[Federal Register Volume 62, Number 38 (Wednesday, February 26, 1997)]
[Rules and Regulations]
[Pages 8613-8615]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-4555]
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Rules and Regulations
Federal Register
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Federal Register / Vol. 62, No. 38 / Wednesday, February 26, 1997 /
Rules and Regulations
[[Page 8613]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-NM-71-AD; Amendment 39-9945; AD 97-05-01]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-200, -300, and -400
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment adopts a new airworthiness directive (AD),
applicable to certain Boeing Model 747-200, -300, and -400 series
airplanes, that requires repetitive inspections to detect cracking of
the front spar web of the center section of the wing, and repair, if
necessary. This amendment is prompted by reports of fatigue cracking
found in the front spar web. The actions specified by this AD are
intended to prevent the leakage of fuel into the forward cargo bay, as
a result of fatigue cracking in the front spar web, which could result
in a potential fire hazard.
DATES: Effective April 2, 1997.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of April 2, 1997.
ADDRESSES: The service information referenced in this AD may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the Federal
Aviation Administration (FAA), Transport Airplane Directorate, Rules
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of
the Federal Register, 800 North Capitol Street, NW., suite 700,
Washington, DC.
FOR FURTHER INFORMATION CONTACT: Tamara Dow, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2771;
fax (206) 227-1181.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) to include an airworthiness
directive (AD) that is applicable to certain Boeing Model 747-200, -
300, and -400 series airplanes was published in the Federal Register on
November 18, 1996 (61 FR 58669). That action proposed to require
repetitive HFEC inspections to detect cracking of the front spar web
along the tangent point of the pocket fillet radii., and repair, if
necessary.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Support for the Proposal
Three commenters support the proposed AD.
Request to Extend Initial Compliance Time
One commenter requests that the proposal be revised to extend the
compliance time for the initial inspection from the proposed 12 months
to 18 months. The commenter requests this extension so that affected
operators will be able to perform the inspection during a regularly
scheduled maintenance visit. The extent of the work involved in the
proposed inspection, and any necessary repair, cannot be accomplished
at a line station, but must be accomplished when the airplane would be
located at a main base where special equipment and trained personnel
would be readily available. The commenter states that the adoption of
the proposed compliance time of 12 months would require operators to
schedule special times for the accomplishment of the inspection, at
additional expense and downtime.
Further, this commenter states that the wing center section front
spar web is inspected currently on some affected airplanes under the
Supplemental Structural Inspection Document (SSID) program, which was
mandated most recently by AD 94-15-18, amendment 39-8989 (59 FR 41233,
August 11, 1994). There have been no reports of cracks found in this
front spar web area during these required inspections. Additionally,
the commenter states that, since June 1995, at least 3 airplanes in its
fleet have undergone either NDT or visual inspections, and no cracks or
other problems were found on the subject front spar web. The commenter
requests that the FAA take this experience into consideration and
extend the proposed compliance threshold as requested.
The FAA does not concur. Leakage of fuel into the forward cargo
bay, as a result of fatigue cracking in the front spar web, is a
significant safety issue, and the FAA has determined that the
inspection threshold, as proposed, is warranted. The FAA considered not
only these safety issues in developing an appropriate compliance time
for this action, but the recommendations of the manufacturer, the
availability of any necessary repair parts, and the practical aspect of
accomplishing the required inspection within an interval of time that
parallels normal scheduled maintenance for the majority of affected
operators.
The FAA points out that the manufacturer recommended that the
inspections begin within 18 months after the release of Boeing Service
Bulletin 747-57A2298, Revision 1, on September 12, 1996; that interval
corresponds to most operators' scheduled ``C'' checks. The FAA took
this recommendation into account, as well as the time that would be
necessary to complete the rulemaking process, and found that a 12-month
initial compliance time should fall well within the time that the
majority of operators have regular maintenance visits scheduled.
As for the results of inspections previously performed on the
affected area, the FAA points out that this AD action was based on
reports from two operators who did find cracking in the wing center
section front spar web on at least three airplanes; the longest crack
found was 17 inches. While those cracks were found on Model 747-100
series airplanes, the FAA maintains that similar cracking is likely to
develop on Model 747-200, -300, and -400 series airplanes up to line
number 744 because those models have the same web thickness and similar
loading as the Model 747-100.
