[Federal Register Volume 65, Number 79 (Monday, April 24, 2000)]
[Rules and Regulations]
[Pages 21633-21634]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-9895]



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 Rules and Regulations
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  Federal Register / Vol. 65, No. 79 / Monday, April 24, 2000 / Rules 
and Regulations  

[[Page 21633]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-88-AD; Amendment 39-11694; AD 2000-08-08]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, and -800 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 737-600, -700, and -800 series 
airplanes. This action requires a one-time inspection to detect 
cracking of the rear spar stiffeners in the wing center section; and 
modification of crack-free stiffeners, or repair of cracked stiffeners. 
This amendment is prompted by a report of severed rear spar stiffeners 
of the center wing, which resulted in cracking in the adjacent keel 
beam structure. The actions specified in this AD are intended to 
prevent failure of the keel beam structure.

DATES: Effective May 9, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 9, 2000.
    Comments for inclusion in the Rules Docket must be received on or 
before June 23, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-88-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: Nenita Odesa, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, 1601 
Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-
2557; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received a report of severed 
rear spar stiffeners of the center wing, which were found during 
fatigue testing of the Model 737-800 series airplane. The cracks were 
located in the stiffeners at the left and right buttock lines 6.15, and 
initiated at fastener holes below the lower chord of the rear spar. The 
broken stiffeners were caused by actual stresses being higher than 
those used for design of the structure. Failure of the stiffeners 
caused cracking in the adjacent keel beam structure. This condition, if 
not corrected, could result in failure of the keel beam structure.
    Model 737-600 and -700 series airplanes have a similar structural 
design and are therefore also subject to the identified unsafe 
condition.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-57-
1253, dated December 16, 1999, which describes procedures for a one-
time high-frequency eddy current inspection to detect cracking in the 
rear spar stiffeners at the fastener holes below the lower rear spar 
chord of the wing center section. For crack-free stiffeners, the 
service bulletin recommends a preventive modification, which involves 
installing nested angles at the stiffeners at the left and right 
buttock lines 6.15. For any cracked stiffener, the service bulletin 
recommends, among other things, replacement of that stiffener. 
Accomplishment of the actions specified in the service bulletin is 
intended to adequately address the identified unsafe condition.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to prevent failure of the keel beam structure. This AD 
requires accomplishment of the actions specified in the service 
bulletin described previously, except as discussed below.

Differences Between the Rule and Relevant Service Information

    The service bulletin recommends that cracked stiffeners be replaced 
and that further repair be accomplished in accordance with instructions 
from Boeing. However, this AD requires that repair of any cracked 
stiffener be accomplished in accordance with a method approved by the 
FAA.

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

[[Page 21634]]

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 2000-NM-88-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, 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 adding the following new 
airworthiness directive:

2000-08-08  Boeing: Amendment 39-11694. Docket 2000-NM-88-AD.

    Applicability: Model 737-600, -700, and -800 series airplanes; 
certificated in any category; line numbers 1 through 321 inclusive.

    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 prevent failure of the keel beam structure, accomplish the 
following:

Inspection

    (a) Prior to the accumulation of the total number of flight 
cycles specified by Table 1, ``Compliance Thresholds,'' as 
applicable, of Boeing Service Bulletin 737-57-1253, dated December 
16, 1999; or within 60 days after the effective date of this AD, 
whichever occurs later: Perform a one-time high-frequency eddy 
current inspection to detect cracking of the rear spar stiffeners 
that are located at the left and right buttock lines 6.15 of the 
wing center section, in accordance with the service bulletin.
    (1) If no cracking is detected in either stiffener: Prior to 
further flight, install the preventive modification on that 
stiffener, in accordance with the service bulletin.
    (2) If any cracking is found in either stiffener, prior to 
further flight, repair that stiffener 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 of the airplane approved by a 
Boeing Company Designated Engineering Representative (DER) who has 
been authorized by the Manager, Seattle ACO, to make such findings. 
For a repair method to be approved by the Manager, Seattle ACO, as 
required by this paragraph, the Manager's approval letter must 
specifically reference this AD.

Alternative Methods of Compliance

    (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 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.

Special Flight Permits

    (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.

Incorporation by Reference

    (d) Except as required by paragraph (a)(2) of this AD, the 
actions shall be done in accordance with Boeing Service Bulletin 
737-57-1253, dated December 16, 1999. 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.
    (e) This amendment becomes effective on May 9, 2000.

    Issued in Renton, Washington, on April 14, 2000.
Charles D. Huber,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-9895 Filed 4-21-00; 8:45 am]
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