[Federal Register Volume 63, Number 183 (Tuesday, September 22, 1998)]
[Rules and Regulations]
[Pages 50495-50498]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-25123]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-257-AD; Amendment 39-10786; AD 98-20-20]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
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SUMMARY: This amendment supersedes an existing airworthiness directive
(AD), applicable to certain Boeing Model 747 series airplanes, that
currently requires repetitive inspections for damage or cracking of the
aft pressure bulkhead, and repair, if necessary. This amendment
continues to require certain repetitive inspections for damage or
cracking of the aft pressure bulkhead, and repair, if necessary. This
amendment removes certain repetitive inspections for cracking of the
bulkhead web to Y-ring lap joint area but retains the initial
inspection for cracking in that area. This amendment also adds a one-
time inspection from the forward side of the bulkhead to detect fatigue
cracking of the upper segment of the bulkhead web, and follow-on
corrective actions, if necessary. This amendment is prompted by reports
indicating that the inspections required by the existing AD may not
detect cracking of the bulkhead web in a timely manner. The actions
specified in this AD are intended to detect and correct fatigue
cracking of the upper segment of the bulkhead web, which could result
in rapid depressurization of the airplane, and consequent reduced
controllability of the airplane.
DATES: Effective October 7, 1998. The incorporation by reference of
certain publications listed in the regulations is approved by the
Director of the Federal Register as of October 7, 1998.
Comments for inclusion in the Rules Docket must be received on or
before November 23, 1998.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-257-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056.
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 FAA, Transport
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at
the Office of the Federal Register, 800 North Capitol Street, NW.,
suite 700, Washington, DC.
FOR FURTHER INFORMATION CONTACT: Bob Breneman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2776; fax (425) 227-1181.
SUPPLEMENTARY INFORMATION: On October 21, 1987, the FAA issued AD 87-
23-10, amendment 39-5758 (52 FR 41551, October 29, 1987), applicable to
certain Boeing Model 747 series airplanes, to require repetitive
inspections for damage or cracking of the aft pressure bulkhead, and
repair, if necessary. That action was prompted by analysis of
inspection reports and the results of testing by the manufacturer. The
actions required by that AD are intended to detect and correct fatigue
cracking of the aft pressure bulkhead, which could result in rapid
depressurization of the airplane.
Actions Since Issuance of Previous Rule
Since the issuance of that AD, the FAA has received a report
indicating that one operator found a 7.5-inch-long crack in the upper
portion of the web of the pressure bulkhead at Body Station 2360 on a
Boeing Model 747 series airplane. Analysis of the cracked bulkhead web
revealed a series of short cracks initiated at the fastener holes
common to the outer chord of the Y-ring in multiple locations. These
cracks propagated rapidly due to fatigue, and joined together to form
the 7.5-inch-long crack.
That airplane had accumulated 25,777 total landings and 74,266
total flight hours at the time the crack was discovered. The upper
portion of the web of the pressure bulkhead of that airplane had been
inspected previously in accordance with AD 87-23-10, and the crack was
discovered during a repeat detailed visual inspection performed
approximately 7,000 landings after the initial inspection. These
findings indicate that cracking of the upper portion of the web of the
pressure bulkhead could develop on the affected airplanes in fewer
landings than the repetitive inspection interval of 7,000 landings that
is mandated by the existing AD.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-53A2275, Revision 6, dated August 27, 1998. That alert service
bulletin describes procedures for, among other things, a detailed
visual inspection performed from the forward side of the bulkhead to
detect cracking of the upper segment of the bulkhead web at the
attachment to the outer chord of the Y-ring. That alert service
bulletin also describes procedures for follow-on corrective actions, if
necessary, which include a surface probe eddy current inspection to
detect cracking of the upper and lower segments of the bulkhead around
the fasteners that attach the web to the outer chord of the Y-ring. The
alert service bulletin also specifies that the manufacturer may be
contacted for the disposition of certain repairs.