[[Page 8614]]
In light of these factors, the FAA has determined that the 12-month
initial compliance time, as proposed, is appropriate. The FAA points
out that, if operators already have accomplished the initial inspection
within the last 12 months prior to the effective date of the AD, they
are given ``credit'' for that inspection as compliance with the initial
inspection requirement of the AD. The final rule has been revised to
clarify this point.
Request To Extend Repetitive Inspection Intervals
One commenter requests that the proposal be revised to extend the
repetitive inspection interval from the proposed 1,400 cycles to 2,000
cycles. The commenter, a U.S. operator, states that it already has
inspected several of the airplanes in its fleet and has found no
cracking. In addition, the commenter points out that the inspection
area will be visually inspected at regular intervals to detect
corrosion as part of the Boeing 747 Corrosion Prevention and Control
Program, which was mandated by AD 90-25-05, amendment 39-6790 (55 FR
49268, November 27, 1990).
The FAA does not concur, since the commenter provided no technical
justification for an extension. The repetitive interval of 1,400 cycles
is based on damage tolerance and crack growth analyses that the
manufacturer performed. Additionally, the interval was calculated based
on accomplishing high frequency eddy current (HFEC) inspections, and
the effectiveness of those inspections in detecting cracking. The FAA
acknowledges that visual inspections to detect corrosion of the area
are mandated by AD 90-25-05; however, the HFEC inspections required by
this AD will provide a much higher level of precision than visual
inspections, and will be able to detect cracking far earlier than could
be discovered by visual inspections alone.
Request To Revise Method of Counting Accumulated Cycles
One commenter requests that the proposal be revised to include a
provision specifying that pressurization cycles of 2.0 psi or less need
not be counted as a flight cycle when determining the number of flight
cycles relative to the proposed compliance thresholds. The commenter
states that cabin pressure is the main contributor to stresses in the
center section front spar web, but a cabin pressure of 2.0 psi would
result in stresses of less than one-fourth the normal operating level.
Further, with a maximum cabin pressure at 2.0 psi, the fatigue damage
per cycle would be reduced by a factor of approximately 100.
The FAA does not concur with the commenter's request. The FAA
considers that flights with less than 2.0 psi cabin pressure may
contribute a negligible amount of fatigue damage to the front spar web
of the wing center section. However, a pressurization cycle of 2.0 psi
or less is a typical pressure used during flight training, and is not
typical of normal operation of the affected airplanes. The FAA does not
consider it appropriate to include various provisions in an AD
applicable to a unique use of an affected airplane. Paragraph (e) of
this final rule provides for the approval of alternative methods of
compliance to address these types of unique circumstances.
Conclusion
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule with the one change described
previously. The FAA has determined that this change will neither
increase the economic burden on any operator nor increase the scope of
the AD.
Cost Impact
There are approximately 485 Model 747-200, -300, and -400 series
airplanes of the affected design in the worldwide fleet. The FAA
estimates that 105 airplanes of U.S. registry will be affected by this
AD, that it will take approximately 48 work hours per airplane to
accomplish the required inspections, and that the average labor rate is
$60 per work hour. Based on these figures, the cost impact of the AD on
U.S. operators is estimated to be $302,400, or $2,880 per airplane, per
inspection.
The cost impact figure discussed above is based on assumptions that
no operator has yet accomplished any of the requirements of this AD
action, and that no operator would accomplish those actions in the
future if this AD were not adopted.
Regulatory Impact
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a
significant economic impact, positive or negative, on a substantial
number of small entities under the criteria of the Regulatory
Flexibility Act. A final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it may be obtained
from the Rules Docket at the location provided under the caption
ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
97-05-01 Boeing: Amendment 39-9945. Docket 96-NM-71-AD.
Applicability: Model 747-200, -300, and -400 series airplanes,
up to and including line number 744, certificated in any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
otherwise 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 (e) of
this AD. The request should include an assessment of the effect of
the modification, alteration, or repair on the unsafe condition
addressed by this AD; and, if the unsafe condition has not been
eliminated, the request should include specific proposed actions to
address it.
Compliance: Required as indicated, unless accomplished
previously.
