series
airplanes only, based on continued mixed operation of lower cabin
differentials, the inspection and modification compliance times
specified in paragraphs (f) and (g) of this AD may be multiplied by
a 1.2 adjustment factor.
General Visual Inspection for Countersunk Fasteners for All
Airplanes
(j) For all airplanes: Prior to the accumulation of 11,000 total
landings, or within 1,000 landings after August 24, 1994 (the
effective date of AD 94-15-06), whichever occurs later, conduct a
general visual inspection, unless previously accomplished within the
last 3,000 landings prior to August 24, 1994, to determine if
countersunk fasteners have been installed in the lap joints listed
in paragraph (j)(1) or (j)(2) of this AD, as applicable, in
accordance with the procedures described in Boeing Service Bulletin
747-53A2312, Revision 2, dated October 8, 1992; or Revision 3, dated
February 8, 2007; except as provided by paragraph (u) of this AD. As
of the effective date of this AD, only Revision 3 shall be used.
Accomplishment of this inspection terminates the inspection
requirements of paragraph (f) of this AD.
(1) For Model 747-100, -200, -300, -400, and 747SR series
airplanes: From body stations (BS) 741 to 1000 at Stringers (S-)34L,
S-34R, S-39L, S-39R, S-44L, and S-44R, and from BS 1480 to 1741 at
S-34L, S-34R, S-40L, and S-40R.
(2) For Model 747SP series airplanes: From BS 520 to 1000 at S-
34L, S-34R, S-39L, S-39R, S-44L, and S-44R, and from BS 1480 to 1741
at S-34L, S-34R, S-40L, and S-40R.
[[Page 58780]]
Corrective Action for Countersunk Fasteners for All Airplanes
(k) For all airplanes: If no countersunk fastener is found in
the upper row of a lap joint during the inspection required by
paragraph (j) of this AD, no further action is required by this AD
for that lap joint.
(l) For all airplanes: If any countersunk fastener is found in
the upper row of a lap joint during the inspection required by
paragraph (j) of this AD, prior to further flight, perform a high
frequency eddy current (HFEC) inspection to detect cracking at all
fastener locations in the lap joint where a countersunk fastener was
found, in accordance with the procedures described in Boeing Service
Bulletin 747-53A2312, Revision 2, dated October 8, 1992; or Revision
3, dated February 8, 2007; except as provided by paragraph (u) of
this AD. As of the effective date of this AD, only Revision 3 shall
be used.
Repetitive Inspections
(m) If no cracking is detected during any inspection required by
paragraphs (l) and (q) of this AD, at any fastener location where a
countersunk fastener was found, repeat the HFEC inspection
thereafter at intervals not to exceed 4,000 landings, in accordance
with the procedures described in Boeing Service Bulletin 747-
53A2312, Revision 2, dated October 8, 1992; or Revision 3, dated
February 8, 2007; except as provided by paragraph (u) of this AD. As
of the effective date of this AD, only Revision 3 shall be used. As
an alternative to the HFEC inspection, operators may perform a
detailed inspection to detect cracking at any fastener location
where a countersunk fastener was found, in accordance with the
procedures described in Boeing Service Bulletin 747-53A2312,
Revision 3, dated February 8, 2007; except as provided by paragraph
(u) of this AD. Perform the detailed inspection within the next
4,000 landings after the HFEC inspection required by paragraph (l)
of this AD, and repeat the inspection thereafter at intervals not to
exceed 500 landings. At any of the subsequent inspection cycles,
operator may use either inspection method provided that the
corresponding inspection interval is used to determine the
compliance time of the next inspection.
(n) If cracking is detected during any inspection required by
paragraph (l), (m), (p), or (q) of this AD, at any fastener location
where a countersunk fastener was found, prior to further flight,
repair and modify that lap joint in accordance with Boeing Service
Bulletin 747-53A2312, Revision 2, dated October 8, 1992; or Revision
3, dated February 8, 2007; except as provided by paragraph (u) of
this AD. As of the effective date of this AD, only Revision 3 shall
be used. Accomplishment of this repair and modification terminates
the repetitive inspections required by paragraph (m) of this AD for
that lap joint.