Explanation of Requirements of Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other airplanes of this same type design, this AD
supersedes AD 87-23-10 to continue to require certain repetitive
inspections for damage or cracking of the aft pressure bulkhead, and
repair, if necessary. In addition, this AD removes repetitive detailed
visual inspections for cracking of the bulkhead web to Y-ring lap joint
area but retains the initial inspection for cracking in that area. This
AD also adds a one-time detailed visual inspection from the forward
side of the bulkhead to detect fatigue cracking of the upper segment of
the bulkhead web, and follow-on corrective actions, if necessary. The
actions are required to be accomplished
[[Page 50496]]
in accordance with the alert service bulletin described previously,
except as discussed below.
Interim Action
This is considered to be interim action. The FAA is currently
considering requiring additional repetitive detailed visual inspections
from the forward side of the bulkhead to detect cracking of the upper
segment of the bulkhead web; repetitive surface probe high frequency
eddy current inspections from the forward side of the bulkhead to
detect cracking of the upper and lower segments of the bulkhead web;
and repair, if necessary. However, the planned compliance time for
these actions is sufficiently long so that notice and opportunity for
prior public comment will be practicable.
Differences Between Alert Service Bulletin and This AD
Operators should note that, although the alert service bulletin
specifies that the manufacturer may be contacted for disposition of
certain repair conditions, this AD requires the repair of those
conditions to be accomplished in accordance with a method approved by
the FAA, or in accordance with data meeting the type certification
basis of the airplane approved by a Boeing Company Designated
Engineering Representative who has been authorized by the FAA to make
such findings.
Operators also should note that the alert service bulletin
specifies accomplishment of the visual inspection prior to the
accumulation of 20,000 total flight cycles (landings); within 250
flight cycles after receipt of Boeing Alert Service Bulletin 747-
53A2275, Revision 6; or within 1,500 flight cycles after the last
visual inspection from the forward side of the bulkhead; whichever
occurs latest. The FAA has determined that such compliance options may
not ensure that all affected airplanes are inspected in a timely
manner.
In developing an appropriate compliance time for this AD, the FAA
considered not only the manufacturer's recommendation, but also the
time necessary to accomplish the inspection (4 hours), and the average
utilization of the affected fleet. The FAA finds that, due to possible
variances in average utilization among airplanes, a grace period of 90
days rather than 250 flight cycles (landings) will better ensure that
the inspection is accomplished on all Boeing Model 747 series airplanes
in a timely manner.
In light of all of these factors, the FAA finds that accomplishment
of the inspection for all affected airplanes prior to the accumulation
of 20,000 total landings, within 1,500 landings after the last visual
inspection from the forward side of the bulkhead, or within 90 days
after the effective date of this AD, whichever occurs latest,
represents an appropriate interval of time allowable for affected
airplanes to continue to operate without compromising safety.
Explanation of Applicability
AD 87-23-10 was applicable to Boeing Model 747 series airplanes, as
listed in Boeing Service Bulletin 747-53-2275, Revision 1, dated August
13, 1987. This AD is applicable to Boeing Model 747 series airplanes,
line positions 1 through 671. This change is being made to more
precisely define the airplanes that are affected. The line positions
are the same as those referenced in the effectivity of Boeing Service
Bulletin 747-53-2275, Revision 1; no new airplanes are added as a
result of this change.
Explanation of Disallowance of Adjustment Factor
Paragraph (g) of AD 87-23-10 specified that, based on continued
mixed operation at lower cabin differential pressures, the compliance
thresholds and intervals specified in that AD for Boeing Model 747
series airplanes could be multiplied by a 1.2 adjustment factor. Since
the issuance of that AD, the FAA has determined that insufficient data
exist to support such an adjustment to flight cycles. In fact, data are
available that indicate that the use of a 1.2 adjustment factor
provides inaccurate data and unjustified relief for inspection
intervals. Consequently, this AD does not allow for such an adjustment
factor, and the provisions of paragraph (g) of the existing AD have not
been included in this AD.
