[Federal Register Volume 63, Number 59 (Friday, March 27, 1998)]
[Proposed Rules]
[Pages 14863-14865]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-8133]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-309-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes. This proposal would require repetitive detailed visual 
inspections to detect corrosion on the rear spar web of the wing center 
section and adjacent bulkhead fittings at body station 1241; and 
corrective action, if necessary. This proposal is prompted by reports 
of corrosion found on the rear spar web and bulkhead fitting. The 
actions specified by the proposed AD are intended to detect and correct 
such corrosion, which could cause cracking of the rear spar web, and 
result in a fuel leak and consequent fire/explosion in the wheel well 
of the main landing gear.

DATES: Comments must be received by May 11, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-309-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207.
    This information may be examined at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Bob Breneman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-2776; 
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 97-NM-309-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. 97-NM-309-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of corrosion found on Boeing Model 747 
series airplanes. The corrosion was found on the rear spar web and the 
bulkhead fitting of body station 1241; corrosion thicknesses ranged 
from 0.030 to 0.250 inch. Investigation revealed that moisture trapped 
between the rear

[[Page 14864]]

spar web and the bulkhead fitting resulted in the corrosion. Such 
corrosion, if not detected and corrected in a timely manner, could 
cause cracking of the rear spar web, and result in a fuel leak and 
consequent fire/explosion in the wheel well of the main landing gear.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-57-
2263, Revision 1, dated December 21, 1995, which describes procedures 
for repetitive detailed visual inspections to detect corrosion of the 
rear spar web of the wing center section and adjacent bulkhead fittings 
at body station 1241; and corrective action, if necessary. 
Accomplishment of the actions specified in the service bulletin 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 require accomplishment of the actions specified in 
the service bulletin described previously, except as discussed in the 
following section.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, while the service bulletin specifies 
that the application of corrosion inhibitor following an inspection 
eliminates the necessity for further inspections, this proposed AD 
would require that the inspection be repeated at regular intervals. The 
FAA has determined that repetitive inspections and corrective action 
are necessary in order to detect and correct corrosion in a timely 
manner and to adequately address the identified unsafe condition.
    Additionally, operators should note that, although the service 
bulletin specifies that the manufacturer may be contacted for 
disposition of certain repair conditions, this proposal would require 
that the repair of those conditions be accomplished in accordance with 
a method approved by the FAA.

Cost Impact

    There are approximately 816 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 236 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
2 work hours per airplane to accomplish the proposed actions, and that 
the average labor rate is $60 per work hour. Based on these figures, 
the cost impact of the proposed AD on U.S. operators is estimated to be 
$28,320, or $120 per airplane, per inspection cycle.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this AD were not adopted.

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 adding the following new 
airworthiness directive:

Boeing: Docket 97-NM-309-AD.

    Applicability: Model 747 series airplanes, line positions 1 
through 816 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 (b) 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 corrosion and consequent cracking of the 
rear spar web of the wing center section and adjacent bulkhead 
fittings at body station 1241, which could result in a fuel leak and 
subsequent fire/explosion in the wheel well of the main landing 
gear, accomplish the following:
    (a) Within 18 months after the effective date of this AD, 
perform a detailed visual inspection to detect corrosion of the rear 
spar web of the wing center section and adjacent bulkhead fittings 
at body station 1241, in accordance with Boeing Service Bulletin 
747-57-2263, Revision 1, dated December 21, 1995. Thereafter, repeat 
the inspection at intervals not to exceed 2 years.
    (1) If no corrosion is detected during the inspection: Prior to 
further flight, apply corrosion inhibitor in accordance with the 
service bulletin.
    (2) If any corrosion is detected during the inspection, and the 
corrosion is within the limits specified by the service bulletin: 
Prior to further flight, accomplish the actions specified in 
paragraphs (a)(2)(i), (a)(2)(ii), and (a)(2)(iii).
    (i) Remove the corrosion in accordance with the service 
bulletin. And
    (ii) Perform a high frequency eddy current inspection to detect 
cracking in the area of removed corrosion in accordance with the 
service bulletin. If any crack is detected, prior to further flight, 
repair it in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate. And
    (iii) Apply corrosion inhibitor in accordance with the service 
bulletin.
    (3) If any corrosion is detected during the inspection, and the 
corrosion exceeds the limits specified by the service bulletin: 
Prior to further flight, repair the corroded area in accordance with 
a method approved by the Manager, Seattle ACO.
    (b) 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

[[Page 14865]]

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

    (c) 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 March 23, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-8133 Filed 3-25-98; 8:45 am]
BILLING CODE 4910-13-U