[Federal Register Volume 72, Number 226 (Monday, November 26, 2007)]
[Proposed Rules]
[Pages 65901-65903]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-22923]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-0226; Directorate Identifier 2007-NM-187-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
Series Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 737-300, -400, and -500 series airplanes. This 
proposed AD would require repetitive inspections for cracking of the 
body buttock line (BBL) 0.07 floor beam between body station (BS) 651 
and BS 676 and between BS 698 and BS 717, and related investigative and 
corrective actions if necessary. This AD also provides an optional 
terminating action for the repetitive inspections. This proposed AD 
results from reports of cracking in the BBL 0.07 floor beam. We are 
proposing this AD to prevent failure of the main deck floor beams at 
certain body stations due to fatigue cracking, which could result in 
rapid decompression of the airplane.

DATES: We must receive comments on this proposed AD by January 10, 
2008.

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, P.O. Box 3707, Seattle, Washington 98124-2207.

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: Nancy Marsh, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,

[[Page 65902]]

1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6440; 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-2007-0226; 
Directorate Identifier 2007-NM-187-AD'' at the beginning of 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.

Other Related Rulemaking

    On July 12, 2001, we issued AD 2001-14-20, amendment 39-12331 (66 
FR 38354, July 24, 2001), applicable to certain Boeing Model 737-100 
and -200 series airplanes. AD 2001-14-20 requires repetitive 
inspections to find fatigue cracking in the main deck floor beams 
located at certain body stations, and repair if necessary. AD 2001-14-
20 also provides for optional terminating action for the repetitive 
inspections. AD 2001-14-20 addresses fatigue cracking in the main deck 
floor beams on Model 737-100 and -200 series airplanes, while this 
proposed AD would address the same unsafe condition on Boeing Model 
737-300, -400, and -500 series airplanes.

Discussion

    Since we issued AD 2001-14-20, several operators have reported 
cracking in the body buttock line (BBL) 0.07 floor beam on Model 737-
300, -400, and -500 series airplanes. The cracks were similar to those 
found on the Model 737-100 and -200 series airplanes, which are 
addressed by AD 2001-14-20. Investigation revealed that the cracks were 
caused by fatigue resulting from pressurization flexure. Failure of the 
main deck floor beam at certain body stations due to fatigue cracking 
could result in rapid decompression of the airplane.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 737-57-1210, Revision 2, 
dated June 13, 2007. For Model 737-300, -400, and -500 series 
airplanes, the service bulletin describes procedures for accomplishing 
repetitive detailed inspections for cracking of the BBL 0.07 floor beam 
between body station (BS) 651 and BS 676 and between BS 698 and BS 717, 
and doing related investigative and corrective actions if necessary. 
The related investigative action includes doing a high frequency eddy 
current (HFEC) inspection of the fastener holes for cracking (1) prior 
to modifying the floor beam, or (2) if any cracking is found in the web 
(between BS 651 and BS 676 and between BS 698 and BS 717) or in the 
upper chord (between BS 651 and BS 676) during the detailed inspection. 
The corrective actions include the following:
     Repairing any cracking in accordance with the service 
bulletin, if cracking is found in the web (between BS 651 and BS 676 
and between BS 698 and BS 717) or in the upper chord (between BS 651 
and BS 676) during the detailed inspection but no cracking is found 
during the HFEC inspection. Accomplishing the repair would eliminate 
the need for the repetitive inspections for the area in which the 
repair is installed.
     Contacting Boeing for repair instructions, (1) if cracking 
is found in the web (between BS 651 and BS 676 and between BS 698 and 
BS 717) or in the upper chord (between BS 651 and BS 676) during the 
HFEC inspections, (2) if cracking is found in the chords or stiffeners 
(between BS 698 and BS 717) or outside the typical crack locations 
(between BS 651 and BS 676 and between BS 698 and BS 717) during the 
detailed inspection, or (3) if cracking is found during the HFEC prior 
to modifying the floor beam.
    The service bulletin also provides procedures for modifying the 
floor beam, if no cracking is found during the detailed and HFEC 
inspections. Accomplishing the modification (optional terminating 
action) would eliminate the need for the repetitive inspections for the 
area in which the modification is installed.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously, except as discussed under 
``Difference Between the Proposed AD and Service Bulletin.''

Difference Between the Proposed AD and Service Bulletin

    The service bulletin specifies 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.

Costs of Compliance

    There are about 1,961 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 599 airplanes of 
U.S. registry. The proposed inspections would take about 4 work hours 
per airplane, at an average labor rate of $80 per work hour. Based on 
these figures, the estimated cost of the proposed AD for U.S. operators 
is $191,680, or $320 per airplane, per inspection cycle.

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 have 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

[[Page 65903]]

on the distribution of power and responsibilities among the various 
levels of government.
    For the reasons discussed above, I certify that the 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket. See the 
ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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 Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0226; Directorate Identifier 2007-NM-
187-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by January 
10, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-300, -400, and -500 
series airplanes, certificated in any category; as identified in 
Boeing Service Bulletin 737-57-1210, excluding Appendix A, Revision 
2, dated June 13, 2007.

Unsafe Condition

    (d) This AD results from reports of cracking in the body buttock 
line (BBL) 0.07 floor beam. We are issuing this AD to prevent 
failure of the main deck floor beams at certain body stations due to 
fatigue cracking, which could result in rapid decompression of the 
airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Inspections and Related Investigative/Corrective Actions

    (f) Before the accumulation of 20,000 total flight hours, or 
within 7,000 flight cycles after the effective date of this AD, 
whichever occurs later: Do the detailed inspections for cracking of 
the BBL 0.07 floor beam between body station (BS) 651 and BS 676 and 
between BS 698 and BS 717, and do all the applicable related 
investigative and corrective actions before further flight, by 
accomplishing all of the applicable actions specified in paragraphs 
B.2. and B.4. of the Accomplishment Instructions of Boeing Service 
Bulletin 737-57-1210, excluding Appendix A, Revision 2, dated June 
13, 2007, except as provided by paragraph (g) of this AD. Repeat the 
inspections thereafter at intervals not to exceed 7,000 flight 
cycles. Installing a repair in accordance with paragraphs B.2. and 
B.4. of the Accomplishment Instructions of the service bulletin, or 
doing the modification in accordance with paragraph (h) of this AD, 
terminates the repetitive inspections for the applicable area only.

Exception to Corrective Action

    (g) If any cracking is found during any inspection required by 
this AD, and Boeing Service Bulletin 737-57-1210, excluding Appendix 
A, Revision 2, dated June 13, 2007, specifies to contact Boeing for 
appropriate action: Before further flight, repair the cracking using 
a method approved in accordance with the procedures specified in 
paragraph (i) of this AD.

Optional Terminating Action

    (h) If no cracking is found during the detailed inspection and 
related investigative action required by paragraph (f) of this AD: 
Accomplishing the modification of the BBL 0.07 floor beam between BS 
651 and BS 676 and between BS 698 and BS 717, as applicable, in 
accordance with paragraphs B.2. and B.4., as applicable, of the 
Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, 
excluding Appendix A, Revision 2, dated June 13, 2007, terminates 
the repetitive inspections for the applicable area only.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (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 appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.
    (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 November 13, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E7-22923 Filed 11-23-07; 8:45 am]
BILLING CODE 4910-13-P