Explanation of Disallowance of Modification
Paragraph (j) of AD 87-23-10 specifies that modification of Boeing
Model 747 series airplanes by installing certain new, improved parts
would constitute terminating action for the inspection requirements of
that AD. Since the issuance of AD 87-23-10, the FAA has determined that
the kit necessary for accomplishment of such modification was never
made available by the manufacturer. Therefore, because it is not
possible to comply with the actions described by paragraph (j), the
provisions of that paragraph have not been included in this AD.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of
this regulation, it is found that notice and opportunity for prior
public comment hereon are impracticable, and that good cause exists for
making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
this rule. Interested persons are invited to comment on this rule by
submitting such written data, views, or arguments as they may desire.
Communications shall identify the Rules Docket number and be submitted
in triplicate to the address specified under the caption ADDRESSES. All
communications received on or before the closing date for comments will
be considered, and this rule may be amended in light of the comments
received. Factual information that supports the commenter's ideas and
suggestions is extremely helpful in evaluating the effectiveness of the
AD action and determining whether additional rulemaking action would be
needed.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the rule that might
suggest a need to modify the rule. All comments submitted will be
available, both before and after the closing date for comments, in the
Rules Docket for examination by interested persons. A report that
summarizes each FAA-public contact concerned with the substance of this
AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this rule must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 98-NM-257-AD.'' The postcard will be date stamped and
returned to the commenter.
Regulatory Impact
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency
regulation that must be issued immediately to correct an unsafe
condition in aircraft,
[[Page 50497]]
and that it is not a ``significant regulatory action'' under Executive
Order 12866. It has been determined further that this action involves
an emergency regulation under DOT Regulatory Policies and Procedures
(44 FR 11034, February 26, 1979). If it is determined that this
emergency regulation otherwise would be significant under DOT
Regulatory Policies and Procedures, a final regulatory evaluation will
be prepared and placed in the Rules Docket.
A copy of it, if filed, may be obtained from the Rules Docket at
the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-5758 (52 FR
41551, October 29, 1987), and by adding a new airworthiness directive
(AD), amendment 39-10786, to read as follows:
98-20-20 Boeing: Amendment 39-10786. Docket 98-NM-257-AD.
Supersedes AD 87-23-10, amendment 39-5758.
Applicability: Model 747 series airplanes, line positions 1
through 671 inclusive; certificated in any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
modified, altered, or repaired in the area subject to the
requirements of this AD. For airplanes that have been modified,
altered, or repaired so that the performance of the requirements of
this AD is affected, the owner/operator must request approval for an
alternative method of compliance in accordance with paragraph (i)(1)
of this AD. The request should include an assessment of the effect
of the modification, alteration, or repair on the unsafe condition
addressed by this AD; and, if the unsafe condition has not been
eliminated, the request should include specific proposed actions to
address it.
Compliance: Required as indicated, unless accomplished
previously.
To detect and correct fatigue cracking of the upper segment of
the bulkhead web, which could result in rapid depressurization of
the airplane, and consequent reduced controllability of the
airplane, accomplish the following:
(a) Within 750 landings after December 10, 1987 (the effective
date for AD 87-23-10, amendment 39-5758), unless accomplished within
the last 1,250 landings [for airplanes subject to a 2,000-landing
repeat inspection interval in accordance with paragraph (b) of this
AD], or unless accomplished within the last 250 landings [for
airplanes subject to a 1,000-landing repeat inspection interval in
accordance with paragraph (b) of this AD], perform a detailed visual
inspection; in accordance with Boeing Service Bulletin 747-53-2275,
dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2,
dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4,
dated March 26, 1992, or Revision 5, dated January 16, 1997, or
Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August
27, 1998; of the aft side of the entire Body Station (BS) 2360 aft
pressure bulkhead for damage such as dents, tears, nicks, gouges, or
scratches; and cracks at splices and doublers, and around the
Auxiliary Power Unit pressure pan cutout; and, for Group 4 airplanes
only, inspect from the forward side, the area adjacent to the window
cutout for damage or cracks.
