[Federal Register Volume 64, Number 244 (Tuesday, December 21, 1999)]
[Proposed Rules]
[Pages 71336-71339]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-32982]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-30-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-200, -300, and -400 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 747-
200, -300, -400 series airplanes, that currently requires repetitive 
high frequency eddy current (HFEC) inspections to detect cracking of

[[Page 71337]]

the front spar web of the center section of the wing, and repair, if 
necessary. This action would require that the existing inspection be 
accomplished at a reduced threshold. This action also would add a 
requirement that the existing HFEC inspection be accomplished on 
repaired areas. This proposal is prompted by reports of cracking in 
repaired areas of the front spar web and cracking of the front spar web 
on an airplane that had accumulated fewer flight cycles than the 
inspection threshold of the existing AD. The actions specified by the 
proposed 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: Comments must be received by February 4, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-30-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9 a.m. and 3 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: Tamara Anderson, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-2771; 
fax (425) 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 99-NM-30-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-114, Attention: Rules 
Docket No. 99-NM-30-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On February 19, 1997, the FAA issued AD 97-05-01, amendment 39-9945 
(62 FR 8613, February 26, 1997), applicable to certain Boeing Model 
747-200, -300, and -400 series airplanes, to require repetitive high 
frequency eddy current (HFEC) inspections to detect cracking of the 
front spar web of the center section of the wing, and repair, if 
necessary. That action was prompted by reports of fatigue cracking 
found in the front spar web. The requirements of that 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.

Actions Since Issuance of Previous Rule

    Since the issuance of AD 97-05-01, the FAA has received reports of 
cracking in repaired areas of the front spar web on Model 747SR series 
airplanes. Also, the FAA has received a report for the first time of 
cracking in the front spar web on a Model 747-200 series airplane. The 
Model 747-200 series airplane had accumulated 13,309 total flight 
cycles, which is less than the 18,000 total landing compliance time 
specified in AD 97-05-01 for certain airplanes.
    The front spar web on Model 747SR series airplanes is identical to 
that on the affected Model 747-200 series airplanes, except there is no 
fuel located behind the front spar web on Model 747SR series airplanes. 
In addition, if the subject fatigue cracking were to occur on these 
airplanes, the cabin pressure would vent through the front spar web and 
then the limiting access holes of the front spar; this would result in 
a loss of pressurization, but not sudden decompression. This would also 
not result in damage to unpressurized areas. Therefore, no unsafe 
condition exists on Model 747SR series airplanes.

Explanation of Relevant Service Information

    Subsequent to the finding of this new cracking, the manufacturer 
issued and the FAA reviewed and approved Boeing Service Bulletin 747-
57A2298, Revision 2, dated October 2, 1997, and Boeing Alert Service 
Bulletin 747-57A2298, Revision 3, dated January 7, 1999.
    The method of inspection in Revision 2 of the service bulletin is 
identical to that described in Revision 1 of the service bulletin 
(which was referenced in AD 97-05-01 as the appropriate source of 
service information). However, Revision 2 revises the inspection 
procedures to include instructions for repetitive HFEC inspections of 
the aft side of the front spar web to detect cracking. These 
instructions were added to allow inspection when a prior repair 
precludes access to the forward side of the front spar web.
    The inspection procedures in Revision 3 of the service bulletin are 
identical to those described in Revision 2 of the service bulletin. 
Revision 3 reduces the inspection threshold and revises the listing of 
current operators of affected airplanes.
    Accomplishment of the actions specified in the service bulletins is 
intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    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 supersede AD 97-05-01 to continue to require 
accomplishment of the requirements of the existing AD and to require 
accomplishment of the actions specified in the service bulletins 
described previously, except as discussed below.

Differences Between Proposed Rule and the Service Bulletins

    Operators should note that, although the alert service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions, this proposed AD would require 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

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approved by a Boeing Company Designated Engineering Representative who 
has been authorized by the FAA to make such findings.

Cost Impact

    There are approximately 485 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 105 airplanes of U.S. registry 
would be affected by this proposed AD.
    The inspections that are currently required by AD 97-05-01 and 
retained in this AD, take approximately 8 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the currently required actions on 
U.S. operators is estimated to be $50,400, or $480 per airplane, per 
inspection cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
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 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-9945 (62 FR 
8613, February 26, 1997), and by adding a new airworthiness directive 
(AD), to read as follows:

    BOEING: Docket 99-NM-30-AD. Supersedes AD 97-05-01, amendment 39-
9945.

    Applicability: Model 747-200, -300, -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 
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 (d) 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, as a 
result of fatigue cracking in the front spar web, which could result 
in a potential fire hazard, accomplish the following:

Restatement of Requirement of AD 97-05-01, Amendment 39-9945

Repetitive Inspections

    (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; Boeing Service Bulletin 747-
57A2298, Revision 2, dated October 2, 1997; or Boeing Alert Service 
Bulletin 747-57A2298, Revision 3, dated January 7, 1999; at the time 
specified in paragraph (a)(1) or (a)(2) of this AD, as applicable, 
until accomplishment of the requirements of paragraph (b) of this 
AD.
    (1) For airplanes that have accumulated 12,000 to 17,999 total 
landings as of April 2, 1997 (the effective date of AD 97-05-01, 
amendment 39-9945): Perform the initial inspection within 12 months 
after April 2, 1997, unless previously accomplished within the last 
12 months prior to April 2, 1997. 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 April 2, 1997, whichever occurs later. Repeat this 
inspection thereafter at intervals not to exceed 1,400 landings.

New Requirements of This AD

Repetitive Inspections

    (b) Prior to accumulation of 12,000 total landings, or within 12 
months after the effective date of this AD, whichever occurs later, 
perform an HFEC inspection to detect cracking of the front spar web 
of the center section of the wing, in accordance with Boeing Service 
Bulletin 747-57A2298, Revision 2, dated October 2, 1997; or Boeing 
Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 
1999. Repeat the HFEC inspection thereafter at intervals not to 
exceed 1,400 landings. Accomplishment of the HFEC inspection 
constitutes terminating action for the repetitive inspection 
requirements of paragraph (a) of this AD.

Repair

    (c) If any cracking is detected during any inspection required 
by paragraph (a) or (b) of this AD, prior to further flight, confirm 
the cracking with secondary procedures in accordance with Boeing 
Service Bulletin 747-57A2298, Revision 2, dated October 2, 1997, or 
Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 
7, 1999. Thereafter repeat the HFEC inspection required by paragraph 
(a) or (b) 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 and has not extended in a diagonal direction, prior to 
further flight, repair in accordance with the service bulletin.
    (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 the length); or if any crack is found that 
would affect an existing repair, prior to further flight, repair 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 Designated Engineering Representative 
who has been authorized by the FAA to make such findings. For a 
repair method to be approved by the Manager, Seattle ACO, or a 
Boeing DER, as required by this paragraph, the approval letter must 
specifically reference this AD.

Alternative Methods of Compliance

    (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 ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of

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compliance with this AD, if any, may be obtained from the Seattle 
ACO.

Special Flight Permits

    (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, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-32982 Filed 12-20-99; 8:45 am]
BILLING CODE 4910-13-U