[Federal Register Volume 74, Number 87 (Thursday, May 7, 2009)]
[Proposed Rules]
[Pages 21278-21281]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-10612]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2009-0429; Directorate Identifier 2007-NM-059-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300 and 737-400 Series 
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain Boeing Model 737-300 and 737-400 series airplanes. This 
proposed AD would require repetitive inspections to detect cracking of 
the aft fuselage skin, and related investigative/corrective actions if 
necessary. This proposed AD results from reports of cracks in the aft 
fuselage skin on both sides of the airplane. We are proposing this AD 
to detect and correct cracking in the aft fuselage skin along the 
longitudinal edges of the bonded skin doubler, which could result in 
reduced structural integrity of the airplane.

DATES: We must receive comments on this proposed AD by June 22, 2009.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this AD, contact Boeing 
Commercial Airplanes, Attention: Data & Services Management, P.O. Box 
3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 206-544-5000, 
extension 1, fax 206-766-5680; e-mail [email protected]; Internet  
https://www.myboeingfleet.com. You may review copies of the referenced 
service information at the FAA, Transport Airplane Directorate, 1601 
Lind Avenue, SW., Renton, Washington. For information on the 
availability of this material at the FAA, call 425-227-1221 or 425-227-
1152.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (telephone 800-647-5527) is in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

FOR FURTHER INFORMATION CONTACT: Wayne Lockett, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6447; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2009-0429; 
Directorate Identifier 2007-NM-059-AD'' at the beginning of

[[Page 21279]]

your comments. We specifically invite comments on the overall 
regulatory, economic, environmental, and energy aspects of this 
proposed AD. We will consider all comments received by the closing date 
and may amend this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    We have received 159 reports of cracks in the fuselage skin aft of 
the wing on 68 Model 737-300 series airplanes with between 16,400 and 
48,000 total flight cycles. Of those cracks, 120 were found between 
body station (BS) 727D and BS 747 and between stringers 14 and 25, on 
both sides of the airplanes. One crack was found above stringer 25 
right (R) at BS 913. Several of the cracks occurred in multiple 
adjacent bays. The remaining cracks were scattered between BS 727 and 
BS 1016.
    A total of 29 cracks have been reported on 29 Model 737-400 series 
airplanes with between 22,500 and 44,600 total flight cycles. The 
cracks on these airplanes were found on both the left and right sides 
of the airplanes between BS 727 and BS 947 in the skin panels between 
stringers 20 and 25. The cracks ranged in length between 0.25 and 5.5 
inches. One operator reported a crack on an airplane with 22,500 total 
flight cycles. The crack was in the skin panel assembly just above 
stringer 25R between BS 727+10 and BS 727, and between stringers 23R 
and 24R.
    On the existing skin panel assembly, the doubler is bonded to the 
skin. At these skin panel locations on the airplane, the in-service 
loads cause a condition that allows cracks to occur along the 
longitudinal edges of the skin where it bonded to the doubler. 
Cracking, if not corrected, could result in reduced structural 
integrity of the airplane.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 737-53-1168, Revision 3, 
dated November 28, 2006 (for Model 737-300 series airplanes); and 
Boeing Service Bulletin 737-53-1187, Revision 2, dated May 9, 2007 (for 
Model 737-400 series airplanes). The service bulletins describe 
procedures for repetitive inspections to detect cracking of the aft 
fuselage skin; and related investigative and corrective actions, if 
necessary.
    For Model 737-300 series airplanes, in areas without modification 
stiffeners installed previously, and for Model 737-400 series 
airplanes, the inspection technique to be used depends on the 
inspection zone. The inspection techniques include: External detailed 
and external subsurface eddy current; external general visual (in areas 
not covered by fairings); external detailed or subsurface eddy current 
(in areas covered by fairings); or external detailed, and either 
external subsurface eddy current or magneto optical imaging.
    For Model 737-300 series airplanes, in areas with modification 
stiffeners installed previously, the inspections include: External 
general visual inspections of the surface of the skin panels for 
evidence of loose fasteners or skin cracking; and a one-time subsurface 
eddy current inspection for evidence of loose fasteners or skin cracks.
    For all airplanes, related investigative and corrective actions 
include the following: Internal general visual and high frequency eddy 
current inspections for disbonding and cracking of the bonded doubler; 
repair or replacement of the skin panel; an internal inspection of the 
chem-milled step in the skin area covered by the doubler; replacement 
of the skin panel and splice plate between body stations (BS) 727 and 
907 and between Stringers 20 and 25; and sending any positive 
inspection results to Boeing.
    In addition, the service bulletins describe procedures for doing a 
time-limited repair, including a detailed inspection for cracking of 
the fuselage skin, and installing a repair doubler; repeating 
inspections of repaired areas; repairing any cracking; making the 
repairs permanent within a specified compliance time; and replacing any 
loose fasteners.
    The service bulletins also specify that repeat inspections are 
terminated in areas where the skin panel replacement had been done, and 
in repaired areas that meet the requirements specified in Table 1 of 
paragraph 1.E. of the service bulletins.
    The compliance times specified in the service bulletins are 
identified in the tables below.

