AD 2000-04-08

[Federal Register Volume 65, Number 37 (Thursday, February 24, 2000)]
[Rules and Regulations]
[Pages 9215-9217]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 00-4116]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-352-AD; Amendment 39-11590; AD 2000-04-08]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200C 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 737-200C series airplanes. This 
action requires repetitive inspections to detect cracking in the lower 
skin at the stringer 4R lap joint, and certain fuselage frames; and 
corrective actions, if necessary. This amendment also provides for 
optional terminating action for the repetitive inspections. This 
amendment is prompted by a report of a fractured frame located at body 
station (BS) 480. The actions specified in this AD are intended to 
detect and correct cracking in certain frames, which, in conjunction 
with multiple site cracking in the lower skin of the lap joint, could 
result in failure of certain lap joints, and consequent rapid 
decompression of the airplane fuselage.

DATES: Effective March 10, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 10, 2000.
    Comments for inclusion in the Rules Docket must be received on or 
before April 24, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-352-AD, 1601 Lind Avenue, SW., 
Renton, WA 98055-4056.
    The service information referenced in this AD may be obtained from 
Boeing Commercial Airplane Group, PO Box 3707, Seattle, WA 98124-2207. 
This information may be examined at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, WA; or at the Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, Washington, 
DC.

FOR FURTHER INFORMATION CONTACT: James G. Rehrl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2783; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received a report indicating 
that a cracked fuselage frame was detected at body station (BS) 480, 
common to the stringer 5R integral shear tie stringer cutout on a Model 
737-200C series airplane. Subsequent investigation revealed that the z-
frame and integral-shear-tie at the stringer cutout were fractured. A 
crack also was detected in the S-5R and S-2R integral shear ties at the 
stringer cutout. A fractured frame at stringer 5R is a concern because 
it is adjacent to the stringer 4R lap joint, which is susceptible to 
multiple site cracking. Although the cracking was detected at BS 480 
only, the frames at BS 500, 500A, 500B, and 520 have a similar design. 
Such cracking in these frames, in conjunction with multiple site 
cracking in the lower skin of the stringer 4R lap joint, could result 
in failure of the lap joint, and consequent rapid decompression of the 
airplane fuselage.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-53A1220, dated October 4, 1999, which describes procedures for a 
low frequency eddy current (LFEC) inspection to detect cracking in the 
lower skin at the stringer 4R lap joint between BS 460 and BS 540, and 
a detailed internal visual inspection to detect cracking in the frames 
at BS 480 through BS 520. The alert service bulletin also describes 
procedures for a preventative modification of the BS 480 frame.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Model 737-200C series airplanes of the same 
type design, this AD is being issued to require repetitive inspections 
to detect cracking in the lower skin at the stringer 4R lap joint, and 
certain fuselage frames; and corrective actions, if necessary. This 
amendment also provides for optional terminating action for the 
repetitive inspections. The actions are required to be accomplished in 
accordance with the alert service bulletin described previously, except 
as discussed below.

Differences Between Service Bulletin and This AD

    Operators should note that, although the alert service bulletin 
does not

[[Page 9216]]

specify repeat inspections following accomplishment of the initial 
internal detailed visual inspection (DVI) to detect cracking of certain 
frames, this AD requires that the internal DVI be repeated at intervals 
not to exceed 2,500 flight cycles, until accomplishment of the optional 
preventative modification of the BS 480 frame. The FAA finds that 
accomplishment of the initial inspection alone would not adequately 
address the unsafe condition. The FAA has determined that 
accomplishment of the repetitive internal DVI will maintain an adequate 
level of safety in the fleet until accomplishment of the preventative 
modification of the BS 480 frame.
    Operators also 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.

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 99-NM-352-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, 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:

2000-04-08 Boeing: Amendment 39-11590. Docket 99-NM-352-AD.

    Applicability: Model 737-200C series airplanes having line 
numbers 292 and subsequent, 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 (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 detect and correct cracking in certain fuselage frames, 
which, in conjunction with multiple site cracking in the lower skin 
of the lap joint, could result in failure of certain lap joints, and 
consequent rapid decompression of the airplane fuselage, accomplish 
the following:

Repetitive Inspections

    (a) Prior to the accumulation of 50,000 total flight cycles, or 
within 600 flight cycles after the effective date of this AD, 
whichever occurs later: Perform a low frequency eddy current 
(sliding probe) inspection to detect cracking in accordance with 
Part 3.A. of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1220, dated October 4, 1999. Repeat the inspections 
at intervals not to exceed 600 flight cycles until accomplishment of 
the requirements of paragraph (b) of this AD.
    (b) Within 2,500 flight cycles following accomplishment of the 
initial inspection required by paragraph (a) of this AD: Perform an 
internal detailed visual inspection to detect cracking in accordance 
with the Part 3.B. of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1220, dated October 4, 1999. Repeat 
the inspection thereafter at intervals not to exceed 2,500 flight 
cycles until the modification required by paragraph (d) of this AD 
is accomplished.

Detailed Visual Inspection

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''


[[Page 9217]]



Corrective Actions

    (c) Prior to further flight, repair any cracking detected by any 
inspection required by paragraph (a) or (b) of this AD 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 (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 
approval letter must specifically reference this AD.

Optional Terminating Action

    (d) Installation of the preventative modification of the BS 480 
frame in accordance with Part 3.C. of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1220, dated 
October 4, 1999, constitutes terminating action for the requirements 
of this AD.

Alternative Methods of Compliance

    (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. 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 3: 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

    (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.

Incorporation by Reference

    (g) Except as provided by paragraph (c) of this AD, the actions 
shall be done in accordance with Boeing Alert Service Bulletin 737-
53A1220, dated October 4, 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, WA 98124-
2207. Copies may be inspected at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, WA; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (h) This amendment becomes effective on March 10, 2000.

    Issued in Renton, Washington, on February 15, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-4116 Filed 2-23-00; 8:45 am]
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