[Federal Register Volume 69, Number 4 (Wednesday, January 7, 2004)]
[Proposed Rules]
[Pages 897-900]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-272]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2002-NM-289-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, and -200C 
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 all Boeing Model 737-100, -200, 
and -200C series airplanes. This proposal would require repetitive 
inspections to detect discrepancies of certain fuselage skin panels 
located just aft of the wheel well, and repair if necessary. The 
actions specified by the proposed AD are intended to detect and correct

[[Page 898]]

fatigue cracking of the skin panels, which could cause rapid 
decompression of the airplane. This action is intended to address the 
identified unsafe condition.

DATES: Comments must be received by February 23, 2004.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2002-NM-289-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: Suzanne Lucier, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6438; fax (425) 917-6590.

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 2002-NM-289-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. 2002-NM-289-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of fatigue cracking of the skins and 
doublers located aft of the wing, between body station (BS) 727 and BS 
1016, and between body stringers 14 and 25, on numerous Boeing Model 
737-100, -200, and -200C series airplanes. On some airplanes, 
reinforcing angles had been installed on the skin doublers; however, 
cracking was detected on both modified and unmodified airplanes. The 
cracking has been attributed to fatigue from a combination of shear 
stresses due to repeated wrinkling of the skin, and the skin chem-
milled pockets configuration. Such fatigue cracking, if not corrected, 
could cause rapid decompression of the airplane.

Related Rulemaking

    AD 90-06-02, amendment 39-6489 (55 FR 8372, March 7, 1990), 
requires numerous modifications to aging Model 737 series airplanes. 
That AD requires, among other things, accomplishment of the preventive 
modification specified in Boeing Service Bulletin 737-53-1065, Revision 
1, dated October 12, 1989, of certain fuselage skin panels in the 
subject area.
    Since AD 90-06-02 was issued, the FAA has received reports 
indicating that several airplanes developed fatigue cracking in the 
fuselage skin panels even after the skin panels had been modified or 
repaired in accordance with that AD. While the cause of this post-
modification or post-repair skin cracking has not yet been determined, 
it is evident that the previous modifications or repairs may not have 
adequately addressed the original fatigue cracking problem.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-53-
1065, Revision 2, dated April 19, 2001, including Evaluation Form. This 
service bulletin describes procedures for various actions on 42 
different groups of airplanes, based on airplane configuration 
differences. The service bulletin includes procedures in different 
areas of the airplane for:
    [sbull] A subsurface eddy current or magnetic optical imaging 
inspection on the exterior skin to detect skin cracking or other damage 
in zones 1 and 3;
    [sbull] An internal HFEC inspection, if cracking is detected during 
the eddy current or magnetic optical imaging inspection, to detect 
cracking along the edge of the tearstrap and disbonding of the bonded 
doubler;
    [sbull] A blind fastener repair, which would extend the interval 
for the next HFEC inspection;
    [sbull] A general visual inspection of the exterior side of the 
skin in Zone 2;
    [sbull] Repair of cracking;
    [sbull] Removal of wrinkles from the skin to allow the repair to be 
done;
    [sbull] Reinspecting unrepaired areas at regular intervals; and
    [sbull] Installation of reinforcing angles, which would extend the 
interval for the next inspection.

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 repetitive inspections to detect 
discrepancies of certain fuselage skin panels located just aft of the 
wheel well, and repair if necessary. The purpose of these inspections 
is to detect fatigue cracking of the skin panels, which could cause 
rapid decompression of the airplane. The proposed inspections are to be 
accomplished in accordance with the service bulletin, except as 
discussed below.

Differences Between the Service Bulletin and the Proposed AD

    Although the 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 approved by a Boeing Company Designated Engineering 
Representative who has been authorized by the FAA to make such 
findings.
    Although the service bulletin recommends that operators report 
certain crack findings, this AD would not require such a report.

[[Page 899]]

Interim Action

    This is considered to be interim action. The manufacturer has 
advised that it is developing an improved preventive modification 
intended to address the identified unsafe condition for unmodified skin 
areas. After this modification is developed, approved, and available, 
the FAA may consider additional rulemaking.

Cost Impact

    There are approximately 1,000 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 390 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 47 to 88 work hours per airplane 
(depending on configuration) to accomplish the proposed inspections, at 
an average labor rate of $65 per work hour. Based on these figures, the 
cost impact of the inspections proposed by this AD is estimated to be 
$3,055 to $5,720 per airplane, per inspection cycle.
    The cost impact figures discussed above are 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 proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

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 2002-NM-289-AD.

    Applicability: All Model 737-100, -200, and -200C series 
airplanes; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To detect and correct fatigue cracking of the skin panels, which 
could cause rapid decompression of the airplane, accomplish the 
following:

Repetitive Inspections: Unmodified Skin Areas

    (a) For fuselage skin panel areas that have not been modified 
with stiffening angles: Before the airplane accumulates 16,000 total 
flight cycles, or within 4,500 flight cycles after the effective 
date of this AD, whichever occurs later, inspect the unmodified 
fuselage side skins just aft of the main wheelwell, and perform all 
follow-on actions, in accordance with Part I of the Accomplishment 
Instructions of Boeing Service Bulletin 737-53-1065, Revision 2, 
dated April 19, 2001. If no cracking, loose fasteners, disbonding, 
or damage is found: Repeat the inspection at the time specified in 
paragraph 1.E., of the service bulletin, as applicable, except as 
provided by paragraph (d) of this AD.