Note 2: Notwithstanding provisions to the contrary in AD 87-23-
10, and in Boeing Service Bulletin 747-53-2275, dated March 26,
1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31,
1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26,
1992, and Revision 5, dated January 16, 1997: For Model 747SR
airplanes operating at a cabin pressure differential lower than 8.6
pounds-per-square-inch (psi), an adjustment factor of 1.2 shall not
be used after the effective date of this AD as a multiplier for
inspection thresholds and intervals specified in this AD.
(b) After initial compliance with paragraph (a) of this AD,
continue to inspect as follows:
(1) For Group 1 airplanes, repeat the inspections required by
paragraph (a) of this AD, at intervals not to exceed 2,000 landings.
(2) For Groups 2 and 3 airplanes, repeat the inspections
required by paragraph (a) of this AD, at intervals not to exceed
1,000 landings; or optionally, at the applicable time specified in
paragraph (b)(2)(i) or (b)(2)(ii) of this AD.
(i) For Group 2 airplanes that operate the entire interval with
aft lavatory complexes or galleys adjacent to bulkheads, repeat the
inspections required by paragraph (a) of this AD at intervals not to
exceed 2,000 landings.
(ii) For Groups 2 and 3 airplanes that operate the entire
interval with an intact protective shield on the lower half of the
forward side of the bulkhead, repeat the inspections required by
paragraph (a) of this AD at intervals not to exceed 2,000 landings;
and perform a detailed visual inspection of the protective shield
for damage in accordance with Boeing Service Bulletin 747-53-2275,
dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2,
dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4,
dated March 26, 1992, or Revision 5, dated January 16, 1997, or
Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August
27, 1998, at intervals not to exceed 1,000 landings. If damage is
found to the protective shield that exceeds the limits indicated in
the service bulletin, prior to further flight, repeat the inspection
required by paragraph (a) of this AD.
(3) For Group 4 airplanes, repeat the inspections required by
paragraph (a) of this AD at intervals not to exceed 1,000 landings.
(c) Within 750 landings after December 10, 1987, or prior to the
accumulation of 20,000 total landings, whichever occurs later,
unless accomplished within the last 3,250 landings; and at intervals
thereafter not to exceed 4,000 landings; perform eddy current,
ultrasonic, and X-ray inspections of the aft side of the BS 2360 aft
pressure bulkhead for cracks; in accordance with Boeing Service
Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August
13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March
29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated
January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275,
Revision 6, dated August 27, 1998.
(d) Within 750 landings after December 10, 1987, or prior to the
accumulation of 20,000 total landings, whichever occurs later,
unless accomplished within the last 6,250 landings; and thereafter
at intervals not to exceed 7,000 landings until the inspection
required by paragraph (g) of this AD is accomplished: Perform a
detailed visual inspection to detect cracking of the BS 2360 aft
pressure bulkhead web to Y-ring lap joint area between radial
stiffeners from the forward side of the bulkhead, in accordance with
Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision
1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision
3, dated March 29, 1990, Revision 4, dated March 26, 1992, or
Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin
747-53A2275, Revision 6, dated August 27, 1998.
(e) If any cracking or damage is found during any inspection
required by paragraph (a), (b), (c), or (d) of this AD, repair prior
to further flight in accordance with Boeing Service Bulletin 747-53-
2275, dated March 26, 1987, Revision 1, dated August 13, 1987,
Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990,
Revision 4, dated March 26, 1992, or Revision 5, dated January 16,
1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6,
dated August 27, 1998.
(f) For the purpose of complying with 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.