Modification of Countersunk Fasteners for All Airplanes
(o) For all airplanes: Prior to the accumulation of 20,000 total
landings or within 1,000 landings after August 24, 1994, whichever
occurs later, modify all fastener locations where a countersunk
fastener was found during the inspections required by paragraph (j)
of this AD, in accordance with the procedures described in Boeing
Service Bulletin 747-53A2312, Revision 2, dated October 8, 1992; or
Revision 3, dated February 8, 2007; except as provided by paragraph
(u) of this AD. As of the effective date of this AD, only Revision 3
shall be used. For purposes of complying with the requirements of
this paragraph, fastener locations that were previously modified in
accordance with paragraph (g) or (n) of this AD do not need to be
modified again. Accomplishment of this modification terminates the
repetitive inspections required by paragraph (m) of this AD for the
modified fastener locations.
Post-Modification Inspections for All Airplanes
(p) For all airplanes: Prior to the accumulation of 10,000 total
landings following the modification required by paragraph (g), (n),
(o), (q) or (s) of this AD, perform an HFEC inspection to detect
cracking at all fastener locations where a countersunk fastener was
found, and repeat this inspection thereafter at intervals not to
exceed 4,000 landings, in accordance with the procedures described
in Boeing Service Bulletin 747-53A2312, Revision 2, dated October 8,
1992; or Revision 3, dated February 8, 2007; except as provided by
paragraph (u) of this AD. As of the effective date of this AD, only
Revision 3 shall be used.
New Requirements of This AD
General Visual Inspection for Countersunk Fasteners and
Modification for Model 747SP Airplanes at Stringer S-46L
(q) For Model 747SP series airplanes having line numbers 201
through 814 inclusive, do the actions in paragraphs (q)(1) and
(q)(2) of this AD at the times specified in those paragraphs.
(1) Prior to the accumulation of 11,000 total landings, or
within 1,000 landings as of the effective date of this AD, whichever
occurs later, unless previously accomplished within the last 3,000
landings prior to the effective date of this AD, conduct a general
visual inspection of the lap joint from BS 520 to 1000 at stringer
S-46L to determine if countersunk fasteners have been installed in
the specified area, in accordance with the procedures described in
Boeing Service Bulletin 747-53A2312, Revision 2, dated October 8,
1992; or Revision 3, dated February 8, 2007; except as provided by
paragraph (u) of this AD.
(i) If no countersunk fastener is found in the upper row of the
lap joint during the inspection, no further action is required by
this AD for the lap joint.
(ii) If any countersunk fastener is found in the upper row of
the lap joint, prior to further flight, perform an HFEC inspection
to detect cracking at all fastener locations where a countersunk
fastener was found, in accordance with the procedures described in
Boeing Service Bulletin 747-53A2312, Revision 3, dated February 8,
2007; except as provided by paragraph (u) of this AD.
A. If no cracking is found, repeat the inspection thereafter in
accordance with the requirements of paragraph (m) of this AD.
B. If any cracking is found, prior to further flight, repair and
modify the lap joint as required by paragraph (n) of this AD.
(2) Prior to the accumulation of 20,000 total landings, or
within 1,000 landings as of the effective date of this AD, whichever
occurs later, modify all fastener locations where a countersunk
fastener was found, during the inspection required by paragraph
(q)(1) of this AD, in accordance with the Accomplishment
Instructions of Boeing Service Bulletin 747-53A2312, Revision 2,
dated October 8, 1992; or Revision 3, dated February 8, 2007; except
as provided by paragraph (u) of this AD. For purposes of complying
with the requirements of this AD, fastener locations that were
previously modified in accordance with paragraph (n) of this AD do
not need to be modified again. Accomplishment of this modification
terminates the repetitive inspections required by paragraph (m) of
this AD for the modified fastener locations.
Adjustments to Compliance Time: Cabin Differential Pressure
(r) For the purposes of calculating the compliance threshold and
repetitive intervals for actions required by paragraphs (f) and (g)
of this AD, on or as of the effective date of this AD: All flight
cycles, including the number of flight cycles in which cabin
differential pressure is at 2.0 psi or less, must be counted when
determining the number of flight cycles that have occurred on the
airplane, and a 1.2 adjustment factor may not be used. However, for
airplanes on which the repetitive intervals for the actions required
by paragraph (f) of this AD have been calculated in accordance with
paragraph (h) and/or (i) of this AD by excluding the number of
flight cycles in which cabin differential pressure is at 2.0 pounds
psi or less, and/or by using a 1.2 adjustment factor: Continue to
adjust the repetitive intervals in accordance with paragraph (h)
and/or (i) of this AD until the next inspection required by
paragraph (f) of this AD is accomplished. Thereafter, no adjustment
to compliance times based on paragraph (h) and/or (i) of this AD is
allowed.