To prevent the leakage of fuel into the forward cargo bay
through fatigue cracks in the front spar web, which could result in
a potential fire hazard, accomplish the following:
[[Page 8615]]
(a) Perform a high frequency eddy current (HFEC) inspection to
detect cracking of the front spar web of the center section of the
wing, in accordance with Boeing Alert Service Bulletin 747-57A2298,
Revision 1, dated September 12, 1996, at the time specified in
paragraph (a)(1) or (a)(2) of this AD, as applicable.
(1) For airplanes that have accumulated 12,000 to 17,999 total
landings as of the effective date of this AD: Perform the initial
inspection within 12 months after the effective date of this AD,
unless previously accomplished within the last 12 months. Perform
this inspection again prior to the accumulation of 18,000 total
landings or within 1,400 landings, whichever occurs later; after
accomplishing the initial inspection, and thereafter at intervals
not to exceed 1,400 landings.
(2) For all other airplanes: Perform the initial inspection
prior to the accumulation of 18,000 total landings or within 12
months after the effective date of this AD, whichever occurs later.
Repeat this inspection thereafter at intervals not to exceed 1,400
landings.
(b) Except as provided by paragraph (c) of this AD, if any
cracking is detected during an inspection required by paragraph (a)
of this AD, prior to further flight, repair in accordance with
paragraph (b)(1) or (b)(2) of this AD, as applicable. Thereafter
repeat the HFEC inspection required by paragraph (a) of this AD at
intervals not to exceed 1,400 landings.
(1) If any vertical crack is found that is less than 10 inches
in length, repair in accordance with Boeing Alert Service Bulletin
747-57A2298, Revision 1, dated September 12, 1996.
(2) If any vertical crack is found that is 10 inches or greater
in length; or if any crack is found that has extended in a diagonal
direction (regardless of length); or if any crack is found that
would affect an existing repair; repair in accordance with a method
approved by the Manager, Seattle Aircraft Certification Office
(ACO), FAA, Transport Airplane Directorate.
(c) In lieu of accomplishing the procedures specified in
paragraph (b) of this AD: If a crack in the front spar web is
detected during an HFEC inspection required by paragraph (a) of this
AD, prior to further flight, operators may accomplish the procedures
for an optional HFEC inspection to confirm cracking, as described in
paragraph III.D.2. of the Accomplishment Instructions of Boeing
Alert Service Bulletin 747-57A2298, Revision 1, dated September 12,
1996.
(1) If this optional inspection is accomplished and cracking is
not confirmed, thereafter repeat the HFEC inspection specified in
paragraph (a) of this AD at intervals not to exceed 1,400 landings.
(2) If this optional inspection is accomplished and confirms
cracking, prior to further flight, repair the cracking in accordance
with paragraph (b)(1) or (b)(2) of this AD, as applicable.
(d) For airplanes that are required to perform an initial HFEC
inspection in accordance with paragraph (a)(1) of this AD: Within 30
days after accomplishing the initial inspection, submit a report of
inspection results, negative or positive, that includes the
information identified in paragraphs (d)(1) through (d)(5) of this
AD, to the Manager, Seattle Aircraft Certification Office, FAA,
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; fax (206) 227-1181. Information collection
requirements contained in this regulation have been approved by the
Office of Management and Budget (OMB) under the provisions of the
Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have
been assigned OMB Control Number 2120-0056.
(1) Airplane serial number.
(2) Total number of landings accumulated.
(3) Total number of hours time-in-service accumulated.
(4) Location, size and orientation of each crack.
(5) Whether fuel leakage resulted from the crack.
(e) 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 Directorate. Operators
shall submit their requests through an appropriate FAA Principal
Maintenance Inspector, who may add comments and then send it to the
Manager, Seattle ACO.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(f) 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.
(g) The actions shall be done in accordance with Boeing Alert
Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996.
This incorporation by reference was approved by the Director of the
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part
51. Copies may be obtained from Boeing Commercial Airplane Group,
P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be
inspected at the FAA, Transport Airplane Directorate, 1601 Lind
Avenue, SW., Renton, Washington; or at the Office of the Federal
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(h) This amendment becomes effective on April 2, 1997.
Issued in Renton, Washington, on February 19, 1997.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 97-4555 Filed 2-25-97; 8:45 am]
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