Repetitive Inspections: Modified Skin Areas

    (b) For fuselage skin panel areas that have been modified with 
stiffening angles in accordance with Boeing Service Bulletin 737-53-
1065, dated April 19, 2001: Within 16,000 flight cycles after the 
modification, or within 4,500 flight cycles after the effective date 
of this AD, whichever occurs later, inspect the modified areas as 
specified in accordance with Part I of Boeing Service Bulletin 737-
53-1065, Revision 2, dated April 19, 2001. Repeat the inspection at 
the time specified in paragraph 1.E., of the service bulletin, as 
applicable, except as provided by paragraph (d) of this AD. If any 
cracks, loose fasteners, disbonding, or damage is found: Repair 
before further flight in accordance with the requirements of 
paragraph (d) of this AD.

Terminating Action for Inspections of Modified Skin Areas

    (c) For fuselage skin panel areas that have been modified with 
stiffening angles in accordance with Boeing Service Bulletin 737-53-
1065, dated April 19, 2001: At the later of the times specified by 
paragraphs (c)(1) and (c)(2) of this AD: Perform a subsurface eddy 
current or magneto optical imaging inspection to detect subsurface 
skin cracks along the edge of the bonded doubler, in accordance with 
Figure 10 of Boeing Service Bulletin 737-53-1065, Revision 2, dated 
April 19, 2001. If any cracks are found, repair before further 
flight in accordance with paragraph (d) of this AD. Accomplishment 
of this inspection and all applicable corrective actions terminates 
the repetitive inspections required by paragraph (b) of this AD for 
the modified areas.
    (1) Inspect within 24,500, but not fewer than 20,000, flight 
cycles after the modification of the skin.
    (2) Inspect within 4,500 flight cycles after the effective date 
of this AD.

Repair: Modified and Unmodified Skin Areas

    (d) If any cracking is detected during any inspection required 
by this AD: Do the actions specified by paragraph (d)(1) or (d)(2) 
of this AD before further flight. Do the actions in accordance with 
Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 
2001, except as required by paragraph (e) of this AD.
    (1) Do a time-limited repair (including a detailed inspection of 
the skin in the area of the repair to detect corrosion and doubler 
disbonding) in accordance with Part III of the Accomplishment 
Instructions of the service bulletin.
    (i) After the time-limited repair has been accomplished: At 
intervals not to exceed 3,000 flight cycles, perform an external 
general visual inspection of the repair to detect loose or missing 
fasteners, in accordance with Part III of the Accomplishment 
Instructions of the service bulletin, until the actions specified in 
paragraph (d)(1)(v) of this AD have been accomplished.
    (ii) After the time-limited repair has been accomplished: At 
intervals not to exceed 4,500 flight cycles, perform an internal 
inspection of the repair to detect cracking or doubler disbonding 
using general visual and high-frequency eddy current methods, in 
accordance with Figure 11 of the service bulletin, until the actions 
specified in paragraph (d)(1)(v) of this AD have been accomplished.
    (iii) If any cracking is found during any inspection required by 
paragraph (d)(1) of this AD: Repair before further flight in 
accordance with paragraph (e) of this AD.
    (iv) If any disbonding is found during any inspection required 
by paragraph (d)(1) of this AD: Repair before further flight in

[[Page 900]]

accordance with Part II of the service bulletin.
    (v) Within 10,000 flight cycles after accomplishment of the 
time-limited repair: Make the repair permanent in accordance with 
Part III of the Accomplishment Instructions of the service bulletin. 
Permanent repair of an area terminates the repetitive inspections 
specified in this AD for that repaired area only.
    (2) Do a permanent repair (including an inspection using 
external subsurface eddy current or magneto optical imaging methods 
to detect cracks at the chem-milled step in each adjacent bay of the 
fuselage skin, a detailed inspection of the skin in the area of the 
repair for corrosion and doubler disbonding, and applicable 
corrective action) of the cracked area, in accordance with Part II 
of the Accomplishment Instructions of the service bulletin. 
Permanent repair of an area terminates the repetitive inspections 
specified in this AD for that repaired area only.

Exceptions to Service Bulletin Procedures

    (e) During any inspection required by this AD, if any 
discrepancy (including cracking) is detected for which the service 
bulletin specifies to contact Boeing for appropriation action: 
Before further flight, repair in accordance with a method approved 
by the Manager, Seattle ACO; 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 Manager, Seattle ACO, to make such findings. For a 
repair method to be approved, as required by this paragraph, the 
approval letter must specifically refer to this AD.
    (f) Although Boeing Service Bulletin 737-53-1065, Revision 2, 
dated April 19, 2001, recommends that cracks found in Zone 2 be 
reported to Boeing, this AD does not require such a report.

Alternative Methods of Compliance

    (g)(1) In accordance with 14 CFR 39.19, the Manager, Seattle 
ACO, FAA, is authorized to approve alternative methods of compliance 
(AMOCs) for this AD.
    (2) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by a 
Boeing Company Designated Engineering Representative who has been 
authorized by the Manager, Seattle ACO, to make such findings.

    Issued in Renton, Washington, on December 30, 2003.
Michael J. Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-272 Filed 1-6-04; 8:45 am]
BILLING CODE 4910-13-P