                                  Table--Compliance Times for Unmodified Areas
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                Action                    Inspection zone 1        Inspection zone 2        Inspection zone 3
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Zone and initial inspections.........    Before accumulating 22,000 total flight cycles, or within 4,500 flight
                                           cycles after the release date of the service bulletin, whichever is
                                                                         later.
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Repetitive inspections...............  Option 1: Intervals not  Intervals not to exceed  Option 1: Intervals not
                                        to exceed 3,700 flight   4,500 flight cycles      to exceed 3,700 flight
                                        cycles after the         after the previous       cycles after the
                                        previous inspection;     inspection.              previous inspection;
                                        or                                                or
                                       Option 2: Intervals not  .......................  Option 2: Intervals not
                                        to exceed 2,100 flight                            to exceed 2,100 flight
                                        cycles after the                                  cycles after the
                                        previous inspection.                              previous inspection.
----------------------------------------------------------------------------------------------------------------


               Table--Compliance Times for Modified Areas
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                Action                   Compliance times for all zones
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Zone and initial inspections.........  Before accumulating 22,000 total
                                        flight cycles or within 4,500
                                        flight cycles after the release
                                        date of the service bulletin,
                                        whichever is later.
Repetitive inspections...............  Intervals not to exceed 4,500
                                        flight cycles after the previous
                                        inspection.
Terminating action...................  Not before 20,000 flight cycles
                                        following modification (Figure 5
                                        of Boeing Service Bulletin 737-
                                        53-1168, Revision 3).
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[[Page 21280]]


Table--Follow-on Actions and Compliance Times if the Time-Limited Repair
                                 Is Done
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 If you do the time-limited repair, you
                 must--                     At this compliance time--
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Do a detailed inspection of the          At intervals not to exceed
 fastener.                                3,000 flight cycles following
                                          the repair.
Replace a blind fastener with a solid    Before the repair has reached
 fastener.                                10,000 total flight cycles.
Do an internal inspection of the tear    Within 4,500 flight cycles
 strap for disbonding and cracks.         following the repair.
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FAA's Determination and Requirements of This Proposed AD

    We are proposing this AD because we evaluated all relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the(se) same type 
design(s). This proposed AD would require accomplishing the actions 
specified in the service information described previously, except as 
discussed under ``Differences Between the Proposed AD and Service 
Information.''

Differences Between the Proposed AD and Service Information

    The service bulletins specify to contact the manufacturer for 
instructions on how to repair certain conditions, but this proposed AD 
would require repairing those conditions in one of the following ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.
    Although the service bulletins referenced in this proposed AD 
specify to submit information to the manufacturer, this proposed AD 
does not include such a requirement.

Costs of Compliance

    We estimate that this proposed AD would affect 516 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD. The average labor rate 
is $80 per work hour.

                                                 Estimated Costs
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                                                                                   Number of
                                                                                     U.S.-
             Action                  Work hours       Parts    Cost per product    registered      Fleet cost
                                                                                   airplanes
----------------------------------------------------------------------------------------------------------------
Inspection to determine          1.................       $0  $80...............          516  $41,280.
 inspection zones.
Repetitive inspections--Option   64................        0  $5,120, per                 516  Up to $2,641,920.
 1.                                                            inspection cycle.
Repetitive inspections--Option   62................        0  $4,960, per                 516  Up to $2,559,360.
 2.                                                            inspection cycle.
Internal inspection............  5, per inspection         0  $1,200............          516  $619,200.
                                  zone (3 zones).
----------------------------------------------------------------------------------------------------------------

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. ``Subtitle VII: Aviation 
Programs,'' describes in more detail the scope of the Agency's 
authority.
    We are issuing this rulemaking under the authority described in 
``Subtitle VII, Part A, Subpart III, Section 44701: General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would 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.
    For the reasons discussed above, I certify 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. 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.
    You can find our regulatory evaluation and the estimated costs of 
compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The FAA amends Sec.  39.13 by adding the following new AD:

Boeing: Docket No. FAA-2009-0429; Directorate Identifier 2007-NM-
059-AD.

Comments Due Date

    (a) We must receive comments by June 22, 2009.

[[Page 21281]]

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to the airplanes identified in paragraphs 
(c)(1) and (c)(2) of this AD, certified in any category.
    (1) Boeing Model 737-300 series airplanes as identified in 
Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 
2006.
    (2) Boeing Model 737-400 series airplanes as identified in 
Boeing Service Bulletin 737-53-1187, Revision 2, dated May 9, 2007.

Subject

    (d) Air Transport Association (ATA) of America Code 53: 
Fuselage.

Unsafe Condition

    (e) This AD results from reports of cracks in the aft fuselage 
skin on both sides of the airplane. We are issuing this AD to detect 
and correct cracking in the aft fuselage skin along the longitudinal 
edges of the bonded skin doubler, which could result in reduced 
structural integrity of the airplane.