(g) Perform a one-time detailed visual inspection from the
forward side of the bulkhead of the upper segment of the bulkhead
web at BS 2360 to detect cracking, in accordance with Boeing Alert
Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998, at
the earlier of the times specified in paragraphs (g)(1) and (g)(2)
of this AD. If no cracking is detected during this inspection, no
further action is required by this paragraph. Accomplishment of this
inspection terminates the repetitive inspection requirement of
paragraph (d) of this AD.
[[Page 50498]]
(1) Within 7,000 landings after the most recent detailed visual
inspection accomplished in accordance with paragraph (d) of this AD.
(2) At the latest of the times specified in paragraphs
(g)(2)(i), (g)(2)(ii), and (g)(2)(iii) of this AD.
(i) Prior to the accumulation of 20,000 total landings.
(ii) Within 1,500 landings after the most recent detailed visual
inspection accomplished in accordance with paragraph (d) of this AD.
(iii) Within 90 days after the effective date of this AD.
(h) If any cracking is detected during the inspection required
by paragraph (g) of this AD, prior to further flight, accomplish a
surface probe eddy current inspection from the forward side of the
bulkhead to detect cracking of the upper and lower segments of the
bulkhead web around the fasteners that attach the web to the outer
chord of the Y-ring, in accordance with Boeing Alert Service
Bulletin 747-53A2275, Revision 6, dated August 27, 1998. Repair any
cracking, prior to further flight, in accordance with a method
approved by the Manager, Seattle Aircraft Certification Office
(ACO), FAA, Transport Airplane Directorate; or in accordance with
data meeting the type certification basis of the airplane approved
by a Boeing Company Designated Engineering Representative who has
been authorized by the Manager, Seattle ACO, to make such findings.
(i)(1) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Seattle ACO. Operators shall submit
their requests through an appropriate FAA Principal Maintenance
Inspector, who may add comments and then send it to the Manager,
Seattle ACO.
(i)(2) Alternative methods of compliance for repairs and
modifications, approved previously in accordance with AD 87-23-10,
amendment 39-5758, are approved as alternative methods of compliance
with this AD.
Note 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(j) 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.
(k) Except as provided by paragraph (h) of this AD, the actions
shall be done in accordance with Boeing Service Bulletin 747-53-
2275, dated March 26, 1987, Revision 1, dated August 13, 1987,
Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990,
Revision 4, dated March 26, 1992, or Revision 5, dated January 16,
1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6,
dated August 27, 1998. These Boeing service bulletins contain the
following list of effective pages:
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Service bulletin referenced and Revision level shown
date Page No. on page Date shown on page
----------------------------------------------------------------------------------------------------------------
747-53-2275, March 26, 1987....... 1-50................. Original.............. March 26, 1987.
747-53-2275, Revision 1, August 1-8, 10-17, 26-51.... 1..................... August 13, 1987.
13, 1987.
9, 18-25............. Original.............. March 26, 1987.
747-53-2275, Revision 2, March 31, 1-8, 10-13, 18, 22, 2..................... March 31, 1988.
1998. 29, 35, 42, 49-53.
14-17, 26-28, 30-34, 1..................... August 13, 1987.
36-41, 43-38.
9, 19-21, 23-25...... Original.............. March 26, 1987.
747-53-2275, Revision 3, March 29, 1-33, 35, 54-57...... 3..................... March 29, 1990.
1990.
42, 49-53............ 2..................... March 31, 1988.
34, 36-41, 43-48..... 1..................... August 13, 1987.
747-53-2275, Revision 4, March 26, 1-60................. 4..................... March 26, 1992.
1992.
747-53-2275, Revision 5, January 1-66................. 5..................... January 16, 1997.
16, 1997.
747-53A2275, Revision 6, August 1-76................. 6..................... August 27, 1997.
27, 1997.
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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.
(l) This amendment becomes effective on October 7, 1998.
Issued in Renton, Washington, on September 14, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-25123 Filed 9-21-98; 8:45 am]
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