Special One-Time Inspection for Cracking of Certain Airplanes
(s) For airplanes with line numbers 630 through 814 inclusive
that meet the conditions specified in paragraphs (s)(1) and (s)(2)
of this AD: Within 300 flight cycles as of the effective date of
this AD, or within 500 flight cycles after the most recent sliding
probe inspection done in accordance with Boeing Alert Service
Bulletin 747-53A2312, Revision 1, dated March 29, 1990; or Revision
2, dated October 8, 1992, whichever occurs later, do a special one-
time HFEC inspection or a special one-time detailed inspection for
cracking, in accordance with the Accomplishment Instructions of
Boeing Alert Service Bulletin 747-53A2312, Revision 3, dated
February 8, 2007. If any cracking is found in a lap joint, before
further flight, repair and modify that lap joint in accordance with
Boeing Service Bulletin
[[Page 58781]]
747-53A2312, Revision 3, dated February 8, 2007; except as provided
by paragraph (u) of this AD. Accomplishment of this repair and
modification terminates the repetitive inspections required by
paragraph (m) of this AD for that lap joint. This special one-time
inspection is not required for lap joints that have been modified in
accordance with paragraph (g), (n), (o), or (q) of this AD.
(1) Airplanes that have not been modified in accordance with
paragraph (g) or (o) of this AD.
(2) Airplanes on which the sliding probe HFEC inspection method
specified in Boeing Service Bulletin 747-53A2312, Revision 1, dated
March 29, 1990; or Revision 2, dated October 8, 1992; was used
during the last skin inspection required by AD 94-15-06.
Actions After the Special One-Time Inspection if No Cracking Is Found
(t) For airplanes specified in paragraph (s) of this AD on which
no cracking is found during the special one-time inspection, do the
applicable repetitive inspections specified in paragraph (t)(1) or
(t)(2) of this AD.
(1) If the special one-time inspection was done using the HFEC
inspection method in accordance with paragraph (s) of this AD,
perform the next inspection required by paragraph (m) of this AD
within the next 4,000 flight cycles after doing the inspection
required by paragraph (s) of this AD, and repeat the inspection
thereafter in accordance with paragraph (m) of this AD.
(2) If the special one-time inspection was done using the
detailed inspection method in accordance with paragraph (s) of this
AD, perform the next inspection required by paragraph (m) of this AD
within the next 500 flight cycles after doing the inspection
required by paragraph (s) of this AD, and repeat the inspection
thereafter in accordance with paragraph (m) of this AD.
Contacting the Manufacturer
(u) Where Boeing Alert Service Bulletin 747-53A2312, Revision 3,
dated February 8, 2007 specifies to contact Boeing for appropriate
action for a repair or inspection, before further flight, do the
applicable action in paragraph (u)(1) or (u)(2) of this AD.
(1) Do the repair using a method approved in accordance with the
procedures specified in paragraph (v) of this AD.
(2) Do the inspection using a method approved by the Manager,
Seattle Aircraft Certification Office (ACO), FAA. For a repair
method to be approved by the Manager, Seattle ACO, as required by
this paragraph, the Manager's approval letter must specifically
refer to this AD.
Alternative Methods of Compliance (AMOCs)
(v)(1) The Manager, Seattle ACO, FAA, has the authority to
approve AMOCs for this AD, if requested in accordance with the
procedures found in 14 CFR 39.19.
(2) To request a different method of compliance or a different
compliance time for this AD, follow the procedures in 14 CFR 39.19.
Before using any approved AMOC on any airplane to which the AMOC
applies, notify your appropriate principal inspector (PI) in the FAA
Flight Standards District Office (FSDO), or lacking a PI, your local
FSDO.
(3) An AMOC that provides an acceptable level of safety shall be
used for any repair required by this AD, if it is approved by an
Authorized Representative for the Boeing Commercial Airplanes
Delegation Option Authorization Organization who has been authorized
by the Manager, Seattle ACO, to make those findings. For a repair
method to be approved, the repair must meet the certification basis
of the airplane, and the approval must specifically refer to this
AD.
(4) AMOCs approved previously in accordance with AD 94-15-06,
are approved as AMOCs for the corresponding provisions of this AD if
the AMOC does not involve using the existing sliding probe HFEC skin
inspection method specified in Boeing Service Bulletin 747-53A2312,
Revision 2, dated October 8, 1992, or an earlier version. In
addition, the provisions of paragraph (r) of this AD must be applied
to AMOCs approved previously in accordance with AD 94-15-06,
amendment 39-8977, where applicable.
Issued in Renton, Washington, on October 5, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E7-20468 Filed 10-16-07; 8:45 am]
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