Compliance

    (f) Comply with this AD within the compliance times specified, 
unless already done.

Inspections, Related Investigative and Corrective Actions

    (g) At the applicable times specified in Tables 1 and 2 of 
paragraph 1.E. ``Compliance,'' of Boeing Service Bulletin 737-53-
1168, Revision 3, dated November 28, 2006 (for Model 737-300 series 
airplanes); or Boeing Service Bulletin 737-53-1187, Revision 2, 
dated May 9, 2007 (for Model 737-400 series airplanes); except as 
provided by paragraph (k) of this AD: Do the applicable inspections 
and related investigative actions to detect cracks in the aft 
fuselage skin panels, by accomplishing all of the applicable actions 
specified in the Accomplishment Instructions of Boeing Service 
Bulletin 737-53-1168, Revision 3, dated November 28, 2006; or Boeing 
Service Bulletin 737-53-1187, Revision 2, dated May 9, 2007; as 
applicable, including Note (f) of Table 1 of paragraph 1.E. And, do 
the applicable corrective actions specified in the Accomplishment 
Instructions of Boeing Service Bulletin 737-53-1168, Revision 3, 
dated November 28, 2006; or Boeing Service Bulletin 737-53-1187, 
Revision 2, dated May 9, 2007; as applicable; except as provided by 
paragraphs (h), (i), and (l) of this AD. Repeat the applicable 
inspections and related investigative actions thereafter at the 
applicable intervals specified in Tables 1 and 2 of paragraph 1.E. 
of Boeing Service Bulletin 737-53-1168, Revision 3, dated November 
28, 2006; or Boeing Service Bulletin 737-53-1187, Revision 2, dated 
May 9, 2007; as applicable.
    (h) If any crack is found during any inspection or corrective 
action required by this AD, before further flight, repair in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53-1168, Revision 3, dated November 28, 2006 (for Model 
737-300 series airplanes); or Boeing Service Bulletin 737-53-1187, 
Revision 2, dated May 9, 2007 (for Model 737-400 series airplanes); 
except, where Boeing Service Bulletin 737-53-1168, Revision 3, dated 
November 28, 2006; or Boeing Service Bulletin 737-53-1187, Revision 
2, dated May 9, 2007; as applicable; specifies to contact Boeing, 
before further flight, repair according to a method approved in 
accordance with the procedures specified in paragraph (m) of this 
AD.
    (i) If any cracking of a repaired area is found during any 
inspection required by this AD, and Boeing Service Bulletin 737-53-
1168, Revision 3, dated November 28, 2006 (for Model 737-300 series 
airplanes); or Boeing Service Bulletin 737-53-1187, Revision 2, 
dated May 9, 2007 (for Model 737-400 series airplanes); specifies 
contacting Boeing for appropriate action: Before further flight, 
repair the cracking using a method approved in accordance with the 
procedures specified in paragraph (m) of this AD.

Optional Terminating Action

    (j) Doing the skin panel replacement in accordance with Part 3 
of the Accomplishment Instructions of Boeing Service Bulletin 737-
53-1168, Revision 3, dated November 28, 2006 (for Model 737-300 
series airplanes); or Part III of the Accomplishment Instructions of 
Boeing Service Bulletin 737-53-1187, Revision 2, dated May 9, 2007 
(for Model 737-400 series airplanes); terminates the inspection 
requirements of paragraph (g) of this AD for that skin panel only.

Exception to Service Bulletin

    (k) Where Boeing Service Bulletin 737-53-1168, Revision 3, dated 
November 28, 2006 (for Model 737-300 series airplanes); or Boeing 
Service Bulletin 737-53-1187, Revision 2, dated May 9, 2007 (for 
Model 737-400 series airplanes); specifies compliance times after 
the release date of those service bulletins, this AD requires that 
the specified actions be done within the specified compliance times 
after the effective date of this AD.

No Reporting Required

    (l) Although Boeing Service Bulletin 737-53-1168, Revision 3, 
dated November 28, 2006 (for Model 737-300 series airplanes); and 
Boeing Service Bulletin 737-53-1187, Revision 2, dated May 9, 2007 
(for Model 737-400 series airplanes); specify to submit information 
to the manufacturer, this AD does not include such a requirement.

Alternative Methods of Compliance (AMOCs)

    (m)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested 
using the procedures found in 14 CFR 39.19. Send information to 
ATTN: Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone 
(425) 917-6447; fax (425) 917-6590. Or, e-mail information to [email protected].
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your principal maintenance inspector (PMI) or 
principal avionics inspector (PAI), as appropriate, or lacking a 
principal inspector, your local Flight Standards District Office. 
The AMOC approval letter must specifically reference this AD.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who has been authorized 
by the Manager, Seattle ACO, to make those findings. For a repair 
method to be approved, the repair must meet the certification basis 
of the airplane, and the approval must specifically refer to this 
AD.

    Issued in Renton, Washington, on May 1, 2009.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E9-10612 Filed 5-6-09; 8:45 am]
BILLING CODE 4910-13-P